Different Drill Bits or Better Technique?

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drw

Donn
Corporate Member
How do you minimize/eliminate tear-out where the drill bit breaks through on the backside of boards? Today I had to drill several 3/8" holes in some SYP using a cordless drill and brad-point drill bits. Initially, I began with the 3/8 bit, but in an effort to solve the problem I tried starting the holes with smaller bits and work up to 3/8, but I still experienced significant tear-out. I also tried different drill speeds, but nothing seemed to solve the problem. Any suggestions?

Thank you,
Donn
 

merrill77

Master Scrap Maker
Chris
Ditto on backing the board with a scrap. To improve on that further, use a bit that scores the circumference, like a brad-point bit.

Chris
 

mark2

Mark
Corporate Member
back it up with scrap or drill thru the piece until just the drill point comes out the bottom then finish the hole from other side
 

pviser

New User
paul
I agree with all of the above. The same applies to any situation -- e.g. router, table saw -- in which the cutting edge is exiting the workpiece. A sacrificial backup piece almost always takes care of the problem.
 

ehpoole

Administrator
Ethan
Like all the other responses, I keep a piece of plywood on hand for backup on the drill press or when hand drilling. You can also use any old scrap of wood lying around that you don't mind punching shallow holes into.

As mentioned, bits with a scoring edge help, but even they will produce some tearout. If not using a backup board, it also helps a great deal to back way off the pressure as you are about to break through. The bulk of the tearout problem is the result of the bit being pushed through the final bit of wood before it has had a chance to finish drilling. This forces the bit to take a very large bite which in turn causes the wood to tearout and splinter -- the bigger the bit the worse the tearout tends to be. It also helps a great deal to have sharp bits, dull bits cut more poorly and slowly and are much more prone to tearing the final bit of wood rather than cutting it.
 

drw

Donn
Corporate Member
Thank you for the input, I am very appreciative. That said, I feel a little sheepish that I didn't think of the solution myself. :embaresse

Donn
 

ehpoole

Administrator
Ethan
Thank you for the input, I am very appreciative. That said, I feel a little sheepish that I didn't think of the solution myself. :embaresse

No reason to feel sheepish, we all have our moments now and then.

Heck, half the time I can't even remember where I set down the tool that was in my hands just 30 seconds earlier. :BangHead:
 
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