Trapezoidal Nut for Prusa i3 MK2 MK3

by Mach0gr Apr 13, 2017
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Hey can you make a TR8*2 non trapezoidal design ? For normal lead screw it would be super nice thanks !

Can you make TR 8x3 ? plz :)

Does this fit the Prusa MK3? Given all the failures people are having with these horrible nuts, surprised nobody is mentioning MK3 on this part.

I don't think this fits the Mk3 and a printed trap nut isn't going to help issues if you are having any. I haven't had any issues with mine and lubed them with PTFE. If you need new trap nuts just give Prusa a ring and they'll ship you a few. I asked for extras when I ordered my 2nd Mk3 and they dropped them in the box for free.

Thanks alpokemon for your information. I actually printed some last night (on my old Lulzbot Mini) in nylon and tried replacing the prusa-supplied nuts today. Right off the printer they turned substantially easier than the ones that came in the kit, and I passed XYZ calibration the first time with them. I have no idea how long they will last, or if my first print will even work, stay tuned. Yes, I will ask Prusa for replacements too, but I expect that to take a week or more. But, so far so good, and these obviously at least fit the MK3 just fine.

Thanks for creating this. I needed the TR8x2, but unfortunately your design is incorrect. I found a correct model and include it here if you want to compare. TR8x2 has a single start and 2mm pitch (moves 2mm per revolution)


The creator didn't make the thread trapezoidal, so it needs some printer tweaking to work, but the lead and pitch is correct.

I don't think Mcmaster has this size.

Can you post where you found it? What is the equivalent part number on Mcmaster Carr?

please make 8x4 version?

Thank you very much for sharing this, it's exactly what I was looking for! :-) It works perfect (for test just printed in PLA), I'll print in nylon or PET-G later.

Nice! This would probably fix my “Z Wobble”


Can I print this with PLA or PETG? Why did you print with nylon? Is there any difference?

Hi, Nylon has low friction coefficient and is ideal material for the exact application. Other materials may work but don't expect to last as long.

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Printed this in nylon and it's so tight the steppers can't turn it. I'm going to try to ream the inside out a bit to loosen it up. It should be snug, not tight.

Hi, thank you for your comments, if you follow this comments thread down, you will notice the differences each one faces when printing this specific part with different materials. Because of the anatomy of the part, printing with Nylon specially, requires some knowledge. Although I have given the necessary slack in the model to fit my print settings and material, yours may be different. Because Nylon tends to melt and the specific part is rather small, building layers quickly can produce not a well printed part. (maybe squashed a little)
Before adjusting any of your settings on your printer I would suggest to try and print 2 or 4 parts on your platform at the same time. This will give enough time on the layers to cool and produce a better output. (At least with using Nylon for this specific model !)

Let me know, Thanks,

Unfortunately I'm in the middle of rebuilding my printer so I can't print new ones until it's working. I'm going to have to ream these out so I can get my Z moving and finish my rebuild. I tested the fit and it seemed tight, but workable. I guess once the weight of the X carriage was added it was too much for the steppers to handle.

Printed with PLA, Works great nice and snug. Thank You

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Does your printer require higher tolerances for this piece to fit? I printed the STL and it was way too loose so I edited the solidworks file to tighten it up a bit. I actually had to change the diameter of the hole from 6.8 to 5.8 Just curious because my machine (prusa mk2S) has auto calibration so im curious to see if it may print holes too big.

Hi, did you use the same material to print with the one I mentioned ? do you have a 8mm lead screw rod ? I indeed had to loosen up the hole and the trapezoidal width to make this print and work fine on my setup.
Nylons like the one I used, tend to warp or print soft so I had to play with my calibration settings and the file itself to get good result. Using another material for sure you would need to tweak your settings and or file. This is why I decided to give the solidworks file out so anyone can alter it to your liking.

I used PETG to print it since I don't have any nylon, and they are 8mm leadscrews im fairly certain. I got the piece to fit nice and snug after a few attempts

OMG what is that beautiful burgundy red filament in the 3rd picture!? I must know! :)

It's Pet-G transparent red filament from Rigid.ink. I have made all parts of my prusa i3 out of this now. It's great !

Thanks for making and posting this! Fits perfectly :)

Seems I got a thread that is a bit more uncommon... Its it possible to make a version for TR8*4(P2)?

that's 8mm nominal diameter
4mm for a single rotation
2 start threads

This is awesome! Thank you so much for sharing it here! :)

It's perfect.
Can you make the thinner part in a longer version?
So 2 cm would be perfect and would make everything more stable. :)

I hope you understand me.

I needed the T8x2. I printed it and got a 7mm bore for the screw. it wont thread down its too small. When scale it up x1.2 it threads perfectly. maybe its my print settings. But I followed advice on here.

I'm not an expert but to my best knowledge it could be your 3d printer calibration. It could be that you are over-extruding or need to calibrate the settings for your specific material/temperature/speed.
For example you may find the following : if you print just one small part on the bed it will not look and measure exactly the same if you print two at a time. This usually, depending on part, is caused because while the model is being print, the material is still warm/not rigid and as the hot end is putting more hot material on top of it, just squashes it down. If you are printing two of these small parts on the bed, the layer has more time to cool down and stabilize. For printing in PLA this is where the need of fans come in. However fans are not advised when printing in Nylon. For the specific part I printed it in Taulman Nylon bridge and had to put my fans on like 15% to get the right dimensions.
In case you use Solidworks, I provided the solidworks file so you can modify it in every aspect.

I use freeCAD. My problem is probably it being abs+ by esun. Also I'm using a delta rostock style printer. 0.2mm nozzle 0.2 layer with 30% infill 4 perimeters and 3 solI'd layers. I'm probably seeing shrinkage. But I don't see how it's 20%. I'm only printing one at a time. Temps are high 280C on my hot end so I'm probably extruding too much like you said. Thermistor tables are off so I have to crank it up to avoid delamination with abs. I'll tweak it and let you know what works for me. My 3d rendering skills are limited. How you got a line on an inclined plain wrapped helically around an axis baffles me. Overall good work man.

Hey! Thanks for this. Would it be possible to make a version of this for T8x2 rods as well? :)

I do not have a rod to test or measure but my understanding is that if I simply remove the two coils from the model we will end up with T8x2.
I will upload a T8x2, let me know if that works for you.


Thanks! I printed the T8x2mm variant today with Nylon Bridge but unfortunately it did not work. Either way, I'll be replacing my X-ends so I can use proper brass nuts, but thank you very much for trying to help me! :)

The ACME is US, in inch and with a 29° angle, the TR8 is metric has an angle of 30° ! Hope you used the 30° angle.
Anyway, the issue is the choice of material. I made TR8 for testing using Igus filament, 0 play, 0 backlash but they require finishing for a perfect fit. In use they work fine but require a bit more torque and a perfect alignment otherwise the torque required is even higher.
Here you would do better to adapt the mounting holes of the brass nuts provided. Easy and will lead to a more usable nut than a printed one in a material not designed for..

Hi, thank you for the info in the acme. I didn't know that.
I have a TR8 lead screw and in my design I have tweaked the angle (20°) and have made the pitch not symmetrical. This I have made so it prints for a better fit.
I would disagree with you about the brass nut. The Brass nut I bought with the lead screw has big backlash and jog.
The one I made and printed from Nylon, I believe will be longer lasting and better for my printer's z axis.