Nasty Material

[tooljockey]

Has anyone out there had any luck milling a material called "thomson rod"?

It is 7/8" diameter, case hardened and when chipped, looks like concrete! One old timer told me Inconel is easy compared to this stuff!

[3R!< W3NG3R]

I turn the hard part with ceramic inserts. After that it is softer and fairly easy to cut. Just make sure not to cut the soft stuff with the ceramic.

[DavidB]

As Eric said once you get under the case hardning should be a bit easier to machine.

 

Can you grind to under the case hardning?

[Colin Gilchrist]

Try Cubic Boron Nitride coated tools for materials with extreme hardness. Ceramic works great, but I haven't seen any ceramic coated endmills.

[Thad]

IIRC, we cut it with a general grade (all purpose machining) carbide insert. We used them for lifter bars on our dies.

 

As the others have mentioned, after you get through the hardened part, it's not bad. The only thing is, when it's round and you're cutting through it, you'll always run into the case hardened part.

 

Thad

[Thee Rickster ™]

We use 2" thompson rod when building our pneumatic

presses/turn and thread ends. On a conventional

lathe.

 

When turning the hardness down with ceramic the

chips come off a stringy bright red.

Hot chips man.

 

After you turn the hardness off it cuts like

butter/carbide.

 

m2c's

[Goldorak]

generaly thompson shafting have a thick chrome layer

the first cut must be under this layer

after it's like 4140ht

 

thomson shafting is noting compare to flame cut stellite!! 5sfm and the chip is red hot

[Allan Brown]

[insert joke about "Thomson rod"]

[New Job]

Easy Dave...

[Fred @ Slate Industries]

I Hit it with a torch till its orange then

let it cool down with air,

Now I can machine it Like 4140.

I do this so I can tap the end of it

on smaller dia's where the hardness goes almost through the whole piece.

[tooljockey]

Thanks everyone. The operation I am performing is simply cutting a keyway slot and a few shallow flat areas-no turning. Soooo, as Thad said, most of what I have to cut deals with the case hardening.

I cannot grind because the 4+ foot length makes it a bit cumbersome, and I have 100's of these to cut, so one set-up is a must!

I am trying some 3/16" Fraisa HX tools @ 1000 rpm/2 ipm/.080 adoc to see if they last.

[Colin Gilchrist]

Let us know how those run. Harvy Tool has minature CBN endmills that would suit your application to cut through the hard casing. I'm thinking a ramp into the casing would cut very nicely. The endmills do need high RPM though. You might need a speed increaser with these things. I would call the guys at Harvey and ask them about your application. I'm curious to see what works on these. EDM would be the only other method I could think of.

 

HTH,

[Kevangel]

quote:

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EDM would be the only other method I could think of

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On long thompson shafts, I have also used Bridgeport mill to grind flats down to soft material...was a long time ago and wore a full coverage helmet with home made arbor and standard surface grind wheel..really need a guard. Oh yeah, "owners" were expendable.

[Kevangel]

Forgot to say, I think we used right angle head and there are maximum RPM call outs for those. Think safety, if this is safe at all. Needed full size wheel to get surface speed up.