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S2019, It is indeed the 21″ bit. I didn’t have to dress the bit or ream the pipe I think it had around a 1/32″ difference from the OD to ID. I did have multiple problems with warpage of my barrel, BIG TIP DON’T cut out your hopper opening before you weld the support legs on. My first attempt looked like a banana, my only stainless welding rods were 1/8″ stick rods, with my 300 amp Lincoln it was tricky.
thanks long, I have been using pp mostly from milk jugs. I will definitely try preheating the mold. I need to get an old toaster anyway to heat up my welding rods.
also the shaft is made for a SDS max drill chuck, which has a 18mm diameter i think. I had to use a 3/4″ split coupling with a sheet metal shim all the way around.
The Screw is made from a 1″ concrete drill bit i found at Harbor Freight Tools, it was only $40 for a set of 3 bits. It was the closest off the shelf item I could find that matched the designed screw from the blueprints.
I had to un-braze the carbide teeth off the end and grind down the shaft on the hopper end of the screw to allow better feeding. It fit surprisingly well inside a 3/4″ Schedule 40 seamless pipe.
Unfortunately I didn’t think to take pictures of it before I ran a batch of plastic through it, Its about impossible to clean it off at this point.
Please note the the end of the second largest casting. It was made with the shorter mold and it developed a mushroomed head at the end when i filled up the mold.
here are some photos of my machine
I am not sure what you mean buy using 11 gauge sheets, this is a factor of 1/4″ plate is a bit bigger than 6mm and 3/16″ plate being a bit smaller than 5mm plate. Our shredder head is sturdy we can shake the knives side to side a tiny amount but that is the only slop in the system.
By the way we are using a 3/4hp 1140rpm with a 39-1 gearbox 29rpm output/1617inch pounds and a chain coupling which seems to work fine. We tried a half coupling with a spider like your unit, but it crushed the rubber spider in seconds. Found out it was only rated for 120 inch pounds.
We are just starting our operation, and we purchased an assembled shredder head on ebay (the cost of laser cutting services here are very expensive). Our unit’s knives/spacers were made with 3/16″ and 1/4″ plate. we have noticed many of the thinner plastics we are working with don’t shear consistently, it seams like lots of plastics wrap around the knives and slide in between the fixed and moving knives.
I did the math on the spacing, sorry for you metric folks my brain works in imperial.
the original design has a 0.0393″-1mm gap between the knives
our American plate has a 0.0625″-1/16″ gap between the knives
Our unit has over 150% of the gap of the metric design do you think this is enough to cause the issues we have been seeing?
please note our head never came with the screen under the shredder and is putting out very course shredded plastic similar to a traditional ribbon paper shredder.