4140 annealed for parts...?

[EmilioG]

Has anyone here worked with 4140 steel to machine parts or fixtures?
I’ve read competing views. Is it tougher than O1 ? I know that hard steels can be tough on cutters.

 

[chips&more]

It all depends on how hard it is? And then you decided on what machining techniques to use. Back in the day, I machined a lot of 4140. And did so with normal HSS. However, nowadays I fancy 1144 & 12L14. I don’t need the metallurgy challenge anymore…Dave

 

[francist]

I've used it for turning parts on the lathe -- I actually like how it handles. I use HSS mostly and it works great. Not a big lathe either -- 6" Atlas.

-frank

 

[JimDawson]

Annealed 4140 machines OK, tougher than mild steel but not bad to machine. O1 is pretty forgiving, but is more prone to work hardening than 4140. Keep cutting speed around 80 SFM for HSS cutters and a manual mill.

 

[Bob Korves]

Machining 4140 you have to be careful not to work harden it while machining it. Do not dwell at the beginning and ends of cuts. Use deep enough cuts to get under the "skin" of the previous pass, and do the same with the feed rate. Do not try to sneak up on your size. When you get close, divide the total remaining stock to remove into a few equal passes, and then keep track of what you are actually achieving on the first passes so you know what to expect on the last one, adjust as required, then go for it. Partially hard 4140 turns very nicely with a good finish, but requires some power and good carbide inserts. Annealed 4140 is difficult to get a really good surface finish with, in my limited experience. I have zero experience with turning full hard 4140.

 

[EmilioG]

This is annealed 4140, not hard. I'm wondering if it's more difficult than O1 tool steel annealed.
I've heard and read the opposite Bob, that 4140 leaves a nice surface finish when cut properly. I've used carbide without problem on O1 and W1.
I've only chipped carbide once because it
I need a good steel for a fixture plate, something that doesn't ding easliy annealed. I'm not heat treating.
Maybe I should just use mild steel and just be careful with it. I just don't like the way 1018 tends to rust.
!2L and A36 is too soft and I don't want any lead content. Which steel would you recommend?

 

[Bob Korves]

This is annealed 4140, not hard. I'm wondering if it's more difficult than O1 tool steel annealed.
I need a good steel for a fixture plate, something that doesn't ding easliy annealed. I'm not heat treating.
Maybe I should just use mild steel and just be careful with it. I just don't like the way 1018 tends to rust.
!2L and A36 is too soft and I don't want any lead content. Which steel would you recommend?

If I wanted to make a fixture plate, I would start here
https://www.bing.com/search?q=ground+steel+plate&pc=MOZI&form=MOZSBR
to look for material. Let someone else make it flat...

 

[Doubleeboy]

This is annealed 4140, not hard. I'm wondering if it's more difficult than O1 tool steel annealed.
I need a good steel for a fixture plate, something that doesn't ding easliy annealed. I'm not heat treating.
Maybe I should just use mild steel and just be careful with it. I just don't like the way 1018 tends to rust.
!2L and A36 is too soft and I don't want any lead content. Which steel would you recommend?

What about mild steel and then case harden with Cherry Red, then grind or if no surface grinder sand it for nice finish.

 

[EmilioG]

I already have flat ground O1 tool steel. I'll probably use that for now. 1" thick pieces. I got them for a good price.
Ground flat stock starts to get expensive over 1/2" thick. These are small 3" x 3" pieces. Thanks to all for your quick replies.

 

[Bobby Bailey]

We machine 4140 as a regular thing, It is the most common gun barrel steel. Using HHS it machines and reams real easy and is easy to get a good finish on.