I think either plywood or hardwood will work fine. I suppose hardwood is often selected because it may be less likely to be damaged by repeated use over time (more durable). Hardwood might be easier to plane down to a perfect fit than plywood-but maybe not. MDF would be stable-but maybe not as durable or workable with a hand plane.

I think that the amount of dimensional change that will occur with a thin strip (e.g. something that fits in the miter slot) is minimal. If the hardwood was wider and thicker then expansion/contraction might be an issue.

 

Plywood works fine. Most of the friction will be the sled riding on the saw. The runners just t need to be snug enough so there is no wiggle.

 

Incra offers metal sled runners. I'll be using them when I build my sled in a short while.

 

My sled uses the Incra runners. They're sweet. That being said, Baltic Birch ply runners would be fine and can easily be tuned with a sharp plane.

 

HDPE can be used. Many woodworking stores sell it pre-cut. It can be planed as well. I wouldn't use MDF in my shop. The humidity would affect it too much.

 

I guess I'm on the other side of the fence…..I use the metal T tracks for my runners on my sleds, jigs, and fixtures….I get them from Rockler, and they work great…3/8s x 3/4 is perfect….The blue ones…!!!! But….I also use hardwood runners when I run out of T tracks…..Never used plywood or HDPE….They will work, though…!!

 

I guess I m on the other side of the fence…..I use the metal T tracks for my runners on my sleds, jigs, and fixtures….I get them from Rockler, and they work great…3/8s x 3/4 is perfect….The blue ones…!!!! But….I also use hardwood runners when I run out of T tracks…..Never used plywood or HDPE….They will work, though…!!

- Rick Dennington

That's an interesting thought as long as the miter slot is exactly 3/4" with no play. Can't imagine that would work for many as it would be very difficult to shave anything perfectly off of aluminum of that length.

As for my thoughts on plywood runners,
I imagine plywood is not used often because it dents and dings easily. It would wear far quicker than any other types being used, IMO.

 

I've only used hardwood. But, I think HDPE would be excellent. It's going to be stable, it's slick. While probably not necessary of you size it right to start, but I would think over tightening a counter sunk screw might deform it a bit to make it wider and tighten against the slot if needed. That's just an idea. No experience if it would work.

 

incra runners are great and affordable

 

I guess I m on the other side of the fence…..I use the metal T tracks for my runners on my sleds, jigs, and fixtures….I get them from Rockler, and they work great…3/8s x 3/4 is perfect….The blue ones…!!!! But….I also use hardwood runners when I run out of T tracks…..Never used plywood or HDPE….They will work, though…!!

- Rick Dennington

That s an interesting thought as long as the miter slot is exactly 3/4" with no play. Can t imagine that would work for many as it would be very difficult to shave anything perfectly off of aluminum of that length.

As for my thoughts on plywood runners,
I imagine plywood is not used often because it dents and dings easily. It would wear far quicker than any other types being used, IMO.

- Rayne

That's why I use the T tracks…because the miters on my saw are exactly 3/4" with no side to side play, and they slide smoothly….Now on my old Craftsman table saw I don't use them, cause the miters are different than on my Unisaw….I use hardwood runners on it…..T tracks are not for everyone, but they are my choice for runners….A lot of the saws, drill presses, and anything that has miters are sometimes different, so the choice is wide open as to what to use…..!! I say whatever works for you is fine….!!!

 

micro jig makes a product called "zero play"-miter bars that expand into the slot. Works well on my orange contractor saw. Whatever you do, don't forget to wax!

 

3/8 ply would work I'm sure. Predrill holes or it might hang up where the screws bulge the wood out. Hpde or uhmw works. I use maple and such. It gets a little tight if There's been a lot of rain but still works fine.

I have an incra miter gauge. My only know is that it only has 3 contact points and can wiggle if the work piece is too long and the 3rd button hasn't contacted yet. If a longer one is available I'll probably go with that one but within it's limits it works like a champ.

 

I used some 3/4" thick PVC trim board to make some runners and it worked well. The manufactured 3/4" width fit perfectly in my table saw miter slot. I'm sure the fit results will vary based on PVC board brand and table saw miter slot.

 

As said the Incra runners are about as good as you can get, very nice, and the adjustability lets them fit any table.

Next is a piece of hardwood, Maple works great and a piece of QS is best, the best look is straight up grain from top to bottom, hardly any movement at all with that.

The problem using plywood here is you are talking about a cut only 3/4" wide, and you plan to shoot several screws through that. Once you screw through it the plys will squish, and move to the side, and sooner probably than later will start to delaminate with you running them through the miter slot. Worse yet if you turned it side ways and screwed through it, it may not last the day.

Short term fine, but I can't see a sled with heavy use lasting a lot more than a month or 3. A less used one may get out to a year. but the Maple will last many years, and the Incra probably many many years.

 

I think they would be somewhat fragile. Perhaps Baltic Birch plywood would hold up better.

 

I've used Baltic birch before. I also put dados on the bottom of sleds to insert runners.

If the jig is going to get used a lot, a little epoxy soaked into the plywood will increase the wear resistance of the runners.

 

You can also make runners from HDPE cutting boards from a dollar store, etc. Cut, drill, done. Inexpensive and stable.

 

I make very few sleds and I make them very accurate and to last a long time. It is worth it to me to obtain accurate runners that won't wear or change dimensions with temperature. Lately, I have been using HDPE.

 

If your sled uses both miter slots, then you can use runners narrower then the slots and force them against the inboard edges of the miter slots before locking down. This method is very useful when using metal runners which are usually never the same dimension as your miter slots.

 

You can also make runners from HDPE cutting boards from a dollar store, etc. Cut, drill, done. Inexpensive and stable.

- Bill White

How would you want to cut the HDPE? Table saw?

 

HDPE can be used. Many woodworking stores sell it pre-cut. It can be planed as well. I wouldn t use MDF in my shop. The humidity would affect it too much.

- Jeff

This is the route I went, having tried hardwood and MDF and having issues with humidity here in the South they both would stick and certain times and then have play at other times. Plywood can be used but it must be a very good grade of plywood, mine wasn't was damaged easily with the putting on and taking off and hanging up .

The plastic ones have been flawless

 

I second the use of HDPE for runners. My other thought is to use baltic birch plywood, but in a different way. I would rip strips from 6mm (1/4") baltic birch; then stack them and glue them together face to face and then trim them to fit the saw slot. Another way would be to use hard wood in place of the plywood , laminating them into a plywood like strip. The laminate would keep the strip from flexing/ bending/ distorting.

 

You can also make runners from HDPE cutting boards from a dollar store, etc. Cut, drill, done. Inexpensive and stable.

- Bill White

How would you want to cut the HDPE? Table saw?

- MikeDVB

Yep, it cuts just fine using standard woodworking tools. It is self-lubricating, so it slides right through the table saw. They probably make blades specifically for plastic, but any carbide blade will work.

Be prepared for a small blizzard of plastic pieces flying everywhere. It also contaminates your sawdust with non-biodegradable material. Clean out the dust bin before and afterwards if you compost your sawdust.

 

You can make perfectly good runners out of 3/4"x 3/8" aluminum or steel bar stock. Aluminum is easier to drill holes in, so I used that. The bar stock is quite cheap, widely available, and usually straight as can be. You'll want to regularly wax it, of course.

 

I used Kreg rails with micro adjustments. They were great. Don't go too far into the final adjustment of the rails until you finish and wax the bottom of the sled, a lot of the resistance you would be trying to correct is actually the sled on the table.

Make them longer, it make the sled easier to slide into the saw.