# Crosscut Sled Runners



## Joel_B (Aug 14, 2014)

Looking for suggestions to attach UHMW runners to the plywood base. The strips I bought fit perfectly into the slots on my TS. I read to position them put the runners in the slots on the TS then use double sided tape to temporarily hold them to the base, then drill holes for screws (But why not just partially drill holes while it is place ?). But I heard that tightening the screws down can cause the UHMW to bow out so it is too wide to fit the slot. This can be avoided by using dowels instead but not sure how well they would hold onto the UHMW.

Thanks


----------



## HammerSmith (Mar 3, 2018)

> Looking for suggestions to attach UHMW runners to the plywood base. The strips I bought fit perfectly into the slots on my TS. I read to position them put the runners in the slots on the TS then use double sided tape to temporarily hold them to the base, then drill holes for screws (But why not just partially drill holes while it is place ?). But I heard that tightening the screws down can cause the UHMW to bow out so it is too wide to fit the slot. This can be avoided by using dowels instead but not sure how well they would hold onto the UHMW.
> 
> Thanks
> 
> - Joel_B


I had to google "UHMW", but I would think that if you drill the pilot holes big enough, maybe it won't spread out like that. ...And I guess the pilot hole won't need to be "nearly" as tight as if it was wood..

When I made my first sled, I happened to have a strip of Purple Heart on hand. That was a great stroke of luck because I found that Purple Heart makes for some excellent runners! It's hard, strong, and naturally waxy… That sled is long gone now, but it lasted quite a while, even survived some weather, and those runners never wore out.

What kind of glue will you use? ...If it won't hurt the table-saw top, I would definitely just glue it all up right there on top of the saw. That way it's foolproof.

I like to make the sled long enough so that it can be flipped upside down and set flat over the top of the saw (it's easier to store that way).

Cheers,

Jim


----------



## Redoak49 (Dec 15, 2012)

I have used wood and UHMW for runners and always spent a lot of time getting the right. With the plastic, you do have to be careful about them expanding when you attach.

I have gone to using the Incra Miter Sliders. Yes, they cost more at around $15-18. But they work great. When one of my sleds gets old and beat up, I take them off and reuse them. They are adjustable to fit your slots exactly the way you want.


----------



## waho6o9 (May 6, 2011)

http://thistothat.com/cgi-bin/glue.cgi?lang=en&this=Plastic&that=Wood :

Clamping can make the difference between success and failure here.
There are so many kinds of plastic its hard to give advice here that applies to them all. If possible try a small test in an area that doesn't show.

Some plastics have a smooth surface finish that can be sanded off with a 120 grit sand paper, for better adhering properties.

Good luck now.


----------



## pontic (Sep 25, 2016)

I tossed my ultra high molecular weight plastic runners for some steel ones that lee valley carries. They have "T" slot washers and threaded screw holes and screws with adjusting allen screws. They come in 19" and 24" lengths. Check them out.


----------



## JBrow (Nov 18, 2015)

Joel_B,

I agree that it makes sense to drill mounting holes in the UHMW runners before temporarily taping the runners to the sled's base. I can understand how a bugle head screw torqued a little too tight could cause the UHMW runner to expand; but cannot say for sure. Nonetheless, this could be avoided if the runner is counter-bored to recess the head of a low profile pan head screw. One such screw would be the pancake head screw illustrated in the link…

https://www.walmart.com/ip/10-x-1-Phillips-Pancake-Head-Sheet-Metal-Screws-410-Stainless-Steel-QTY-100/287632374?wmlspartner=wlpa&selectedSellerId=477&adid=22222222227092406630&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=c&wl3=212112109143&wl4=pla-367070061794&wl5=9015804&wl6=&wl7=9015807&wl8=&wl9=pla&wl10=111838589&wl11=online&wl12=287632374&wl13=&veh=sem


----------



## wormil (Nov 19, 2011)

Use a panhead screw and countersink with a forstner bit. Countersunk screws wedge themselves into the hole and bulge the sides of the plastic.


----------



## runswithscissors (Nov 8, 2012)

Button head screws look like the best bet of those shown. But the countersink will leave a tapered hole at the bottom. A forstner would give you a flat bottom hole. I had the same problem with the flat head screw swelling the runner because of the taper under the head.

I have seen uhmw plastic glued with contact cement, after roughing it up, but I'm not aware of any glue that works really well on the stuff.


----------



## RichT (Oct 14, 2016)

I'd screw it from the top. Use an appropriate sized drill and countersink and use flathead screws. If you do get any swelling in the runner, you can trim it with a shoulder plane if you have one, or even just a chisel if you don't. There's no worry about cutting too deep with a chisel, since the rest of the runner will give you the tight fit you need.

That said, the way I make my runners is to use an extremely hard wood and pass it through the planer until it just fits on edge in the miter slot. Then you can rip off strips that are just narrower than the depth of the slot. You can keep the remainder of the board for more runners as you need them. I find that much easier than trying to rip the piece to the width of the slot, which is how most instructions say to do it. Finally, wax the runners and the bottom of whatever jig you are making to ensure it glides smoothly.


----------



## Breeze73 (Jul 14, 2016)

2P-10 or any cyanoacrolite glue would work well to temporily tack them in place until you get some screws to lock them in.


----------



## HammerSmith (Mar 3, 2018)

When I build a sled, I like to use 1/4" plywood for the base. The thinner ply means the saw can cut deeper… and a 10" blade with a 6" stabilizer only leaves 2" depth of cut… minus 1/4" for the base, leaves only 1-3/4" depth of cut… and it only gets worse for beveled cuts.. But I like to use that stabilizer whenever possible.. it saves a lot of sanding.

I see a lot of sleds that have 3/4" plywood for a base, and I can see that making it easier for attaching jigs and such, but I like the thin base material. Sometimes it's a crucial feature…

I use the sliders to hold the thin plywood flat. The sliders are the key to a good sled imo.. 
Hardness, rigidity/strength, and stability, are the key features I look for. But everything is a trade-off… Not to mention the "what I have on hand at the time" factor…

I like to leave the runners sticking out on the front of a sled, and I'll bet that purple heart is much better than any kind of plastic for that sort of thing… The other advantage is, after the glue dries, you don't even need the screws anymore.. I only use the screws to clamp it while the glue dries.. My current sled still has the screws in it, but I'm sure they're not even necessary anymore.


----------



## Joel_B (Aug 14, 2014)

i think will try screwing in from the top. Seems the easiest and most foolproof and less chance of the plastic deforming. Hopefully the screws will hold in the plastic

Thanks


----------



## HammerSmith (Mar 3, 2018)

> *i think will try screwing in from the top. *Seems the easiest and most foolproof and less chance of the plastic deforming. Hopefully the screws will hold in the plastic
> 
> Thanks
> 
> - Joel_B


I can't even imagine any other way to do it Joel… just make sure you drill the pilot holes big enough, since plastic is much harder than wood..

Lay your runners in the grooves, set your base on top, and make sure the base is perfectly flush with the front of the saw. That's your square edge. Add a strip of glue on the runners, then clamp the base to the saw top in perfect orientation, and then drill your pilot holes… six screws in each runner is plenty… after the glue dries, the screws ain't even necessary anymore.

Getting that front edge of the base perfectly flush with the front of the table makes it a lot easier to get your fence perfectly square…


----------



## Lazyman (Aug 8, 2014)

I would drill the pilot holes while sitting on the saw but I would not drive the screws in yet. If you want to make sure that nothing moves while you are drilling, you can drive one screw in just far enough so that it holds things in place while you drill the rest of the holes. Before driving in the screws, very slightly counter sink the pilot holes in the runners before driving in the rest of the screws. When you drive in the screws, it often causes the wood to sort of mushroom out and putting a relief there will prevent that from distorting the runners. Countersinking the holes on the underside of the sled instead would work too. You could do that beforehand and then drive the screws in while as you drill the holes into the runners.


----------



## Joel_B (Aug 14, 2014)

I read about one more approach which is drilling and tapping holes in the UHMW and using a machine screw.
I did a test with a 10-32 screw and it worked pretty good so I think I will give it a try.


----------



## RichT (Oct 14, 2016)

> I read about one more approach which is drilling and tapping holes in the UHMW and using a machine screw.
> I did a test with a 10-32 screw and it worked pretty good so I think I will give it a try.
> 
> - Joel_B


That makes total sense. You'd avoid any swelling that way.


----------



## Joel_B (Aug 14, 2014)

Also looking for plans to build the sled. Simple and basic would be best, but added features that are worthwhile I would consider.

Thanks


----------



## RichT (Oct 14, 2016)

> Also looking for plans to build the sled. Simple and basic would be best, but added features that are worthwhile I would consider.
> 
> Thanks
> 
> - Joel_B


I have three different sizes, but they all are based off of the William Ng design. Very simple and easy to make. https://wnwoodworkingschool.com/5-cuts-to-a-perfect-cross-cut-sled/

There are tons of others from simple to ones that do everything. I prefer to build specialized jigs and sleds for individual tasks, but whatever works for you is what matters.


----------



## moke (Oct 19, 2010)

I have a couple of things I do when I use UHMW runners…I predrill and countersink a little deeper than needed….I use double sided tape….I don't want CA on my nice saw stop….I then clamp the ends, get two screws into the middle, then work my way to the ends. Does it expand? Yes…..I then mark the side with a sharpie and run it back and forth, pull it off, pull the handle off a file and put it upright and work the area where the sharpie is worn. Sometimes I have to do that a couple times…..then I wax it with Johnson's paste wax, the whole bottom…..they are usually a little stiff until they get waxed. I have some very smooth sleds.

I'm not saying this is the only way, or the best way, I'm saying it works for me.


----------



## Jon_H (Jun 21, 2016)

> I d screw it from the top. Use an appropriate sized drill and countersink and use flathead screws. If you do get any swelling in the runner, you can trim it with a shoulder plane if you have one, or even just a chisel if you don t. There s no worry about cutting too deep with a chisel, since the rest of the runner will give you the tight fit you need.
> 
> - Rich


Ditto



> i think will try screwing in from the top. Seems the easiest and most foolproof and less chance of the plastic deforming.
> 
> - Joel_B


Double-Ditto


----------



## Lazyman (Aug 8, 2014)

+1 on the William Ng sled. Even if you build another sled, his YouTube video about building the sled has a good section on making it square using the 5-cut method. He just recently released another video about making a miter sled or attachment for a cross cut sled that is perfectly accurate that is worth a look.


----------



## dschlic1 (Jan 3, 2013)

I built a one sided sled. I used a UHMW runner. Because I used only one runner, I cut a dado in the right location on the bottom of the sled. The runner fits tight into that dado, and then I used flat head screws to secure it to the base. Because the dado held the runner into position, I did not have to tighten the screws very much.

With two runners you could have one side in a dado, and let the other float. No glue will adhere to UHMW, it is a close cousin of Teflon.


----------



## HammerSmith (Mar 3, 2018)

> Also looking for plans to build the sled. Simple and basic would be best, but added features that are worthwhile I would consider.
> 
> Thanks
> 
> - JoelB


Here's a couple pics of my newest sled, and some considerations I had when I made it… And some things I will do differently next time too..



















*~The Fence*

I used clear fir for the fence because I already had some nice quarter-sawn pieces. They used be part of an exterior wall on a local house, so they're already perfectly acclimated and they're very stable. The house was at least 40-50 years old… I planed em nice and flat, so they're very stiff and straight on their own..

I didn't want to use plywood because it won't stay flat if it gets wet. And I don't have an indoor shop, so it's already been wet a few times.

I kept the height of the fence comfortable for my hand. With my thumb hooked over the top, I can still easily reach the base with my finger if needed. Also, if the fence gets too tall, it would make it harder to reach over it with clamps.. The height of the fence is a trade-off… Sometimes, a really tall fence is great feature, but, sometimes it's a disadvantage too.

3/8" up from the bottom of the fence, I pre-drilled a few nice holes for attaching stop blocks when needed.. If I'm only making a few pieces, I'll trust the pony-clamps. BUT. If I'm making a lot of pieces, or if it's a super crucial cut (especially a mitre), I always add some screws to lock it in place for sure. And I'm sure I'll pre-drill many more holes in it, as needed. The Douglass Fir doesn't mind at all, as long as it's pre-drilled 

My fence isn't adjustable like Mr. Ng's is… But I put the extra time in when I attached it, and it came out pretty darn good. I tested it before the glue dried, by cross-cutting a clean plywood rip, 16" wide, then flipped one side, and the fit was still beautiful. That was good enough for me  ...Mr Ng is a madman with those calipers! I thought that stuff was just for building engines! My hair is .003" thick, and's he's measuring to .001"? Lol, that's some crazy stuff right there! ...But at least he did come right out and admit that he "overbuilds" everything.

*~The Blade Box*

The blade box on mine is way too big, and way too close to the top of the fence. It interferes with clamping things…

The reason I made it that big, is because I wanted to use the runners to help hold the fence square. The big box helps to beef up the fence too..

I might wind up taking a jigsaw to the top of that blade box one day… But, next time I'll just make gussets to attach the runners to the fence… I liked that tiny blade box that Mr Ng used on his sled… My next one will look more like that..

*~The Runners*

I like having the runners sticking out the ends for two reasons…

It aids in stability across the length of a long cut.

And when I lean it up somewhere, it's never resting on the fences.

As for stability, I absolutely disagree with Mr Ng about fitting wood runners that tight to the table saw slots! That's some craziness! I'm sure that any kind of wood, even the most stable of them, will move at least_ .020" over the course of seasons. I think he was just showing off with that part… The fact is, the runners are so long that a slight bit of slop will NEVER show up in your cut…. Never… I think it's much more important that the sled slides nicely in all seasons, and a little bit of slop is actually a good thing. ...A sticky sled can be dangerous… kinda like a dull knife..

I guess that doesn't apply if you're using plastic runners, but Purple Heart is better than any plastic I ever saw if you want the runners to stick out on the ends. Purple Heart is some strong, stable, waxy, wood.

The runners on my new sled are Mahogany. It's what I had on hand… It works ok, but one of the front tips is already broken. Next time, I'm gonna get some more Purple Heart for the runners, even if I have to buy it.. I guess Eucalyptus, or Ipe, or Teak, would make for some excellent runners too.

*~The Base*

I always used 1/4" Luan Ply because it's common out here. It's not the greatest for the weather, but it's pretty good, and it's easy enough to press it down flat to the top of the saw. And it stays reasonably flat because the runners hold it flat. Even when it gets wet…

The biggest problem with Luan is that it starts to delaminate if it gets wet too many times. But it can survive quite a few drenchings. And, even when it does delaminate a little, it's still functional for longer pieces.
---------

A little waviness in the base is a minor issue, as is a little slop in the runners.

But the fence MUST stay flat, straight, and square to the runners on both planes. The fence is everything and, imo, the fence and the runners are the two must crucial parts.

The fence and the smooth sliding motion are the two most crucial things for me.

Cheers,

Jim


----------



## pontic (Sep 25, 2016)




----------

