Drill Pushing Chips Out the Back

ddavelarsen

ddavelarsen

Joined
Dec 7, 2000
Messages
5,179
You'd think after all these years drilling stuff I'd have figured this out by now, but I haven't. Whenever drilling handle materials, the bit pushes a little "crater" out the back side when it goes through. I drill into a wood base hoping to alleviate that, but I still get some. Most recently I chipped out a piece of paper Micarta, but I get it with bone, horn, and to a lesser extent wood too.

I run the drill at a slow speed, and try to back off the pressure when I can feel it about to break through. My bits are not all new, but I don't mess with obviously dull ones.

Any ideas? Maybe I'm running my drill too slow? Bits duller than I think?

Okay, off to the shop for a few hours, have a great day.

Dave
 
I know this works with thicker wood, not sure about thin stuff or micarta...hit the back first, and drill down a little bit, then go from the front and go all the way through. Or, when you're almost done and the tip of the bit begins to poke through, flip it over and go from the back.
 
Don't feel alone Dave,I have this happen to me also,It doesn't matter what I try I still have this problem.My fix for it has ben to try and leave the material a little oversized and sand the push out away..As long as it doesn't chip out a big piece on the back I just drill back through to clean the hole up and set my pins on stag and horn that is not oversized..
Good luck.
Bruce
 
Try to find some pilot tip bits. I got lucky and found a grab bag of solid carbide aircraft bits with the collar on the end of the shaft. Most of them are double length which helps alot for drilling out hidden tang handles. The pilot tip goes through first and the secondary flutes follow up like a milling bit and there is no chip out. The best part about the bits I found was the price. I found them on Ebay and won the bid at $7.50 for 32 different bits in several sizes. The sizes aren't standard fractional sizes. They're rated in thousandths. I just use my caliper to find the closest match for my pin stock.

Iv'e used the 'drill till the bit starts coming out the other side and flip it' method too. That works great. Good luck.
 
I run my drill speed at about 640 for handle mat. I also use a light drop of safe tap and always use sharp bits.
I've made a precision ground drill block which is 1 1/2" sq. X 6" long. About 2" from the end I drilled a hole 5/16"dia. X 1/2" deep. I fill that hole with cutting fluid. That way as I drill I just move the part, dunk the bit and continue. On break thru the bit automatically gets dunked again which helps cool after drilling. No more having to take your hands off to wipe your bit with a brush of cutting fluid.

Patrick R. Nihiser
Knifmaker
 
Have you tried drilling through with a smaller drill, and then going through with the larger one? This way you have a hole that the larger drill can follow and then drill from the front side so if it does push out a crater it will be on the inside where no one will see it.
Chuck
 
Great ideas! I'll incorporate some version or combination of the drill-from-the-other-side from now on. Max, sure would be nice to score a bunch of bits like yours, I'll keep my eyes peeled. Fortunately it's not usually so bad that I can't just grind the crater away like Bruce said. But I'd sure like to get a nice clean cut, just for compulsiveness' sake. :D

Thanks,
Dave
 
Try putting a piece of masking tape on the far side of a wood handle and use a smaller bit as a guide hole
TJ Smith
 
When drilling materials that can chip I always follow one or more of the following procedures:

1) if at all possible drill from the "outside" so that any chipping will be on the hidden side of the piece.

2) Always make a pilot hole with a smaller bit then, using increasingly large bits, reach the size you need. The bits will function as mills, not as drill bits, thus avoiding big chips.

3) take notice of the thickness of the material, drill almost trhu and then complete the hole from the other side, or make a bevel on the side the bit will exit from with the same bit so that you won't be piercing a flat surface.

For scales, for example, drill a pilot hole with a small bit, then mill a bevel with a larger bit on the inside: the sloping angle will make so that when the larger bit exits, the piece will not chip. Then mill it to proper size from the OUTSIDE with a larger bit.
 
Wood working supply houses sell drill bits that eleminate this problem. I think they are called forsner drill bits. They cut from the outside of the hole first. Do a great job but may not come in the size you are using. They come in standard sizes.
 
You could also try grinding the point off a standard twist drill bit so the end is flat & square to the shaft of the bit.

Sort of a "roll your own" Forstner for smaller holes. Not sure if it'll work the way you want, but you probably already have one in the right size that needs to be sharpened anyway.

If it doesn't work just grind the point back on it and all you lost is some time and about an 1/8 of an inch off the length of the bit. :p
 
Don't forget to clamp your piece you are drilling to the backing. Makes a difference!
Lynn
 
Lots of good tips! I've had good luck with masking tape, light pressure, and a piece of scrap to back it up. I run my finger nail over the tape to get it to adhere tightly. I really like the blue masking tape better.
 
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