MTFCA Forum

Working on my recently rescued 27 Tudor and got a very insect damaged driver rear wheel. Attempting to remove it has been fruitless and has resulted in the center bolt of the puller to bend and crack after 4 smacks with a 4 pounder. I was able to extract the bolt from the puller but the threads need to be chased and the bolt replaced. Thread gauge says it is 10 tpi but measures .730 across the threads. What the heck is that? Is that considered 3/4”? Hoping some machinist can set me straight

Measured mine, it is 3/4 - 10.

Thanks Jeff, friend of mine went out and measured his and agrees with yours at 3/4-10. His puller is the same one I have so I went back out thinking maybe I didn’t zero the calipers. The first caliper I used out of my tool box was my utility pair from HF which has always been very close. I grabbed my Mitoyo from the gun room and confirmed the .729. I checked at three different locations on the bolt and they all are within .001. It is the stock bolt for the puller. Not sure how it could stretch by hitting it, just the opposite I would imagine.

There is a tolerance connected to the major diameter of screw threads.
For a 3/4 10 external thread the max is .750 in.
The minimum diameter is .735 for a class 2 thread..
And .737 for a class 3 thread.
Often you will find that the major diameter is below the minimum, particularly with economy applications.
Art Mirtes

.730 diameter sounds believable for a 100 year old machine screw thread. Most of these parts were produced when the National thread standards were in their infancy... so not surprised when profiles and dimensions are slightly off our modern standards

Very good information! Sometimes I forget I am playing with 100 year old parts and technology. I was able to acquire a new 3/4-10 bolt and tap today and put the puller back together. I stuck the puller back on the hub got out a long pipe wrench that would rest on the ground to hold the hub while I just about stood on the bolt wrench. Still would not come loose so I hit it several times with a 4 pounder, still nothing! Frustrated I felt like I needed to walk away so I took my 22 out for a 10 mile ride. When I came back I hit it one more time and it popped right off. I win!