Delrin on a table saw

[invertedflight]

Does anyone have experience cutting delrin plastic on a table saw? I'm trying to make 1" squares out of .25" sheet, which means I first have to rip it into strips, then crosscut into little squares (that is, if the terminoligy still holds for plastic).

I think I've got the crosscutting down with a little crosscut sled I made (miter saw works too). I'm having a lot of trouble making nice strips though - the edge comes out pretty bad, I think because the thin strip starts to vibrate and/or flex due to the plastic heating.

I'm using the stock blade on my Bosch 4000-09 saw, but I'm willing to buy a different one if it will help. I looked at some plastic cutting blades, but they seem to have a lot of teeth, which I can't imagine will help keep the plastic from heating.

I need to make about 200 squares, btw.

Thanks for any suggestions!

-Chris

[Beezer]

Have you tried using a featherboard mounted to the guide on your tablesaw to hold the strips down against the table, to prevent them from vibrating?

[Geof]

The featherboard is a good idea. Also run a sheet of plywood partly through the blade so your Delrin is well supported very close the the blade.

But MOST IMPORTANT get a triple chip blade. The type used for non ferrous metal cutting; regular wood blades are not adequate.

Another thing about cutting any plastic is that you must not let the blade dwell in one spot and you need to minimize blade contact area. This means on a table saw just have the blade high enough to penetrate the material However, this does increase the chance of kickback which is why the featherboard is a good idea. Feed through at a nice steady rate and don't back up. If you some reason you have to stop feeding turn the saw off and wait for the blade to stop before trying to lift the material clear. To reduce friction a bit a good lubricant is just plain soap rubbed on the blade; when it is stationary of course.

edit:
It does seem counterintuitive that lots of teeth, which is what many of the triple chip blades have, reduces heating. But the heating is caused by rubbing not cutting. The heat generated at the chip is carried away mostly with the chip when you have a nice sharp blade and are feeding at a fairly good rate. With many teeth your blade actually spends less time in any point in the cut.

[Beezer]

The sheet of plywood is a good idea or see if you can purchase a "zero-clearance throat plate" that will fit your model tablesaw or just make one yourself. You can make them from a piece of sheet masonite but I prefer to use HDPE (High Density Polyethylene).

Here is a little article I found on them.
http://www.diynetwork.com/diy/hi_too...733825,00.html

Make sure to use push-sticks. Fingers don't grow back.

[HayTay]

Inverted,

You could try making the strips about 1/3 - 1/2 of the sawblade width larger for the first full cut. After that move the guide over to the desired strip width and make the final cut. It's usually easier to remove a small amount of material and there should be less friction as only one side of saw blade is in contact with the plastic on the final cut.

Of course, use a featherboard and follow the other safety precautions and suggestions listed in the other postings as well.

I need to make about 200 squares, btw.

If we may ask, "Whatcha makin'?"

HayTay

[invertedflight]

Thanks for the ideas guys, but I'm not sure I understand entirely on either account.

Where am I going to mount a featherboard? I'm cutting a thin strip from a larger sheet...did you mean a featherboard to hold the work against the table, or against the fence, or both? I'm not sure a featherboard is going to be effective in helping me push a large sheet through.

Also, what do you mean by pushing a piece of plywood partway though?

I've found that a 1" strip of .25" delrin warps a decent amount after/during the cut. I can't detect any amount of heat in the plastic immediately after the cut but it definetely warps (the cut side expands). Leave the piece alone for a bit and it straightens out. The cut does show some signs of melting/rubbing.

One thing I noticed about my current blade is that is the teeth don't have any relief from the work. I'm not sure if there's a term for it, but the friction could be eliminated if the tooth got less wide from tip toward the center of the blade.

I'm ordering some new blades to tryout (for both my table and miter saw) - should I get a special plastics cutting blade, or just go with the metal cutting one? I was thinking I'll probably also be doing acrylic and aluminum on my table saw.

Thanks,
Chis

[HayTay]

MicroMark.com Featherboard Instructions with photo

This should clarify the featherboard reference. Use one or both depending on how large of plastic sheet you're cutting. Definitely use the vertically mounted one on the guide.

Hope this helps,

HayTay

[Geof]

Mr HayTay beat me too it but here is another link.

http://www.justclamps.com/featherboars.htm

And the link really does take you to a page showing featherboards not flying male pigs

What I mean by pushing the plywood part way is to take a piece of 1/2" ply and run it along your rip fence until the far end is just past the blade but still have a decent length in front of the blade. Because you have just made the cut in the plywood the slot is the same width as the blade. This makes it pretty well impossible for your plastic to stick to the blade and get dragged down into the slot in the table.

With the correct blade nice and sharp and the correct feed rate which you find by experiment your cut surface should be nice and clean with no sign of melting or rubbing just the tooth marks.

You should be able to find a triple chip blade marked as suitable for non ferrous metals and plastic

[ViperTX]

The other thing you can do is get a blade with tooth count up in the 80 or so range.....

[vfsi]

The hot ticket for plastic is to saw cut it over size by 1/8. Then use a jointer (purchase from Home Depot, Menards, Lowes for under $300) to finish to size. The surface finish is as good as a milled surface with 5% of the effort and .01% of the investment. A saw cut edge will always be a saw cut edge.

The longer the piece the easier it is to finish. You will have to make a fixture to hold the pieces for the 1 inch jointer cut.

This works with Polypro, PE, UHMW PE, Delrin, PVC..........

[invertedflight]

I took some delrin over to a friend's shop and he put an amazing edge on the sheet with his jointer. He then cut a strip with his table saw, which had an acceptably flat and straight edge. I think he used a ripping blade to cut it - it was definetely a low tooth count blade.

Just looking at the edge from the jointer makes me want to buy one, although I really don't have the space right now. I've never even used one before - would I be able to safely push thin strips through? How can I set it up so that I can get a constant size strip every time without having to measure and adjust? Can I run aluminum through it?

Thanks,
Chris

[invertedflight]

BTW, my best method right now is shave a nice edge on the sheet stock, cut an oversized strip off the stock, then shave a nice edge off the strip. I'll have a new blade or two tomorrow, so I'll try that along with some featherboards/guides.

I think I have to buy a jointer and a planer now....