a little help with metric thread sizes please..........

[Foolwitools]

Hi Guys,

We have a little electric twin motor cat, I think MRC made it a long time ago..........

The props are held on the shaft between 2 nuts , no pin or drive dog.

Well, we lost one of the nuts. We have a great hardware store in our neighborhood that usually has every strange nut and bolt size but not this time.

I think it's metric. the nut will go onto a 4-40 screw, but it's sloppy and would surely strip if tightened. it's too small to be 6-32

the 3mm screws and nuts they had seem to be the right diameter, but the threads are too fine.

Anyone have any ideas? Or what I need?

Bob the Fool :blink:

 

[Ray Sametz]

Bob, Try 5-40. Ray

 

[jetpack]

If the shaft measures right on 1/8" I would agree with the 5-40. There is also an oddball metric size which is a 3.5mm which usually isn't shown on most metric tap and drill charts.

 

[RCUK John]

M3.5 is used to secure all electrical sockets and switches in housing.

See http://www.newmantools.com/tech/threadm.htm for a list of metric coarse threads.

There are some "bastard" sizes (typically M16 x 1.5) based on ISO standards which are used for conduit and electrical fittings.