What's new
What's new

Questions on shop finishing practices


Aug 24, 2021
I recently started a new job and have a few questions. I am newish to the manufacturing field so forgive my ignorance.

This is a small shop, just two of us, each running a CNC lathe. We primarily make small aluminum parts and finish/prep in house, typically for anodizing. All parts are manually deburred/finished/polished. This is done by chucking each part in a small lathe and rubbing with Cratex and/or various grits of scotchbrite. A lot of the edges of the parts are deburred by using X-Acto blades.

Recently I have been asked to pick out tiny metal pieces left in knurls with an X-Acto knife (for anodizing prep) while looking through a microscope. This takes a tremendous amount of time and seems extremely inefficient. I have asked my boss the reason for this and he said that it's always been done this way.

The time it takes to manually polish/rub each part is huge and picking the knurls is even more extreme, not to mention carpal tunnel inducing. Am I crazy or is this common practice? Is there a simple solution to this? Are these guys just stuck in a "if it works, don't fix it" mindset?

From a bit of research it seems like a vibratory bowl/tumbler and/or a small sandblasting unit would be a good route to go. Faster, more efficient, result in more consistent parts and safer to perform.

Examples of parts:

I appreciate any insight, thanks!


  • parts.jpg
    20.3 KB · Views: 18
If you ask me, and it seems you were, the workflow in your new shop is very, very inefficient. You might try suggesting a tumbler or vibratory polisher. Hell, even a quick swipe with a wire brush for the knurls. But you might get no traction. In which case you should either learn to live with the way they do things or find another job to keep your sanity intact. ;)
Thinking a stiff nylon brush might remove chips without marking finish
Big fan of tumbling, but it is a different looking finish and might not be what the customer wants

You can't program a small corner radius or whatnot to break the edges on those?
I could see some work on the chuck side being necessary, but other than wiping with a bit of scotchbrite those parts ought to come out nice
I tumble a bunch of my parts to deburr sharp edges and for some things it works well. As Gustafson said it gives a different look though. And it won't remove chips from knurls in all probability.

I think your knurl problem ought to be solved in the machine. Maybe more coolant to keep the chips out while the knurls are being made. Maybe cut knurls instead of form knurls. From my limited experience there's no magic formula here. Keep tweaking. Sometimes I follow knurling with a fine wire wheel to brush burrs off the end. For anodizing you need to be careful not to contaminate the part in such a way that it will mess up the anodizing.

Also, order of operations can affect how much deburring. Tumbling does not really do a good job removing large hanging rolled over burrs. I have found that changing to order of operations so that big burrs that get raised are as often as possible removed by the next operation.

You do need to be willing to experiment though. I think the "we've always done it that way" is a killer attitude. On the other hand my last employer was a huge big stupid company. To try combat the "we've always done it that way" mentality they would embrace every new idea. I came away from this experience with my own saying- "90+% of new ideas are stupid ideas". You need to have common sense in what to run with.
Sounds like an ongoing job. Before the next time you run these, look at getting a cut knurl. They give you a lot cleaner knurl with less hanging fines.