Hardening ball on end of fine threaded stud

[DanBrub]

I’m looking for options to harden an 8mm dia ball machined with a 5mm x .05 pitch threaded extension that is 23 mm long. I don’t have the ability to thread after heat treating the entire part and am concerned that a normal heat treat would damage the thread crests so am thinking of ways to just treat the ball. Any easy solutions! The material has not been chosen but can be any heat treatable material so if that helps a recommendation please advise.

 

[MrWhoopee]

It really shouldn't be that hard (!) Run a nut up over the threads under the ball, flame harden the ball and remove the nut. Not sure I'd even bother using the nut.

Which material depends on what's available and how hard it needs to be. O-1 drill rod (silver steel across the pond) is readily available and gets up to the low Rc-60 range.

 

[Garwood]

A friend has made a ton of parts like this.

Make a fixture to hold a ball bearing on the end of your rod. Silver braze it on.

With a good fixture you can hold a couple tenths alignment.

 

[DDoug]

Stand the stud up in a pan of water with the ball above the water.

 

[eKretz]

My 2¢: make the ball with a female thread so you can change the threaded portion if necessary.

 

[Conrad Hoffman]

Make a copper cup to go against a steel ball and spot weld the ball on a shaft.

 

[dgfoster]

First thing to do would be to just try making one---I'd suggest 0-1 as recommended by MrWhoopee. There will be no appreciable damage to the threads from torch hardening. You can just torch harden it by bringing it up to a non-magnetic temp, dip it into canola (or any) oil and swish it around rapidly. If you are making a lot of parts, harden a batch, put them on a sheet and temper them in an oven or kiln. If you are worried about decarb of the threads, you COULD use a anti-decarb powder. I have some, but would not bother on this part.

This should be super easy.

Denis

 

[jim rozen]

1) use standard 8 mm hard ball.
2) drill with carbide drill for appropriate size
3) press in M5 threads that have been turned down for press fit.

 

[dgfoster]

Depending on the end use of the ball, simply drilling a hole in the hardened ball and Loctiting in a hardened threaded shaft would be a simple solution as well.

Denis

 

[awander]

Whew--those are some mighty fine threads-or did you mean 0.5?

 

[LexD]

Whew--those are some mighty fine threads-or did you mean 0.5?

Yes, the position of the decimal point is rather important.

 

[Joe Gwinn]

I’m looking for options to harden an 8mm dia ball machined with a 5mm x .05 pitch threaded extension that is 23 mm long. I don’t have the ability to thread after heat treating the entire part and am concerned that a normal heat treat would damage the thread crests so am thinking of ways to just treat the ball. Any easy solutions! The material has not been chosen but can be any heat treatable material so if that helps a recommendation please advise.

Does the ball need to be hard all the way through, or can it be case-hardened?The old gunsmith approach was to heat the ball a bit and dip it into some kind of sugar, and then heat it up to a red heat and hold for a while, then quench it in water. Temper if needed.

 

[DanBrub]

Does the ball need to be hard all the way through, or can it be case-hardened?The old gunsmith approach was to heat the ball a bit and dip it into some kind of sugar, and then heat it up to a red heat and hold for a while, then quench it in water. Temper if needed.

Thx Joe…cause hardening would be sufficient for the intended application. Just wasn’t sure I could get the ball up to the case hardening temp and soak it long enough the get the carbon into the surface to a reasonable depth without the heat also moving up the threaded section and causing thread damage

 

[DanBrub]

Yes, the position of the decimal point is rather important.

Yea, 0.5 not .5! Not sure I could even begin to single point a .05! Those tricky decimals got me good this time

 

[strokersix]

Use the head of a cap screw as the ball material. Turn the head into a ball. Might not be a complete ball but maybe that's ok. How hard does it need to be? Just a random thought.

 

[Joe Gwinn]

Thx Joe…cause hardening would be sufficient for the intended application. Just wasn’t sure I could get the ball up to the case hardening temp and soak it long enough the get the carbon into the surface to a reasonable depth without the heat also moving up the threaded section and causing thread damage

As others have pointed out, one can protect the stem and threads.

The modern equivalent to sugar is Kasenit. There are many how-to videos.

 

[R. Dan]

I wouldn't be surprised that there might be a tooling ball available out there somewhere that is exactly what the op needs.

 

[Erich]

17-4 ph. In the solution treated state it machines fine. Heat treat is 900F for 1 hour.
Won't do squat to the threads.

 

[boslab]

Bucket and oxy acetylene, stick hand in water holding the ball sticking out of the water, heat til red hot, pull under water, aka spot hardening
Mark

 

[MrWhoopee]

Bucket and oxy acetylene, stick hand in water holding the ball sticking out of the water, heat til red hot, pull under water, aka spot hardening
Mark

I like it! Just make sure it's water-hardening (W-1), not oil hardening, or it may crack.