Unisaw Torsion Box Fence Table

Ger21 said:

Building the box

My old fence extension table was just a piece of 3/4" MDF with plastic laminate on top. 8+ years with a PC7518 hanging from it put a pretty good sag in it. I reinforced it with some 1×6 poplar, but that was a temporary fix. Since it's my main router table, I need something extremely flat, so I can do precision work with it. The plan is to build a torsion box table. I'll be using the existing steel angle at the Unifence and outfeed table to support the front and back. This dictates that the top extends beyond the torsion box to rest on the steel. I'll be building some legs to support the end. I'd like to build a cabinet for blade and bit storage, but I need to see how much room I have with a router hanging under the table.

I use an Incra Jig Ultra for my fence. It'll be mounted to the top using 1/4-20 T-nuts inside the top, and studded plastic knobs. To give me more flexibility, I'm putting a series of T-Nuts, so that I can move the fence in 5" increments. It's a 16" fence, but being able to move it will give me over 24" between the bit and fence, if needed. I can also mount the router fence at the end of the table, and get the full 50"+ use from my Unifence.

I'm also using an array of T-Nuts for featherboard and fixture mounting. It's hard to allow for all possible situations, but hopefully the layout will be flexible enough.

I like my Unifence, but one issue is the fact that there's nothing holding the back down, and that the back can flex a bit when pressure is applied at the back. To fix these issues, I extended the back row of T-Nuts for the router fence all the way across the table. I'll be making some hold down fixtures for locking the ear of the fence in place when needed. I won't use these often, but where high precision, or extra rigidity is needed, they'll be available.

I started, by throwing the top on my CNC router, and routing the holes for the T-Nuts. I also counterbored them so the nuts are recessed, although I didn't really need to do that. I also routed dado's for the front to back torsion box ribs. This just made it a little easier to build. And last, while it was up there, I rough cut the hole for the router. I'll CNC a jig that bolts to the T-Nuts for the finish plate opening, when I figure out what to do for plates. Btw, the top is 3/4" Medex (water resistant MDF). I got it for free, and wasn't using it for anything else. The entire torsion box is built from scrap, and won't cost anything.

Because of the motor cover door, the maximum thickness of the top can only be 3". For extra rigidity, the two ribs on each side of the cutout are 1" appleply. The rest of the ribs are 1/2" MDF.

Before gluing in the ribs, I shimmed the top flat on my saw and sagging outfeed table. Once it was flat, I applied the bottom sheet (1/2" MDF) with glue and staples.

I have an idea for a durable top surface for this table, and a few others I want to build. I'm going to attempt an 1/8" endgrain veneer top. I'm hoping for the stablity of MDF, and the durability of butcher block. Here's the plan. First, cut a million little endgrain "tiles". Then, attach them to the top using CA glue. Just a little in the corners, as I don't want to coat the entire bottom. When the entire top is covered, I'll saturate it with epoxy resin. The intent is that the epoxy will flow all the way through, actually bonding to the MDF. This will basically create a plastic top, that should be very stable. Once the epoxy cures, I'll surface the entire top with the CNC router to get it perfectly flat. I'll need to thoroughly seal the entire box, to prevent any warping in the summer. If this doesn't work, and cracks (or worse), I can always put it back on the CNC and route the "veneer" off. We'll see how it goes.

Not sure how long this entire project will take. I start a new job tomorrow, and may need to invest a bit of my personal time in that for the next few months.

Click to expand...

Ger21 said:

Building the box

My old fence extension table was just a piece of 3/4" MDF with plastic laminate on top. 8+ years with a PC7518 hanging from it put a pretty good sag in it. I reinforced it with some 1×6 poplar, but that was a temporary fix. Since it's my main router table, I need something extremely flat, so I can do precision work with it. The plan is to build a torsion box table. I'll be using the existing steel angle at the Unifence and outfeed table to support the front and back. This dictates that the top extends beyond the torsion box to rest on the steel. I'll be building some legs to support the end. I'd like to build a cabinet for blade and bit storage, but I need to see how much room I have with a router hanging under the table.

I use an Incra Jig Ultra for my fence. It'll be mounted to the top using 1/4-20 T-nuts inside the top, and studded plastic knobs. To give me more flexibility, I'm putting a series of T-Nuts, so that I can move the fence in 5" increments. It's a 16" fence, but being able to move it will give me over 24" between the bit and fence, if needed. I can also mount the router fence at the end of the table, and get the full 50"+ use from my Unifence.

I'm also using an array of T-Nuts for featherboard and fixture mounting. It's hard to allow for all possible situations, but hopefully the layout will be flexible enough.

I like my Unifence, but one issue is the fact that there's nothing holding the back down, and that the back can flex a bit when pressure is applied at the back. To fix these issues, I extended the back row of T-Nuts for the router fence all the way across the table. I'll be making some hold down fixtures for locking the ear of the fence in place when needed. I won't use these often, but where high precision, or extra rigidity is needed, they'll be available.

I started, by throwing the top on my CNC router, and routing the holes for the T-Nuts. I also counterbored them so the nuts are recessed, although I didn't really need to do that. I also routed dado's for the front to back torsion box ribs. This just made it a little easier to build. And last, while it was up there, I rough cut the hole for the router. I'll CNC a jig that bolts to the T-Nuts for the finish plate opening, when I figure out what to do for plates. Btw, the top is 3/4" Medex (water resistant MDF). I got it for free, and wasn't using it for anything else. The entire torsion box is built from scrap, and won't cost anything.

Because of the motor cover door, the maximum thickness of the top can only be 3". For extra rigidity, the two ribs on each side of the cutout are 1" appleply. The rest of the ribs are 1/2" MDF.

Before gluing in the ribs, I shimmed the top flat on my saw and sagging outfeed table. Once it was flat, I applied the bottom sheet (1/2" MDF) with glue and staples.

I have an idea for a durable top surface for this table, and a few others I want to build. I'm going to attempt an 1/8" endgrain veneer top. I'm hoping for the stablity of MDF, and the durability of butcher block. Here's the plan. First, cut a million little endgrain "tiles". Then, attach them to the top using CA glue. Just a little in the corners, as I don't want to coat the entire bottom. When the entire top is covered, I'll saturate it with epoxy resin. The intent is that the epoxy will flow all the way through, actually bonding to the MDF. This will basically create a plastic top, that should be very stable. Once the epoxy cures, I'll surface the entire top with the CNC router to get it perfectly flat. I'll need to thoroughly seal the entire box, to prevent any warping in the summer. If this doesn't work, and cracks (or worse), I can always put it back on the CNC and route the "veneer" off. We'll see how it goes.

Not sure how long this entire project will take. I start a new job tomorrow, and may need to invest a bit of my personal time in that for the next few months.

Click to expand...

Ger21 said:

Building the box

My old fence extension table was just a piece of 3/4" MDF with plastic laminate on top. 8+ years with a PC7518 hanging from it put a pretty good sag in it. I reinforced it with some 1×6 poplar, but that was a temporary fix. Since it's my main router table, I need something extremely flat, so I can do precision work with it. The plan is to build a torsion box table. I'll be using the existing steel angle at the Unifence and outfeed table to support the front and back. This dictates that the top extends beyond the torsion box to rest on the steel. I'll be building some legs to support the end. I'd like to build a cabinet for blade and bit storage, but I need to see how much room I have with a router hanging under the table.

I use an Incra Jig Ultra for my fence. It'll be mounted to the top using 1/4-20 T-nuts inside the top, and studded plastic knobs. To give me more flexibility, I'm putting a series of T-Nuts, so that I can move the fence in 5" increments. It's a 16" fence, but being able to move it will give me over 24" between the bit and fence, if needed. I can also mount the router fence at the end of the table, and get the full 50"+ use from my Unifence.

I'm also using an array of T-Nuts for featherboard and fixture mounting. It's hard to allow for all possible situations, but hopefully the layout will be flexible enough.

I like my Unifence, but one issue is the fact that there's nothing holding the back down, and that the back can flex a bit when pressure is applied at the back. To fix these issues, I extended the back row of T-Nuts for the router fence all the way across the table. I'll be making some hold down fixtures for locking the ear of the fence in place when needed. I won't use these often, but where high precision, or extra rigidity is needed, they'll be available.

I started, by throwing the top on my CNC router, and routing the holes for the T-Nuts. I also counterbored them so the nuts are recessed, although I didn't really need to do that. I also routed dado's for the front to back torsion box ribs. This just made it a little easier to build. And last, while it was up there, I rough cut the hole for the router. I'll CNC a jig that bolts to the T-Nuts for the finish plate opening, when I figure out what to do for plates. Btw, the top is 3/4" Medex (water resistant MDF). I got it for free, and wasn't using it for anything else. The entire torsion box is built from scrap, and won't cost anything.

Because of the motor cover door, the maximum thickness of the top can only be 3". For extra rigidity, the two ribs on each side of the cutout are 1" appleply. The rest of the ribs are 1/2" MDF.

Before gluing in the ribs, I shimmed the top flat on my saw and sagging outfeed table. Once it was flat, I applied the bottom sheet (1/2" MDF) with glue and staples.

I have an idea for a durable top surface for this table, and a few others I want to build. I'm going to attempt an 1/8" endgrain veneer top. I'm hoping for the stablity of MDF, and the durability of butcher block. Here's the plan. First, cut a million little endgrain "tiles". Then, attach them to the top using CA glue. Just a little in the corners, as I don't want to coat the entire bottom. When the entire top is covered, I'll saturate it with epoxy resin. The intent is that the epoxy will flow all the way through, actually bonding to the MDF. This will basically create a plastic top, that should be very stable. Once the epoxy cures, I'll surface the entire top with the CNC router to get it perfectly flat. I'll need to thoroughly seal the entire box, to prevent any warping in the summer. If this doesn't work, and cracks (or worse), I can always put it back on the CNC and route the "veneer" off. We'll see how it goes.

Not sure how long this entire project will take. I start a new job tomorrow, and may need to invest a bit of my personal time in that for the next few months.

Click to expand...

Ger21 said:

End Grain Veneer Top (or "What did I get myself into")

I mentioned in the previous entry, my intent to use an 1/8" endgrain veneer on the table top. Rather than dive in head first (and break my neck), I thought it might be a god idea to make a small sample to test the viablility of this.

I cut a few pieces of endgrain birch, and glued them up on some scrap Extira. A few days ago, I applied the epoxy, pouring it on, and warming it with a heat gun to thin it, and allow better penetration, as the goal is to have it fully penetrated and bond the veneer to the substrate. After curing for a few days, I mounted the sample on the CNC, and routed about .01" off the top. Got a nice, smooth finish.

What I really needed to see, was if the epoxy went all the way through. So I routed away half of the sample, and left about .01" of the endgrain left on the substrate. Success!. You can see the spots where the CA glue was used to attach the pieces, as it started to tear away. But everywhere else, where the epoxy penetrated, the veneer is still attached.

Just to be sure the epoxy did penetrate into the Extira, I made two more passes of .005", just slightly into the Extira. You can see the spots where the CA glue was, and you can clearly see the epoxy everywhere else. So I'm confident I can move forward and I'll have a good solid bond.

Now, here's the bad part. This is a lot of work. I spent about 4-5 hours, and got about 7" covered. The table is about 60" long. Although the first row took quite a bit longer than the rest. The rest of the rows go fairly fast.

One problem is that because the scrap I'm using is fairly short (~12"), I really couldn't plane or joint it. The majority of it was exactly 3/4" thick, but a few pieces vary a little. For the width, I cut them on the table saw, using a caliper to try to get the fence set to exactly 1-1/2". Due to tension in the wood, the width varies a little as well. The end result is a few very small gaps here and there (less than 1/64") which I may fill with some slivers, or an epoxy sawdust filler. Hopefully I can get the top done in the next two weeks. I need to do the epoxy on a weekend, as I'll need to keep the garage warm for at least two days for it to cure, so I'd rather be working in the garage while I'm paying to heat it. It's warm today, but it'll be back to around 20° by the end of the week.

Click to expand...

Ger21 said:

End Grain Veneer Top (or "What did I get myself into")

I mentioned in the previous entry, my intent to use an 1/8" endgrain veneer on the table top. Rather than dive in head first (and break my neck), I thought it might be a god idea to make a small sample to test the viablility of this.

I cut a few pieces of endgrain birch, and glued them up on some scrap Extira. A few days ago, I applied the epoxy, pouring it on, and warming it with a heat gun to thin it, and allow better penetration, as the goal is to have it fully penetrated and bond the veneer to the substrate. After curing for a few days, I mounted the sample on the CNC, and routed about .01" off the top. Got a nice, smooth finish.

What I really needed to see, was if the epoxy went all the way through. So I routed away half of the sample, and left about .01" of the endgrain left on the substrate. Success!. You can see the spots where the CA glue was used to attach the pieces, as it started to tear away. But everywhere else, where the epoxy penetrated, the veneer is still attached.

Just to be sure the epoxy did penetrate into the Extira, I made two more passes of .005", just slightly into the Extira. You can see the spots where the CA glue was, and you can clearly see the epoxy everywhere else. So I'm confident I can move forward and I'll have a good solid bond.

Now, here's the bad part. This is a lot of work. I spent about 4-5 hours, and got about 7" covered. The table is about 60" long. Although the first row took quite a bit longer than the rest. The rest of the rows go fairly fast.

One problem is that because the scrap I'm using is fairly short (~12"), I really couldn't plane or joint it. The majority of it was exactly 3/4" thick, but a few pieces vary a little. For the width, I cut them on the table saw, using a caliper to try to get the fence set to exactly 1-1/2". Due to tension in the wood, the width varies a little as well. The end result is a few very small gaps here and there (less than 1/64") which I may fill with some slivers, or an epoxy sawdust filler. Hopefully I can get the top done in the next two weeks. I need to do the epoxy on a weekend, as I'll need to keep the garage warm for at least two days for it to cure, so I'd rather be working in the garage while I'm paying to heat it. It's warm today, but it'll be back to around 20° by the end of the week.

Click to expand...

Ger21 said:

Finishing the top

It's been a while since I started on this, but was busy with my new job. But the weather forced me back into action.

We're having an unseasonably warm spring. 8 inches of snow melted in a few days, then rain, and 50°-60° temps. And a huge amount of humidity. I went out in the garage the other day, and was terrified to see the pieces that I ad already glued down loose on the torsion box. The humidity had expanded them so much that they were popping loose, actually tearing the surface of the MDF. And the torsion box was actually getting a slight crown on top. I immediately turned on the furnace, and let it run all week at about 65°, to remove the humidity. After a week, the torsion box flattened back out, at least to within 1/64" or so.

I carefully removed the loose pieces, and glued them back down with some more CA. They had to go back in the same place, because they had spots of MDF attached to them. Keeping them organized was a bit tricky, as I had to re-glue about 50 pieces, maybe more.

Once I had the majority of the loose ones back down, I started work on the rest of the top. I wasn't too concerned if there were still a few loose ones in the middle, as the epoxy should glue them in place.

When I started before, the "tiles" didn't fit as well as I'd have liked, because I didn't really prepare them properly. Rather than have gaps, I carefully fitted any that weren't tight. This took a tremendous amount of time. This time, I didn't have time on my side, so I didn't worry about any gaps. I actually found that it was much easier to split "filler" pieces off the tiles with a chisel, and tap them into place, filling all but the smallest of gaps. So I managed to finish tiling the top in a few hours Saturday and Sunday.

Today, I started to apply the epoxy, to seal out the moisture, and firmly bond the tiles to the top. One thing I noticed was that some how, the two very small drops of CA glue are showing all the way through the 1/8" thick tiles. I used a gel CA, and used very little, so this surprised me. I didn't see this in the small sample I made. Maybe when I route it flat they won't be as visible. Anyway, another surprise, was that I put about 1/2 gallon of epoxy on it. And I just checked on it, and it's all soaked in. It probably would soak in another cup or two. But I'm pretty sure that it's soaked all the way into the MDF. (I sure hope so)

Here's a few pics right after I applied the epoxy, a few minutes ago. Tomorrow I'll flood the bottom of the box with Polyurethane, to seal it up good. Saturday I'll route it flat, and rabbitt the edges to apply some trim pieces. Maybe bubinga, as I got a bunch from work. When it's al done, it'll be coated with several coats of polyurethane, and wet sanded to a glass smooth finish. Can't wait to finish and start using it.

Click to expand...

Ger21 said:

Finishing the top

It's been a while since I started on this, but was busy with my new job. But the weather forced me back into action.

We're having an unseasonably warm spring. 8 inches of snow melted in a few days, then rain, and 50°-60° temps. And a huge amount of humidity. I went out in the garage the other day, and was terrified to see the pieces that I ad already glued down loose on the torsion box. The humidity had expanded them so much that they were popping loose, actually tearing the surface of the MDF. And the torsion box was actually getting a slight crown on top. I immediately turned on the furnace, and let it run all week at about 65°, to remove the humidity. After a week, the torsion box flattened back out, at least to within 1/64" or so.

I carefully removed the loose pieces, and glued them back down with some more CA. They had to go back in the same place, because they had spots of MDF attached to them. Keeping them organized was a bit tricky, as I had to re-glue about 50 pieces, maybe more.

Once I had the majority of the loose ones back down, I started work on the rest of the top. I wasn't too concerned if there were still a few loose ones in the middle, as the epoxy should glue them in place.

When I started before, the "tiles" didn't fit as well as I'd have liked, because I didn't really prepare them properly. Rather than have gaps, I carefully fitted any that weren't tight. This took a tremendous amount of time. This time, I didn't have time on my side, so I didn't worry about any gaps. I actually found that it was much easier to split "filler" pieces off the tiles with a chisel, and tap them into place, filling all but the smallest of gaps. So I managed to finish tiling the top in a few hours Saturday and Sunday.

Today, I started to apply the epoxy, to seal out the moisture, and firmly bond the tiles to the top. One thing I noticed was that some how, the two very small drops of CA glue are showing all the way through the 1/8" thick tiles. I used a gel CA, and used very little, so this surprised me. I didn't see this in the small sample I made. Maybe when I route it flat they won't be as visible. Anyway, another surprise, was that I put about 1/2 gallon of epoxy on it. And I just checked on it, and it's all soaked in. It probably would soak in another cup or two. But I'm pretty sure that it's soaked all the way into the MDF. (I sure hope so)

Here's a few pics right after I applied the epoxy, a few minutes ago. Tomorrow I'll flood the bottom of the box with Polyurethane, to seal it up good. Saturday I'll route it flat, and rabbitt the edges to apply some trim pieces. Maybe bubinga, as I got a bunch from work. When it's al done, it'll be coated with several coats of polyurethane, and wet sanded to a glass smooth finish. Can't wait to finish and start using it.

Click to expand...

Ger21 said:

Finishing the top

It's been a while since I started on this, but was busy with my new job. But the weather forced me back into action.

We're having an unseasonably warm spring. 8 inches of snow melted in a few days, then rain, and 50°-60° temps. And a huge amount of humidity. I went out in the garage the other day, and was terrified to see the pieces that I ad already glued down loose on the torsion box. The humidity had expanded them so much that they were popping loose, actually tearing the surface of the MDF. And the torsion box was actually getting a slight crown on top. I immediately turned on the furnace, and let it run all week at about 65°, to remove the humidity. After a week, the torsion box flattened back out, at least to within 1/64" or so.

I carefully removed the loose pieces, and glued them back down with some more CA. They had to go back in the same place, because they had spots of MDF attached to them. Keeping them organized was a bit tricky, as I had to re-glue about 50 pieces, maybe more.

Once I had the majority of the loose ones back down, I started work on the rest of the top. I wasn't too concerned if there were still a few loose ones in the middle, as the epoxy should glue them in place.

When I started before, the "tiles" didn't fit as well as I'd have liked, because I didn't really prepare them properly. Rather than have gaps, I carefully fitted any that weren't tight. This took a tremendous amount of time. This time, I didn't have time on my side, so I didn't worry about any gaps. I actually found that it was much easier to split "filler" pieces off the tiles with a chisel, and tap them into place, filling all but the smallest of gaps. So I managed to finish tiling the top in a few hours Saturday and Sunday.

Today, I started to apply the epoxy, to seal out the moisture, and firmly bond the tiles to the top. One thing I noticed was that some how, the two very small drops of CA glue are showing all the way through the 1/8" thick tiles. I used a gel CA, and used very little, so this surprised me. I didn't see this in the small sample I made. Maybe when I route it flat they won't be as visible. Anyway, another surprise, was that I put about 1/2 gallon of epoxy on it. And I just checked on it, and it's all soaked in. It probably would soak in another cup or two. But I'm pretty sure that it's soaked all the way into the MDF. (I sure hope so)

Here's a few pics right after I applied the epoxy, a few minutes ago. Tomorrow I'll flood the bottom of the box with Polyurethane, to seal it up good. Saturday I'll route it flat, and rabbitt the edges to apply some trim pieces. Maybe bubinga, as I got a bunch from work. When it's al done, it'll be coated with several coats of polyurethane, and wet sanded to a glass smooth finish. Can't wait to finish and start using it.

Click to expand...

Ger21 said:

Endgrain is hard to sand.

After thoroughly sealing the bottom and sides of the torsion box with a quart of polyurethane, it was time to surface the top flat. When I placed my 4 ft level on the bottom, it appeared to be flat to within < 1/64". But for some reason, it appeared the top top had a slightly larger crown along it's length, maybe 1/32" or so. So I lowered the bit to the surface, and started cutting just enough to not miss any spots. At first I was getting what appeared to be a very rough and torn surface, so I greatly increased the RPM, and it looked a lot smoother, but was a lot louder. I normally route at 15,000 or less, but cranked it up to about 22,000.

My CNC can only cut about 45" long, so I had to turn it around to cut the other side. But before turning it around, I recut the plate hole and rabbitt, making the rabbitt perfectly parallel to the surface. I'm going to make some custom 3/4" thick phenolic plates. I've got a large chunk of 10mm phenolic plate, and I'll laminate it into two layers with epoxy, and CNC a rabbitt to fit. If I have any problems with the phenolic, then I'll get some custom aluminum plates machined. But the phenolic should be fine, and I have enough to make about 6 plates. I keep my 7518 mounted to a plate, and a 690 as well. I also have a spare 690 base that I'll mount. Different plates will have different hole sizes. For most of the time, I'll use a plate with a small hole, maybe 1" or so. This should work great for 90% of the router table work I do.

I plan to use this leveling system that I found here:

http://lumberjocks.com/PurpLev/blog/13430

I'll make a jig with the CNC to accurately locate and drill the holes.

Once I turned it around to finish the surfacing, I noticed that there must have been a slight twist in the box. Where the surfacing passes met, it was flush on the back, but a little high on the front. I made another pass, removing .002", and the front came out perfect. The slight discrepancy is at the end of the table where the Incra fence will mount, so even if there was more variation, it wouldn't have really mattered.

As you can see in the pic, there were a lot of tool marks from the router removing 1/2" per pass. Unfortunately, the router is not quite perpendicular to the table, and leaves a slight ridge. Fortunately, the ridge is only about .002" high. You can barely feel it However, endgrain birch saturated with epoxy is extremely hard to sand.

As for the rough surface I thought I was getting. It turns out that as soon as I start sanding, the (perceived) roughness disappeared almost immediately. But the ridges were another story. After a quick sanding, they can no longer be felt, but you can still see them. I spent about an hour to get it to this point. I'm tempted to get out the belt sander, but am too afraid of a mistake. Belt sanders can do tremendous damage in seconds. But I do have a really good one, a 4×24 Bosch with variable speed. I might try it at a slow speed to see if it works. I also tried a scraper, which helps, but that doesn't remove much material either. I don't want to remove much material, but man, that .002 is HARD to sand.

Today's goal is to get the top sanded, and rabbitt the edges and insert a bubinga border. Maybe 3/8"x3/8". The front edge needs a bevel to match the Unisaw.

I also may need to order a piece of stainless steel angle to attach the table to the Unisaw table. Right now, there's an 1/8" steel plate, with some small tabs bolted to it. I'd like something a bit more secure, as the current table is only supported in 3 small places at the saw. Right now, mu plan for mounting is to use countersunk stainless screws through the top, and through the steel angle on the 3 sides, and use locknuts under the angle. This is a much better method than the standard 3/4" lag screws from underneath.

One last thing. I'm really unhappy witht he spots from the CA glue bleeding?? through. Hopefully, the polyurethane finish will minimize it. Other than that, I'm pretty happy. As of right now, I have a near perfectly flat router table, that won't sag.

And one more last thing. Before I route through the surface to expose the T-Nuts, I'll be completely finishing the table with a few coats of polyurethane. I don't want the polyurethane to get into the threads.

Here's a short video showing the surfacing operation.

Click to expand...

Ger21 said:

Endgrain is hard to sand.

After thoroughly sealing the bottom and sides of the torsion box with a quart of polyurethane, it was time to surface the top flat. When I placed my 4 ft level on the bottom, it appeared to be flat to within < 1/64". But for some reason, it appeared the top top had a slightly larger crown along it's length, maybe 1/32" or so. So I lowered the bit to the surface, and started cutting just enough to not miss any spots. At first I was getting what appeared to be a very rough and torn surface, so I greatly increased the RPM, and it looked a lot smoother, but was a lot louder. I normally route at 15,000 or less, but cranked it up to about 22,000.

My CNC can only cut about 45" long, so I had to turn it around to cut the other side. But before turning it around, I recut the plate hole and rabbitt, making the rabbitt perfectly parallel to the surface. I'm going to make some custom 3/4" thick phenolic plates. I've got a large chunk of 10mm phenolic plate, and I'll laminate it into two layers with epoxy, and CNC a rabbitt to fit. If I have any problems with the phenolic, then I'll get some custom aluminum plates machined. But the phenolic should be fine, and I have enough to make about 6 plates. I keep my 7518 mounted to a plate, and a 690 as well. I also have a spare 690 base that I'll mount. Different plates will have different hole sizes. For most of the time, I'll use a plate with a small hole, maybe 1" or so. This should work great for 90% of the router table work I do.

I plan to use this leveling system that I found here:

http://lumberjocks.com/PurpLev/blog/13430

I'll make a jig with the CNC to accurately locate and drill the holes.

Once I turned it around to finish the surfacing, I noticed that there must have been a slight twist in the box. Where the surfacing passes met, it was flush on the back, but a little high on the front. I made another pass, removing .002", and the front came out perfect. The slight discrepancy is at the end of the table where the Incra fence will mount, so even if there was more variation, it wouldn't have really mattered.

As you can see in the pic, there were a lot of tool marks from the router removing 1/2" per pass. Unfortunately, the router is not quite perpendicular to the table, and leaves a slight ridge. Fortunately, the ridge is only about .002" high. You can barely feel it However, endgrain birch saturated with epoxy is extremely hard to sand.

As for the rough surface I thought I was getting. It turns out that as soon as I start sanding, the (perceived) roughness disappeared almost immediately. But the ridges were another story. After a quick sanding, they can no longer be felt, but you can still see them. I spent about an hour to get it to this point. I'm tempted to get out the belt sander, but am too afraid of a mistake. Belt sanders can do tremendous damage in seconds. But I do have a really good one, a 4×24 Bosch with variable speed. I might try it at a slow speed to see if it works. I also tried a scraper, which helps, but that doesn't remove much material either. I don't want to remove much material, but man, that .002 is HARD to sand.

Today's goal is to get the top sanded, and rabbitt the edges and insert a bubinga border. Maybe 3/8"x3/8". The front edge needs a bevel to match the Unisaw.

I also may need to order a piece of stainless steel angle to attach the table to the Unisaw table. Right now, there's an 1/8" steel plate, with some small tabs bolted to it. I'd like something a bit more secure, as the current table is only supported in 3 small places at the saw. Right now, mu plan for mounting is to use countersunk stainless screws through the top, and through the steel angle on the 3 sides, and use locknuts under the angle. This is a much better method than the standard 3/4" lag screws from underneath.

One last thing. I'm really unhappy witht he spots from the CA glue bleeding?? through. Hopefully, the polyurethane finish will minimize it. Other than that, I'm pretty happy. As of right now, I have a near perfectly flat router table, that won't sag.

And one more last thing. Before I route through the surface to expose the T-Nuts, I'll be completely finishing the table with a few coats of polyurethane. I don't want the polyurethane to get into the threads.

Here's a short video showing the surfacing operation.

Click to expand...

Ger21 said:

Endgrain is hard to sand.

After thoroughly sealing the bottom and sides of the torsion box with a quart of polyurethane, it was time to surface the top flat. When I placed my 4 ft level on the bottom, it appeared to be flat to within < 1/64". But for some reason, it appeared the top top had a slightly larger crown along it's length, maybe 1/32" or so. So I lowered the bit to the surface, and started cutting just enough to not miss any spots. At first I was getting what appeared to be a very rough and torn surface, so I greatly increased the RPM, and it looked a lot smoother, but was a lot louder. I normally route at 15,000 or less, but cranked it up to about 22,000.

My CNC can only cut about 45" long, so I had to turn it around to cut the other side. But before turning it around, I recut the plate hole and rabbitt, making the rabbitt perfectly parallel to the surface. I'm going to make some custom 3/4" thick phenolic plates. I've got a large chunk of 10mm phenolic plate, and I'll laminate it into two layers with epoxy, and CNC a rabbitt to fit. If I have any problems with the phenolic, then I'll get some custom aluminum plates machined. But the phenolic should be fine, and I have enough to make about 6 plates. I keep my 7518 mounted to a plate, and a 690 as well. I also have a spare 690 base that I'll mount. Different plates will have different hole sizes. For most of the time, I'll use a plate with a small hole, maybe 1" or so. This should work great for 90% of the router table work I do.

I plan to use this leveling system that I found here:

http://lumberjocks.com/PurpLev/blog/13430

I'll make a jig with the CNC to accurately locate and drill the holes.

Once I turned it around to finish the surfacing, I noticed that there must have been a slight twist in the box. Where the surfacing passes met, it was flush on the back, but a little high on the front. I made another pass, removing .002", and the front came out perfect. The slight discrepancy is at the end of the table where the Incra fence will mount, so even if there was more variation, it wouldn't have really mattered.

As you can see in the pic, there were a lot of tool marks from the router removing 1/2" per pass. Unfortunately, the router is not quite perpendicular to the table, and leaves a slight ridge. Fortunately, the ridge is only about .002" high. You can barely feel it However, endgrain birch saturated with epoxy is extremely hard to sand.

As for the rough surface I thought I was getting. It turns out that as soon as I start sanding, the (perceived) roughness disappeared almost immediately. But the ridges were another story. After a quick sanding, they can no longer be felt, but you can still see them. I spent about an hour to get it to this point. I'm tempted to get out the belt sander, but am too afraid of a mistake. Belt sanders can do tremendous damage in seconds. But I do have a really good one, a 4×24 Bosch with variable speed. I might try it at a slow speed to see if it works. I also tried a scraper, which helps, but that doesn't remove much material either. I don't want to remove much material, but man, that .002 is HARD to sand.

Today's goal is to get the top sanded, and rabbitt the edges and insert a bubinga border. Maybe 3/8"x3/8". The front edge needs a bevel to match the Unisaw.

I also may need to order a piece of stainless steel angle to attach the table to the Unisaw table. Right now, there's an 1/8" steel plate, with some small tabs bolted to it. I'd like something a bit more secure, as the current table is only supported in 3 small places at the saw. Right now, mu plan for mounting is to use countersunk stainless screws through the top, and through the steel angle on the 3 sides, and use locknuts under the angle. This is a much better method than the standard 3/4" lag screws from underneath.

One last thing. I'm really unhappy witht he spots from the CA glue bleeding?? through. Hopefully, the polyurethane finish will minimize it. Other than that, I'm pretty happy. As of right now, I have a near perfectly flat router table, that won't sag.

And one more last thing. Before I route through the surface to expose the T-Nuts, I'll be completely finishing the table with a few coats of polyurethane. I don't want the polyurethane to get into the threads.

Here's a short video showing the surfacing operation.

Click to expand...

Ger21 said:

7 coats of polyurethane and counting.....

The day after my last post, I routed the rabbitt around the edge, and glued in the Bubinga border. I used a block plane and scraper to get it even with the rest of the top. I gave up on sanding out the tool marks from the surfacing operation, thinking the polyurethane would make them disappear. Almost, but not quite.

From what I've seen, it appears that the epoxy didn't actually seal the end grain, it just ran right through it. I applied the first coat of polyurethane very heavy. Two hours later, and I saw that it had all soaked in completely. But it did seal it a bit. Subsequent coats have started to build, but it's still soaking into the spots from the CA glue. Very, very strange. I was applying one coat, then the next day, sanding smooth, and another coat. After 5 coats, I thought I was getting close. After the 6th coat, I waited two hours, and applied another. Due to the heavier coat, I need to wait a bit longer for it to cure. It looks like it may take up to ten to fully fill all the end grain. Once filled, I'll wet sand with mineral spirits and 400 grit on a flat block, and finish with 600 grit, for a satiny smooth finish. Then, I'll throw it back on the CNC, and open up the holes to reveal the 30+ threaded inserts, and remove a little more material around the router plate opening. It wasn't quite deep enough the first time. 3 coats of poly soaked into the MDF rabbitt, so it should just need a light wipe on coat for the final sealing when re-cut.

While waiting for polyurethane to dry, I figure I should design the cabinet that'll go under this new top. To get a really good idea of what it'll look like, I figured I should model the whole saw. Here's a little bit of AutoCAD work.

Click to expand...

Ger21 said:

Almost ready to mount

I lost count, but I think I have now applied about 12 coats of polyurethane. Nearly 1/2 gallon. After about 7 coats, the endgrain finally stopped soaking it in. So at that point, I basically had a 3/32" thick "plastic" top, as hard as a butcher block. Which is exactly what I wanted.

I tried to put the poly on as thick as possible, sanding down all the high spots between coats. After the 7 coats, I realized it wasn't as flat as I'd like, as I was sanding through the poly in some spots, but not in others. So I took my scraper, and scraped off all the excess poly. The endgrain is so hard that the scraper wouldn't cut into it. So now I had fully filled and sealed endgrain, with no poly on top. Then added another heavy coat of poly. At that point I stated wet sanding (using mineral spirits as the lubricant) with a wood block and 240 grit wet or dry paper. Got it smooth as glass, then another coat, and wet sand again. Still sanding through the poly in spots, though. But since I'm happy with the flatness, I thinned the poly down, and applied a really thin coat. Waited 2 hours, and added another.

Went out last night and used the ROS and 220 grit, and took off all the shiny spots, then rubbed with steel wool. And saw that I've still sanded through the finish in spots. I could wax it and leave it, as no one would really notice, but instead, I added another coat of poly.

But before the poly, I loaded it back on the CNC, and re-routed the plate opening for the last time. It wasn't quite deep enough, so I went down to nearly 1/2". Then I put an 1/8" bit in, and routed pockets for the heads of the leveling screws, and a starter hole. I'll drill a small block on the drill press to help me finish drilling the holes perpendicular to the table. Then I'll tap them and use 1/4-20 stainless button head socket screws to level the plate. The plate will be 1/2" phenolic, with a slight rabbitt around the edge. I'm going to make 4 plates, 2 for the 690 base and 2 for the 7518. 1 each with a 1" hole and 1 each with a 2-1/2" hole.

Here's a close up of the Bubinga edge. You can see a small patch that I used to fill in the gaps when laying down the blocks.

I was going to get some stainless angle to mount the table to the saw, but I came up with an easier solution. I measured the 1/8" plate that was already mounted to the saw, and used the CNC to make a cleat to screw the table to. It's 1" baltic birch plywood, notched around the 3 large bolts that hold the plate to the table. I'll also use the stock Delta angle for the front and back.

So, after I spend half the day in the yard, here's the plan. Sand the last coat of poly. If I sand through again, I'll thin the poly and wipe on two more very thin coats tomorrow, and steel wool to finish. I need to pick up some wax at HD today.

Throw it back on the CNC, and route the holes to access the T-nuts.

Make a jig to locate and drill the mounting holes in the top, and countersink them. Set it in place and bolt it down. Make some temporary legs to hold it up. The cabinet to go under it will have to wait until the fall.
With any luck, I'll have it mounted tomorrow. At least by the end of the week.

Hopefully as soon as it's back together, I can clean up the garage enough to do some work. I need to design a new fence to bolt to the Incra Jig. It'll have vacuum, and T-nuts for featherboards and fixtures.

Here's an AutoCAD screenshot with the Incra Jig attached.

Click to expand...

Ger21 said:

Almost ready to mount

I lost count, but I think I have now applied about 12 coats of polyurethane. Nearly 1/2 gallon. After about 7 coats, the endgrain finally stopped soaking it in. So at that point, I basically had a 3/32" thick "plastic" top, as hard as a butcher block. Which is exactly what I wanted.

I tried to put the poly on as thick as possible, sanding down all the high spots between coats. After the 7 coats, I realized it wasn't as flat as I'd like, as I was sanding through the poly in some spots, but not in others. So I took my scraper, and scraped off all the excess poly. The endgrain is so hard that the scraper wouldn't cut into it. So now I had fully filled and sealed endgrain, with no poly on top. Then added another heavy coat of poly. At that point I stated wet sanding (using mineral spirits as the lubricant) with a wood block and 240 grit wet or dry paper. Got it smooth as glass, then another coat, and wet sand again. Still sanding through the poly in spots, though. But since I'm happy with the flatness, I thinned the poly down, and applied a really thin coat. Waited 2 hours, and added another.

Went out last night and used the ROS and 220 grit, and took off all the shiny spots, then rubbed with steel wool. And saw that I've still sanded through the finish in spots. I could wax it and leave it, as no one would really notice, but instead, I added another coat of poly.

But before the poly, I loaded it back on the CNC, and re-routed the plate opening for the last time. It wasn't quite deep enough, so I went down to nearly 1/2". Then I put an 1/8" bit in, and routed pockets for the heads of the leveling screws, and a starter hole. I'll drill a small block on the drill press to help me finish drilling the holes perpendicular to the table. Then I'll tap them and use 1/4-20 stainless button head socket screws to level the plate. The plate will be 1/2" phenolic, with a slight rabbitt around the edge. I'm going to make 4 plates, 2 for the 690 base and 2 for the 7518. 1 each with a 1" hole and 1 each with a 2-1/2" hole.

Here's a close up of the Bubinga edge. You can see a small patch that I used to fill in the gaps when laying down the blocks.

I was going to get some stainless angle to mount the table to the saw, but I came up with an easier solution. I measured the 1/8" plate that was already mounted to the saw, and used the CNC to make a cleat to screw the table to. It's 1" baltic birch plywood, notched around the 3 large bolts that hold the plate to the table. I'll also use the stock Delta angle for the front and back.

So, after I spend half the day in the yard, here's the plan. Sand the last coat of poly. If I sand through again, I'll thin the poly and wipe on two more very thin coats tomorrow, and steel wool to finish. I need to pick up some wax at HD today.

Throw it back on the CNC, and route the holes to access the T-nuts.

Make a jig to locate and drill the mounting holes in the top, and countersink them. Set it in place and bolt it down. Make some temporary legs to hold it up. The cabinet to go under it will have to wait until the fall.
With any luck, I'll have it mounted tomorrow. At least by the end of the week.

Hopefully as soon as it's back together, I can clean up the garage enough to do some work. I need to design a new fence to bolt to the Incra Jig. It'll have vacuum, and T-nuts for featherboards and fixtures.

Here's an AutoCAD screenshot with the Incra Jig attached.

Click to expand...