Block grinder problem

[Stobal]

I have a 7" 1/2 hp block grinder that I thought I picked up for a steal but upon taking it apart the left spindle threads are completely destroyed. Is there any way to recut threads on this? I know that they would be reverse threads. Can anybody help me out on what to do? Can I still use the right side if I cannot repair the left?
Thanks in advance,

 

[exmaxima1]

I have a 7" 1/2 hp block grinder that I thought I picked up for a steal but upon taking it apart the left spindle threads are completely destroyed. Is there any way to recut threads on this? I know that they would be reverse threads. Can anybody help me out on what to do? Can I still use the right side if I cannot repair the left?
Thanks in advance,

If you invest in a left-hand threading die you could fix them. Mcmaster sells a cheapo that would probably work: http://www.mcmaster.com/#2667a477/=y2dry8

Or just use the right side. Or keep looking for a replacement shaft/rotor.

 

[stonesfan68]

I had a similar problem with the block grinder that I bought, and I purchased the left-hand die from McMaster-Carr and it solved the problem. If I recall correctly, the threads are 1/4-20, but double-check that on the other side.

 

[jakemac]

They should be bigger than 1/4-20 on the arbor. Depending on the grinder, they're more likely to be 5/8" or 3/4".

 

[exmaxima1]

They should be bigger than 1/4-20 on the arbor. Depending on the grinder, they're more likely to be 5/8" or 3/4".

On the 1/2hp they are 1/2" or 5/8", and being a 7-inch model it's most likely the latter. The die I suggested was a 5/8-18 LH thread

 

[Packard V8]

the left spindle threads are completely destroyed.

The die can clean buggered threads, but it can't make material where the steel is just gone.

Where that was the case, I cut off the threaded portion of the shaft to just as long as the bore of an aftermarket LH threaded arbor of the kind used to convert a standard shaft motor into a buffer or grinder. I wrapped the damaged threads with electrician's tape to get a snug fit in the bore and then tightened the two set screws to hold it in place. Worked fine.

jack vines

 

[larry4406]

If the shaft threads are truly damaged beyond repair, could he not turn it down to the next smaller size and thread it?

 

[Stobal]

Ordered a 1/2" 20 LH thread die. We will see if it can be recovered. If not can the shaft be removed and taken or sent to a machinist?

 

[exmaxima1]

Ordered a 1/2" 20 LH thread die. We will see if it can be recovered. If not can the shaft be removed and taken or sent to a machinist?

Please confirm that's a 7" grinder. I am shocked that Craftsman would use a 1/2" arbor on a 7" grinder
Is that a split-phase motor?

 

[Stobal]

I used the nut from the other side to figure out the size.