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topic 0620

Rinsing blind holes


Does anyone know of a completely effective, yet cost efficient method for removing finishing solutions from small, blind threaded holes? We have a critical application with numerous 6-32x1/2"deep holes. We have tried multiple rinses, vigorous agitation, hand shaking, and OHSA approved air nozzles. Nothing is 100%. I welcome your suggestions!

Chris Jurey, Past-President IHAA
Luke Engineering & Mfg. Co. Inc.
supporting advertiser
Wadsworth, Ohio

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bill vins
Bill Vins
microwave & cable assemblies
Mesa (what a place-a), Arizona 


In addition to ultrasonics as suggested by Bill, there may be other approaches depending on the process. For example, sulfuric acid anodizers use such approaches as bicarbonate neutralization, or a nitric acid dip to supplant the sulfuric acid. But these ideas may be inappropriate for plating solutions.

Another very important idea is hot, or at least warm, rinsing. I once saw a presentation by Berl Stein of NiCoForm where he demonstrated and graphed how important rinse temperature is in these applications.

What about forced air drying? Is the problem general rusting, or is it an identifiable chemical remain from a process?

Finally, how about plugging the holes? You might want to talk to a masking supplier about this possibility.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


The answer is a processing centre that applies the chemicals and then washes and vacuum dries them to eliminate chemical entrapment. Components are rotated in jigs during processing. A range of systems are available to suit most applications.

Peter Young

Plugs are a way, but they are time consuming. If you can not afford ultrasonics, try putting the rack in your cleanest rinse tank, preferably a hot one, shake the rack and try fill as many of the holes with water. The harder it is to get the plating solution out of the holes, the more likely it is that the clean water will prevent the ingress of plating/cleaning solutions. If possible, rack the part holes down so that it traps air.This would work on only a few percent of the parts. A final solution that I have used is modifying an air chuck with a piece of tubing that has been heated and drawn to a point, and then cut off at an appropriate diameter. This is hooked up to water and used to flush holes. It works, but is a cheap last resort solution if you can not afford the high dollar solution.

James Watts
- Navarre, Florida


The perfect solution for drying blind holes, as well as any other parts consists of a high volume, low pressure, portable air heating unit that runs on 110 volt electricity, and an air hose for drying out blind holes or parts.

Stephen Blagden

If you're using an air hose, hook up a tube with a fresh water supply allowing the water to drip over the nozzle end.when you spray the air the water will be forced into the hole

Ray Salchow
metal finishing shop - Cincinnati, Ohio

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