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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| Author: | Heath Blair [ Sun Jul 27, 2008 3:08 pm ] |
| Post subject: | pre tap or just pre drill lexan for a screw? |
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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| Author: | Billy T [ Sun Jul 27, 2008 3:30 pm ] |
| Post subject: | Re: pre tap or just pre drill lexan for a screw? |
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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| Author: | DYeager [ Sun Jul 27, 2008 4:59 pm ] |
| Post subject: | Re: pre tap or just pre drill lexan for a screw? |
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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| Author: | gozierdt [ Sun Jul 27, 2008 7:43 pm ] |
| Post subject: | Re: pre tap or just pre drill lexan for a screw? |
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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| Author: | Bob Garrish [ Sun Jul 27, 2008 7:49 pm ] |
| Post subject: | Re: pre tap or just pre drill lexan for a screw? |
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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| Author: | Heath Blair [ Mon Jul 28, 2008 12:13 am ] |
| Post subject: | Re: pre tap or just pre drill lexan for a screw? |
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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| Author: | WaddyThomson [ Mon Jul 28, 2008 12:09 pm ] |
| Post subject: | Re: pre tap or just pre drill lexan for a screw? |
Bu, only tap if you really think it will be fulfilling!
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