Thread: Materials used on Threaded lathe spindles.

Originally Posted by pipeclay

On the Hercus forum there is thread about screw on adaptors for the Hercus lathe spindle.
A post arose in regards to the particular grade of steel being used in the adaptor.
The material is 4140.
Could any members give there opinion on the Pro's and Con's with using 4140 for screw on adaptors.

Hi Pipeclay,

I don't see why 4140 wouldn't be a reasonable choice, but I'm happy to be corrected. I assume you aren't intending to heat treat it, so that means 28-32 Rc.

Pro's would include good machinability, and availability. Con's are it's difficult to weld, tends to crack.. but I don't think you are welding it..

I note that a lot of commercial chucks are "semi-steel", which is cast iron with a varying proportion of steel (unknown alloy) added. If anyone knows what exactly qualifies as semi-steel, I'd be interested.... been thinking I'll throw in some steel scraps into the next cast iron pour and see what comes out..

Back to the question, I can't think of any substantial reason not to use 4140..

Regards
Ray

HI pipeclay,
I once had a Model 'A' 9" Plain Bearing Lathe, but I Sold it and ended up with a Hafco AL-960B Lathe. If I was going to make a Screw on Adaptor for a Hercus Lathes Spindle, I certainly wouldn't make it out of 4140. The reason that I wouldn't use 4140 is that it is quite a hard Material as it is (without being hardened or tempered). Being such a hard Material if something were to go wrong IE a Jam Up the 4140 is likely to Damage the Thread on the Lathes Spindle upon ie Removal.

The Material that I would choose to make the a Screw On Adaptor for a Hercus Lathe
out of would be either 1040, 1045 or Cast Iron. The reason that I would choose either of the three materials is, because all of them are softer than the Lathes Spindle. Being a softer Material they are all less likely to cause any Damage to the Spindle Thread should any problems occur during a Machining Operation on the Lathe. I seen somewhere recently (might have been in the Hercus Forum) that 1045 was used for the Lathes Spindles. I imagine that the 1045 would have been Hardened and Tempered thus making it harder than plain 1045.
I believe the reason that Backplates for Lathe Chucks on Threaded Spindle Lathes are made from Cast Iron is, because Cast Iron is less likely to Bruise the Lathes Spindle Thread than what Steel is. Just My opinion.

HI RayG,
I don't know if this anwers Your Question about Semi Steel or not, but here is a Weblink Semi-steel - Wikipedia, the free encyclopedia

Originally Posted by steran50

The Material that I would choose to make the a Screw On Adaptor for a Hercus Lathe
out of would be either 1040, 1045 or Cast Iron.

1040 and 1045 would be as hard as 4140.. it is the carbon content of steel that solely determines final hardness after heat treatment..

It will all depend on what hardness you buy your material.... I am sure most 4140 sold in Australia is what is called pre-hard.... That is, it is sold already hardened... I asume 1040 and 1045 is sold the same way...

HI RC,
What I didn't State in My Post was that I would not bother to either Harden or Temper either of the Materials that I chose to use. The reason being as I want the Material I chose to be softer than the Lathes Spindle so as to lessen the likelyhood of any damage to the Lathes Spindle Thread should Problems arise when using the Lathe.
As as I know too 4140 is Sold Prehard. 1045 can be Sold in a Normalised form. 1040 well its not that hard of a Steel anyway.

Hi .RC, Steran50,

Just a clarification, 4140 comes either annealed or pre-hardened, the pre-hardened state is NOT fully hardened it's only around 28-32 Rc, after heat treatment it's much harder 46-52 Rc.

If 4140 being too hard is the problem for using it on spindle adapters, you could always anneal it, and then it would be softer than the 1045.

Regards
Ray
.

HI RayG,
Thanks for the Handy Info on the 4140, I was not aware that it was available in Annealed Form. I did know that 4140 Steel can be made harder though. All the same thats Good Info to know, Thankyou Ray.