Drilling tang holes

M

Matlock

Joined
Jun 26, 2002
Messages
125
I know this has been brought up a few dozen times before and for drilling tang holes in metal that is hard, in my case 52100, carbide is the way to go. I know the spade drills are very expensive, and I have heard that masonry bits can be used in a pinch, but I was wondering about these carbide glass drilling bits from Harbor Freight ? http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=42829 They are the same price as their masonry bits but are much shorter and I would think they would flex less. Any thoughts?

Matt Matlock
 
The good thing about the masonery bits is that there is more steel holding the carbide piece in. I have a feeling that you might rip the carbide right out of those (just a hunch). I've even ripped them out of the stone bits before. :)
 
Not intending to hijack this, but I drill tangs after profiling, before any tapering, thinning or whatever. This was based on advice from Jerry Hossum from a few years back.
 
I'll back that one up -- definitely do it before heat-treat, but I assume this is for those "oops" times. :D
 
The last one I tried was 52100 before heat treat and even with cobalt bits I had a hard time getting 2 1/2 holes drilled before it work hardened and dulled the bit. Mabe I just suck at drilling (read: don't go slow enough and use enough oil) :D

Matt Matlock
 
From time to time I had a hard time drilling through my tangs with cobalt bits. I mentioned this to a Lawson salesman. The sales person suggested I try their bits. Sure enough they have been a better bit in every way. I don't know what they are made of but the sales person claimed they would drill into something that is rockwell 65.
I like them and gladly pay the price.
 
Spade bits (preferred) or double-flute bits with plenty of coolant are the best, but drawing down the tang after HT is probably the best way. I've done it a bunch of ways before. I still do. Before HT. After. Its all good if you have the gear. These days I try to do before HT, and at least get a small pilot hole made before I haft the blade.
 
Matlock said:
I know this has been brought up a few dozen times before and for drilling tang holes in metal that is hard, in my case 52100, carbide is the way to go. I know the spade drills are very expensive, and I have heard that masonry bits can be used in a pinch, but I was wondering about these carbide glass drilling bits from Harbor Freight ? http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=42829 They are the same price as their masonry bits but are much shorter and I would think they would flex less. Any thoughts?

Matt Matlock
Click to expand...

I'm at a loss trying to figure out why you guys are torturing yourselves over this. Solid carbide twist drills are not that expensive.

I tried using a masonary bit. It was an abismial failure. It didn't drill 2 complete holes. And I used a good one. Vermont American. The carbide shattered half way through the second hole. The problem with any type of spade bit is thet they don't clear the chips as they drill. They are probably sharpened at too steep of an angle also.

I have solid carbide bits I have drilled dozens of holes with and they're still sharper than most HSS bits are new and un-used. Have you ever drilled a soft metal like brass and seen the cuttings come off the drill in a long curly strip? You can do the same thing in hardened steel with a solid carbide drill.


Drew
 
Burchtree said:
I'll back that one up -- definitely do it before heat-treat, but I assume this is for those "oops" times. :D
Click to expand...

I have almost decided to stop drilling the tang before I heat treat. It seems lately I change my mind before the blade comes back.
 
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