Panel Jig Woes

[David Carter]

Having just purchased my own table saw a weeek ago, I set out today to build a panel jig (the saw I borrowed for previous builds didn't have miter slots). I bought MDF and some oak boards for the rails and backer board. I cut the rails and made sure they slid through the slots. Then I glued the MDF board down onto the rails and let it sit for several hours to dry.

When I came back to work on it some more, much to my disappointment, I discovered that the rails were not perfectly straight, and now that they were glued to the MDF panel and couldn't flex at all, they would not slide through the slots freely. I had to rip the rails off the MDF, and now I'm back at square one without any good ideas on how to proceed.

The only way I can think of to get around it is run the oak board that the rails are cut from through a planer to make sure it's perfectly flat, but I don't have one and don't know anyone who does.

Any other ideas? As useful as the panel jig is, I have no intention of spending a whole lot of money on it. Right now I'm just ticked at the oak boards I bought that have now gone to waste.

[AntonZ]

I couldn't find anything that fit the slots on my table saw, so I used aluminium U profile that slides along both sides of the table rather than through the slots. Not as good as the real thing, especially since nothing forces either side to not wander away from the table, but it works good enough for me.

While I'm at it, here's another mod applied to my jig. It seemed to me the thing is somewhat vulnerable while not at the table. The jig is practicaly cut in two equal parts, which are only held together by the push bar. No problem when it's on the table, but mine is stored away from the table most of the time. So I made a simple addition to connect both sides at the other end. It is attached before taking the jig off the table. Will make a pic one of these days for clarification.

[dextermcneil]

Don't bother with wood for the rails. When ever the humidity changes they'll swell or contract and either wobble in the channels on the saw or else stick like you wouldn't believe. And this is the last thing you want to happen to you while you're trying to cut wood!

What I've used in the past is UHMW polyethylene. The stuff is pretty easy to work with and is slipperier than owl poo. You can get it at most industrial plastics supply places. I buy mine as 3/8 thick by 3/4 wide rectangular bar stock from McMaster Carr. This size fits in my Delta Unisaw miter slots and I understand is the most common size for miter slots on table saws. Anyway, the McMaster Carr catalog number is 8702K72, current price is $1.29/ft for a five foot long piece. www.mcmaster.com Great company, reading their catalog I've discovered more things I never knew existed before. Their entire catalog is on their website.

Hope this helps!

[David Carter]

Don't bother with wood for the rails. When ever the humidity changes they'll swell or contract and either wobble in the channels on the saw or else stick like you wouldn't believe. And this is the last thing you want to happen to you while you're trying to cut wood!

What I've used in the past is UHMW polyethylene. The stuff is pretty easy to work with and is slipperier than owl poo. You can get it at most industrial plastics supply places. I buy mine as 3/8 thick by 3/4 wide rectangular bar stock from McMaster Carr. This size fits in my Delta Unisaw miter slots and I understand is the most common size for miter slots on table saws. Anyway, the McMaster Carr catalog number is 8702K72, current price is $1.29/ft for a five foot long piece. www.mcmaster.com Great company, reading their catalog I've discovered more things I never knew existed before. Their entire catalog is on their website.

Hope this helps!

Thanks. I just placed an order for some 3/4" x 3/8" strips. How did you attach the strips to the panel?

[Jeff Beaird]

Don't bother with wood for the rails. I've used in the past is UHMW polyethylene. The stuff is pretty easy to work with and is slipperier than owl poo. Hope this helps!

+1
This also works very well for protecting the backs of my T39 when loading it in my truck.

[dextermcneil]

Don't bother with wood for the rails. When ever the humidity changes they'll swell or contract and either wobble in the channels on the saw or else stick like you wouldn't believe. And this is the last thing you want to happen to you while you're trying to cut wood!

What I've used in the past is UHMW polyethylene. The stuff is pretty easy to work with and is slipperier than owl poo. You can get it at most industrial plastics supply places. I buy mine as 3/8 thick by 3/4 wide rectangular bar stock from McMaster Carr. This size fits in my Delta Unisaw miter slots and I understand is the most common size for miter slots on table saws. Anyway, the McMaster Carr catalog number is 8702K72, current price is $1.29/ft for a five foot long piece. www.mcmaster.com Great company, reading their catalog I've discovered more things I never knew existed before. Their entire catalog is on their website.

Hope this helps!

Thanks. I just placed an order for some 3/4" x 3/8" strips. How did you attach the strips to the panel?

I put the strips in the miter slots with one end hanging over the table by about an inch, lined up my sled on the table with the edge of the sled meeting the end of the strips, then drilled through both. Counter sink the hole in the plastic and put a flat head wood screw up into the wood of the sled. Slide the whole thing to the other end and repeat. Then draw a line between the two holes and put in additional screws every 4 inches or so. I'm not sure what adhesive will stick to the UHMW poly, and I like the idea of being able to replace them, though by the time they need replacing the rest of the sled will be shot and ready for the scrap heap.

The plastic is pretty easy to work with, standard wood working tools will do the job, though you have to be careful of heat with power tools as it will gum up the cutting edge and you'll have to stop and cut the plastic off the tool.

[dbaldock]

... I'm not sure what adhesive will stick to the UHMW poly, ...

Polyethylene is like Teflon - it's really difficult to glue. If you need to glue it, you might try BonDuit® Conduit Adhesive.

Take Care,
David Baldock

[Harley]

I'm not sure what adhesive will stick to the UHMW poly,.....

Hardly anything at all where there will be some force involved.

I have just refurbished some venetian blind machines that have lots of little UHMW poly parts and nearly all of them are tapped and screwed.

For a couple of slat guides that have very little force, I used Ados F2 contact adhesive and this worked OK - note I said OK - but any sideways force like a gentle hit with a hammer - they come off.

There may well be some specialised glues but I am unaware of them

[Frankenspeakers]

I'm not sure what adhesive will stick to the UHMW poly,.....

Hardly anything at all where there will be some force involved.

I have just refurbished some venetian blind machines that have lots of little UHMW poly parts and nearly all of them are tapped and screwed.

For a couple of slat guides that have very little force, I used Ados F2 contact adhesive and this worked OK - note I said OK - but any sideways force like a gentle hit with a hammer - they come off.

There may well be some specialised glues but I am unaware of them

The only intellligent thing that a certain plant manager (known for his incompetence and bootlicking) has said was that someone could develop an adhesive that would stick to polyethylene, they would have a winner.

Drill, tap, and screw it. The only other way to reliably attach PE is to weld it.

[Harley]

Drill, tap, and screw it. The only other way to reliably attach PE is to weld it.

Actually I am glad you said to tap it because what some people do not realise is that because it's so user friendly for screws, the expansion away from the screw could cause bulging.

In this case where a relatively snug fit is required to run in a slot, too bigger gauge of screw will make it jam. Being PE of course it is simple to tap, all you need is the tap and the right sized drill - no expansion then.

[dextermcneil]

Drill, tap, and screw it. The only other way to reliably attach PE is to weld it.

Actually I am glad you said to tap it because what some people do not realise is that because it's so user friendly for screws, the expansion away from the screw could cause bulging.

In this case where a relatively snug fit is required to run in a slot, too bigger gauge of screw will make it jam. Being PE of course it is simple to tap, all you need is the tap and the right sized drill - no expansion then.

On mine I drilled clearance holes through the PE, counter sunk them, then used wood screws to attach the PE to the bottom of the sled. The screws bite into the wood, not the PE. Doing it that way meant that I could do the entire operation while both the PE and the sled were sitting on the table saw. And that meant that everything lined up right the first time. Always nice when that happens!

[SoundInMotionDJ]

Don't bother with wood for the rails. When ever the humidity changes they'll swell or contract and either wobble in the channels on the saw or else stick like you wouldn't believe. And this is the last thing you want to happen to you while you're trying to cut wood!

This is too much worry for nothing.

Sand the bottom of the sled base smooth, working up to 220 grit. Poly is nice, but overkill.

Cut the runners from a hardwood (oak is fine). Fit them in the miter slots, and ensure that they will "ride freely". Coat with yellow glue, and then put the cross cut sled base on the runners. The sled base should be "mostly" square to the saw top at this point. Clamp the rails to the sled base one one edge (or both, if everything is long enough), add weight to the sled over the runners, and let it dry ON THE SAW.

When the glue is dry, make sure that the sled with slide freely on the saw. If not, then force it through a range of motion a few times. You will be able to see on the runners where they are binding. Relieve those edges with a small hand plane or sand paper. Repeat until the sled moves freely.

Next, get some neutral (clear?) wood wax and coat the runners. Move it through the range of motion on the saw several more times. Re coat with wax if anything binds again. I find that I need to re coat the runners with wax 3 to 4 times a year.

Here is the key:

AFTER the runners are on and running smoothly...then attach the back and front rails to the sled base. Attach the "front" rail (this does not need to be square to the blade. Raise the blade as high as possible, and cut "halfway" through the sled base. Stop the saw. Now, using the biggest framing square that will fit, attach the back rail. Take you time. Your cuts will only be as square as the back rail.

I like to attach one edge of the back rail with a screw. I clamp the other edge and then work to get it square. After I think the back rail is square, I put a second screw in the other edge. Then I cut through the rest of the sled base. Now I can cut a board on the sled and check it for square. Precision counts. Take you time. When I'm sure that the back rail is as square as I can get it, I add more screws and then start building something else.

--Stan Graves

[Harley]

On mine I drilled clearance holes through the PE, counter sunk them, then used wood screws to attach the PE to the bottom of the sled. The screws bite into the wood, not the PE.!

Wow...and I thought I lived in an upside down world - how simplke, why didn't I think of that?

You must have had to slide each side out a little to get access to screw in - right?

[dextermcneil]

On mine I drilled clearance holes through the PE, counter sunk them, then used wood screws to attach the PE to the bottom of the sled. The screws bite into the wood, not the PE.!

Wow...and I thought I lived in an upside down world - how simplke, why didn't I think of that?

You must have had to slide each side out a little to get access to screw in - right?

Yep. Let it hang over one side of the table, attach, shove the whole mess to the other side of the table, let it hang over, attach, flip it over and fasten in a few more places. Done. Time to cut the slot in the base, then square up the end fence blocks and attach. I have several different size sleds and I've made them all the same way. It's really quick with the poly for the rails. No fussing with ripping oak strips, making sure they fit, worrying about keeping them waxed so they don't change size as the humidity swings from 15% in the winter to 90%+ in the summer, etc. My large sled (30 x 40 inches) has some of the thin self adhesive UHMW poly film stuck to the bottom so that it slides really easily across the saw table.

[dextermcneil]

Don't bother with wood for the rails. When ever the humidity changes they'll swell or contract and either wobble in the channels on the saw or else stick like you wouldn't believe. And this is the last thing you want to happen to you while you're trying to cut wood!

This is too much worry for nothing.

Sand the bottom of the sled base smooth, working up to 220 grit. Poly is nice, but overkill.

Cut the runners from a hardwood (oak is fine). Fit them in the miter slots, and ensure that they will "ride freely". Coat with yellow glue, and then put the cross cut sled base on the runners. The sled base should be "mostly" square to the saw top at this point. Clamp the rails to the sled base one one edge (or both, if everything is long enough), add weight to the sled over the runners, and let it dry ON THE SAW.

When the glue is dry, make sure that the sled with slide freely on the saw. If not, then force it through a range of motion a few times. You will be able to see on the runners where they are binding. Relieve those edges with a small hand plane or sand paper. Repeat until the sled moves freely.

Next, get some neutral (clear?) wood wax and coat the runners. Move it through the range of motion on the saw several more times. Re coat with wax if anything binds again. I find that I need to re coat the runners with wax 3 to 4 times a year.

Here is the key:

AFTER the runners are on and running smoothly...then attach the back and front rails to the sled base. Attach the "front" rail (this does not need to be square to the blade. Raise the blade as high as possible, and cut "halfway" through the sled base. Stop the saw. Now, using the biggest framing square that will fit, attach the back rail. Take you time. Your cuts will only be as square as the back rail.

I like to attach one edge of the back rail with a screw. I clamp the other edge and then work to get it square. After I think the back rail is square, I put a second screw in the other edge. Then I cut through the rest of the sled base. Now I can cut a board on the sled and check it for square. Precision counts. Take you time. When I'm sure that the back rail is as square as I can get it, I add more screws and then start building something else.

--Stan Graves

Stan,
With all due respect, I have to disagree. The poly strips are reasonably cheap and come in the right size to fit most saws out of the box. They're dimensionally stable. Before I started using the poly strips, the waxed oak and waxed maple I used would still change size as the humidity here went from 15% in the winter to 90%+ in the summer. Build the sled in the summer and it was too loose in the winter. Build it in the winter and it wouldn't go through the saw in the summer. And in either case, it took time to make sure the wood strips were cut and fitted to the right size. I used to build sleds like you describe. Now I use the poly for the rails and I'm making sawdust on another project that much faster.

The rest of your advice on taking your time and going for precision when attaching the rear fence is spot on. You have to get that rear fence as close to a perfect 90 degrees with respect to the saw blade as you can.