Drill & Tap 1/4-20 in Tompson/C ML Hammer-bolt?

R

RogerBarker

Guest
Guys,

I want to drill & tap 1/4-20 about 1 inch deep in the face of my TC Thunderhawk hammer-bolt. Chucked the hammer in a lathe at work and regular drill wouldn't touch it - too hard. Then used ball headed, diamond impregnated, dremel tool in lathe followed by drill and got about 1/8 inch in, not the full diameter of the #7 drill. So, I'm thinking this part is case hardened, and I need to use the diamond headed dremel tool to larger diameter than the drill, then the drill should go in.

Do you think this approach will work?

How do you recommend I do this?

I'm obviously a novice with access to a lathe.

Thanks for your input.

Roger Barker
 
If the

hammer-bolt is investment cast or formed out of some powder metal, it may be hard all the way thru. Which means you may not be able to get a good clean hole of a diameter for tapping. And if it is hard all the way thru you won't be able to tap it. At least not with conventional taps. I spent 32 years as a tool and die maker at Cessna aircraft and I gave up ever tapping hardened steel. If we needed a hole in hardened steel we made a new part and hardened it after all the holes were drilled and tapped. It may be possible to tap hardened steel but we never found it to be something we could afford to do. Max
 
I see

where you got about 1/8 deep with drill. That is past any case harden depth. A carbide drill might get you the depth you want. Carbide does not always drill a nice hole, sometimes oversize, but tapping 1' deep will be near imposible if it is hard all the way thru. A tap broken off 1/2 inch down will have to be removed by electrical discharge method and that leaves hard spots also. I don't know how to edit so this is another post. I am not sure you are wanting to do a practical thing. Maybe posible, but practical? Max
 
I would not attempt what your doing as well, I'm sure that part is hardened and then tempered for toughness. It needs to stand up to repeated blows so I dought it is case hardened. Even if you drill the hole, the most likely outcome will be a broken tap in your hole.
 
Hi Max,

Thanks for the info. I guess I need to find out what the bolt-hammer is made of. I was thinking that as a last resort a carbide drill and tap could be used.

Roger
 
Lots of Luck

Lots of luck with a carbide tap,They were made for high speed machining of softer materials,They are very brittle and break easy.
 
If you dont use the right speed and feed or hesitate you can actually harden the parts as you try and drill them. I tried to lighten a SS hammer on a ruger and did not use enough coolant and i hesitated and the heat from drilling hardened the part, game over:rolleyes:. That is of course if it is not already full hard. good luck.
 
Carbide

I don't know a thing about TC's, but I agree that the piece is probably an investment casting, or some type of powdered metal tech, tempered all the way through. Most case will be only .010 or so

A Carbide Drill and a Carbide Tap will do it, possibly you could go one size bigger on the tap to take some of the torque off the tap. Also, be very sure you get tyhat tap stared dead straight, that is usually the big culprit in tap breakage.

Good Luck. I have been a machinist for 40+ years, and I do not like doing things like what you are attempting..........jackie
 
Roger,

Easiest way to do this is going to be by annealing the part and then drilling and tapping. Whether this is easily done or not depends on the material. If the hammer alloy is of normal water or oil tool steel makeup, then just heating it up to a nice blue color all over and setting it aside to cool should allow you to drill and tap it with good tools. If it is air hardening steel, then heating it up won't always do the trick (unless you have an atmosphere furnace around to give a real slow cool without scaling), but even with air hard materials you usually get some softening by heating it to 800-900 F. or so. Powdered metals often use secondary hardening processes during their heat treatment and often get harder at 900-1000 F., so heat won't work too well on those materials.

Before you anneal you need determine if the part needs to remain at it's current high hardness or whether a lower hardness will be acceptable. Most of these types of parts don't need to be as hard as the manufacturer makes them, but it really is dependent on the parts' function.

Scott
 
Guys,

Thanks for all the input. My plan at this point is to talk to Thompson Center to find out what the part is made of and the heat treating done. If I have to anneal the part, drill & tap, and redo the heat treating, I can probably do this. I have a tube furnace available where I can get to 2000F under various atmospheres. I'll let you know what I find out and how it works out.

Roger
 
Roger.
What type of modification are you trying to make to your bolt and what would be the intended purpose.
Perhaps there is another route you could take.

Chuck.
 
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