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Shredder modifications – 1″ Hex Hole parts

This topic contains 46 replies, has 29 voices, and was last updated by  Butte Metz 2 years ago.

keesdeligt keesdeligt

Shredder modifications – 1″ Hex Hole parts

12/05/2016 at 09:47

Finally found some time to update and add some shredder issues, I’ve read in some topics.

For “Oldfashioned” 😉 countries not (yet) working in Metric.
The rotating knifes and spacer, with a 1″ Hex. Hole. Easier to find in some countries I guess.

And to reduce the lasercosts a little, I took a older prototype frame from the shelf, made from Square tube and some flatiron. Worked well and strong enough, but we opted for the lasered version in the end, because it is easier to align and always square.
The ‘older’ version is also easier to change, being it smaller or wider to Fit when 5 and 6 mm sheet is not available. Do the Math Yourself, and adjust the tubelength a little.
On one side You need to close the gap between sieve and frame with piece of sheet, should be no problem.

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10/11/2016 at 21:03

Look this project:

29/05/2016 at 08:22

Modified Hopper 2.1.

Made a drawing of a hopper prototype we used in the workshop.
Witch, I think, is safer and easier to use.
Holds or even Pushes the material down.
No need to put your hands inside.
Can be made of any material you want.

21/05/2016 at 07:45


I did some recounting on the Laserfiles quantity’s.
Knife 3 changed from 5x to 4x
Fixed Knife small from 15x to 14x
Changed the description of the 6 mm bearingspacer to 34x34x6mm

See the PDF

Regards Kees

09/06/2016 at 13:38

@keesdeligt I didn’t understand if these sizes are for those that use the imperial system or for us who use the metric system.

also, I have a big doubt.. do you have special units in the nederlands? 🙂
do you by any chance have products that use the inches or the Whitworth standard?
this question is also for @davehakkens

I’m asking this because I see weird sizes in your files that don’t match up with products we have here in Spain:
nut and bolt sizes, threaded bars, and now, especially for the extrusion machine, I can’t find a tube that has 26mm in diameter inside. I Spain It doesn’t exist.
I found one that is 26,9 or one that is 25

I will have to lathe with a drill head a 25mm tube, but that is more costly as nobody wants to weld a 26mm drill onto a large rod to put into the lathe :S.

Let me know about the sizes please

14/09/2016 at 14:05

Hey Everybody,
i am thinking to use a Bike instead for a Motor.
Could somebody help me, how i need to transform the Bike that i can make up enough Power on the Shredder or wont this be Posible?

23/06/2016 at 21:21

Would it be possible to publish individual step files of the rotar blades and static cutouts in the the shredder. I am in the us where we don’t have ready or inexpensive access to metric plate. I’d like to create a cad version of the shredder box using standard English plate sizes. I realize it’s just a matter of stacking the plates up and placing a spacer at the end or shortening the box. However I’d like to check it in cad before I have a bunch of parts laser cut. I have opened the .step version of the assembled shredder in autodesk inventor and it opens correctly but loses all of the dimensions, parameters and sketches from the individual parts. I’ve also downloaded fusion and looked for the sketches defining each blade to no avail. I know I could pull the individual dxf drawings and import them to create new parts for each blade and then reassemble them but I’d rather use inventors capabilities to resize things like the hex hole that’s cut into each one in one shot. Also which cad system did you use to create all the plans with?

09/06/2016 at 21:15

Hi @lyricalpolymath a.k.a. @beltran ..
If you can be more specific on witch sizes?.
Always thought spain was a european metric country, but you are half way there! At least you are driving on the right side off the road ;).
Spending 25 years of my life on Drawing and building machinery, maintaining repairing and servicing machines from Sweden to Spain and from Russia to California. I found the only common things are Drivechains, Plumbing and fittings.
In the Netherlands we work with SI (Système international d’unités) by Law since the 70’s.
So I do not know how to make a drawing to fit all, if you can, please feel free to try. I posted some laserfiles for 1″ hex shafts, posted a shredder frame easy to adapt for alien-like US gauge sheets. So if anyone can tell me what to adapt or make a alternate drawing no problem. IMHO the download package is just a guideline.

Back to your question :).
We could lay our hands on a 26mm seamless tube for the injection machine, so looked for a tube to fit around that. Came up with a seamless tube almost 1″ (easy to make the 1″thread on). So that was a easy choice for the extruder as well.

If a 25.4mm (1″) or 25mm drill is easy to find in spain, perhaps a 1″inch tube is easy to find?

Regards Kees

13/05/2016 at 21:59

how do you mean loading into freecad?
The file contains 4 dxf’s to sent to the laser service and a pdf for the tube frame, that is all there is to it.
Not familiar with freecad but it should load basic dxf files I guess?

I could consider it make a step file of the shredder available, that should work for most 3D cad software

14/12/2018 at 12:47

Apart from hex rod length and hopper size/mesh length etc. No reason why shredder can’t be made bigger by simply adding more blades. 14 blades needs 200-300Nm to do its job as discussed elsewhere, but I expect only 1 or 2 are ever needing maximum torque at once with this number of blades.
If 14 blades needs 2kW at 70rpm then:
28 blades at 35rpm would also be 2kW and same output rate achievable.
28 blades at 70rpm would be 4kW with double output rate.
Likewise 7 blades at 70rpm would work with a 1kW motor assembly or
7 blades at 35rpm would only need 0.5kW.

Power [kW]=(blade thickness/6mm) * #blades * rpm /490

24/04/2018 at 10:49

You are asking for too much buddy @goodandbasic 🙂
In the official Precious Plastic Kit you can find all parts in milimetric steel with 27mm hex holes. If you want to use 1″ hex bar instead then just download the files from this topic and replace the ones in the official PP kit.

If you want to use imperial steel (1/8″, 3/16″ and 1/4″), I made a conversion and can be found HERE. On my conversion, I use 1″ hex holes

24/03/2018 at 03:09

@listva There is are only meant to be 14 moving knives for some reason there is an extra one! and also for fixed one I’m not sure why this.

07/06/2017 at 13:47

Original was 2 kW.

31/08/2016 at 07:30

@landrovermanuk Go for it, and let us know the results of your shredding test 😉
The good thing about experimenting with a paper shredder is that they cost a bargain, so in case that the project doesn’t work as expected, you won’t lose much.

27/08/2016 at 00:43

Thanks for your reply.
Think I could still be tempted to try it with a larger motor.
If for no other reason than apart from the motor, it would cost next to nothing to build and the motor could be transfered into a full size shredder at a later date…

25/08/2016 at 20:37

@landrovermanuk this has been attemped already, but paper shredder are not that good for this job. Depending on the type of plastic you use and the quantity of plastic, they will get clogged.

Look at this topic for more info: http://onearmy.world/community/forums/topic/plastic-bags-2/

25/08/2016 at 15:45

How about using the blades from an office paper shredder?
Most modern paper shredders are capable of shredding CDs and credit cards.
The blades, guides and possibly even the frame from the shredded with a larger motor would make a cheap plastic shredder…

07/06/2016 at 09:14

Hi All,

is there a possibility to have the design of a bigger shredder,

a shredder which can have a capacity of 50 to 100 kg per hour, with this you can make people in Africa think about a micro business for recycling.

thanks in advance

04/07/2019 at 02:49

I upgraded my current specs to 1.25 inch aka 32mm hex bar and 1 inch bearings.

M14 grade 8 bolts that have the heads cut off and TIG welded on with lock nuts.


BTW you MUST I can not stress it enough use lock nuts or lock washers and the best grade of bolt you can source/afford


Earlier machines had issues with nuts constantly vibrating loose and one time a loose nut somehow got into the cutting blades from the hopper.




18/02/2019 at 23:21

heyy thank you so much for this,

So if i used the blueprints from the precious plastic portal, I cant use a 1″ hex bar? Because I just cut my laser parts, and I see the hole in the  cutting blade is 1 1/16″,

The blue prints ask for a 27mm hex bar, i am confused

02/01/2019 at 21:51

What software do you use for the 3d model, to download and thus be able to observe the model?
Did you also want to know what software you use to make the code for laser cutting? since I have aspire 8.0 and I do not know if I can open it in the

19/04/2018 at 23:39

I’ve got an idea. Could someone here compile a program that allows the user to drag and drop different sizes of material, numbers of blades, blade type, size of hex bar, box or tube frame, etc, and then have the program spit out the dxf files for the shredder? There seem to be a lot of mixes between metric and imperial sheet steel and the above mentioned options. The program could simply have the models for all the options pre-designed, and then compile them into a single file from the intersection of the factors. The program should be visual drag and drop to make it easy to use, and it could be built into this website. The program should also calculate the combined thickness of the blades and modify the sides of the box or tube frame. Output could be divided into two sets of files, dxfs for cutting and pdfs for the remaining blueprints.

24/03/2018 at 23:20

Yeah, thank you for the info. I’ve already calculated that mismatch on the blueprint)

23/03/2018 at 12:46

Hi guys!
Sorry for stupid question, but how many knives are there actually in the shredder?
There are 3 individual .dxf files for 15 moving knives (3 types x5), but in the “overall” .pdf blueprint there are 14 moving knives. The same thing with fixed ones (15 vs 14).
I tryed to find exact answer here on forum, but I couldn’t. On different photos here people has also different number of blades.
Please, could somebody make it clear? Thanks

16/02/2018 at 02:27

@dotcom22 The knife are all the same, the lñittle holes are just to help when mounting on the e bar but if you want you can choose and try different settings.

16/02/2018 at 01:10

Hello everybody

Please I’m unclear about Knives piece… It seem Knives 1/2/3 have exactly the same dimension/specification except the fact they have 1/2/3 small hole “for help?” when mounting the shredder. Could you confirm please ??

I looked the video but I don’t get well the concept and the use of theses hole and for what exactly is necessary. Is not possible to have 14x of any knives?

Probably a stupid question or I miss something somewhere….

Thank you

14/02/2017 at 17:15

i am also looking to design a bigger shredder. how do we upgrade this existing design? and does anyone know the output of the original shredder?

13/12/2016 at 23:37

Hi @xxxolivierxxx,

Thanks for the link!

I had originally looked into changing the whole design to imperial units, but decided against it since the replacement of 5mm and 6mm knives and spacers with 3/16 and 1/4 inch would have left a significantly bigger gap, rather than 1mm total (0.5mm on each side), it would have been almost 1.6mm (0.8mm on each side).

I really don’t know what effect this would have, but I assumed that it was designed this way for some reason so I didn’t want to mess with it too much. Maybe the plastic would bend rather than cut and would jam the shredder or something. Anyways, since I went with the 3/16 and 6mm combination, my gap will still be a bit bigger, but less so, around 1.24mm (0.62mm on each side). I’ll let you guys know how it works, and if it’s no big deal then the switch to full imperial might also work.

I also looked at the design you linked, and it seems to have much bigger gaps between blades, with the 1/4 and 3/8 combination they are a full 1/8 inch (more than 3mm, 1.6mm on each side). So if that is a potential issue, then it might be a problem.

If anyone is interested, I would be happy to make and post the dxf files for the switch to 3/16 and 1/4 that I initially proposed, but I won’t be cutting or testing it myself. It will take me a bit of time since I’m still new to CAD software and I do it manually one point at a time, but give me the word and I’ll get right on it.

01/12/2016 at 05:08

I had trouble finding a 27mm stainless steel hexagon bar in the various visited ironworks. I found a carbon steel rod in this dimension. I would like to know if it is acceptable to use this bar for machining the hexagonal shaft of the shredder.

13/11/2016 at 21:48


I figured out how to make the changes using QCAD, a free and open source CAD software. For anyone who might need to do this, it was a simple matter of clicking on the path and scrolling down in the property editor window to change the X and/or Y coordinate for each point, or index. There seemed to be two layers to the DXF file, so I did it for both. I’m new to CAD software, so I’m not sure but I assume this is normal.

@keesdeligt, as I’m not super confident with this stuff, would you be mind checking my files (and maybe my method) to make sure I didn’t do anything strange or potentially disastrous?

Thanks in advance,

13/11/2016 at 19:51


I did see that one, but thought it would be nicer to adjust the laser files, to make sure it is perfectly square and aligned. If you do have some time to make some modified DXF’s it would be great, as I still haven’t figured out how to do it myself. I will keep trying though 🙂

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