Stainless vs. Mild steel grinder parts

I was wondering if there was a price comparison between stainless steel and mild steel shredder parts? Even if it is just a ‘ballpark’ figure?

Also if there was an argument for laser cut or water cut parts?

I presume stainless wold be much more durable time wise? If you have sometimes dirty or partially wet plastic then mild steel might introduce rust into ground parts?


Exactly, we used stainless steel to avoid rusting (if there is still some liquid in the bottles) and because it’s harder. But then again it’s more expensive. Honestly I have no idea exactly how much depends where you get it. I guess the best way is to ask around at the local metal man.

No argument for laser, plasma or water-cutted.
Best to find/most affordable?

Just got the outstanding bits from my laser guy today. The stainless spacers came out a tighter fit on the shaft than the mild steel so i ended up having to file each one by hand. With a small file and no vice it took me three hours. The end result was a success though – the blades sit and mesh into each other much better now than with the thinner mild steel spacers.

With the mild steel and stainless together it looks like a zebra-shredder…

Hi @paulfreed,

congrats!! the first pictures I see here of a almost finished shredder :).

Running smoothly ???
Some things I found with the preciousplastic proto’s.
– Be sure to debur the lasered parts, I used a belt sanding machine. Some might use some straightening as well. When you are sanding, sharpen the knifes a little, laser corners are always rounded. The outside of knifes and fixed knifes should be smooth, prevents the plastic from sticking on the rough surface.
– Running smooth, needs some fine tuning and thinkering 🙂
A tiny little play on the shaft knifes is oke, not to much to prevent them from hooking? on the fixed knifes.
Bearing makes could have different dimensions, so you can vary the bearing shims. grind them down a little ore use a other thickness. use the shims @gaudo mentioned.

I found a food or drink can, is easy to make your own shims.
You can use shim for the side plates as well…

regards Kees

Hi @keesdeligt

I’m not a mechanical bloke (more electrical), so I really appreciate the tinker tips -thanks!

Yes, It seems to run smoothly enough until a blade edge catches one of its counterpart stationary blades. I’m sure (I hope) the spacing will be much better once i receive the re-lasered parts i’m anxiously waiting for. I’m hoping not to have to use shims, but cheers for the advice with the tin cans (I was wondering what to do there)!


PS for everyone else out there, here you can see the play i’ve still got…

This is really a bad luck!

Perhaps you can save your shredder using bering spacers.
They starts, if i remember well, from 0.1mm thick and seems to me 0.2 and 0.3mm is also available.
It’s enough find one with compatible inner diameter.


It seems that stainless does have better tolerances.
A lesson learned there for me – only stainless from now on!

Well, I’ve just learnt that this stuff can have huge tolerances, something to do with the way they roll it out when they make the sheets.
So, be specific when ordering your cutting pieces, because a few point something millimeters off adds up to lots of mm over the shaft length.

Not sure if SS has better tolerances. Anyone know?

Anyone else had this misfortune?

Hi Paul,

looks great!!!

Where can I order the laser Cut parts for this price?


Here is my finger tight mild steel version so far…

Any tips on how to get the thing running nice and smoothly?

I’ve just started the shredder in mild steel.
I had it laser cut for R 1323 (about 80 euros).
Stainless was quoted at about 30%-40% more.
Will let you guys know how it pans out.

Thanks Gerd.
I’m in South Africa.

It looks great from far, but its far from great – I have just realized my laser guy’s 6mm wasn’t quite 6mm. Its more like 5.7mm. That makes an error of almost 4mm over the shaft length. Well, at least i think thats the problem. Anyone agree? Agrrrr!

Thats my first pitfall so far so beware guys!

has any one tried with HSS? I think this would be the best solution, asuming the price does not get to high!

Hi All
I was wondering what type of lifespan can one expect from the shredder blades. Assuming we use reasonably clean feed stock.


I was just wondering if aluminium could be used instead… at least for the shredder’s teeth?

Hi Cyrille,

244€ sounds pretty good. Indeed I also think steel laser cutters are still much too expensive for FabLabs (from what I’ve seen).

There’s a cnc plasma cutter here in Brussels, but the edge quality isn’t nearly good enough for this application.


I’ve found the following prices from a local laser cutting company here in Barcelona.

€182.35 VAT incl. mild steel (S-235)

€244,9 VAT incl. stainless steel (304 L.C)

I’m still waiting for offers from another few companies from around. Unfortunately the Fab Lab’s here in Barcelona don’t have laser cutters capable of cutting steel.



Thanks for sharing your information. Very useful for us!
Luckily the second one gets better, still quite expensive though.
Potentially you could try a local Fablab, if they are around. Much cheaper but you need some basic understanding of the machinery…

Just got another price:

Stainless steel grade 304 364.21€ inc vat


**mild steel 244.78€ inc vat



Hello all,

Just got the first price back for the shredder parts, they are as follows:

Stainless steel grade 304

472.72€ for all parts in 3,6 and 6mm. excluding vat @ 21% so 572.00€ in total

Mild steel grade ST37

360.94€ for all parts in 3,6 and 6mm. excluding vat @ 21% so 437.00€ in total

I’ll keep adding figures as they come in 🙂