DIY Hammer Mill

[Bidgee]

Thought I post up some details of a DIY hammer mill I've been working on. Still a work in progress but I'm nearly there. The original aim was to make it semi portable, able to be driven by a 125mm cordless grinder so sampling can be done on site. It's a little bigger than I planned and the 125mm struggles to start (brushless motor issue I think) but it runs well once going. At home I run it with a 100mm corded grinder. The main reason for the size is that I got the steel pipe cheap. For a better portability and to reduce the abuse on the grinder I'd use 200mm ID pipe if it did it again. Wall thickness on the pipe could also come down a lot too.

Dimensions.

Pipe casing - 300mm ID with 12mm wall.
Side plates - 5mm mild plate.
Shaft 20mm with ball bearing either side.
Inlet and outlet both 90mm SHS 1.5mm wall.
Hammers are mild steel chain with 8.8 HT bolts in the outer link.
Outlet screen is drilled holes in the pipe casing. Originally 2mm but the milled dust was not exiting and the holes clogged easily. I rebored about 50% to 4mm and it works much better. I also added plates to the drive shaft that act as a fan to push the milled dust out the screen.

I've milled plenty of good looking mineralised rocks from old mine sites and found precisely zero gold. The struggle is real .

Bidgee

 

[davsgold]

yes they work very well, this is the one I made, it has crushed rocks and produced gold so keep at it ay

 

[Bidgee]

Nice setup and good result. Do you take in the field or just process at home?

 

[davsgold]

I take the rocks home and process them at home, the angle grinder that drives it is a 240v and not cordless and the whole setup is a bit bulky to take on the trip to WA from NSW so I find it easier to take the rocks home

This is a few of the rocks, just break them down in a dolly pot to a manageable size then into the mill

 

[Ausgold]

Good looking setup, I have a smaller set I made up on a 5" angle grinder, sure beats a dolly pot.

 

[Aussiedigs]

I take the rocks home and process them at home, the angle grinder that drives it is a 240v and not cordless and the whole setup is a bit bulky to take on the trip to WA from NSW so I find it easier to take the rocks home

This is a few of the rocks, just break them down in a dolly pot to a manageable size then into the mill
View attachment 14441

Mate, that is awesome. How did you connect the shaft to the grinder if you don’t mind me asking?
Cheers.
Al.

 

[davsgold]

Mate, that is awesome. How did you connect the shaft to the grinder if you don’t mind me asking?
Cheers.
Al.

the grinder has a 14mm thread, where the flat nut goes to hold the discs, so I had the 1" shaft for the mill turned/drilled on a lathe and 14mm internal threaded so it is all on center and works quite nice.

If you need to disconnect the grinder, then just hold the button in on the grinder and use a spanner on the shaft where the half chain links are and undo it

cheers dave

 

[Aussiedigs]

the grinder has a 14mm thread, where the flat nut goes to hold the discs, so I had the 1" shaft for the mill turned/drilled on a lathe and 14mm internal threaded so it is all on center and works quite nice.

If you need to disconnect the grinder, then just hold the button in on the grinder and use a spanner on the shaft where the half chain links are and undo it

cheers dave

Awesome, thanks Dave.