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rloo
11-18-2008, 04:59 PM
Looking to find out if anyone can tell me what type of steel is commonly used for the tool holders. We're looking to make our own to save some $$. Ideally a grade that's strong and rigid but would "give" in the event of an impact? Thanks!

Geof
11-18-2008, 05:49 PM
Hot rolled C1018, plenty strong enough but ductile enough to yield a bit if you bash it.

You can also use cold rolled but depending on what machining is done on it a piece of cold rolled can distort as the rolling stresses are relieved.

If you want easy machining use C12L14 it has a yield strength a bit below 1018 but is much easier to machine and, particularly, tap.

CarbideBob
11-18-2008, 10:51 PM
Commercial toolholders will normally be 4140, typically heat treated to 42Rc but just about any steel will work for low volume uses.
Milling cutters are often made from 4140 pre-hard because they warp too much in heat treat.
Bob

mc-motorsports
11-18-2008, 10:53 PM
Yep, 4140, the ones I make are made from prehardened material 36-38 Rc, lathe tool holders.

Geof
11-18-2008, 11:01 PM
Commercial toolholders will normally be 4140, typically heat treated to 42Rc but just about any steel will work for low volume uses.
Milling cutters are often made from 4140 pre-hard because they warp too much in heat treat.
Bob

The bolt on tool holders and boring bar holders on Haas machines are definitely not 42Rc and they do not machine like 4140. Similarly all the tool holders on the manual machines I used to have were all non-hardened low or medium carbon steel. Milling holders are a different thing they are hardened and ground.

rloo
11-19-2008, 09:42 AM
I suppose it might depend on the tool holder application but some people feel that the type of steel should be able to "give" in case of an impact and not be too hard that it could damage the carriage or spindle. Any thoughts?

Geof
11-19-2008, 10:20 AM
I think there is some validity in the 'give' idea. The peak forces involved in stopping something over distance of 0.01" are ten times what occurs if something is stopped over a distance of 0.10". I think the 'give' displayed in this picture may have helped save my spindle bearings in a recent crash, my worst ever.

http://www.cnczone.com/forums/attachment.php?attachmentid=59470&d=1210645888

rloo
11-19-2008, 10:44 AM
Nice illustration Geof, I was probably not specific enough in my original question as it might be different in my case... The "tool holder" I was refering to is one where you'd bolt on a carbide bit and then place into the machine. It may be reffered to as the "shank"? We've been buying these from Mitsubishi to use in our screw machine gang posts.

mc-motorsports
11-19-2008, 07:11 PM
The bolt on tool holders and boring bar holders on Haas machines are definitely not 42Rc and they do not machine like 4140. Similarly all the tool holders on the manual machines I used to have were all non-hardened low or medium carbon steel. Milling holders are a different thing they are hardened and ground.

I don't think he means a "tool holder" in the respect your refering to, more of a tool post. I think he means more of an insertable turning tool. 4130 36-38 Rc, prehardened, the pocket flatness and angles are critical depending on the insert being held.

CarbideBob
11-19-2008, 07:56 PM
Toolholder mounts or "nests" and bushings are harder so they won't wear.
6150 or 8620 somewhere in the low 60's Rockwell.

Insert holders will range for 32-48 Rc depending on who yet get them from.
Different mfgs have differing specs. One advantage to the softer holders is that you can easily cut them to length on a a bandsaw.
Bob