Tumbling... Vibratory? Rotary? Media? What setups do you guys have?

[aarongough]

Hey all!
I've been thinking lately about trying out some non-directional finishing via tumbling. I like how it looks and I think it's a finish that would work well for my hard use knives.

I've been reading the various threads on bladeforums about other people who've experimented a bit with it, but I haven't found too much info on what setups exactly work for different people.

I've noticed that most of the vibratory tumblers seem to be on the smaller side, and that getting a larger one is going to cost well over $1000. From a size perspective I could do much better with a homebrewed rotary tumbler, but I'm not exactly sure how the finish will differ in appearance. Also not sure whether the finish will look significantly different... I have a small 10-1/4" vibratory tumbler that I'm going to try out once I get some media, but the plan is to go to rotary for the extra capacity.

The setup that I'm contemplating right now is a 12x14" rotary barrel tumbler, with 5/8x3/8" Angle Cut Tri Stars in 'M' grit as my first step, then porcelain burnishing media as my second step. The goal would be to tumble finished knives whole (handles and all), not sure yet whether that will end up working out.

Blades will be taken to 900 grit or so and heat-treated before tumbling unless I'm advised otherwise...

Any and all advice welcomed and appreciated!

 

[Nathan the Machinist]

When you tumble a blade with a handle on it, the scales prevent the media from getting in the nook in the transition between the scales and the ricasso which will leave some visible weirdness in that nook. But if you tumble blades without scales you'll get a rounded edge on your tang that creates a sloppy gap between the scales and the tang.

I use accurate holes in my tang and scales so the scales can go on and off and repeat in the same spot. I grind things flush and remove the scales and put on some modified scales that will keep my tang edges crisp but allow the media into the nook on the ricasso then tumble them. Then when I put the scales back on things are nice and flush with the scales ground and the tang tumbled.

Media can get very expensive, particularly if you get it from places like MSC.

Try these guys out: http://www.candmtopline.com

And last, but not least: be aware that a tumbled finish is not a short cut, it does not hide sins very well. You need a good finish on the knife (400 grit) before going into tumble or it will be messy coming out. The only thing a tumbler does that actually saves you the maker a lot of work is it applies a nice edge break everywhere that used to require a couple minutes with sand paper to do by hand...

 

[aarongough]

When you tumble a blade with a handle on it, the scales prevent the media from getting in the nook in the transition between the scales and the ricasso which will leave some visible weirdness in that nook. But if you tumble blades without scales you'll get a rounded edge on your tang that creates a sloppy gap between the scales and the tang.

I use accurate holes in my tang and scales so the scales can go on and off and repeat in the same spot. I grind things flush and remove the scales and put on some modified scales that will keep my tang edges crisp but allow the media into the nook on the ricasso then tumble them. Then when I put the scales back on things are nice and flush with the scales ground and the tang tumbled.

Media can get very expensive, particularly if you get it from places like MSC.

Try these guys out: http://www.candmtopline.com

And last, but not least: be aware that a tumbled finish is not a short cut, it does not hide sins very well. You need a good finish on the knife (400 grit) before going into tumble or it will be messy coming out. The only thing a tumbler does that actually saves you the maker a lot of work is it applies a nice edge break everywhere that used to require a couple minutes with sand paper to do by hand...

Thanks for the response Nathan!
I had figured that the tumbled finish would show up flaws, I had that experience when I was working on the pens I produced. Found I had to take them to a pretty high finish before I put them in the tumbler... The advantage I found to the tumbled finish was that you could then chuck the pen in your pocket where it would bounce around with keys and change and such, and the finish wouldn't look any different.

I've noticed that I can spend all the time in the world putting on a nice hand-rubbed satin finish and then it doesn't take very long out in the bush to make it look pretty rough. Baton it through some wood that's a bit gritty or sandy and that finish is now badly and visibly marked. Same goes with any sand or dirt that gets into the kydex sheath. I've noticed that some of my customers hesitate to use their knives because they like the pristine look too much. I'm hoping that the tumbled finish will make the blades seem a bit less precocious and also keep the blades looking reasonable for a longer period of time.


Your idea of having a special pair of scales for the tumbling makes a lot of sense!

What I was kind of thinking of doing was to heat-treat the blade (leaving the tang a little oversize), tumble it, fit the scales to the blade (which would involve grinding the edges of the tang and the spine) and then re-tumbling it quickly after the scales are fitted. That way all the surfaces get the finish... Not sure if it would work or not. I guess the other option is to tumble the blade after heat-treat and then fit the scales to it afterward. The edges of the tang and the spine of the knife would then have a belt finish on them instead of a tumbled finish, but the contrast might look ok. Making special scales for the tumbling process like you did is also an option.

I had a quick chat to Dan at C&M Topline yesterday, he was very helpful! The prices on their media seem reasonable too. I just wanted to get a better feel from some other makers about what had worked out for them.

 

[aarongough]

Also, Nathan: what media are you using? It sounds like it's pretty aggressive if it's rounding off the edges of your tangs so quickly!

 

[Hesparus]

I've been curious about this process, as well. Nathan: does the 400 grit finish need to be a hand finish or can it be a 400 grit machine finish?
Thanks,
Chris

 

[Nathan the Machinist]

Also, Nathan: what media are you using? It sounds like it's pretty aggressive if it's rounding off the edges of your tangs so quickly!

You need pretty aggressive media to do anything to a knife steel. But you could be using corn cob, you're still gonna round off the edges of your tang. The process hits the corners first and those edges on the tang need to stay sharp. They'll be long gone before you acquire any kind of a frost finish.

 

[Nathan the Machinist]

I've been curious about this process, as well. Nathan: does the 400 grit finish need to be a hand finish or can it be a 400 grit machine finish?
Thanks,
Chris

It doesn't matter. If hand finished, things like fish hooks aren't a problem. But any deep scratch will never erode away. I tumble milled finishes all the time and it works okay if I did a good job on the mill.

In reality, a really really good 220 finish will frequently clean up. I like the yellow Klingspore belts for this because they're good about not gouging or having any stray piece of large grit in there. But if you take it to 400 it will clean up more reliability.

 

[Huntsman Knife Co. LLC.]

Hey Aaron,

I do stonewashed finishes on most of my blades. Its by far the toughest finish out there and is great for knives that will be used hard and beat up.

I have a tumbler from Northern Tool. It was $1500. You're a resourceful guy and im positive you could make one for much, much less.

I use triangular ceramic media and tumble in either cool mist or WD 40. People tumble dry but I think it works better wet. Both liquids also prevent rust and clean the blade which is nice.

What nathan said about rounding edges on the handles is absolutely true but this is easy to overcome. You can see this on SURVIVE! knives where the edges are rounded and the scales arent flush.

My process for tumbling is this-

finish to 320 then tumble the blade for a good long time. I tumble for 2 hours or more generally. Sometimes up to 6.

Then take it out, put on your handle, marry it and then tumble again for about 15 minutes to give the satin areas a nice finish. If necessary hit your handle material again with high grit paper to take out any scratches the tumbler may have caused.

One thing to watch out for is really thin grinds. If you take your blade past .015 the media will absolutely destroy your edge in no time. I lost 1/8th inch of steel of a knife I took down to .005 and tumbled for an hour without checking it.

Also be careful about tumbling differentially tempered blades together as the hard edges can hit the soft flats and cause massive gouges that are tough to repair.

Also tumbled blades don't throw sparks with flint strikers. you may want to leave the spines on your blades satin if spark throwing is important to the customer

 

[aarongough]

You need pretty aggressive media to do anything to a knife steel. But you could be using corn cob, you're still gonna round off the edges of your tang. The process hits the corners first and those edges on the tang need to stay sharp. They'll be long gone before you acquire any kind of a frost finish.

Gotcha, yeah that makes sense.

Hey Aaron,

I do stonewashed finishes on most of my blades. Its by far the toughest finish out there and is great for knives that will be used hard and beat up.

I have a tumbler from Northern Tool. It was $1500. You're a resourceful guy and im positive you could make one for much, much less.

I use triangular ceramic media and tumble in either cool mist or WD 40. People tumble dry but I think it works better wet. Both liquids also prevent rust and clean the blade which is nice.

My process for tumbling is this-

finish to 320 then tumble the blade for a good long time. I tumble for 2 hours or more generally. Sometimes up to 6.

Then take it out, put on your handle, marry it and then tumble again for about 15 minutes to give the satin areas a nice finish.

One thing to watch out for is really thin grinds. If you take your blade past .015 the media will absolutely destroy your edge in no time. I lost a an eighth inch of steel of a knife I took down to .005 and tumbled for an hour without checking it.

Hey mate!
Glad to hear you like the finish for hard use knives, I like the idea of an un-fussy finish and tumbling certainly seems to fit the bill!

Sounds like the process is pretty straightforward for you which is great! How have you found the corrosion resistance of the final finish to be?

-Aaron

 

[Huntsman Knife Co. LLC.]

Gotcha, yeah that makes sense.



Hey mate!
Glad to hear you like the finish for hard use knives, I like the idea of an un-fussy finish and tumbling certainly seems to fit the bill!

Sounds like the process is pretty straightforward for you which is great! How have you found the corrosion resistance of the final finish to be?

-Aaron

If I do a carbon steel like 52100 I usually acid wash it as well but overall I havent had any issues with rust. For steels like 3V an up chromium content wise the stain resistance is similar to a belt finish I think. Definitely not a rust magnet like a bead blasted finish or similar.

An acid etched stone wash is the ultimate hard use finish IMO!

 

[NickWheeler]

It's threads like this that keep me believing in this sub-forum. :thumbup:

Good questions with awesome answers by guys that have actually done the work. Thank you Nathan and Hunter for the detailed posts--- very cool stuff.

I would love to add this finish to my capabilities. You guys gave me some things to ponder for sure.


A local blacksmith has a really interesting rotary tumbler he made from a retired 100# propane tank (laying horizontal). His "media" is 100% composed of slugs from the punch press on his Ironworker.... Needless to say, it would not work well for blades. But it had me thinking about stuff. It does seem like a vibratory unit would be better than a rotary, but IDK.

 

[Overmountain]

This is a tumbler finish I use a lot on hard users. I will take the piece to a polish, then tumble with ceramic triangles and WD-40. After that is a clean up, rub down with 0000 steel wool. Then an etch in diluted FeCl and again wipe clean. Then a dunk in black oxide chem and straight back in the tumbler. This is the wiped clean finish from that. (With the bevel touched to 400 on the belt...)

For simple C steel the finish seems to be plenty deep enough and close enough in color to the natural patina that it converts without ever looking blotchy. I have done this on several hard users and had it hold up well. Seems like it likes to hold oil pretty well. Of course this is done sans scales...

Oh, BTW its a larger RCBS vibratory tumbler. Will fit up to an 8"ish overall piece. I also use corn cob with polishing compound for a brighter finish without the elbow grease sometimes. I would love to have a larger tumbler or two, as especially in reloading they are indispensable.

I also use a mix of solvents and media for old tools. It's a recipe I got from an old tool collectors bible. Makes it nearly impossible to see my repairs most of the time. And gives them a uniform appearance the collectors have come to expect...

-Eric

 

[aarongough]

Beautiful knife and finish mate! Do you have any pics of an acid stonewash?

This is a tumbler finish I use a lot on hard users. I will take the piece to a polish, then tumble with ceramic triangles and WD-40. After that is a clean up, rub down with 0000 steel wool. Then an etch in diluted FeCl and again wipe clean. Then a dunk in black oxide chem and straight back in the tumbler. This is the wiped clean finish from that. (With the bevel touched to 400 on the belt...)

For simple C steel the finish seems to be plenty deep enough and close enough in color to the natural patina that it converts without ever looking blotchy. I have done this on several hard users and had it hold up well. Seems like it likes to hold oil pretty well. Of course this is done sans scales...

Oh, BTW its a larger RCBS vibratory tumbler. Will fit up to an 8"ish overall piece. I also use corn cob with polishing compound for a brighter finish without the elbow grease sometimes. I would love to have a larger tumbler or two, as especially in reloading they are indispensable.

I also use a mix of solvents and media for old tools. It's a recipe I got from an old tool collectors bible. Makes it nearly impossible to see my repairs most of the time. And gives them a uniform appearance the collectors have come to expect...

-Eric

Very cool looking finish Eric! Love the dark lustre that it has, could definitely get into that!

I notice you guys are all using vibratory tumblers... Was there a specific reason for going that way? It does seem that rotary tumblers are less common.

The gent I spoke to at C&M Topline seemed to think that a rotary tumbler would work just fine, but it would be slower than a vibratory and the finish would come out a bit different as the media 'slides' rather than 'hammers'.

I actually have the makings of a crude rotary tumbler kicking around the shop. I may well get some media and try identical pieces in both the small vibratory and the makeshift rotary before I make any purchasing decisions.

 

[Huntsman Knife Co. LLC.]

Aaron,

I usually do acid etched stone washed finishes on big blades. Here's two different styles that I use.

1.) Is a standard stonewash that is then etched. It looks about the same just darker. You have to finish the whole blade to 320 for this to work so I don't use it on machetes anymore.

2.) This is what I call a "heavy" stone wash with etch. For this method I attach bungee chords to the tumbler so it bounces vs. simply passing the material gently over the blade. This is a really nasty tough finish. The ceramic bits scratch a little differently and basically work more aggressively. For this technique I etch the blade and then tumble it afterwards.

Maybe this is the kind of finish you would get with a rotary tumbler? I'm not sure but its a great way to finish blades that you don't have time to give a good high grit belt finish first.

 

[aarongough]

KalEL, those all look amazing. The first one I particularly like...

How do you find the stonewash then etch finish holds up? When I was acid-etching O1 blades I found that the finish wore off a bit easily for my liking, but I was also doing pretty bad stuff to those blades. Lots of batoning and chopping hardwoods. Can't say that I've found Cerakote to hold up much better though.

 

[Huntsman Knife Co. LLC.]

I think the stonewash then etch holds up about as well as anything. I've beaten the hell out of the blade in the first picture and it still looks about them same, just has lots of wood gunk hammered into it. The great thing with an acid washed finish is that if it ever comes off it can always be reapplied by the customer with some vinegar etc...

This is why I'm against blade coatings in many circumstances, it eventually wears off and the customer can't fix it. I may coat some machetes in the future if the customers want it but from my perspective a finish that can be perpetually maintained and restored is the best.

Also maybe someone can shed some light on this. I swear acid etching is a dark art. Sometime Ill etch a blade and I can wipe all of the finish off with my finger. Other times Its very tough to get off and holds up well. Does anyone know why an acid etched finish sometimes doesn't "stick?"

 

[Overmountain]

I think the stonewash then etch holds up about as well as anything. I've beaten the hell out of the blade in the first picture and it still looks about them same, just has lots of wood gunk hammered into it. The great thing with an acid washed finish is that if it ever comes off it can always be reapplied by the customer with some vinegar etc...

This is why I'm against blade coatings in many circumstances, it eventually wears off and the customer can't fix it. I may coat some machetes in the future if the customers want it but from my perspective a finish that can be perpetually maintained and restored is the best.

Also maybe someone can shed some light on this. I swear acid etching is a dark art. Sometime Ill etch a blade and I can wipe all of the finish off with my finger. Other times Its very tough to get off and holds up well. Does anyone know why an acid etched finish sometimes doesn't "stick?"

Aaron, I have access to both types... vibratory and rotary... I have used both for gun parts and shell casings but just vibratory for knives. I tend to use dry media such as corncob and polish or walnut shell in the rotary and not the ceramic triangles. The triangles I keep wet with WD-40 and while you can switch back its a pain and never actually gets all the WD-40 out... So keeping the bigger rotary dry makes sense to me. It can do 1000-1200 pistol sized shelm casings as opposed to my vibratory doing 500. The finish with the dry media seems to be similar. The rotary has paddles and drops the media to a degree so it is similar. Will have to dive in and try it with the ceramic stones. Can fit a bigger blade. You can also change the angle of these machines and change the media flow and fall.

I don't think I can remember a single blade I've done where I didn't use the tumbler at some point. Even if its just to knock off decarb and then polish. It's a great elbow grease saver IMO and can leave a durable finish...

As to Superman's question... I love acid etching. On lots of stuff. It just leaves patterns that can't be duplicated by any mechanical process. In simple carbon steel, I have noticed a distinct relationship between martensite presence and the darkness of the oxide formed during FeCl etching. It seems to 'stick' best if neutralized quickly, usually with baking soda and water at a boil, and quick drying afterward with no contact of the steel and a finger, etc. It also seems to do with how smoked my FeCl solution is. Which, btw, FeCl PCB etchant can be freshened back up with addition of a little muriatic acid. And, in the case of my last but of damascus, what finish I left it at prior to etch. At a full polish I got contrast, but it just rinsed away. It looks cool and is a neat gray, but lacks the dark black that usually brings out the steel without having to etch as deep. This was forged very close so has a few marks, but this is what I mean. Gray...

Here I left it at 5-600ish (trizact A something...) and tried the boiled baking soda deal. Straight from an etch to the baking soda water solution.

This one wound up being rubbed to a little lighter tone with steel wool. But the finish was tough.

I feel the same way about coatings. I love them for guns, but for some reason not knives. There are exceptions, like when a color scheme is just right (newer member here just did one that looked stellar... sorry, can't remember screenname...) On the one tac knife I do, I resisted the urge to cerakote it. Instead etching deep and black oxiding it. The reports seem to indicate it holds up as well or better than some of the coated blades... And yes, easily repairable.... Deep scratches in my blade's particular case can be colored with aluminum black from Birchwood Casey. Available nearly everywhere.

So, basically I really have no idea either. But I love playing with the stuff and seeing what comes out. And I always like the down and dirty true hard use look of a knife with this treatment. Polished steel looks great for some stuff, but my hard users are gritty and grainy. BTW I really love the way etched WI looks...

Sorry to write the second book of 'War and Peace' on your thread Aaron. Hope it keeps going as I'd like to see more examples and descriptions myself.

-Eric

 

[Varga Knives]

Aaron - this may not help you out much because you already have some tumblers but it could help someone. There is plenty of info on the web for going the cheap route and this is also great for someone just experimenting.

The blade below was taken to 400 grit then cleaned with acetone and then denatured alcohol. Dipped in a 50/50 FeCL and vinegar solution for five minutes. Sprayed and cleaned with windex and rubbed with 0000 steel wool. Repeat the acetone and alcohol cleaning and repeat the FeCL, etc. Put in a container with about 3 pounds of Harbor Freight ceramic media a handful of smallish smooth stones (for good measure) and WD-40. I used an empty rock salt container (I went through enough of them this winter) as it's tough plastic, large and has a handle. I let it dangle at the end of my arm and did a vigorous wrist twist for ten minutes. I think in this case I also cleaned it up, dipped it again and repeated the stonewashing. I love the finish (but not so much the handle on this one). I plan on giving it a lot of use in the next two weeks to see how it holds up.

 

[Patrice Lemée]

Thanks guys, good stuff! Saved for future reference.

 

[Daniel Fairly Knives]

I do a quick 5-15 minute stonewash in a small HF vibratory tumbler with ceramic media and windex. I find the key is to keep the media clean, put it in a colander and clean with soap and water if it appears to be dirty.

Here's a recent one done this way... maybe 20 minutes on the Titanium.




Dark pic but shows the bevel finish. I took the bevel to 600 grit and the flats to 220, blasted then tumbled. A quick acid etch will give the finish more contrast, this one was not etched.