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Collection, Preservation and Display of Old Lawn Mowers

New Member - Help with crankshaft thread

Hi, having taken ownership of a Suffolk Colt Motor Mower, I was hoping somebody would be able to clarify the type of thread on the end of the crankshaft?

I am correct in thinking it is: left hand 3/8 inch UNF. Attach Photo.

If so can anybody point me in the direction of a source of a die to be able to reform this thread.


Many thanks Jim



wristpin Fri, 04/11/2016

3/8" x 24tpi -  LEFT HAND THREAD.

Early ones had a plain nut with a tab washer, later ones a plain washer and nyloc type nut.

An HSS Die will set you back just over £20 + carriage and vat but if the thread is not too badly damaged you could use the thread file to clean it up but before I splashed out on a die I had reasonable success by taking a spare nut, cutting through one flat, spreading the nut just enough to screw it over the threaded portion of the crank and then clamping it tight together with "mole grips" and winding it off clockwise. This was reasonably effective in cleaning up an iffy  thread without removing metal .  

I second the recommendation for Tracy Tools - dealt with them for years, excellent products and service.