Threaded key inserts, Need hard material 1

[dalegoldston]

I am looking for a 400 series S/S Key insert or some other material that is more durable, all that I have been able to find is carbon steel and 303, which both are not sufficiant for my needs. Any help with vendors would be greatly appreciated.

Thanks
Dale

 

[MintJulep]

http://www.cartech.com/products/wr_...ml?leftn=our_products&lefto=empty&lefti=empty

 

[Kenneth]

Key-locking threaded inserts manufactured from A-286 are widely used in aerospace under NAS1395 and MS51830 part numbers. A-286 is a highly "durable" material...

http://www.spstech.com/aero/prod_lit/insert_brochure.pdf

http://www.alcoa.com/fairchild_fasteners/catalog/pdf/Tridair-Keenserts_Inserts_and_Studs.pdf

 

[dalegoldston]

Thanks Kenneth, Do you know of any other key inserts made from different materials or is pretty much it. I havent had much luck finding any other.

Thanks
Dale

 

[GBor]

I'm not a materials expert, but you may also want to look at Nitronic 50 or Nitronic 60. I've used them in the past for similar applications. You could also look at precipitation hardened steels (15-5, 17-8), but they are probably more expensive than the A-286 that Kenneth suggested.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group

 

[Kenneth]

I note that SPS lists Inconel 718, 17-4 PH and Titanium as material options on page three of their document I linked above (first link).

But I'll hazard to guess these may be vendor parts numbers and/or "specials" that will have limited sources and availability (and higher costs/leadtimes) compared to the MS and NAS standard part numbers. The MS and NAS parts are relatively readily available as "Stock" items from multiple distributors, and largely available due to the distributor's volume purchasing) in quantities less than the full production run/setup that a manufacturer is probably going to want to charge you for a "special".

If your quantity requirements are less than staggering and you can live with any of the standard materials, I'd strongly suggest the specification/use of the MS or NAS parts.

 

[dalegoldston]

Well seems that alcoa can help me out with a 4140 chrome molly insert or a A286 that are in stock. So thanks for all the help I believe I am out of the dog house. Well till next time.

Thanks
Dale

 

[Tmoose]

How are the non-durable inserts failing?

 

[rorschach]

A-286 is a corrosion resistant alloy, 4140 is not, so if corrosion is or could be an issue, go with the A-286 ones and save yourself some heartache.

 

[dalegoldston]

The carbon steel inserts are stripping out the first few threads. Our test guys use pnumatic tools for installing and removing assemblies and these are tearing up the threads in the inserts. Also there should not be any moisture present during the use of this fixture it is a vibration fixture.

Thanks
Dale

 

[Kenneth]

While a higher strength insert material may minimize insert stripping at the present bolt thread length of engagement and torque level, check to make sure that that your test guys are using bolts of adequate length to fully engage the internal insert threads when installed in your stackup(s). Inserts "stripping out the first few threads" is a pretty darn good indication that the bolts being used probably aren't long enough.

 

[rorschach]

some rules you need to implement in your vibe test shop if you have not already done so.

Make sure you have the proper length bolt. Never run a fixture with too short a bolt. You should ALWAYS have at least 1.5D of thread engagement, but do not exceed maximum engagement depth as damage to the vibe table will usually result.

Make sure you have torqued it to the proper torque. running a fixture with incorrect torque can lead to excessive movement of the payload and poor coupling if it is too loose, and can break heads off if it is too tight. Ideally you want to torque to around 85%-90% of yeild. This leaves little margin for error, final torquing should therefore be done with a calibrated micrometer type torque wrench, not an impact gun.

 

[yates]

Kenneth is 100% right. Take a look at bolt length before you take the tyrouble to change insert material.