Shredder alignment issues

Hi All

I am having some issues getting the blades to line up perfectly.

I can not seem to source the 4 bearing attachment bolts here in Australia

they are hex drive, flat countersunk head bolts with a nonstandard size thread of 10.5mm.

any ideas where I might find some with the nut?

how have you worked around this problem?

@jsk555 hi, have you got some photos of the issue, which blades are you talking about, do you mean that the axle blades are getting caught on the stationary opposing blades?

if so , what you need to do is grind the spacers down a small amount, or all of the surfaces where the lazier cutter will have created a rough surface.

i got my counter sunk bolts from ebay, mine where just M10 though, so a little loose on the frame, but shouldn’t matter when you tighten it, as the washers for the axle line it up anyway… .


I had the same difficulties when assembling my shredder, I just did a lot of testing around for one or two hours tightening the screws and loosen them again until it was smooth. Now I had to dismantle the thing again to get a better blade sequence, so I have to go through that process once again… :’D

Ahoy people

good to know that it is not my own incompetence and everyone else has had issues.

I was thinking of the best work around and I came to the conclusion that perhapse a combo of getting the holes cut to size and a specialty bolt being machined could help axle alignment.

what grade sandpaper should I use to grind it all down with? I am using a belt sander.

Hey @timslab, just wanted to let you know that it worked like a charm! Thanks so much for your help!
For future reference, I’ll briefly explain how I ended up doing it, it might be helpful for others:
1. assemble shredder housing without fixed blades, only rotating blades.
2. figure out at which position of the bearings the axle rotates best and mark it.
3. reassemble shredder completely, leave bearing bolts open.
4. put bearings in best position, and tighten bolts little by little. As soon as you notice more friction, give the axle or the bearings a SMALL tick with a hammer to put it in a better position. (I had to put one more up, and the other one more down)
5. continue to fasten little by little, until bolts are completely fastened.

Thanks a lot @timslab! Will try this first thing in the morning.

@faro360 I can run you through the steps I took to align them:
*Shredder is fastened together*
*bearing bolts are only a bit tight*
*Blades are scraping/catching somewhere.
Press and pull on either side of axle to align the bearings so that there’s no resistance. Axle straight.
Then mark as precisely as possible (pencil/marker) where the bearings are positioned.
Disassemble shredder walls and fasten the bearings exactly where you marked them.
I think it’s quite important to use lock nuts to ensure than once tightened in place, the bearings won’t move.
Hope it works out.

Ps, the actual bearings are designed to move within the housing to accommodate any misalignment issues (and I suppose highlight them too). You just gotta stick at it until they’re perfect 🙂

@timslab thanks for such a quick reply! I’m pretty sure you’re spot on, because I noticed the bearings or not placed exactly straight in the bearing housing, they are at an angle. Now, how do I fix this? How do you align the bearings?

@faro360 I actually had a similar problem… What could be happining is that the bearings of either side are not completely parallel/coincident. When you tighten the bolts, the bears might be moving causing the entire axle to sit at an angle.
It took me quite a bit of time to get the bearings aligned and fastening the bolts to ensure they won’t slip any further.

Hey guys,

I’m facing the same issue, can’t get the shredder aligned properly. The problem here seems to be related to the bearings. All bolts of the housing are well tightened and the shredder turns fine (not completely smooth, but good enough I think) as long as the bolts that attach the bearings to the housing are not completely fastened. But when we tighten these bolts, the axe won’t turn anymore. I’ve added some pictures so you can have a look. I’m talking about the green bearing house and the two bolts that attach it to the inox housing. Any suggestions on how to fix this? We’ve tried sanding down the blade spacers, but I don’t think that’s where the problem is because it turns fine when the bearing bolts are not fastened.

Is there a specific order in which to fasten the bolts. Should we fasten the bearing bolts first, before tightening up the housing bolts? Should we leave the bearing bolts a little looser? I don’t think it would be a good idea because if they unloosen further when the shredder is operating, the bolt heads might damaged the shredder blades…

This is one of the pitfalls of laser cutting, apart from the rough surface. Because the laser burns through from one side, the kerf (width of cut) is not constant, it is always wider on the top surface leaving you with edges that are not square.

@jsk555 you could take a fair bit off, just be sure its the absolute right thing to do, and not any other potential reason its not lining up

my laser cutting service made a mess of the parts i ordered, i fixed the issues by belt sanding all the faces and sides a small amount,
dave does this in the video, you might need to take more off the faces if your box isn’t fitting snug,
0.2mm of sanding in each blade will equate to approximately 5.0mm tighter after doing all faces as there is a lot of parts. ?

@jsk555, when I first assembled my shredder the blades were also a little off… I found this was because the blades were not being pressed tightly together. I fixed it by making 2 thin metal washers and putting them on either side of the axle. This ensured that blades were tight and couldnt move at all…

Another problem could be in the laser cutting? I originally had some parts cut but the actual laser was not square with the workpiece.

What is the maximum gap between the fixed blade and the active blade that we can have?

Yeah, I also think that it supposed to be M10, I can get the bolts for you, but I think the shipping time is kinda long. Send me a message if you want me to send it.