SCM440 case harden

[APW]

Hello everyone,
I have a customer who asked to machine some emergency 5C collets for them and case harden to 40-50rc. I bought the collets from Lyndex and they told me the steel is SCM440 however my heat treat company isnt familiar with that material. Have you guys heat treated SCM440 or heat treated 5C collets, if so what process did you use?

Thank you for you help.

 

[taiwanluthiers]

I thought case harden is only for low carbon steel...

I think SCM440 is just another name for 4140 steel, so it heat treats like 4140 steel.

 

[EmGo]

I thought case harden is only for low carbon steel...

Not entirely ... nitriding is a form of case hardening and it works on various high-carbon steels. But I s'pect he is referring to carburizing, which does not make sense on 4140.

 

[richard newman]

Can you heat treat a finished collet without distorting it and requiring re-grinding?

 

[MrWhoopee]

For the hardness specified case-hardening should not be necessary. It is at the upper end of the hardness range for simple heat-treating of 4140. Case-hardening is possible for higher hardness requirements but not recommended as it can result in a brittle product. Distortion is likely in either case.

 

[4GSR]

I offer one suggestion here. Do not cut the collet fingers all the way thru. Of course, may not have this option if you bought these already split. Leaving them partially split will allow you to nitride the collets without the collet fingers going all over the place. Another suggestion is to have them ION nitrided. Almost no distortion using this process. Also QPQ would be the choice of any surface treating for hardness. Again, very little distortion using this process. There are sources for any of these processes here in Texas. The only real problem is cost. Most have a minimum charge. Ken

 

[dian]

yes, it will ion plasma nitride up to 650 hv and a 0.6 mm case. its done around 1000°f and gets you good surface finish.

 

[guythatbrews]

Ion nitriding may be the thing if you are looking for wear properties only. Ask your heat treater what they think. It's kinda expensive. Any other heat treat will likely not be good.

Have you tested the purchased collet hardness? I agree they ought to be above 40 already.

 

[DDoug]

Hello everyone,
I have a customer who asked to machine some emergency 5C collets for them and case harden to 40-50rc. I bought the collets from Lyndex and they told me the steel is SCM440 however my heat treat company isnt familiar with that material. Have you guys heat treated SCM440 or heat treated 5C collets, if so what process did you use?

Thank you for you help.

When you asked Lyndex about the material, why didn't you ask them how to heat treat ?...

 

[Matt_Maguire]

If the 4140-42 (.40-.45C) is tempered @ 800°F after the quench you get a 45Rc (430BHN) part, about 210Kpsi tensile & 190ish yield for strength.

I’d suspect the emergency blanks aren't that hard… If it were for low use I’d prolly see if the heat treater had an induction HT tool that would fit in the bore after machining. I can’t remember seeing any that could work in a 1/2” hole though.

Agree that nitriding gets the hard skin but it’s cashy.

Good luck,
Matt

 

[dian]

you just have to find somebody who puts it into the "oven" with something else. the process will not be optimized, but it doesnt have to be in this case.

(the last little part i did cost me nothing.)

 

[taiwanluthiers]

Or get a few refractory bricks, stick a propane torch in it until it reaches the right temperature, then dunk it in oil or something.

 

[taiwanluthiers]

It all depends on the OP's budget.

Want it done on the cheap or done right with correct schedule and specification, it's going to cost.

Just want it harder than annealed? Torch and refractory brick should do.

 

[DDoug]

Or get a few refractory bricks, stick a propane torch in it until it reaches the right temperature, then dunk it in oil or something.

You can only doo R-8 Collets that way.....

 

[taiwanluthiers]

Can do NT40 fixtures if necessary...

 

[michiganbuck]

Seems like the Lyndex brand is claiming greater hardness.

https://www.lyndexnikken.com/images/files/ER.collets.pdf

 

[dian]

Can do NT40 fixtures if necessary...

how do you recommend to heat it with the torch?

 

[taiwanluthiers]

You encase it in fire bricks then stick a torch in it. It may take some time, but it will heat the part to the right temperature.

 

[EmGo]

You encase it in fire bricks then stick a torch in it. It may take some time, but it will heat the part to the right temperature.

It'd maybe be better if you didn't talk about things where you don't have a clue.