Why can't I drill a 1/4" hole?

J

Jason Fry

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Jun 5, 2008
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3,215
I've been using brand new Norseman stub length bits, drilling through 1/8 and 3/16 1080. I used a new 3/16 bit and drilled 11 holes and still had a little more left on the bit. I used two new 1/4" bits and only got two holes each before they squealed out and quit cutting. Running at my press' slowest speed, 620 RPM. What am I missing? Why the heck can't I get the 1/4 holes to work?
 
what type of 1080 did you get. I would guess it was hot rolled as rolled. Have you normalized the material if not annealed it? All these things go a long way in making it easier to drill. If you are using cold rolled annealed stock then there is a problem with the drill bits. I have used some cheap bits that will not drill worth beans. If all else fails get a carbide drill and go at it that way.
 
A C Richards said:
what type of 1080 did you get. I would guess it was hot rolled as rolled. Have you normalized the material if not annealed it? All these things go a long way in making it easier to drill. If you are using cold rolled annealed stock then there is a problem with the drill bits. I have used some cheap bits that will not drill worth beans. If all else fails get a carbide drill and go at it that way.
Click to expand...

I was going to say pretty much the same thing, my first guess would be that you are just having bad luck hitting carbides or spots of pearlite with the 1/4" bit, if the material is hot rolled and has not had any subsequent annealing.
 
interesting.... could be a number of things.. I noticed a similar thing while skeletonizing liners, at first it was cake 1/8, 3/16, and 1/4" holes no problem... then I went back to throw a few more holes in it, I had major difficulty.. I even tried new bits, to no avail...

I had to use a starter 1/8 to finish off to 3/16..

maybe the steel hardened?? IDK, as I used the same bits to blast through bar stock...

maybe you got it to harden while drilling??
 
As others have stated, you probably have "Hot Rolled" 1080 which can be difficult to drill through. If you don't want to Anneal it (Or have the ability to) you should go the Carbide Bit route. They are pretty expensive and easy to break, but they will tear through it and mine seem to last quite a while as long as I am careful.

another possibility is you "Work Hardened" your material by getting it too hot when drilling.

Driling tips:
1. Mark drill point with punch to eliminate bit walking
2. Slow Drill Speed (< 500 rpm if possible)
3. Drill pilot hole (1/8" works well)
4. Use cutting fluid or oil to lubricate and reduce heat
5. let the bit cut, don't apply too much pressure to speed up the process
6. Make sure material level and secured
 
I'm sure one of the forum's seasoned machinist's will chime in... but from what I recall you want to run drill bits FAST, and with plenty of pressure. It may seem counter-intuitive to do that when you first think about it, but the slower you drill and the less pressure you put on, you are wearing the bit more and by going slower there is more heat buildup.

I drilled 5/8th holes with no pilot or cutting fluid. Ran my press at 1580 RPM (2nd fastest it can go with pulleys) and used good pressure. It drilled 8 holes with no problems, and the brand new bit still feels as sharp as it did coming out of the package.

Now this was through PG O-1 that was fully annealed (or at least I assume) so it COULD very well be your steel in the end... but I did manage to burn a few 1/4 bits on the same steel months ago when I first started making...

Edit: I repeat I am no expert... but this has worked for me. Everyone has their own way of doing things and get results they are happy with in a variety of ways.
 
Try annealing it, then use cobalt bits. Carbide should not be required, and soft steel can cause carbide bits to chip or break.
 
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