Help Request, Another drilling acrylic/lucite question.

bvartist · Post by **bvartist** » Fri Jun 08, 2007 10:19 am

In an effort to "broaden my horizons" I've been experimenting with acrylic stem material. I haven't had an problem drilling the airway. The problem I have is drilling an accurate mortise for delrin tenon. I use the same 5/16" forstner bit I use to drill mortises in briar and ebonite, but every time I try drilling lucite the mortise is too big. So far I've tried cutting fluid,(with no success), and drilling more slowly, (no success either). I have yet to try using a smaller forstner bit, or drilling a pilot hole.(I see some potential problems with that) Any suggestions before I ruin the whole lucite rod????

David

hazmat · Post by **hazmat** » Fri Jun 08, 2007 10:25 am

You may need to find a bit that's just slightly off of 5/16 to allow for that. I know the lucite/acrylic melts faster than ebonite and it sounds like this is the culprit here. May also be the bit you're using, not that it's off in any way, just that the forstner seemingly has more metal rubbing against the inside of the mortise while it's cutting. Have you tried a standard jobber bit that you know is a good fit for your delrin?

bvartist · Post by **bvartist** » Fri Jun 08, 2007 10:35 am

I think the problem is two-fold. Ebonite and briar will "relax" a little after drilling. Resulting in a mortise that is slightly smaller than the drill size. And acrylic doesn't do that. And it still may be the bit is causing too much heat, even drilling only one turn or less on my tailstock (about 1/12"). I have a brad point bit I have used for mortises, but had the same problem using it as I did with the forstner. I may try a 9/32 forstner at some point. Not available locally so I'll have to order one.

hazmat · Post by **hazmat** » Fri Jun 08, 2007 10:39 am

Turn a tenon instead of using delrin

bvartist · Post by **bvartist** » Fri Jun 08, 2007 2:07 pm

Excellent solution! Now if I had the $$$ to drop on a Taig and room in my shop to put the darn thing!!!

hazmat · Post by **hazmat** » Fri Jun 08, 2007 2:09 pm

Ahhh.. I see. I wrote that under the impression that you had a lathe of some sort you could turn one on.

Taigs don't take up very much room at all.

I'm sure you could find the room for one!

bvartist · Post by **bvartist** » Fri Jun 08, 2007 2:12 pm

No, my lathe skills aren't good enough to turn a decent tenon on my Delta Midi, and have it fit right!

bvartist · Post by **bvartist** » Fri Jun 08, 2007 2:16 pm

hazmat wrote:Taigs don't take up very much room at all. I'm sure you could find the room for one!

You'd have to see my workshop to know why I got a good laugh out of that one! I have one 6' workbench with my Delta Midi bolted to it, and the rest of the work surface shares time between my 10" disk sander, bandsaw and belt sander.

hazmat · Post by **hazmat** » Fri Jun 08, 2007 2:47 pm

I know the feeling. My Taig sits on a wooden TV tray until I need to use it, at which point it gets moved to my tiny work bench. I have a basement, but I don't keep much but my sanding/cutting tools down there. I keep my drill press, lathe and "finishing area(read: the same bench I do EVERYTHING on)" in the back room of my apartment and it's a tight fit. If I add anything else, I'm going to have to stop drinking beer to fit.

ckr · Post by **ckr** » Fri Jun 08, 2007 8:50 pm

David,

Is it a new and different piece of delrin. I have had bits that fit very snug and I would switch stock and find it not as snug. I grabbed another piece and it was as snug as the first. I know metalsonline works to tight tolerances, but it has happened. The difference, while noticable was not enough to toss the rod.

Other than that possibility, no clue.

bvartist · Post by **bvartist** » Fri Jun 08, 2007 10:58 pm

Nope, same Delrin rod I've been using for a while. I glued up 3 other stem blanks at the same time I was working with the acrylic, two ebonite and one cumberland, had no problems with any of the other three. I used the same drill bit, the same lathe speed, etc. but the mortise in the acrylic was large enough for the delrin to wobble. And my subsequent two attempts turned out the same, loose.

Post by **KurtHuhn** » Sat Jun 09, 2007 9:05 am

FWIW, this happens with me as well. The only way I've been able to solve it is to use a fast cutting spiral bit for most of the mortis and then bottom it with the 5/16" forstner.

Since acrylic is so sensitive to heat, I think that it expands and then cools quickly, changing the size of the mortis. The only way to solve that is to stay ahead of the heat, or work quickly enough that heat doesn't have time to be generated.

bvartist · Post by **bvartist** » Sat Jun 09, 2007 9:31 am

Thanks Kurt, I'll give a spiral bit a try. I've got lots of practice material now!

I'm also thinking of drilling a pilot hole, say 1/4" and then finishing the mortise with a 5/16". Maybe less material to remove with the larger bit will keep the heat to a minimum?? Worth a try I think.

Heinz_D · Post by **Heinz_D** » Sat Jun 09, 2007 10:02 am

I don't know if I can describe it correctly, but for acrylic it may be an alternative way to use a separate tennon...

Nylon or delrin are buyable in different diameters as example at http://www.janzen-pfeifen.de/frameset.html

If you can drill a centered, fitting hole into the stem, you can glue this tennons with two-component-adhesive. That'll work well and I do so for stems with 9 mm filter chamber.

The only other way in my eyes is to turn the tennon!

By the way: To cool down temperatur while working with acrylic you can use oil (WD40). Use it liberaly and slow down your machines...

bvartist · Post by **bvartist** » Tue Jun 12, 2007 2:15 pm

KurtHuhn wrote:The only way I've been able to solve it is to use a fast cutting spiral bit for most of the mortis and then bottom it with the 5/16" forstner.

That worked! Thanks Kurt!

Post by **KurtHuhn** » Tue Jun 12, 2007 7:25 pm

bvartist wrote:
KurtHuhn wrote:The only way I've been able to solve it is to use a fast cutting spiral bit for most of the mortis and then bottom it with the 5/16" forstner.
That worked! Thanks Kurt!

No problem. I'm just glad it works for someone else besides me. That proves that I'm not weird.

Or maybe it proves that you're also weird....

bvartist · Post by **bvartist** » Wed Jun 13, 2007 11:11 am

KurtHuhn wrote:
No problem. I'm just glad it works for someone else besides me. That proves that I'm not weird.

Or maybe it proves that you're also weird....

Maybe a little of both???

Heck, if it works, I don't care if its weird.