Pilot holes

[pflaming]

I ofte have a difficult time to drill holes in metal with a hand drill. I center punch and use oil yet bits do not cut.  On larger bits I do a pilot hole, should I always do such. I realize I should know this by now, but I don’t? Will a worn drill chuck be a factor? 
 

Thank you for your indulgence for an old man.

[Todd B]

My dad always said to use pilot holes on larger sizes. But, I bought a very high quality set of bits at the Iola car show years ago and the salesman said never use a pilot. Just drill it 

[Los_Control]

My biggest problem I do start with a smaller bit and work my way up .... I just do not have a large enough drill  bit for my "pilot house truck"  to fit.

[kencombs]

Select your pilot hole size with caution.  Too large for the final size and the stress for the bigger bit is moved too far out on the cutting edges and will result in chipping and/or dulling.  IMO, no pilot under 5/16, maybe 3/8 if you have good quality, sharp bits.  And match the drill speed to the bit/metal combo.  One of the advantages of 2spd, variable speed cordless tools.

 

I'm almost your age Paul, and finally resigned my self to spending the money necessary for Cobalt bits in the most used sizes.  I hate to do that since I tend to abuse and break smaller bits.  But it's worth every penny.  Last week I broke the chuck retaining screw in my DeWalt 1/2" cordless.  Using it for a starter to test run a little Honda pressure washer engine that was missing the recoil.  Broke of flush.  My normal set of HS steel bits wouldn't cut it.  Pulled out a Cobalt, cut like butter.

 

Another example:  I welded up some bosses on my clutch housing to provide  a location to drill and tap new trans mounting holes.  Because of the existing holes location it was necessary to drill 3/8" holes that were partly in the Nickle weld, partly in the original cast iron and partly in one of the orginal holes that was plugged with a bolt, epoxied in place and cut flush.  Good Cobalt drill, no pilot, no problem.  But that one was on the drill press.

Edited May 17, 2020 by kencombs

[DJ194950]

I was told by a machinist to use a pilot drill bit that just barely bigger that the web of the drill bit size of the larger drill to be used. The Web is the cross section between the flutes of the drill bit. (The sharp center).  Hope I am clear of the explanation. The is no need to progressively drill larger and larger holes to get up to where you want to end up. I have drilled up to 2" holes using this method.

 

Say a 1/2" drill bit has something like a 1/8" web (off the top of my head). Therefore a 1/8" or barely larger will allow the 1/2" bit to easily drill the hole and will be centered and round not oversized and out of round.

 

DJ

[Merle Coggins]

Paul,

Either you need to invest in a better set of drill bits, or learn how to sharpen drill bits. If the drill bit won’t cut it’s either dull or the steel you are drilling is harder than the bit. 

[pflaming]

The body of this Sportster is hard and thick, like a tank.  I just viewed a video on sharpening bits. Will learn how. 

Edited May 18, 2020 by pflaming

[plymouthcranbrook]

In addition to a good drill set I have discovered the miracle of air drills. Especially after your get started the high speed will really help cut. Of course lubrication is more essential than with a smaller slower drill as heat can really build up.