Work Hardening , drilling a hole in a tractor pin

This weekend I tried to drill a hole in a pin that holds the bucket on my backhoe . I had to grind down the pin in a spot so I could start the hole . I got @ 3/4's through the pin & then seems all progress stopped . I even used a new 1/4 " bit . Could I have work hardened the bottom of the hole I was drilling ? How can I finish the hole ? Would a Cobalt bit work ?
thanks
animal

animal12 said:

This weekend I tried to drill a hole in a pin that holds the bucket on my backhoe . I had to grind down the pin in a spot so I could start the hole . I got @ 3/4's through the pin & then seems all progress stopped . I even used a new 1/4 " bit . Could I have work hardened the bottom of the hole I was drilling ? How can I finish the hole ? Would a Cobalt bit work ?
thanks
animal

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It sounds like you were using a cordless drill. My guess is that you pressed the trigger and ran it as fast as possible.
Yes it probably work hardened.
Cobalt might help, but not if you run it wide open again, you'll just fuck up that drill also.
Get a new drill, go slow and use some kind of oil. Get past the hard spot and finish the hole.

Did sparks come out of the hole whilst "drilling" ?

Sounds like you're trying to drill all the way through. If you can put up with a little distortion or misalignment of the hole, drill from the other side to meet.

Another possibility is to use a new, never used masonry bit to break thorough the hardened area. Use dry, in something like a bit brace so you can go SLOW and put lots of pressure on it.

Scottl said:

Another possibility is to use a new, never used masonry bit to break thorough the hardened area. Use dry, in something like a bit brace so you can go SLOW and put lots of pressure on it.

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Just what I was thinking but sharpen it first. It will go all the way through if you clear the chips.

Yep , I was using a cordless drill with oil . No sparks . So this afternoon I spun the shaft 180 & hit it with a grinder & slowly ground till I could see the heat mark from the other side . I ground a bit more & then hit it with a freshly sharpened drill bit & I'm in business . Smaller pins installed & backhoe sold this afternoon .
thanks to all
animal

Pins are typically induction hardened 1045.....cheap ,and a hard skin........In fact ,Ive found that with the downward force of a radial arm drill,the hard case can be drilled at a slow speed with cobalt HSS drills..............I have also found that most masonry drills have a rockdrill type of rounded cutting edge,however a very few have edges like metal drills.....not advantageous in stone,but they cut a neat chip in steel.......The other point is the insert is cheaply secured with a blob of brazing metal,and if the carbide tip comes off in your drillhole ......then diamond is your next option.

Try to drill from the other side or just get a new pin and start over

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animal12 said:

This weekend I tried to drill a hole in a pin that holds the bucket on my backhoe . I had to grind down the pin in a spot so I could start the hole . I got @ 3/4's through the pin & then seems all progress stopped . I even used a new 1/4 " bit . Could I have work hardened the bottom of the hole I was drilling ? How can I finish the hole ? Would a Cobalt bit work ?
thanks
animal

Click to expand...

Buy a carbide tipped masonry drill bit, go to the bench grinder (with any wheel, doesn't matter) and sharpen the point. I go fairly shallow on the relief angle and I'd try a standard point angle. I've done this may times in VERY tough steels. Worked fine for me every time I've tried it. You're PROBABLY going to shatter the carbide tip on exit. The last time I did this was drilling two 3/16" holes in AUS-8A stainless. It was hardened to high 50's Rockwell C. Last time I had to do this, I used a regular A/O wheel on a 6" bench grinder to sharpen the bit. Didn't bother swapping wheels or anything. It worked fine. Shattered the bit when it broke through the second hole. But I attribute that mostly to me being to heavy handed with the drill press.

*OR if it's for someone else and it's REALLY important, maybe buy a carbide twist drill. That said, that piece of AUS-8A I was drilling was a pin hole in the tang of a finished knife blade, which I wouldn't consider inexpensive.

thanks , I'll give the masonry bit a try next time I'm in a situation like this .
thanks
animal

Rickyb said:

Just what I was thinking but sharpen it first. It will go all the way through if you clear the chips.

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The Bosch stone bits are already sharp.