material/heat treat choice for hot working

[UncleFrank]

We're winding 3/16 steel rod around a 5/16 mandrel to make something that looks like a spring several inches long when completed. We're heating the wire red hot, with a torch I assume, as we wind it around the mandrel.

The mandrel has a partially thru hole close to the end, similar to the eye of a needle, to hold one end of the 3/16 wire as we wind it so there's only about 1/16 edge distance left on the 5/16 mandrel.

The eye end has broken off and the mandrel shows some degredation from heat. I suspect the original mandrel was 5/16 drill rod since that's readily available.

Is there a better material choice for the mandrel or a specific heat treating process for drill rod that might extend the life of the mandrel?

 

[Pattnmaker]

H13 Will work much better for your application. Don't have my heat treaters guide handy for Rockwell that gives you max strength. Sure you can find it online.

If you're going to do a low tech shop ht H13 is way different than typical drill rod. Heat to a yellow ( hotter than most steels). Air quench a fan can help. Then heat to where you can barely just see a dull red held in a darker place in the shop. In the shadows. This is a good thing for hot cutting tools. I suspect it will work for a mandrel.

 

[Thunderjet]

Is there a better material choice for the mandrel or a specific heat treating process for drill rod that might extend the life of the mandrel?

Inconel, if you can find it.

Try here:
Object moved

 

[implmex]

Hi UncleFrank:
Inconel is available from McMaster Carr, but not in 5/16" diameter...only 1/4 and 3/8.
So you'd have to find another source or have a bar centerless ground to diameter for you.

Another choice is High Speed Steel.
You can get 5/16" drill blanks from McMaster for cheap.
It's harder than a woodpecker's lips so you may have some fun putting your cross hole in it unless you have access to a sinker EDM.
In a pinch you can do it with carbide, but it's a fun challenge.

HSS is super strong and tough, with excellent red hardness, but you can break it if you try hard enough.
So you may bust one from time to time.
But a 6 bucks a pop, who really cares?

Cheers

Marcus
Implant Mechanix • Design & Innovation > HOME
Vancouver Wire EDM -- Wire EDM Machining

 

[Erich]

Why are you doing this hot? Lots of spring winders can form 3/16 music wire COLD.

 

[52 Ford]

Inconel was my first thought, too.

Going to be a pain in the butt to make that through-hole without EDM.

HSS would be a good choice, but again - making the through-hole is going to be challenging without sinker EDM.

What about 309SS?

OR you could use a mandrel with a through bore and run coolant through it...? I dunno.

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[gbent]

Just out of curiosity, how do you get the end of the wire out of the hole after you have hot wound the wire around the mandrel?

 

[52 Ford]

Just out of curiosity, how do you get the end of the wire out of the hole after you have hot wound the wire around the mandrel?

Put the lathe in reverse and unwind the wire from the mandrel

I'm joking. You cut the bit if wire that's in the hole off of the coil and slide it off the mandrel.

These are my favorite wire cutters. Crescent H.K. Porter 0890MA $37.09 Compact Bolt Cutter with Flush Cut Blades and Plastic Dipped Handles | Zoro.com Knipex makes an identical pair.

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[52 Ford]

Just out of curiosity, how do you get the end of the wire out of the hole after you have hot wound the wire around the mandrel?

https://youtu.be/jAawhg6JtyY

Here's a great video talking about making springs on a lathe. I recommend watching it. Even if you already know how to, it's just an entertaining video.

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[UncleFrank]

Thanks for all the replies. I really appreciate it.

The shop uses a cutoff wheel on the 90degree end to remove the "spring" from the mandrel.
I noticed the different materials usually come 3/8 but we have centerless so could come up with 5/16 dia.
I'm sure we have some inconel somewhere but probably sheet/plate not rounds. I might be wrong; I'll check.
We have a dedicated heat treat shop that, I hope, can handle whatever we decide to use.

The shop isn't actually making a spring. They part the "spring" off eventually into little donuts for some kind of washer-looking part. I don't know who came up with that part design or the tooling concept but whatever.

The video did give me an idea. Use a cap screw and a little clamp against a notch in the mandrel to hold the wire instead of the partially thru hole which would also eliminate the cutoff wheel oprn. I'd thought about a notch and a C-clamp but didn't figure that would hold well enough.