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Acrylic stems with Pimo Tool issue

Posted: Wed Jan 27, 2016 12:19 pm
by Rbraniganpipes
Hey guys,

I just recently started using acrylic blanks for stems, and have been having an issue getting my tenons to look smooth after turning. I am using the PIMO tenon tool to turn the tenons. What happens is i get little gouges in the tenon, almost as if the cutter isn't cutting the tenon smoothly.

Is this due to the speed of cutting?
Do i need to continuously crank the tailstock wheel to keep the cutter moving so that it doesn't stop and cause the marks?
What speed is appropriate for cutting? I am worried about the acrylic getting too hot during turning.
Could the carbide cutter not be in the right position or just slightly off angle?
Is my guide hole too big? I drill a 1/8 hole.

I tried cutting tenons larger than needed, and then sanding them down to remove the lines, but it just seems like the cutter should be able to do a better job of making the cut.

I learned the hard way that if you don't wait for the acrylic to cool before attempting to fit the stem, you will get melted acrylic inside your mortise.

Re: Acrylic stems with Pimo Tool issue

Posted: Wed Jan 27, 2016 12:35 pm
by sandahlpipe
The gouges are the reason I ended up getting rid of the tenon turning tool and getting a metal lathe. There really isn't a great alternative to a metal lathe for turning tenons, though other methods can provide adequate results.

The issue with the tenon turning tool is that it tries to take off too much material if you have it set to the final diameter of your tenon. Set it to make the tenon bit large and then adjust it again to take off the last pass. You want to have a continuous, slow feed rate for the tool. Alternatively (since I think I heard you have a wood lathe), you could take off the bulk of the material with lathe tools and then take a light pass with the tenon tool.

And yes, you will want to make sure you let the acrylic cool. Melting it isn't good. :-) You might consider applying some oil to the guide rod to minimize friction inside the airway.

Re: Acrylic stems with Pimo Tool issue

Posted: Wed Jan 27, 2016 1:15 pm
by Rbraniganpipes
Ok that's a good idea. I will try taking material off with other tools and then use the tenon tool for the final cutting. Do you ever apply any oil to the wood lathe track to keep the tail stock sliding easily? If so what should I apply?

Re: Acrylic stems with Pimo Tool issue

Posted: Wed Jan 27, 2016 1:19 pm
by sandahlpipe
A little way oil goes a long way. You'll want to apply it lightly whenever the tailstock starts to get stuck when moving. I'd use something more like vegetable oil for anything that goes in the airway though.

Re: Acrylic stems with Pimo Tool issue

Posted: Wed Jan 27, 2016 2:09 pm
by scotties22
For your wood lathe you are going to want to get some Boeshield T9. It's a super duper good lube that has a bit of wax in it. You spray it on and then wipe off the excess. Once it dries you are good to go. It will make the banjo and tailstock slide beautifully. My favorite part about it is that it doesn't stay greasy so you don't have sawdust all caked up all over your lathe. (Thanks Chas for recommending it!)

http://www.woodcraft.com/product/03Q56/ ... spray.aspx

As far as lube on the guide pin I would start with a bit of bees wax or go old school Sas and squirt some soapy water on it as you go.

I still use my wood lathe to cut tenons. I use the Easy Wood Tool with the square cutter head. I take the tenon down to about a thousandth over what I need and then sand until it fits perfectly. It's a bit tedious, but it's what I have and it works. After 3 years I only have to start over on about 1 in 15 tenons, so my success rate is pretty darned good.

Re: Acrylic stems with Pimo Tool issue

Posted: Thu Jan 28, 2016 1:41 pm
by pipedreamer
You could make a tool out of a wrench, the size you want.Sharpen the short end of an open wrench and epoxy the other end{after cutting it off} into a handle at least 10 inches long.Usually 2 inches in the handle and no more than 4 inches for cutting tool works. If you have the technique, Scottys' way is fast and works well….The EZ wood tools are top of the line, but expensive.A cheap wrench is a couple of bucks???It could tied you over till getting another way :thumbsup: Hope this helps.

Re: Acrylic stems with Pimo Tool issue

Posted: Tue Feb 02, 2016 11:38 am
by Sasquatch
I think you are on the right track here... try a bunch of light passes rather than cutting for final right away. I would also use plenty of soapy water on the cut as scottie mentioned - keeping acrylic cool is the key. Slowest speed you have.

But if you are already on a lathe... just cut the tenon with a skew chisel or even a parting tool. It's really not that hard to fit 'em by hand.

Re: Acrylic stems with Pimo Tool issue

Posted: Tue Feb 02, 2016 12:14 pm
by Ratimus
Delrin. :twisted:
You woul also avoid the horrible squeak of acrylic on briar.