Official Luthiers Forum!

im building a williams binding jig with the dave white modification. ive never worked with lexan before. im curious if i need to pre tap the holes in the lexan sub base to hold it to the small lazy susan? or can i just pre drill them and screw directly into the hole? i dont want to split the lexan. im not even sure how easy that would be. any advice would be appreciated.

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sweat the small stuff.

Always tap!

Drill at very slow speed use a small amount of light cutting oil and light pressure. I usually squirt a small amount of oil on my finger and just rub it on the fluted sides of the drill, to avoid a mess, you don't need much. You'll get a very clean hole, then tap normal. Lexan/polycarbonate likes to melt if drilled to fast.

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Billy Dean Thomas
Covina, CA

"Multi famam, conscientiam, pauci verentur."
(Many fear their reputation, few their conscience)

If you grind just the slightest flat on the front of each drill flute, so that there is a vertical face scraping the plex, rather than a sharp angled lip "scooping" the hole, you'll have no tendency for the bit to self-feed in the plastic, and the breakout through the other side won't be so abrupt and destructive.

I would tap the hole, and I would drill the tapping hole a bit oversize of the recommended, since the tap will try to exert a bit of a wedging effect as it cuts. Just don't torque way down when you run the bolt in.

Dan

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Dan
http://www.acme-archtops.com

Always tap lexan and most plastics. If you don't, you will create high compressive
stresses around the screw holes, and cracks will often develop from these stresses,
sometimes a long time after the screw is inserted.

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Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

Always tap. If you can get your hands on one, use a machine (spiral) tap rather than a hand tap. They don't auto-align, so you need to eye up your hole to make sure it's straight, but they put a whole lot less stress on the material. I do all my tapping, by hand or not, with machine taps now.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

so let me get this straight, what you are saying is that i should always tap? well, thanks for that advice guys. i guess ill have to borrow some taps from my dad. hes the machinist. not sure how i ended up in working wood.

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sweat the small stuff.

Bu, only tap if you really think it will be fulfilling!

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Waddy

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