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How to recover from mistake...how to create a rabbet in a finished frame

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Forum topic by BB1 posted 12-06-2021 02:18 AM 2053 views 0 times favorited 40 replies Add to Favorites Watch
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BB1

2802 posts in 2178 days


12-06-2021 02:18 AM

This relates to the knife display project that I received advice previously. I have the box done, magnets in place to hold the knives and was working on the “frame face” this weekend.

I had planned to hold the plexiglass in a rabbet but purchased the wrong adhesive so decided to try just mounting the plexiglass in a groove. Well, I didn’t keep it protected and it was scratched along the way. Sigh..
I knew better…

So, busted out the plexiglass and want to salvage all my work and materials for the frame (even did splines for the mitered corners – a first for me!). So my question is…how can I rabbet this (going down to the level of the prior groove)

I’m thinking rabbet bit with bearing?

But how do I do this safely at my router table?


40 replies so far

View Dave Polaschek's profile

Dave Polaschek

9277 posts in 1913 days


#1 posted 12-06-2021 02:54 AM

Not sure how I’d do it with a router, but in my shop, I would set the depth on my circular saw correctly for the depth of the rabbet, and plunge in far enough from the ends that I could cut most of the rabbet with the circ saw, then come back and finish up with a chisel into the corners.

But the fact that you’re cutting down to an existing groove seems to make the whole process a lot easier. At least to me.

-- Dave - Santa Fe

View sawdust66's profile

sawdust66

46 posts in 79 days


#2 posted 12-06-2021 02:56 AM

Yes, from what you are describing the easiest way would be to use a rabbet bit. Just make sure you have the right bearing installed for the width you need. And then take multiple passes until you reach the depth of your groove. The only thing you will need to do a the end, is chisel out the corners, since the rabbet bit will make a radius at the corners. I would test on scrap first specifically for the width. The current project I’m working on has an example of this you can see here.

-- Chris, Pennsylvania

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BB1

2802 posts in 2178 days


#3 posted 12-06-2021 03:56 AM

Dave – yes, having the depth already set by the groove “should” make this easier. I don’t think I feel confident with my circular saw to be accurate – and the small size would be a challenge on the Amory side.

sawdust66 – your picture is what I hope to accomplish. I think the bit I have is right on with regard to the distance from the edge. Just trying to picture how to use it safely on the router table. Maybe l’ll need to consider hand-held.

View WoodES's profile

WoodES

202 posts in 3021 days


#4 posted 12-06-2021 04:24 AM

Take small bites by raising the bit slowly into the work. Maybe 3 passes minimum. It will help keep the breakout from being a problem.

View sunnybob's profile

sunnybob

95 posts in 96 days


#5 posted 12-06-2021 05:02 AM

Its completely safe on the router table, as long as you make sure you move the wood in the right direction.
Cutting on the inside of a square means you have to go the opposite direction to the normal.
There are a lot of google pictures of this but for some reason i cant paste them here. Instead of moving to wood right to left as you normally would, if youre cutting on the back of the bit you need to move the wood left to right.

The only way you can make several passes with a bearing cutter is to have a selection of bearing sizes and keep changing them. Depth of cut would depend on the wood being used. something brittle like white oak or bubinga might break out in one pass, softer woods normally fare ok. Test the wood by using a scrap piece and see if you get break out.

View AlaskaGuy's profile

AlaskaGuy

6825 posts in 3640 days


#6 posted 12-06-2021 05:35 AM

Like this.

https://youtu.be/ZQ5Ke5CLzEI?t=605

-- Alaskan's for Global warming!

View Madmark2's profile

Madmark2

3247 posts in 1919 days


#7 posted 12-06-2021 08:57 AM

Unless otherwise specified, motors rotate clockwise when you’re sitting on it. That means that from the top your router turns CCW, the cutter is coming at you on the left.
On the outside you route turning the piece CCW. On the inside you rotate CW.

-- The hump with the stump and the pump!

View BB1's profile

BB1

2802 posts in 2178 days


#8 posted 12-06-2021 12:43 PM

Thank you for all of the info.
The wood is oak so likely prone to chipping. To use the bearing, I’m thinking that I won’t be able to raise slowly into the frame. Also, I don’t have multiple size bearings. Would I be able to take light passes gradually getting to the point the bearing would ride on the part toward the front of the groove? This is the bit I have and the depth from the bearing to the edge is (amazingly) a match to the depth of the groove.

View LeeRoyMan's profile

LeeRoyMan

2375 posts in 1057 days


#9 posted 12-06-2021 02:03 PM

I don’t know how much experience you have, but for me in this situation,
I would do a climb cut first. Just taking enough off to cut into the wood.
This will help eliminate chipping when you run the rest of the cut going the normal direction.
If you have never done a climb cut (going reverse direction) be extremely careful, the bit can grab and throw the wood.

View Tony1212's profile

Tony1212

654 posts in 3065 days


#10 posted 12-06-2021 02:27 PM

The router bit is probably the easiest and fastest way to do it, but like you said, it’s oak and likely to splinter.

I would probably use a 1” or 1.5” chisel and chisel it back to the bottom of the groove. By the time you get the router setup and ready to use, it might take just as long.

“Ask 10 woodworkers how to do something and you’ll get 13 different answers.”

-- Tony, SW Chicago Suburbs

View hotbyte's profile

hotbyte

1129 posts in 4306 days


#11 posted 12-06-2021 02:45 PM

I would also think a chisel. Maybe a shoulder plane once you’ve exposed enough of the front lip for reference (corners would still be chisel work).

That’s a great quote!!!

“Ask 10 woodworkers how to do something and you ll get 13 different answers.”

- Tony1212


View BB1's profile

BB1

2802 posts in 2178 days


#12 posted 12-06-2021 02:58 PM

LeeRoyMan – definitely not “experienced” – just enough time with the hobby to start to know what I don’t know! This seems so simple, but lot of things to consider so I don’t ruin the frame that I’ve already spent so much time putting together.

I thought about chiseling but I’m not very good with hand tools. Guess this might be a “learning opportunity” more so than time saving. I do worry about the oak chipping out so may give it a try first and then maybe could just clean up the edge at the router table?

View squazo's profile

squazo

345 posts in 2976 days


#13 posted 12-06-2021 04:14 PM

you can buff out those scratches. if you have a grinder, get some buffing attachments and compounds. probably cheaper to rabbet it though

View BB1's profile

BB1

2802 posts in 2178 days


#14 posted 12-06-2021 05:15 PM

squazo – I did try some diy ways to buff out scratches on a test piece but wasn’t acceptable given the black background of the display interior will highlight any imperfections. Thus, I busted it out last night and started the process of figuring out plan B (or, given the development…might be on plan C, D, E…)

View splintergroup's profile

splintergroup

6319 posts in 2553 days


#15 posted 12-06-2021 05:45 PM

I think you are on the right track with the rabbet bit. These cut surprisingly clean. The router table would be the easiest way to use it, just cut CCW for inside perimeters and increment the bit height so each cut maybe chomps away 1/16” to 1/8”.

I use the same bit for my lamp shade frames where I’m taking out a 1/2” x 1/2” rabbet. I’ll usually do this in 1/8” bit height increments and do a skim cut by hand (where the bearing is not making contact with the wood) on the final pass.
This provides a slight undercut so any wood fibers will tend to not break into the area above the cut. This takes some experience to get a feel for, but works well.

As an alternative since you only have one bearing (You can buy bearing kits for these bits), you can make a simple jig.
This is overkill, but is quite functional.

Assuming you need to cut 1/2” deep, if you had the extra guide bearing and wanted to cut 1/4” deep you would choose one that is 1/4” larger in radius.

As an alternative you can use shims.

Cut some strips of wood the thickness of the area between the frame face and your rabbet (the area you are not going to be cutting out). Their width should be the depth you want to set for your first cut (the 1/4” in the above assumption)

On some scrap plywood that is the outer dimensions of your frame or larger, place the frame centered on the plywood..
Cut to length and arrange these strips around the inside perimeter of your frame and glue to the plywood.

Basically the shims ride between the router bit bearing and frame, reducing the depth of cut. The plywood holds them in place.

In use, the plywood is slipped over the top of the frame such that the shims are positioned against all four inside edges.
Raise the router bit so that it will allow its bearing to ride against the shims while cutting. You make your CCW pass and keep raising your bit until the inside lip has been removed.

Pop off the plywood/shims, lower the router bit to your starting height, and repeat.

(probably easier to buy the bearing set or borrow someones rabbet bit set 8^)

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