[4]

Boring a hole in hardened steel?

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

Cadillac STS

Active User
H-M Platinum Supporter ($50)
Joined
Jul 20, 2012
Messages
765
Here is the project. I have a Wabeco D6000E metal lathe. I have a set of MT2 collets I had from something else. I thought if I bought a socket with MT2 taper inside and straight parallel outside I could easily put the collet in the chuck for quick occasional work on small things. Got the socket online. It is nice and fits perfectly for what I want to do EXCEPT I need to drill or bore a hole in the end of it so I can put a bolt through to reach the MT2 collet and tighten it up. The thing seems to be hardened and I can only scratch it with a center drill (It does have a hold about a mm deep and wide center in the end.) Put an endmill in the lathe tailpiece and it just scratches it. Any ideas I can use to get the 5/16 hole through the 1/4 inch thick bottom of this socket? Thought about de-hardening it if possible to work on it but don't know how and don't want to get it out of shape for work with later.
 

Ray C

Platinum
Staff member
Registered
Joined
Nov 16, 2012
Messages
5,215
If an endmill is only polishing it, chances are it's Rockwell 60 (or possibly 62) which is about as high as things typically go. In a homeshop environment, you're pretty much limited to A) using a pencil grinder and trying to grind past the hard surface; which must be done on entrance and exit B) anneal it which has the bad side-effect of softening more than just the area you want to drill. I guess the other options are to take it to a machine shop and have them use EDM. I have no experience with that and don't know how precise of a hole that makes.

Not sure what kind of socket it is but, generally, sockets are made of pretty tough stuff that can be hardened quite deeply.

Ray



Here is the project. I have a Wabeco D6000E metal lathe. I have a set of MT2 collets I had from something else. I thought if I bought a socket with MT2 taper inside and straight parallel outside I could easily put the collet in the chuck for quick occasional work on small things. Got the socket online. It is nice and fits perfectly for what I want to do EXCEPT I need to drill or bore a hole in the end of it so I can put a bolt through to reach the MT2 collet and tighten it up. The thing seems to be hardened and I can only scratch it with a center drill (It does have a hold about a mm deep and wide center in the end.) Put an endmill in the lathe tailpiece and it just scratches it. Any ideas I can use to get the 5/16 hole through the 1/4 inch thick bottom of this socket? Thought about de-hardening it if possible to work on it but don't know how and don't want to get it out of shape for work with later.
 

Tony Wells

Platinum
Registered
Joined
Jan 22, 2011
Messages
7,069
If carbide won't cut it, and there are just a few situations when the proper application of carbide won't at least work, although perhaps not the best production solution, there is another approach you might consider. If the bottom is only 5/16" or so thick, you could cut it off with an abrasive saw, then build a 5/16" thick slug with a hole in it that would back up your drawbar.

I wouldn't rule out carbide though. I too have machined out quite a few taps with it, so it can be done. I believe the exact mechanism that allows carbide to cut such hard materials is the extremely localized heat that softens the material enough to allow it to be cut. I know I have ground 4 sided pyramid points, about 45° angle, and run them as fast as the mill would go, and using an air hose to keep the tiny, very hot chips clear, and cut over 1/2" depth into a HSS tap. You probably should try a standard center-cut end mill first, then the pyramid point, then possibly consider chopping it off.
 

Cadillac STS

Active User
H-M Platinum Supporter ($50)
Joined
Jul 20, 2012
Messages
765
If carbide won't cut it, and there are just a few situations when the proper application of carbide won't at least work, although perhaps not the best production solution, there is another approach you might consider. If the bottom is only 5/16" or so thick, you could cut it off with an abrasive saw, then build a 5/16" thick slug with a hole in it that would back up your drawbar.

I wouldn't rule out carbide though. I too have machined out quite a few taps with it, so it can be done. I believe the exact mechanism that allows carbide to cut such hard materials is the extremely localized heat that softens the material enough to allow it to be cut. I know I have ground 4 sided pyramid points, about 45° angle, and run them as fast as the mill would go, and using an air hose to keep the tiny, very hot chips clear, and cut over 1/2" depth into a HSS tap. You probably should try a standard center-cut end mill first, then the pyramid point, then possibly consider chopping it off.

Thanks for the advise about carbide. I went to our local Precision Tool store and got a carbide endmill and it worked. I was amazed it cut right through hard at first then right through as expected with the hardened metal.

I thought about cutting the end off but it is so much easier and nicer with just having a hole in it.
 

pdentrem

Active User
Registered
Joined
Jan 28, 2011
Messages
2,118
Carbide was the way to go.

Just a note about the EDM idea. The machines can hold almost unbelievable size. We have not used a ram/plunge style except for burning out broken bolts etc. After using center find they go right down the center, period. In the shop we have 2 Wire EDM Sodicks and they are OLD! They can hold an easy .0001", new machines are much better than that!
Pierre
 

Tony Wells

Platinum
Registered
Joined
Jan 22, 2011
Messages
7,069
Pierre is dead on about EDM. I'm investigating a wire machine now for some work I do, and can get. Holding tenths is childsplay with EDM. Ram/sinker style can hold close tolerance as well. The main drawback is they aren't the speediest machines in the shop, but there's the tradeoff. Slow and accurate, or fast and a little rough. They can also generate very fine surface finishes if needed, or leave a pretty rough surface if permissible. I have subbed out quite a bit of EDM work, and it always impresses me. Doesn't matter if it is hard or not, as long as it conducts electricity, you can cut it with EDM.

And if you're ambitious enough, you can build one yourself, either a sinker or a wire machine. There is a Yahoo group that is pretty active in support of design and build of homebrew EDM. I'm undecided....I have the capability of building one, just maybe not the time to make is the smart thing to do. Meanwhile, I'm looking around for a used wire machine.
 
[5] [7]
Top