Needed a longer tumbler - so I made one

MTBob

MTBob

Well-Known Member
I've been using "Tumblers Tumbler" for stone washing small knives, but it's too short for larger knives. So, I decided to use the 2x72 grinder to roll a 4" PVC pipe. A design concept similar to others I've seen on the InterWeb.

1608756929016.png
I set the pipe so it just touches the 2" contact wheel, using a 36 grit belt. Adding rubber to the pipe gives a bit more grip.
1608757270682.png
I'm thinking a set of 4 swivel casters might have worked better. But, so far after tumbling several blades, this seems to work OK.
Also, I think a 6" pipe might work better than this 4" pipe. A 6" pipe will turn slower and allow for better tumbling action.
1608757302613.png
 
Keep in mind that if you make one of these, it's really important to slow the speed way down, ideally with a VFD. That's why I used a 2" contact wheel to rotate the 4" pipe. If the pipe turns too fast the material inside will not tumble, it will just spin due to centrifugal force. I run my KBAC 27 around 20%, just above the stall point with the pipe touching the contact wheel.
 
That's pretty neat!! But if you are doing this on blades for the finish, doesn't it put all the scratches the same direction (ie perpendicular to the edge)?
 
razor-edge-knives said:
That's pretty neat!! But if you are doing this on blades for the finish, doesn't it put all the scratches the same direction (ie perpendicular to the edge)?
Click to expand...
Great comment! I think you are right, in this example there is a tendency to have marks / scratches laterally across the blade, as this photos shows. This isn't too evident with a general view of the blade surface. But, looking closely, the lateral marks are evident. However, in this case I am using a severe media, it's a 70 grit, triangular shaped tumbling "rock" I bought from HF. I think it may be too coarse and too big (about 3/4" on each side) for this application. In the past I've just used crushed driveway rocks and they seem to be less aggressive and give a good finish. I'll blast the finish off this blade and give it a run with driveway gravel and see what the difference is.
Another factor related to this is how the grit media falls as it rotates in the pipe and touches the blade. I think a larger diameter pipe, say 6", would allow the blade to fall through the stones rather slide through as it is likley doing with a 4" pipe. Adding some kind of internal baffle inside the pipe might help... though I'm not sure what that looks like yet.
I must admit I don't have a lot of experience with stone washing (tumbling) knives, so those with more experience at this might want to add their comments.

1608827326956.png
 
Do you add water? I add some water to mine. I'm using the same ceramic from Horrible Freight and every time I use it I take a hammer and break some of them up, I'm probably thru about half of them now.
 
bladegrinder said:
Do you add water? I add some water to mine. I'm using the same ceramic from Horrible Freight and every time I use it I take a hammer and break some of them up, I'm probably thru about half of them now.
Click to expand...
Now that is a terrific idea. On the next run I'll bust up the stones and add some water. I might even add some 70 grit blast media, that might make the stuff more like a slurry.
 
MTBob said:
Great comment! I think you are right, in this example there is a tendency to have marks / scratches laterally across the blade, as this photos shows. This isn't too evident with a general view of the blade surface. But, looking closely, the lateral marks are evident. However, in this case I am using a severe media, it's a 70 grit, triangular shaped tumbling "rock" I bought from HF. I think it may be too coarse and too big (about 3/4" on each side) for this application. In the past I've just used crushed driveway rocks and they seem to be less aggressive and give a good finish. I'll blast the finish off this blade and give it a run with driveway gravel and see what the difference is.
Another factor related to this is how the grit media falls as it rotates in the pipe and touches the blade. I think a larger diameter pipe, say 6", would allow the blade to fall through the stones rather slide through as it is likley doing with a 4" pipe. Adding some kind of internal baffle inside the pipe might help... though I'm not sure what that looks like yet.
I must admit I don't have a lot of experience with stone washing (tumbling) knives, so those with more experience at this might want to add their comments.

View attachment 76396
Click to expand...
Very cool. I was wondering because I have one of these mjr tumblers which is about 7-8" diameter inside (30 lb barrel) and when I put folder blades in it works perfect but for longer blades it puts them all the same direction for the most part (leaves a noticeable pattern perpendicular to the edge)

Yeah water inside with the rocks will help a ton!
 
You must log in or register to reply here.
Back
Top