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world gathers for metal finishing
Q&As since 1989


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Dirty blind threads

Hello Jack,

I work for a medical device company which is in the business of manufacturing orthopaedic surgical instruments. We're currently struggling with the successful cleaning of a surgical instrument made of 455 custom s/s. The problem area is a blind 10-32-unc thread which when checked with a Q-tip [affil links] after passivation and cleaning still shows residue. We've clean the parts in an ultrasonic cleaner with micro 90 before we heat treat and at final inspection before we put them through the passivation & cleaning line. We still get mixed results. I think it's heat treat scale which is loosened up at passivation but we can't figure out how to prevent it. Can you help?

Lionel Fuentes
Manufacturing Engineer - Mahwah, NJ, U.S.A.
2004

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The KISS principle in this case is to either insert a plug in hole because of its small size a 10-32 screw. Don't mess with chemicals and cleaners.

AF Kenton
retired business owner - Hatboro, Pennsylvania
2004

Yep, you have a big ouch. Heat scale, dirt, or just metal. The only thing worse than heat treated 400 series, is heat treated400 series with blind holes, and the only thing worse is heat treated 400 series with blind holes and EDM.

Jon Quirt
- Minneapolis, Minnesota
2004

If you want the cleanest blind holes and threading, two words come to mind. "Steam Cleaner" Stick the nozzle in the hole and blast away. I also clean my threads with isopropanol and a compressed air blast right on my lathe. Saves a ton of problems later.

Jeff Swayze
things - Kelowna, B.C., Canada
2004