4130 chromoly

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Dave_C
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Location: Springfield. MO.

4130 chromoly

Post by Dave_C »

I have a request to do some work to fabricate a pair of airplane axels for a new Bearcat kit plane.

This pair of axels will be made from a 1-1/2" cold rolled bar of 4130. I don't know yet if the spec is for pre-hard or some other variant but here are my questions since I have not worked with 4130 in the lathe.

The tooling I have for the job is a center drill, a 1/4" x 12" bit, a 3/8" x 12" bit, both of which fit in my drill chuck in the tailstock and I also have a 1" MT3 bit that fits directly in the tailstock.

The only thing I have to do to these "axel" stubs is to bore a 1" hole in one end about 5" deep and then thread the outer end for the castle nut.

The reason for the 1" hole is just to make the part lighter!

Questions: Is there a risk of work hardening the part if I don't get a good bite on the bit? What do you say constitutes a "good bite"?

I've read some text that say to run it dry, others say wet?

What SFM with HSS bits would you recommend?

Dave C.
I learn something new every day! Problem is I forget two.
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GlennW
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Re: 4130 chromoly

Post by GlennW »

You will get different results depending on the temper of the stock, Annealed, Normalized, or Quenched and Tempered.

I prefer working with harder stock, but I don't turn anything dry, I use flood cutting oil, so, what I do doesn't apply to most. Machining though seems to work well dry with carbide end mills as long as you can put enough speed and feed to it to take the heat out with the chip.

I imagine the stock will be Normalized at the minimum which puts it around 97k tensile.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
choprboy
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Re: 4130 chromoly

Post by choprboy »

I have turned a bunch of 4140, 1-4" pins/collars/threaded rods, no idea what temper, whatever IMS sells. A bit of brushed on cutting oil, HSS drills and threading/boring tooling, or high speed and carbide inserts. Chips come of hot and can take a bit of fiddling with speeds and feeds to make a clean chip (vs. long strings), but leaves a great finish.
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GlennW
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Re: 4130 chromoly

Post by GlennW »

You might consider grinding a radius on the corners of that 1" drill.

I'd drill it to about 7/8" and then bore the rest with at least a 1/32" radiused tool bit.

Better concentricity, better finish.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
johnfreese
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Re: 4130 chromoly

Post by johnfreese »

The material in the annealed state turns and drills easily. Speeds will be a bit lower than for mild steel, about 85 sfm for HSS tools. Both carbide and HSS work well. In the re-hardened state it can be turned and drilled relatively easily. Speeds will be about 70 sfm for HSS tools. As to the design details like corner radius, etc. follow the plans exactly.
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Dave_C
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Re: 4130 chromoly

Post by Dave_C »

Thanks for the feedback!

I think I have enough info to get the job done..

Dave C.
I learn something new every day! Problem is I forget two.
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