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Forum topic by Joel_B posted 03-04-2018 05:52 PM 1852 views 0 times favorited 23 replies Add to Favorites Watch
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Joel_B

347 posts in 1495 days


03-04-2018 05:52 PM

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, Encinitas, CA


23 replies so far

View HammerSmith's profile

HammerSmith

137 posts in 198 days


#1 posted 03-05-2018 01:36 AM


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

-- ~Jim

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Redoak49

3448 posts in 2103 days


#2 posted 03-05-2018 02:04 AM

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.

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waho6o9

8343 posts in 2691 days


#3 posted 03-05-2018 02:21 AM

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.

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pontic

625 posts in 723 days


#4 posted 03-05-2018 02:22 AM

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.

-- Illigitimii non carburundum sum

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JBrow

1366 posts in 1034 days


#5 posted 03-05-2018 02:26 AM

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

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Woodknack

12329 posts in 2494 days


#6 posted 03-05-2018 02:27 AM

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

-- Rick M, http://thewoodknack.blogspot.com/

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runswithscissors

2818 posts in 2139 days


#7 posted 03-05-2018 04:20 AM

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.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View Rich's profile (online now)

Rich

3506 posts in 703 days


#8 posted 03-05-2018 04:36 AM

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.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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Breeze73

94 posts in 795 days


#9 posted 03-05-2018 04:38 AM

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

-- Breeze

View HammerSmith's profile

HammerSmith

137 posts in 198 days


#10 posted 03-05-2018 05:17 AM

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.

-- ~Jim

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Joel_B

347 posts in 1495 days


#11 posted 03-05-2018 06:45 AM

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, Encinitas, CA

View HammerSmith's profile

HammerSmith

137 posts in 198 days


#12 posted 03-05-2018 07:27 AM

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…

-- ~Jim

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Lazyman

2383 posts in 1501 days


#13 posted 03-05-2018 02:19 PM

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.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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Joel_B

347 posts in 1495 days


#14 posted 03-06-2018 05:11 AM

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, Encinitas, CA

View Rich's profile (online now)

Rich

3506 posts in 703 days


#15 posted 03-06-2018 05:16 AM


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.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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