UHMW Fence question

[Southwood]

Can UHMW be worked the same as wood? Routed, cut like any other wood product.

[rofl]

pretty much.

[tomapple]

Here is a list of tips for cutting, planing etc.:

http://groups.google.com/group/uhmwtips

[dow]

Yep.

I should add that I just made sides for my fence out of 3/4" UHMW and got them installed last night. Sorry, I didn't take pictures, but what I did was:
rip two pieces 3" wide by 35" long (the scrap piece that I was able to get was that length already)
decide which is the top and which is the bottom edge and mark the bottom (sharpie works fine and nobody will ever see it)
clamp the two slabs ON THE SAME SIDE of the fence, flush with the bottom of the fence.
use a 1/4" bit to drill through the mounting holes in the fence and the two slabs
take them to your drill press and use a 3/4" Forstner bit to drill the pockets for the bolt head and nuts to go (you'll have to mess with the depth a little. It's deeper than you'd think)
put it all together, using 1/4" bolrs, 3-1/2" long, flat washers and lock nuts.

I haven't routed them for T-track yet, but that's on the list in the near future.

Tom: That's a great source of useful info. Thanks. I've bookmarked it.

Hope this helps.

[Southwood]

Great link provided there. I going to try and do mine today.

Dow, I assume you just used the 3 factory holes?

[chrisexv6]

Another question: wouldnt you want to drill the holes in the UHMW so that the pieces are flush *with the table top* instead of the bottom of the factory fence? I figure the gap between factory fence and table top could be pretty annoying, and can be fixed by new fence faces.

[tomapple]

You don't want your fence to sit right on top of the table (as it will be prone to get sawdust underneath it which would throw it out of square with the table when you lock it down). I set the fence faces on my saws 1/32 above the table top.

[chrisexv6]

Ahh, OK.

Would you also want to shim the faces so that they are wider at the back of the blade than the front? I think that helps with safety (Ive tried a lot to get the fence itself to lock down that way, but I cant seem to get it to be wider at the back of the blade than the front........even with turning both allen screws to set "unequal" clamping)

[rofl]

sure you could shim it if that's what you want to do.

I wouldn't shim unless it was to even out some problem with the fence myself.

[Roadster280]

Surely you want the fence faces absolutely parallel with the blade across its entire length? If there is movement allowed at the back of the fence, the blade will act as a pivot and cause the wood to tend to move left at the front as the cut progresses (assuming the fence is on the right of the blade).

Even if it doesn't cause kickback or binding, I would thing it would give you an imperfect cut.

[dow]

Great link provided there. I going to try and do mine today.

Dow, I assume you just used the 3 factory holes?

Yep. Someone, I think it was Ashman? drilled two more holes, but I don't think it's necessary. I see no bowing of the pieces.

As for the poster who asked about having the fence "wider at the back" do you mean that you want to have the fence slightly skewed so that there's more clearance at the back of the blade than at the front? If so, then you adjust that with the two allen screws on the T part of the fence.

[Southwood]

Well got it completed. Really easy. Used just the 3 orgional holes that where provided. Made it 3/4 longer each end and 3'" tall. Moved the tapes by heating with an old blow dryer I keep in the shop, for just such emergencys.

[indianrider]

Yep.

I should add that I just made sides for my fence out of 3/4" UHMW and got them installed last night. Sorry, I didn't take pictures, but what I did was:

You think you could post pictures of both sides of the fence. That would be real helpful. Thanks. I am going to order UHMW from peachtree this week. Thanks.

[dow]

You think you could post pictures of both sides of the fence. That would be real helpful. Thanks. I am going to order UHMW from peachtree this week. Thanks.

Sure. I'll try to take some tonight.

[chrisexv6]

I thought I read somewhere that a slight amount of toe-out of the fence (i.e. its further out from the back of the blade than the front) provides a small amount of extra safety........since the wood is cut to the correct dimension at the front of the blade, any toe out after it would help keep the material free from binding back on the blade. At least thats my understanding.

And as for adjusting it, Ive tried to get a little toe out, but once I have some, the set screws are so far in its hard to slide the fence. if I back them out to be able to slide it again, I lose the toe out.....and I also want the screws in more to prevent "slop" when sliding (when the fence is so loose on the track that it gets stuck between the front rail and the front rail bracket).

[dow]

I thought I read somewhere that a slight amount of toe-out of the fence (i.e. its further out from the back of the blade than the front) provides a small amount of extra safety........since the wood is cut to the correct dimension at the front of the blade, any toe out after it would help keep the material free from binding back on the blade. At least thats my understanding.

Yes, that has been mentioned several times on here. I think that it's discussed in the 4511 availability thread, and probably elsewhere. As I recall, the amount of toe-out recomended was minimal -- I'm thinking 0.005" or so. Fie thousands run-out over a 35" fence isn't much at all -- just enough to keep the board out of the rear of the blade.

And as for adjusting it, Ive tried to get a little toe out, but once I have some, the set screws are so far in its hard to slide the fence. if I back them out to be able to slide it again, I lose the toe out.....and I also want the screws in more to prevent "slop" when sliding (when the fence is so loose on the track that it gets stuck between the front rail and the front rail bracket).

Use the two screws in tandem to get the slop out of the fence, and then use them in opposition to adjust the toe-out on the fence. For example, if you're using the fence on the right side of the blade, and want toe-out, you'd loosen the right screw a smidgen and tighten the left screw a smidgen, and then check it. Make a tiny change and check it, and then make another tiny change. I found that a dial indicator works great for this. Harbor Freight has them for about $10, with an adjustable magnetic base for another $10. I used the magnet to stick it down to the miter bar on my incra miter guage and then slid the gauge in the miter slot to compare the front and back ends of the fence.

[DaveWoodWork]

I have also read that a tiny amount (less than 1/16 inch) of increased blade-to-fence distance at the back end of the fence is acceptable when ripping solid wood that might be reactive. This is wood where the cut line might spring open a little wider than the kerf due to stresses in the wood that are relieved when the wood is cut. Such wood includes wet wood, figured wood, and wood that has been warped.

For non-reactive woods, such as plywood, the fence should be exactly parallel to the blade.

The Europeans have dealt with reactive wood by using a shortened fence, which they can slide so that it extends no more than 1 to 2 inches beyond the front teeth of the saw blade. Now if the cut line springs open beyond the initial cut, there is nothing for the wood to press against to cause kickback or binding problems.

I plan to build an auxiliary fence that extends only 1-2 inches beyond the front saw teeth that I can easily attach to my main fence when cutting reactive wood. My main fence will stay perfectly parallel to the blade. Has anyone seen plans for a simple and easily installed/removed shortened fence?

[chrisexv6]

I have also read that a tiny amount (less than 1/16 inch) of increased blade-to-fence distance at the back end of the fence is acceptable when ripping solid wood that might be reactive. This is wood where the cut line might spring open a little wider than the kerf due to stresses in the wood that are relieved when the wood is cut. Such wood includes wet wood, figured wood, and wood that has been warped.

For non-reactive woods, such as plywood, the fence should be exactly parallel to the blade.

The Europeans have dealt with reactive wood by using a shortened fence, which they can slide so that it extends no more than 1 to 2 inches beyond the front teeth of the saw blade. Now if the cut line springs open beyond the initial cut, there is nothing for the wood to press against to cause kickback or binding problems.

I plan to build an auxiliary fence that extends only 1-2 inches beyond the front saw teeth that I can easily attach to my main fence when cutting reactive wood. My main fence will stay perfectly parallel to the blade. Has anyone seen plans for a simple and easily installed/removed shortened fence?

Two thoughts come to mind:

1. Make your fence faces meet with a lap joint, but that might not be very accurate unless the lap joint is perfect enough to leave a truly flat face.

2. Make an aux fence that just sits on top of the stock fence (and/or your fence faces), and have the blade side of the fence not run the full length. Should be easy to make, just a box with no bottom and one side is actually a partial side, depending on the distance of the blade from the front of the fence.

[dow]

Yep. Someone, I think it was Ashman? drilled two more holes, but I don't think it's necessary. I see no bowing of the pieces.

UPDATE: I went out to the shop last night, and I was wrong. There was some deformation in the straightness of the UHMW slabs. I believe this to be a result of my hame-headed approach to tightening bolts, i. e. if tight is good, then REALLY tight must be REALLY good.

So I removed the bolts and washers, and re-assembled it with just the bolts and lock nuts. Part of the reason for really cranking down on the bolts initially was to make sure that the lock nuts were tight enough. The bolts were a tad too short with the washers, but tne next size bolts would have been too long. When tightening (this time), I only tightened it enough to make sure that nothing would move, not enough to make sure that nothing would EVER move. The deformation is much less, and I'll look at it again tonight to see if it needs additional bolts. What happened, when I tightened it too much is that the ends of the fence slabs pushed out away from the side of the fence.

indianrider: I didn't get the pictures yet. See paragraph above for reason :D.