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Parametric Nut Trap for Mostly Printed CNC

by GeoDave, published

Parametric Nut Trap for Mostly Printed CNC by GeoDave Jul 2, 2015


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Update 12/8/2016:
Added an image of the part dimensioned the variables described for further clarification.

I needed to make a nut trap that would fit with my customized tool holder I am designing to fit a Mastergrip rotary tool I bought at Costco years ago, so I decided to make this part parametric.

Spacing for my tool holder is 53mm distance between holes.

I made a parametric drill jig that will help you drill holes to use with this nut trap. Here is the link to that part: http://www.thingiverse.com/thing:910707

Here is the link to the mastergrip rotary tool holder I made using this size nut trap: http://www.thingiverse.com/thing:909366

You can also open this with Thingiverse Customizer.
Here are the links I used to show me how to get this to work in the customizer.

Here are the links I used for help in making this work in the makerbot customizer.


Here is the link to the openscad template mentioned in the 1st instructable for making your openscad files work with the customizer


Open this with the Customizer or edit any of the variables in the openscad file to adjust it to your liking. The NutSpacing variable is main variable to change, but there are 11 other vaiables you can change. I included the 53mm spacing file I used for the tool holder I am using.

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the customizer dosen't seem to be working

Seems to be a problem everywhere on thingiverse. Take a look at this thread.


Thank you for the info. A comment in the tread said you could download OpenSCAD ( http://www.openscad.org/downloads.html#snapshots ) and edit the included .scad file.
I did this, and it worked great.

I'm creating an IE version with 25mm od tube with 21mm walls. Maybe I just need to print the US version of this?

I checked my 3/4" EMT & that does measure 21mm for the I.D, so sounds correct if your 25mm OD measure 21mm I.D.

I also just checked the sizes of Alted's type F (25mm OD) & J (25.4mm OD) to see what he sizes these for because someone will probably also ask this.

For the 25mm you are using which is type F, set the variable
THNT_Dia=22.5; //Type F 25mm OD

For the 25.4mm you are using which is type F, set the variable
THNT_Dia=22.9; //Type J 25,4mm OD

This should be Line 16 in the openscad file or the 2nd variable if you open this in the thingiverse Customizer.

Thanks for the reply (dunno why Thingiverse didn't tell me you'd replied).

One more question - Do the default values work for M4 nuts and bolts or the almost unobtainable M3.5 ones? It looks like the latter do I'll get tweaking.

3.6mm diameter I think you are referring should be sized for M3 screws or #6 screws. You can change that diameter if you want. That is the size that worked best for me. I usually make the diameter a little bigger than the size screw so I do not have to thread it into the plastic so much. If you change from M3 to M4 screws, you will also have to change the M3 Nut Dia. variable.

Thanks, and yes, I think I'll go for M4 as the Makita (not universal) tool mount I'm using is printed and will easily accommodate M4 cap head screws. M3 just seems a bit small for this task!

For the record, I replaced M3 for M4 throughout and used -

M4Dia=4.2; //Dia. of Hole

Yes, some of these are smaller than your M3 dimensions, but they work. Thanks for the design. Drilling jig next!

Glad it worked for you. I probably should have changed those variables to something like Hole_OD instead of using M3 in the name. Glad it worked for you. The nice thing about using openscad for the designs makes it easy to change any of the variables to meet your needs.


Thanks for this usefull tool but i would like to pint out a problem in your parametric calc.

First of all, that part is a cylinder cut in half so if we want it to fit it correctly inside the tubes/conduits, the height of the parts should be half the diameter (or width it's the same thing here).

So if you input 22 for diameter, you should get 11 for the height of the part sothat it can fit perfect and touch all inside the inner tube.

The problem here with your parametric nut trap is that you don't get half the diameter for the height, you get less.
Example: For a diameter input of 22.5mm you get 10mm height where it should be 11.25. This cause the part to have a gap with the upper part of the inner tube, it does not touch all the inside wall of the tube/conduit creating excessive stress on the part when you tight the screws of the tool holder.

The original part does not have this problem, so don't know if you could modify it... but that would be cool.

Thaks for your work and keep on ! ;)

Thanks for the question. I took a look at this & seems my variable names were probably not clear. If you change the variable Z_Origin = 0, I think you will get what you want. -2 will subtract 2mm from the radius & 0 will make it the same as the radius. For me having the part slightly less than the Radius worked better & thought that was what the original part did, but I may not be remembering that correctly.

I added a dimensioned image with the variable names added on the 2nd image which should clarify this.

Let me know if that answers your question.

Thank you for this as well, You just saved me more time!
Dang you're good!

You are welcome. It is nice to be able to add something back to the community. I enjoy doing the parametric designs. Some of my newer parametric design calculations have given me a bit of a headache, but it is always cool to see the parametric calculations work.

Pretty sweet, is there a link you could give me to teach me the basics on how you got that working?

I just added those links in the Thing info of how I got it to work with the customizer. I was very happy at how well that worked. This part lends itself very well to being parametric. I originally had meant to leave the Z origin variable out, but since it showed with the rest of them, I left it in. I am also thinking I might be able to make a customizable tool holder openscad file, but that maybe too complicated.

Thanks for the comment.