Nightmare Materials

[FZR1KG]

So I got this free chunk of Ampco 22 I think. I know it was Ampco but it would take me awhile to find out which one. For some unknown reason I decided it would be a good idea to fix my Vevor lathe by making a tapered gib holder on the underside of the saddle with the stuff.
Let me just say, it was not a good idea.
Hard to cut, blunts good sharp US made endmills like they were made of Chinese mild steel.
I refused to give up so completed the job. Figured I'd learn something. I did. I learned I should select better materials, and most importantly, to recognize a bad mistake early on and not keep going.
I also did learn that milling this stuff requires zero or even a back rake. Anything else is likely to chip it or destroy the endmill.
It also hates being drilled. I hate it, so I figure we're even.

I'm sure others have had similar horrible materials to machine. Let us know so we can avoid them too!

 

[Ulma Doctor]

1086, 4340, and D2 steels are not friendly

 

[WobblyHand]

Made a lathe spider out of 4340. Was not easy to machine.

 

[mmcmdl]

Invar , Hastelloy , Inconel . etc etc etc .

 

[GT-6 Racer]

That Ampco 22 should machine reasonably well. Only Brinell 400 or about RC43-45 or so for hardness. Maybe too high surface speed ? Hss won’t last especially if too fast. Should use carbide. Needs to be held rigid as it will tend to grab. Backlash could also be a problem.

4140HT is one of my favorite materials where a reasonably hard mater is needed and heat treat is not desired. Durabar ductile iron is nice too.

 

[Jake M]

So I got this free chunk of Ampco 22 I think.

I didn't know what that was, so I googled it. Amongst the descriptive results I found (I know what it is now....), I stumbled on this- I can't vouch for it, but you might be interested

https://www.ampcometal.com/documents/ampco_vs_steel.pdf

 

[FZR1KG]

That Ampco 22 should machine reasonably well. Only Brinell 400 or about RC43-45 or so for hardness. Maybe too high surface speed ? Hss won’t last especially if too fast. Should use carbide. Needs to be held rigid as it will tend to grab. Backlash could also be a problem.

4140HT is one of my favorite materials where a reasonably hard mater is needed and heat treat is not desired. Durabar ductile iron is nice too.

Ah, so that made me have to find the actual Ampco type.
Turns out it was easier than I thought. Ampco 26.
Zero elongation material. Even the manufacturer admits its a pita to machine. Instead of cutting it chips off unless your tool angles are right. Machining it reminds me more of scraping than cutting.

I was given a worn out block from a SS forming machine by a toolmaker friend. The toolmaker hated working with it too. Lasts damn near forever in tough service applications, but it is no fun to work with. I didn't have a powerful mill at the time so slow was all I could go. Carbide tended to chip really fast. But I didn't know about the rake angle at the time, not that I had anything in carbide that would have worked. The only endmill that worked was a back cutting endmill. I found out later that's what the manufacturer recommends too.

 

[FZR1KG]

I didn't know what that was, so I googled it. Amongst the descriptive results I found (I know what it is now....), I stumbled on this- I can't vouch for it, but you might be interested

https://www.ampcometal.com/documents/ampco_vs_steel.pdf

I finished the job about 6 months ago. I sure wish I researched it first. I just assumed it would be pretty easy with quality endmills.
I still have some of it laying around but am highly reluctant to use it. Does look purdy though.

 

[benmychree]

Machining Ampco 18 is only mildly irritating, 22 is a big pain in the ass.

 

[GT-6 Racer]

This is good to know. Really have to need the material properties to justify the pain.