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M3 grub screws don't fit

Posted by adenton 
M3 grub screws don't fit
March 30, 2017 08:30PM

I noticed that the M3 grub screws are not fitting my stepper driver pulley. My local hardware store doesn't have anything smaller than a M4... I'm assuming I need either an M2.5 or M2. Does anyone have any experience with this? I looked online but I won't know if they fit, and I'd have to buy, like, 50 even though I just need 2.

Re: M3 grub screws don't fit
March 31, 2017 12:39AM
Drill with M2.5 and tap to M3?

Might be easier than other solutions.

Alternatively, if you can find an M2.5 screw that fits, then you can cut the end off and dremel a flat into it, and use a flat screwdriver. Hobby shops have a multitude of small screws.

Edited 1 time(s). Last edit at 03/31/2017 12:40AM by nebbian.
Re: M3 grub screws don't fit
March 31, 2017 02:38AM
Buy new pulleys?

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: M3 grub screws don't fit
March 31, 2017 06:27PM
99p for 10xM2.5 grub screws from China on ebay...or £2.59 for 5 M2.5 grub screws delivered from the UK..
Re: M3 grub screws don't fit
April 02, 2017 07:29PM
Find a new hardware store. Hardware like you describe isn't rare or hard to find, if your store doesn't have them, move along to one that does.

I like the idea of using a regular screw to identify the pitch.

Could it be SAE (English) 6-32, 4-40? The shorter the hole, the finer screw you need to use. Tapping a bigger hole may not work because the edges of the screw could interfere with the radius of the pulley or you wouldn't have enough threads engaged to work.
Re: M3 grub screws don't fit
April 02, 2017 09:51PM
Worth noting it's usually good to use non-grub screws when you can. If you have the space, put in full-size socket-cap screws. You can get more torque with less chance of stripping. Just be sure to grind or cut the ends for a better gripping profile.
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