Building a media tumbler.

J. Hoffman

Dealer - Purveyor
I've been considering making a tumbler for finishing knives. Today I found a .25 HP Baldor Gear reduction DC motor. The specs are 90VDC, .25 HP, 175 in/lb torque with 20 RPM. Number one, is that enough power for a tumbler, and how do I go about powering a 90 VDC motor.

I'm also up for suggestions on what to use for the tumbler container.

Thanks in advance.

Jess Hoffman
 
I have a Variable Frequency Drive I could sell you. It's new in the box. It's a DC drive rated from 1/50 hp to 3/4 hp. The brand is Pentadrive.

Nema enclosure is watertight and dust tight

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As has been mentioned, you'll need a DC drive/controller for that motor...... the DC controllers are very similar to modern VFDs..... the best advice is to search for "DC motor controller" as a broad search on the net, then narrow it down to what you want/need from there.
Personally, I think 20 RPM is a bit slow for a tumbler.....even with top end media, it would take days to finish out blades.

I tried to build a tumbler at one time, using a 5 gallon farm chemical container...... it was pretty much a goat rope.

For a number of years now I've been using the large vibratory tumbler from Harbor Freight: http://www.harborfreight.com/18-lb-vibratory-bowl-with-liquid-drain-hose-96923.html along with the ceramic "triangle" media. The size makes it good for up to about a 3 1/2" hunter sized blade. For larger then that you're likely going to have to go with one the "professional" model tumblers such as: http://www.kramerindustriesonline.com/vibratory-finishing-systems/db-series/db300.htm

The problem with tumblers is there's really nothing in the middle....you either have the 18lb ones for around $170, or you have to jump up to $1,000+

For blade finishing I far prefer vibratory to rotating tumbler...... the vibratory models just plain work better and much faster, usually not more then a few hours, where as it can literally be DAYS with a rotating style tumbler.
 
I've been considering making a tumbler for finishing knives. Today I found a .25 HP Baldor Gear reduction DC motor. The specs are 90VDC, .25 HP, 175 in/lb torque with 20 RPM. Number one, is that enough power for a tumbler, and how do I go about powering a 90 VDC motor.
I'm also up for suggestions on what to use for the tumbler container.
Thanks in advance.
Jess Hoffman

i would look at lapidary suppliers. http://www.therockshed.com/ i have purchased several disc sander heads from these folks, they are reasonable in price, offer good service, and will talk with you on the phone to make sure you get what you need. here is a link for DIY tumbler http://tomaszewski.net/Kreigh/Minerals/Homemade.shtml. go to ebay to find a dc drive, then you could remove the gearbox and go direct drive. good luck
 
If you're a tinkerer and good with electrical stuff, you can build a simple DC power supply for a motor pretty easily. I made one a long time ago with a variac, a bridge, and some big caps. I'm sure there tons of "how to's" on the net for homebrew power supplies. Obviously, store bought would better by removing the hassle factor.
 
I've been wondering if one of those 2 sack concrete mixers would work for tumbling blades. Anyone have any experience with them?
 
That sounds to me like a really good idea, especially for larger blades. I'm anxious to hear if anyone's tried it. Sure, as Ed says it may have to run a lot longer but what is the alternative for big blades, or a bunch of blades?

I used my vibratory bowl that I clean my brass in along with the ceramic media from HF, just to see if it would work okay. Good gracious, talk about noise.
 
I converted an old wood lathe I wasn't using into a rotary tumbler. Geared it way down and chucked a 1" dowel rod in the spindles and used that for a drive wheel to spin a 4" PVC container filled with HF media. Sacrificed a cheap skateboard for the idler wheels.
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Chris
 
the one thing i noticed when looking at tumblers for rocks, most of them are softer than hardened steel, is they are talking about tumbling for days. when i visited the Rock Shed last year, you could hear their tumbler before you entered the store. when i asked the sales person about it, they laughed and said it is always on, always tumbling, and that after the first week the only time you notice it is when it is stopped to be loaded or unloaded.
 
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