Suitable Stainless Steel for Jig Fixture Without Heat Treatment

[JCReynolds79]

Hi All,

Sorry but this is a request for suggestions as my knowledge of various stainless grades is not great.

We are designing a jig for inspection. Part of this jig is a fixture, used to calbrate the jig. This fixture is basically 3 plates, bolted/dowelled together (to form a book-end shape, if you know what I mean). This bolted assembly is then finish ground (on selected pads) to size. We originally specified 440C plus heat treatment to get it very hard to be wear resistant, as this is a tool that will be handled and taken in and out of the jig, put on shelf etc, so just wanted to make it hard wearing. We decided that heat treating the bolted assembly might prove difficult and add perhaps unnecessary cost, so want to just try and make it from something reasonably hard that will not need heat treating after.

Our initial idea was to still go for 440C but without the heat treatment, seeing as it is quite hard annealed anyway...but this might be costly. I was wondering if there were any cheaper/more appropriate options? I am thinking 304/316 is too general purpose. Want to find something harder that someone can machine/grind for us and avoid the post heat treatment.

Thanks in advance.

Regards,

Jon Reynolds

 

[EdStainless]

Either you need some wear resistance, or you don't.
You could use 440C, or even a PH grade such as 17-4PH.
But in either case the final grinding would need to be done after they are heat treated and assembled.
Most angle blocks are cast as single pieces, then hardened, and finish ground.

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P.E. Metallurgy, Plymouth Tube

 

[JCReynolds79]

Hi EdStainless,

Thanks for the response. So if the 440C or 17-4PH was supplied in a form able to be machined (annealed) would it not be very hard, compared to say 304/316? Is it "pointless" unless I heat treat after majority of machining, then assemble, then final grind? I was just hoping for something harder than 304/316 without having to heat treat, but still be able to make.

If only I could cast I would be happy, but this is a 1-off so not an option.

Regards,

Jon Reynolds

 

[EdStainless]

The 17-4PH might be a good option.
Reasonable to machine in the annealed condition and simple aging treatment with not much distortion.
This would make your final grinding much easier.

If something is reasonable to machine then it probably isn't hard enough for good tooling.

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P.E. Metallurgy, Plymouth Tube

 

[tbuelna]

It seems highly unusual that you would use a calibration fixture under conditions where it will suffer abrasive wear. Do you have some procedure for monitoring the condition of the calibration fixture?

I don't know the exact configuration of your calibration fixture's control surfaces/features, but if wear of these surfaces is a concern then I'd suggest using a piece of very hard material (like SiN) bonded to a welded & stress relieved stainless steel frame at each control surface location, that can be finish ground. These adhesive bonded ceramic pads can be replaced/reworked fairly easily if excessively worn.

 

[JCReynolds79]

Hi, thanks again for replies. I am not expecting the tooling to be 'worn' during use. Its when the setter is inserted and removed from the jig it sets that I am just trying to protect for, as it will inevitably get knocked about a bit. Maybe put on a shelf/workbench too hard, etc...just trying to make it a bit robust.

Maybe I could make it out of something not quite as fancy as 440C, just something a bit cheaper/machinable. Machine each separate plate, heat treat each plate, THEN do my assembly and final grind...

How about a 410 grade?

Regards,

Jon Reynolds

 

[EdStainless]

I still think that 17-4PH would be a good option.
It is reasonably easy to work with.

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P.E. Metallurgy, Plymouth Tube