Messed up crank threads

[Drew Back]

What would be the correct die size to clean up the threads on a long stroke crank shaft??

[beezermacc]

I don't know the answer to your question but, when it is unlikely to find the correct die, I use a thread file. I usually get there in the end!

[Greybeard]

Yes, I found a thread file very useful while BSA'ing

[morris]

Not sure if it's the same for a longstroke, but on both my plunger and SA it's 3/4 x 20 tpi

[duTch]

 You'd be hard pressed to find a Left Hander for the timing pinion/pump drive nut
 
 But funny enough in my box of taps the other day, I found a LH 1/4 WW

[Drew Back]

Its on the cush drive side luckily

[Drew Back]

the 3/4 20 would be right for the cush drive side right??

[The Artful Bodger]

If you've damaged the first couple of threads you might find a problem getting a die to start square. The trouble with cross threading with a die is it will really screw up those first few threads! A thread file will allow you to use the undamaged threads for alignment to clean up the starting threads.
Colin

[muskrat]

A die or die nut is my 1st choise followed by a thread file.
If you have a spare cush nut you can cut it in half (cross section), put it over the thread past the damaged bit. Use a hose clamp to hold it together and wind it off over the damaged bit.
Cheers

[terryk]

Or you can put it in a lathe and chase the thread with the correct ground tool. You wont have to put balance weights on bigend journals just run it very slow which you have to anyway with threading. Find a mate with a big enough lathe.

[duTch]

...in an ideal world... 

Or you can put it in a lathe and chase the thread with the correct ground tool. You wont have to put balance weights on bigend journals just run it very slow which you have to anyway with threading. Find a mate with a big enough lathe.

 In a slightly less ideal world, I used same as muskys suggestion a while ago to reinstate my genny gear thread, and it worked a treat; my first choice, that is

If you have a spare cush nut

...

[chaterlea25]

Hi All,

You'd be hard pressed to find a Left Hander for the timing pinion/pump drive nut

The timing side is 9/16 x 20 LH, which is the same as bicycle pedal crank thread
A local "proper" bicycle shop should have a tap for reclaiming this (at least mine had )

Recently I needed to find a M12 x 1mm LH nut for a little Ducati Bronco ?
I found a tap on ebay from China for a couple of bucks to make one
Tracy tools were about £35 

Cheers
John

[morris]

Tracy tools were about £35 

Kicking in an open door here, but good tools don't come cheap...

[muskrat]

Pay peanuts = get monkeys.
I never skimp on tools. Broken the odd knuckle using cheap spanners.
Cheers

[bsa-bill]

but good tools don't come cheap...

Yep but paying someone to use their good tools  ain't cheap either, obviously if it requires skills they have and you don't then fair enough.
I have got the price of a tool back on one job on a few occasions and if you reckon you won't use it again there's always Ebay