Threading hardened shaft

[Captain K]

Been watching the Clough42 tool post grinder series on YouTube. It’s well done and I’d like to copy it for the most part. Having said that I’m not crazy about his method to retain the spindle, set screws.

My question is what are the chances of threading a hardened shaft with a carbide insert? How about DOC, speed, lube? It’s a collet extension as shown in the link

https://www.ebay.ca/itm/302894733149

[nickel-city-fab]

I've had no problem doing hardened stuff with carbide. Just need to take extra care on the setup making sure everything is tight, and go slower, using less DOC.

[Toolguy]

Same here. Don't try to hog it. Nice easy cuts, don't need high RPM just because it's carbide.

[old mart]

I have had no trouble putting spanner flats on the earlier er collet arbors which are medium hard, using solid carbide and would not hesitate to try single pointing with carbide inserts. I always use tapping oil, slow rpm and small cuts down to 0.001" depth towards the finish. Not a job for HSS, even cobalt.

[MrWhoopee]

Most likely only hardened into the Rc 45-50 range anyway, so not that hard. Shouldn't be that difficult.

[Fasturn]

I've had no problem doing hardened stuff with carbide. Just need to take extra care on the setup making sure everything is tight, and go slower, using less DOC.

Only thing to add is feed with the compound rest @ 29.5 ° dont feed straight in with the cross slide. It creates more tool presure that way. Threads on most lathes are progressive. 1st cut .010, 2nd .006 3rd .004- and so on- DOC. Tap magic, moly-Dee or the other lubes will be fine. You can always turn slower on tuff steel, but too fast and your tool may break or dull. If your lathe is small, reduce those DOC in half. As others said....... take it. Slow!

Built a spindle using that same ER -20 holder 2 yrs ago for spinning wire EDM. Worked well, hope yours does too.

[chipmaker4130]

You're talking about the shank, right? Are you sure its even hardened?

[Fasturn]

I have bought alot of Chinese tool holders over the years and they seem to be 38 -40 Rc scale. Not a problem for a lot of shops, but my 300lb lathe can be challenged. Right tool and experience Goes a long way.

[Captain K]

You're talking about the shank, right? Are you sure its even hardened?

Yes, the shank. No, I’m not.

Clough42 believed his was so he didn’t try and thread it. He also has a bench top lathe.

I have a Colchester Student. It’s obviously not a huge lathe but should handle this with ease.

I will order the shank and report back here with my findings

[Captain K]

Reporting my findings. No trouble at all to single point thread the shank. It is from a far away land so of course your results may vary. I don’t believe it was hardened at all, a file cut it no problem

[Bented]

If you do not know the actual material condition it is not possible to predict the outcome.

There is a world of difference between 50 and 65 on the Rockwell Scale.

That being said, it is unlikely that an ER collet holder is terribly hard so have at it.
Also at $18.00 you have little to lose.

[john b]

After watching Clough42 video 24 where he tries out the grinder. I believe he would have got better results if he had been running the lathe in reverse, like you are supposed to run a toolpost grinder.

[JRouche]

It’s well done and I’d like to copy it for the most part. Having said that I’m not crazy about his method to retain the spindle, se

I think you are ok. I did not do the link, I never do.

I have turned some hard metals. I never asked for info, didnt need to. Most of my questions were already asked and answered here. Just the way it is. JR

They say high grade carbide or whatever needs to tun at so much SFM. I say BS.

In a production shop maybe. Wrong Garage folks, mine is a Two Car.. JR

[Captain K]

It seems you guys did not read my last post. The spindle arrived and had been threaded with no problem.

[JoeLee]

There are a lot of variables involved.
The software for my Vardex thread cutting tools / inserts calculates the number of passes and DOC depending on a few other things.
An example for a 3/8" - 16 thread in low alloy non hardened steel is as follows.

Passes details P1 0.0070 inch P2 0.0058 inch P3 0.0053 inch P4 0.0041 inch P5 0.0034 inch P6 0.0030 inch P7 0.0027 inch P8 0.0025 inch P9 0.0023 inch P10 0.0022 inch

In softer materials like aluminum you can break the rules, and there are a few different working methods like flanking.
On finer pitches I can do both sides in one pass till completed but in deeper larger pitches I have to flank the sides using the compound to avoid chatter.

After a while you kind of get the feel for it. If your cutting up against a shoulder you should cut a relief groove or get real good a backing out and stopping fast.

JL..............