Polishing Engine Cases in a Vibrating Tumbler

[Dan McEntee]

    The title of this post pretty much explains what I want to do. When rebuilding engines that have seen a lot of time in use or abuse can use a sprucing up. I got a decent deal on a Harbor Freight Vibrating Tumbler and have been researching different type of media. I have seen many other parts in my work history that have been through this process to deburr parts and put a polished finish on them. I think this is how Fox, and maybe others, used to polish their cases in a production environment. My late younger brother had a very large tumbler that was big enough to put motorcycle tanks in and besides using it to process parts he had machined he also used to to remove rust from inside motorcycle tanks by filling them with one type of media for that job and then put a different kind in the bin for it to ride on.

   I got a tub of some triangular ceramic media when I bought the tumbler, and first experiments with that on some Fox cases weren't too encouraging, and I think they may be too big. I got some walnut shell media off eBay and tried that for a quit tumble and I think it may be for a final finish.

   Does anyone have any experience with cleaning up engines cases with this method? Be tween model engines and motorcycle parts I think I can get some good use from this but want to see what media others might be using to save me from buying something I don't need. I'm watching some YouTube videos and other internet research also.
  Thanks in advance!!
  Type at you later,
   Dan McEntee

[Jim Svitko]

I never tried polishing engine cases in a vibrating tumbler.  My only experience with tumblers and the various polishing media has been to clean brass for ammo reloading.

As far as polishing media goes, the only things I have are corn cob and walnut shells.  I have seen some of those products treated with what appears to be jeweler's rouge.  I have added some brass polish to untreated media and that worked pretty well to polish the ammo brass.

If you used this tumbling method to polish engine cases, is there any concern about getting all the polishing debris out of the engine?  I suppose if properly washed out, none would be left to cause any internal engine damage during normal running.

[Peter in Fairfax, VA]

No question Duke Fox used a tumbler, as I saw it in a video Randy Linsalato has on youtube made at the Fox factory.  There is a MECOA channel on youtube.  No idea what media Duke used.

[Motorman]

I would think anything that would polish the case would ruin the machined areas and good luck cleaning threaded bolt holes. 

[Lauri Malila]

You'd better plug all the holes to protect the insides & threads from abrasion. I'd make the plugs from nylon or similar. L

[Dan McEntee]

I never tried polishing engine cases in a vibrating tumbler.  My only experience with tumblers and the various polishing media has been to clean brass for ammo reloading.

As far as polishing media goes, the only things I have are corn cob and walnut shells.  I have seen some of those products treated with what appears to be jeweler's rouge.  I have added some brass polish to untreated media and that worked pretty well to polish the ammo brass.

If you used this tumbling method to polish engine cases, is there any concern about getting all the polishing debris out of the engine?  I suppose if properly washed out, none would be left to cause any internal engine damage during normal running.

     Cleaning and polishing shell casings for ammunition reloading is quite common from what I've seen. Depending on how much you shoot, it seems like guys use equipment ranging from a simple rock tumbler to the units like I bought from Harbor Freight. In corresponding with one vendor, describing what I want to do, they said the same materials used for brass should work for cast aluminum also. The machine in the Mecoa video looks like a cement mixer, but may actually be a tumbler for deburring and polishing. In manufacturing, this process is done usually after all machining processes are finished, and getting material like walnut shells out of holes is not a problem. It's not as violent a process as some might think. Some of the ceramic media is just too large to get where it doesn't belong. In a lot of practices, this is the last process that is done to some parts, and are often just blown off with an air hose and then packaged. It can be aggressive enough to be used to remove rust from steel parts, and gentle enough to do what I'm wanting to do and not damage the finished product. using the correct media is the key. If the parts are small, polishing them by hand is cost prohibitive too time consuming. Fox did it to make their end product look more appealing and was probably done right before final assembly of engines. They probably ceased doing it just as a labor and time saver, eliminating one whole step. I worked in the automotive parts rebuilding business for 10 years rebuilding torque converters for automatic transmissions, and the small parts that we ordered in often had these little stones in the boxes or stuck in a part but was easily found and removed, and many of these were finished, machined parts. It's a simple process but still must be done correctly.
  Type at you later,
   Dan McEntee

[Andre Ming]

Yes, Fox Mfg used a tumbler to get the shiny finish on the cases circa '72-'75. (I left Fox Mfg in Oct '75 for the final time.)

The tumbler itself looked like a small cement mixer. (And knowing Duke, it could have been just that!) The cases were polished during Second Operations, before any drilling/tapping. (I think.)

The medium used were small, chromed, spherical "marbles" w/an edge around the circumference. Memory has me thinking they were about 1/4"  or less in overall diameter.

I cannot remember how long the cases were tumbled, but I do remember the noise when in operation as I walked past the tumbler on the way to/from the restroom.

Good luck in your quest.

Andre

[doug coursey]

heres a link gene papes article on how he cleans old engines he buys and and shows his tumber and the media he uses and before and after pictures..
 http://flyinglines.org/gp.col13.html?fbclid=IwZXh0bgNhZW0CMTAAAR3Cyo5ayCnCtEJ7v8A0UVzQKEBKHq6j3w_TKkmNZne16_GDl8VOTAzTZm4_aem_ATrnWvX8NeF37nkMLjyyFPEmjsL5do1e57gvSw1B-RkSjn9o4S8g0Smbf2x6b5XW2vznCzJ2nREMMNnN8FQdpCQK

[Gerald Arana]

You'd better plug all the holes to protect the insides & threads from abrasion. I'd make the plugs from nylon or similar. L

Please explain to me why not just put the original bolts back into the holes and tumble away?

Makes sense to me, Jerry

[Lauri Malila]

 Sorry Gerald, I was a little unclear.
 Of course, you can put whatever that fits in the screw holes. What I mean with plastic plugs, is that I'd make those to plug all the openings and to protect all machined surfaces. L

[Sean McEntee]

I would think anything that would polish the case would ruin the machined areas and good luck cleaning threaded bolt holes.

You think cleaning sand out of threads is hard?  Not much of a motorman, are you…

[Robert Zambelli]

We did a lot of tumbler polishing at Xerox back in the 70s and 80s.
This was mostly for exposed knobs and handles.
As I recall, we used a slurry of walnut shells and polishing compound.
Worked very well and the slurry seemed to last forever.
Strictly cosmetic - not for deburring.

Bob Z. (mechanical engineer at Xerox for 18 years)

[Motorman]

You think cleaning sand out of threads is hard?  Not much of a motorman, are you…

I guess you can ask the speed and racing guys that question but, cleaning absolutly every spec of sand out of deep 4-40 holes? yeah I'd caution against having to do that by plugging the holes. Either way just trying to give your old man some friendly advise, sad you have to make a statement like that.

MM

[Dan McEntee]

I guess you can ask the speed and racing guys that question but, cleaning absolutly every spec of sand out of deep 4-40 holes? yeah I'd caution against having to do that by plugging the holes. Either way just trying to give your old man some friendly advise, sad you have to make a statement like that.

MM

     I'm not talking about using sand or any similar kind of abrasive. I'm talking about POLISHING with appropriate media. I don't think you have any experience in that area of processing just from reading your post. Sean know what work I have done for a living and other experience I have in my back ground and knows that getting a 4-40 threaded hole clean for me is pretty easy, but I'm not even remotely thinking of using material like that. I never said anything about SAND BLASTING, although I have done that to all sorts of engine cases and son of a gun if I didn't manage to get those cases cleaned, repaired, engines rebuilt, motorcycle that it was for restored and then raced it through the woods 100 miles from my truck and back again!!  I am talking about POLISHING, and you may not know but there is a difference!! I'm talking about media that is way bigger than the #43 size hole that is drill in the cases. He was just sticking up for his old man, but fear not, I am more than capable of seeing that this task gets accomplished once I find a source for the proper media. So, you can sleep well tonight knowing that I have this job well in hand. Once I get a few other irons out of the fire I intend to get back on this.
   Type at you later,
    Dan McEntee

[Dan McEntee]

We did a lot of tumbler polishing at Xerox back in the 70s and 80s.
This was mostly for exposed knobs and handles.
As I recall, we used a slurry of walnut shells and polishing compound.
Worked very well and the slurry seemed to last forever.
Strictly cosmetic - not for deburring.

Bob Z. (mechanical engineer at Xerox for 18 years)

     This is kind of where I think I need to go. Tumbling for deburring and polishing are two different areas, I am beginning to see. I have used a lot of products in my time that have been through both, but I have never had to do it myself, and just trying to flatten out the learning curve and make it a whole lot shorter. I haven't had the time to research if there are any brick and mortar suppliers in my area to visit and ask questions, but once I get some other projects and activities out of the way, I'll get back to this. I got some good information here from the thread and will build on that. Thanks for the responses!
     Dan McEntee

[katana]

     I'm not talking about using sand or any similar kind of abrasive. I'm talking about POLISHING with appropriate media. I don't think you have any experience in that area of processing just from reading your post. Sean know what work I have done for a living and other experience I have in my back ground and knows that getting a 4-40 threaded hole clean for me is pretty easy, but I'm not even remotely thinking of using material like that. I never said anything about SAND BLASTING, although I have done that to all sorts of engine cases and son of a gun if I didn't manage to get those cases cleaned, repaired, engines rebuilt, motorcycle that it was for restored and then raced it through the woods 100 miles from my truck and back again!!  I am talking about POLISHING, and you may not know but there is a difference!! I'm talking about media that is way bigger than the #43 size hole that is drill in the cases. He was just sticking up for his old man, but fear not, I am more than capable of seeing that this task gets accomplished once I find a source for the proper media. So, you can sleep well tonight knowing that I have this job well in hand. Once I get a few other irons out of the fire I intend to get back on this.
   Type at you later,
    Dan McEntee

Just to be pedantic ANY substance used for polishing will be abrasive - it has to be or it won't do anything! The use of sand in a tumbler will and can produce mirror finishes on hard substances like steel or pebbles - used in jewelery trade for years. Use on aluminium could produce a good shiny finish but timing needs to be watched as it will scour / wear the surface. There is also the question of whether to dry tumble or wet / slurry tumble - both have merits. Personally I'd treat a metal casting with finished machined surfaces like a thing to be powder coated ie. block up any cavities / holes / threads that you don't want coated or touched and tumble away - no harm practicing on a scrap engine first!