Cordless drill motor

Hi there,

I want to use 4 cordless drill motors to power a mobile robot, but I need some assistance determining the thread size of the motor axis. The motor is from a B&D cordless drill and when the chuck is removed, a thread is revealed. This is almost a standard thread on all cordless drills, but I can't figure out the size/type of it in order to buy a corresponding nut.

Approximate dimensions are
- Outer diameter: 12.5 mm (0.492 in)
- Pitch: 1.3 mm (0.051 in)

I guess the dimensions correspond to an American standard. Anyone with special knowledge on cordless drills?

That sounds like it's a 1/2 inch, 20 TPI thread. TPI = teeth per inch. It could be Unified Fine (UNF). See this page for other possibilities.

Edit, you may have more luck getting British cycle threaded nuts from a bicycle shop.

Mike.

Seems like a good match - at least based on the UNF. I think the next step is to purchase a UNF nut to check the fit.

Thanks Mike

The British cycle thread does not seem to be available with 1/2" and 20 TPI - none of the BSC charts contain it.

If you look half way down the link I posted 1/2 inch BSCycle is available in 20 and 26 tpi.

Mike.

Ok, did not look for it there, but went straight to Google
Strange how other tables only show the 26 TPI and not 20 TPI like your table shows.

I'll stick to the UNF, due to the availability in my country.

Thanks again

If you can easily get UNF then go for that. I think getting UNF here in Australia would be nigh on impossible hence my bicycle suggestion. BTW, bicycle pedals appear to be 1/2 inch 20 tpi.

Mike.

Looks like you have to measure a bit more carefully, e.g. use a pitch gauge: See: **broken link removed**

1/2-20 and 1/2-24 seem like possibilities.

KeepItSimpleStupid: I have only used a slide gauge as I don't own a pitch gauge myself (unfortunately), but it doesn't look like a 1/2-24 (UNF)