PVC pipe charcoal grinder

I’ve been trying to build a charcoal grinder and studying other people’s builds. This post is my attempt to gather some of the information I have collected.

It seems like Gary Gilmore’s grinder is one of the most popular.

Gilmore Grinder

Gilmore Grinder2

From a description on one of Gary’s videos, it is made from 3" steel pipe with 1/2" square teeth welded on.

Another charcoal grinder is from Chuck Whitlock where he used 12" long pipe with 1/2" teeth.

Kristijan Leitinger made his grinder tractor powered.

Cody Edison Tate made his simple grinder using flat barstock as the cutters.

Take round bar and flat bar, drill holes in the flat bar and braze or weld into teeth.

Then opposite of that make the static teeth with about a 3/8" gap.

Then I found a post by Bruce Southerland.

I’m not positive this particular one is made out of PVC but I think it is and the bolts and nuts used as the teeth looked easy.

My main problem was lacking a piece of steel pipe big enough to make my grinder. I used a smaller one that is about 2-1/2" outside diameter with a few teeth welded on and it works but it is powered with a hand crank and is slow and dusty to use.

I did have a piece of PVC pipe that is 3 inch inside diameter and 3-1/2 inch outside diameter. The circumference of a 3.5" circle conveniently is very close to 11 inches which is the size of a normal piece of paper here. I just had to fold it up and wrap it around the pipe to divide it.

I marked it out and drilled a bunch of 1/4" holes.

Checking my jar of assorted nuts, bolts, and washers, I picked out a couple different combinations for the teeth.

The inch long bolts with 2 nuts gave me a bit over 1/2" high teeth. The 3/4" long bolts with one washer gave me about 3/8" high teeth.

These will still need tightened down and I need to make some plugs for the ends of the pipe and figure out how I’m going to drive it but it should grind my charcoal faster than what I have been using assuming this idea works.


For anyone finding this thread now or later, another option I looked at was Tom’s design.

There’s a video on the post above that one and a bit further down some more information about that design where Tom says:

I don’t think the size of the pipes is real important as long as the inner one is an inch OD smaller than the ID of the outer half pipe. I think the half pipe could even be made out of well braced PVC.

I didn’t have the right combination of pipes but will keep this design in mind in case I find the right pipes.

Not to get off topic but in between the post linked above and Tom’s comment about the half pipe possibly being made using PVC Matt has a video of a nice way to make charcoal.

I’ve been collecting my charcoal from the house furnace.

The heat from burning out the tars was used to heat the house and the glowing coals gets grabbed with tongs or sometimes a little shovel and put in a cast iron Dutch oven. Next time I check the fire that charcoal has cooled and gets dumped into a bigger metal barrel with a good lid.


brian, thank you for the good documentation…keep us on information how it goes on!
for hot glowing coal cool -down is best to use small diameters like milk cans with for example, i have, with 20 liters ( the contenitors but can also be higher…)
thicker diameter causes longer time for cooling down and some more loss of charcoal…goes to ash…
my observations with the differnt sizes of containers i use…
not all my containers have a good sealing lid, so , on the top i give a layer of about 5 cm of ash, a bit compressed, on the coal for sealing…


These are the buckets that work best for me for cleaning the ash and char out of my wood stove. Lids seal very tight.

If I am making char in my retort I take the lid with the stack off and just lay a regular top on the barrel. It burns whatever oxygen is still in the barrel and creates a vacuum that sucks the lid down tight.


I think you are onto something. It might crack and need reinforcement but definitely worth a try. I’m guessing you will be okay until you hit a brand…

Actually you might get away with filling it with cement


You should try just chopping up the charcoal with shovel; with the charcoal inside a drum or container. Its a lot faster, less work and no dust to breath in.

What I do is Ill chop up the top layer and as I do that I then shovel it out onto a screen and screen the dust, and fines out. Then chop up the next layer and repeat. Any large pieces I miss I just pick out and put back in the drum.


I agree with Matt, the shovel is all I use and some screen for the sizes of Charcoal I want. Big pieces I use in my Charcoal grill. As a matter of fact I just loaded it up and put the torch to it to cook some chicken with some Sweet Mesquite Seasoning for dinner with garden green beans.


I’m a believer in investing in your fuel processing infrastructure. Once the problem of generating fuel quickly and easily is solved, gasification is a lot closer to being practical.
One consideration is your desired throughput. If all you need is a few gallons now and again it probably doesn’t just justify a powered system. Drive on it (under a folded tarp), chop it with a shovel…
I don’t want to mess with fuel processing very often because of the mess and so I have fuel ready at hand, so I went with something that will do hundreds of gallons an hour.


Some tips, fwiw:
**Use a sharp tooth profile that limits crushing
**Stagger the teeth so that an open gap is available for pieces that are already small enough to drop through without additional crushing.
**Char crushing is low power so make the grinder long to increase throughout
**Design for easy cleanout after the inevitable jam…you don’t want to have to empty the hopper to clear a jam
**Drive it with a slack belt to act as a slip clutch for those jams
**Avoid screens, they’re the worst…try fan winnowing instead
**A half inch gap/tooth is great for small engines


No argument here but I have a reason for how I do it. For 7 months a year we are making ash and char in the wood stove, burning between 7 and 9 full cords of hardwoods, depending on the harshness of the weather. Stove produces about 15 gallons of ash/char a week. I dump that into a 32 gallon metal trash can until that’s full and then process it. Did it the other day. Took about an hour total. separated the ash from the char. About a 18 gallon of ash and the rest charcoal. Then I store the ash to add to the compost bins and to spread on the hills of my road when they get icy. This is an important commodity here. I then grind the char in my little hand cranked grinder and then vibrate the finds through a quarter inch screen. About three quarters comes out as fuel and one quarter as bio-char, part of which also goes into compost. The rest is saved. I may screen the uncharged bio-char and store it for water purification if necessary but I have not had to use that for anything yet so I have plenty stored. As I said, this 32 gallons takes about a hour to process and it is a little messy but I need and use everything I get out of the process so it’s well worth it to me. I agree with Chuck that a longer grinder is better but I can grind a five gallon bucket through mine in a couple of minutes with a manual crank and I’m not trying to set any speed records for any of these steps. I’m not off-grid and only run the gasifier a couple of times a week just for shits and giggles. If I were using it daily I would rethink how I do it.


All good suggestions.

The plastic pipe could crack but hopefully it let’s me prove my design if/when I get a bigger steel pipe.

I have been using a combination of my old grinder and just breaking up the charcoal with a shovel. Sometimes I even put it in without any processing other than screening out the ash and the finest dust but I’d like to have enough of a supply of ready to use charcoal that I don’t need to use the unprocessed charcoal or resort to running on gasoline.

It does look like the smaller pieces helped with keeping the hopper heat down and with the moisture problems I was having when I was using bigger pieces of charcoal. It also gives me more run time before I need to refill it.

I haven’t been running the generator as much since the weather is getting colder and most of the work on the gasifier is done but I was running it 2 to 4 hours a day at full load running the welder using a bucket or two of charcoal. The bigger gasifier takes more charcoal to fill it so I need more at once so I want to get my grinding and screening faster and easier.

I’d also like to run more than just the generator now that I have 2 gasifier. I’m not ready to run a car or truck but would like to get the little tractor converted to charcoal and set up my old foundry for casting aluminum parts although that wouldn’t need processed or even clean charcoal. Raw wood worked for that but had to feed it more often. Store bought charcoal briquettes worked good too but the cost added up fast.

Mostly my use is for the generator since a lot of my tools are not close enough to run off grid power. A big part of my reason for running on homemade fuel is just because I can. It still is fun knowing I am running on fuel I made myself plus it does save money not needing to buy gasoline or run to town to buy more fuel.


I made some wooden plugs for the pipe ends but didn’t get the center hole lined up perfect. Still don’t have a way to drive it but I stuck it together good enough to test out the idea.

There’s too much space for the charcoal to fall through but my off center hole was part of that problem and the angle iron should be a little further down. Cost me another little drill bit because I used angle iron from a bed frame.

The idea looks like it could work though.

The pieces that fell through were bigger than I want but it didn’t take much force to cut or break up the few pieces I used for the test.

I don’t have a long enough piece of round stock so I used a piece of rebar for my test.

I have ideas on how to attach the axle shaft to the pipe but don’t have the materials here to do it yet. I’m probably going to run this with a hand crank. Powered would be nice but it looks like this will grind fast enough by hand and that would let me feel if any brands or nails get caught before it breaks.

I might end up giving up on using the PVC if I can find the right piece of pipe. A 1 pound disposable propane cylinder is about the right size. The nuts and bolts seemed like a good idea. The drilled holes helped keep everything lined up. Making the two different lengths could be some of the reason it didn’t make as small of pieces as I hoped but I thought it would help grab the charcoal instead of letting it bounce over the teeth like my last grinder does.


Brian don’t forget to keep your eye out for a cheap or free wood chipper just a small one , just stick a small dc motor on it and away you go .


You are probably fine with PVC for quite a while. If you power it, you want something that slips, but you will want that if you have metal too.

If you add a motor, you probably don’t want it to spin super fast. I will stand corrected as others have more experience in this area, but I am guessing the slower it goes, the less shattering occurs to break it into tiny pieces and create dust. I am only mentioning it, because you may need to scrounge for pulleys, a gearbox, or controller to help slow it down.


I use a 12/24 volt dc wheel chair motor that has a gearbox built in , variable speed and plenty of torque . on 24volt it spins around 80 rpm, slower on 12 volt around 60rpm from memory


As a test I dumped a bucket of charcoal from the furnace into my bigger wood chipper.

Instead of actually starting up the chipper, I just repeatedly pulled the starter cord. The picture above is the result. It was shaken so the fine dust is at the bottom and the largest pieces are at the top.

I don’t think this one has a screen because the pieces came out bigger than I expected but it was a lot faster than how I had been doing it and this size should work once I separate out the ashes and dust.

The side normally use for chipping larger branches has knife blades that should chop the charcoal into finer pieces but it was still jammed full of small sticks and leaves from the last use and isn’t easy to get back out without pushing it into the blades but I don’t have any gasoline in that chipper right now.

I fed the charcoal into the big top hopper where normally just leaves or smaller pieces would go. I had to reach inside the outlet shoot and spin the flywheel backwards a couple times to clear out jams.

Later today I might put some gasoline in the chipper and clear out the other feed shoot. Then I’ll try feeding some more charcoal in that side using the pull starter as the drive. It made puffs of dust each pull. Actually running it would probably just make clouds of dust plus it would throw the charcoal all over. My bag has a hole in it and I didn’t really want to get it covered in charcoal dust.


that is the hammermill part.

Those can be kind of hard to find in the states. A lot of people switched to mobility scooters. Which I believe have the same motor but just one instead of two like a wheelchair (which could also be used), and a lot of people use them for robotics projects.


Thanks Sean. I did save a scooter motor but never tried to remove it from the axle and wheels.

I tried feeding some more charcoal into the chipper side.

This is what I started with.

The little bit in the bucket is what I was able to get before I jammed up something and now I can’t move it at all. Must have missed a stick when I tried to clean it out.

The short time it was working it made a lot more dust. This chipper is pretty new and I don’t want to modify it but might be able to get a different one but they seem to be directly coupled to the engine so I’m not sure if a DC motor can be hooked up easily or not. I never took one apart that far.


Brian, Sean,
You can maybe find a surplus “90Vdc” permanent magnet industrial gear motor as well. I bought a small one, and it runs just fine on lower voltages. That was a while ago, expensive new but outfits like Grainger have them. Sometimes on industrial junk at the scrapyard. I built a T-shirt ink dryer once…


Windshield wiper gear motors might get the job done. They are around 0.1 HP and easy enough to scavenge at the junk yard. If you need more power you might run two rollers on the same axis and power them from either side with separate motors.