Broaching stainless steel

SDE · Jun 1, 2015

An engineer said that I should slow the speed down as slow as it will go and I should be ok. The bar is an involute spline designed for cast iron. When the bar was about 2/3s thru the part the pounding sound changed pitch and I stopped the pull and got the engineer. He had heard me all the way in the office. I slowed it down some more and he said to stop because he did not the bar to be broken. Anyone with any experience broaching SS? Theses are specials for a customer in the Dairy industry.
Thank you
SDE

DetailDave · Jun 1, 2015

If it is a through key way (not blind) we Wire edm quite a few splines and key ways in stainless. It is expensive but a lot of customers would rather not risk breaking a broach and possibly scraping a part.
Good luck

SDE · Jun 1, 2015

The salesman told the customer that we could fill the order in a week. We need to assemble it and then test it to check on how the SS interacts with the other components. If we can not do the broaching in house, that will add two weeks minimum.
Thank you
SDE

Hendrik · Jun 2, 2015

The problem of machining stainless steel (be it drilling, milling, turning, etc.) is that the chips tend to weld to the cutting piece. Going slow and repeated cleaning of your broach may help. There are special anti seize fluids/pastes available for stainless. See link below. abundant application of these may help you get through your order with your broach intact.
HTH, Hendrik
Google search for

SDE · Jun 2, 2015

I had wondered if there was a lubricant that could be used beside just the coolant. I will pass this along to our engineer. I wish Kingsford had told us about this, when they were asked about the broach bars ability to cut SS.
Thank you
Steve

RM-MN · Jun 2, 2015

You need to explain to the salesman that the next time he promises a stainless steel part to be done in a week that you will be using his nose for the broach.

JF in MI · Jun 2, 2015

Do you think it could have work hardened? I don't know much about SS except that there are numerous alloys.

Hendrik · Jun 2, 2015

Good thought; one cannot rule out work hardening.
I'm sure though that SDE is not cherishing the thought of having to (repeatedly?) anneal the pieces he's working on.

JMS/.MN · Jun 2, 2015

or another body part....

Ken Macfarlane · Jun 2, 2015

Do you have a shaper to plug away at it without breaking a broach? There is a broad range of metals falling under the label of stainless and lots of them are a pain to machine. Galling, work hardening, just simply hard etc.

SDE · Jun 2, 2015

They used a .062 slitting saw, and cut the part on two sides. I thought by using a hydraulic press, the part would break, after all, they had cut it as close to the bar as they could. The part did not break, but the bar did. The new bar will take about 3 months to arrive and I have a job that I need it for today.

When I got to my supervisor's office he said that Cal said he needed to go home and change his pants. Maybe Cal did what I said, when it broke.
As they say, good news travels fast. He knew before I said one word.
SDE

Ken(MI) · Jun 3, 2015

The answer is in your original post, the broach is designed for cast iron, not stainless steel, stainless doesn't present any particular problems when using the proper tooling and lubricants, it will pull harder than cast iron, and you need to monitor tonnage closely and make sure the broach is completely free of chips between pulls, and the one rule you must never break is about maximum length of cut for the particular broach being used, the length of cut you can get away with in cast iron will be significantly more than a broach with the same pitch in stainless. My guess would be that the problems you have came from exceeding the maximum length of cut, compounded by an improper grind on the teeth for the material being cut, and possibly use of the wrong coolant, oil should never be used on cast iron, and for maximum tool life, should always be used on stainless and most other tough alloys. Most of our broaching work is on tough, pre-hardened alloys, exotics, and stainless, we turn away cast iron work because we just are not set up for it. What is the spline you are trying to cut and where are you located? We may be able to help. Good luck, I've been where you are, and it's no fun.

Spook · Jun 3, 2015

(quoted from post at 06:44:13 06/03/15) The answer is in your original post, the broach is designed for cast iron, not stainless steel, stainless doesn't present any particular problems when using the proper tooling and lubricants, it will pull harder than cast iron, and you need to monitor tonnage closely and make sure the broach is completely free of chips between pulls, and the one rule you must never break is about maximum length of cut for the particular broach being used, the length of cut you can get away with in cast iron will be significantly more than a broach with the same pitch in stainless. My guess would be that the problems you have came from exceeding the maximum length of cut, compounded by an improper grind on the teeth for the material being cut, and possibly use of the wrong coolant, oil should never be used on cast iron, and for maximum tool life, should always be used on stainless and most other tough alloys. Most of our broaching work is on tough, pre-hardened alloys, exotics, and stainless, we turn away cast iron work because we just are not set up for it. What is the spline you are trying to cut and where are you located? We may be able to help. Good luck, I've been where you are, and it's no fun.

We used to broach cylinder blocks and bearing caps, cast iron, dry.

Broaching stainless steel

SDE

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DetailDave

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SDE

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Hendrik

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SDE

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RM-MN

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JF in MI

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Hendrik

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JMS/.MN

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Ken Macfarlane

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SDE

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Ken(MI)

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Spook

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