Advice on how to fix reverse threads on my crankshaft??

[300ex_#387]

On my Grizzly 700 I have some reversed threads messed up that hold my wet clutch on. I'm not sure of the size and pitch yet. Can you get a die for reverse threads this big in metric? Would a normal machine shop be able to fix this with ease? The threads are still there but need to be tapped. Ive tried a thread file and it just will not cut it. I really dont want to have to replace a crank because of this so Im just asking for other opinions.

[300ex_#387]

Here is a picture of the shaft with the nut on. I dont have any pictures of the threads but this gives you an idea.

[wilkin250r]

McMaster has reverse thread up to 20mm. They get kinda pricey, you might be looking at $40 or more, but certainly cheaper than a new crank.

First step, obviously, is to get the size and pitch.

[300ex_#387]

Originally posted by wilkin250r
McMaster has reverse thread up to 20mm. They get kinda pricey, you might be looking at $40 or more, but certainly cheaper than a new crank.

First step, obviously, is to get the size and pitch.

Thanks. I'm have a hard time finding out the size and pitch right now. It has to be close to 20mm. I'm worried that when I do tap it that the threads will hold. It is supposed to be 100lbs tightened down.

[CJM]

Im not exactly sure how that shaft works/is setup, but is it possible to drill a hole in the shaft? This is an all else fails scenario, but I wonder if you could drill a hole and drive a roll pin in to hold the nut in place?

Other idea would be to go slightly larger either metric or standard. Very next size, you get the tap and the nut and go to town. If its only slightly larger you might be able to get away with it.

Another idea is to take the crank out, weld the thread area up very well so its smooth and cut the threads again.

Just some ideas..

[blacknblue#2]

Originally posted by CJM
Im not exactly sure how that shaft works/is setup, but is it possible to drill a hole in the shaft? This is an all else fails scenario, but I wonder if you could drill a hole and drive a roll pin in to hold the nut in place?

Other idea would be to go slightly larger either metric or standard. Very next size, you get the tap and the nut and go to town. If its only slightly larger you might be able to get away with it.

Another idea is to take the crank out, weld the thread area up very well so its smooth and cut the threads again.

Just some ideas..

good ideas but most these cranks are hardened. drilling that with a basic hand drill would be near impossible. If it come to taking the crank out i would just spend the money on a new one while your that far into it. imo

[300ex_#387]

I should be able to repair these threads but finding the size of die I need is giving me a hard time. The first 8 threads are basically shot but the last 10 or so are fine. The nut really only sets on the last 10-12 threads so as long as I can get a die I should be ok. I'm just going to take it to a machine shop and have them size it out for me and order a die. I'd rather let them try and fix the threads instead of taking the chance of having to tear down the motor for something this small. Ive done so many searches of other people with this problem and cannot find one thread on any forum stating the size and pitch. I'll just let the machine shop do it.

[blacknblue#2]

Originally posted by 300ex_#387
I should be able to repair these threads but finding the size of die I need is giving me a hard time. The first 8 threads are basically shot but the last 10 or so are fine. The nut really only sets on the last 10-12 threads so as long as I can get a die I should be ok. I'm just going to take it to a machine shop and have them size it out for me and order a die. I'd rather let them try and fix the threads instead of taking the chance of having to tear down the motor for something this small. Ive done so many searches of other people with this problem and cannot find one thread on any forum stating the size and pitch. I'll just let the machine shop do it.

If you have enough good threads to fill the entire nut then what i have done before is take a dremel tool and basically grind big taper out of the first couple bad threads...taper it down to the good threads.