The Triumph Dolomite Club - Discussion Forum

The Number One Club for owners of Triumph's range of small saloons from the 1960s and 1970s.
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PostPosted: Thu Jan 18, 2018 4:34 pm 
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If you are designing something like a hub-puller with a screw thread what would you choose as the thread form ?
O.K. I can see that the larger the diameter of the forcing bolt the better ...
but I was looking at my commercially produced ones.
The small gear puller has a coarse metric thread.
The large 3 legged puller has a funny square section coarse thread.
My really large hub-puller has a large forcing screw but with a very fine thread.
What is technically the best please ? Or does it not matter ?
Thanks,
Tony.


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PostPosted: Thu Jan 18, 2018 6:42 pm 
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Joined: Wed May 17, 2017 5:28 pm
Posts: 520
Location: NANTWICH.
I would have thought the fine thread for really heavy duty? All my big pullers have got a fine thread.
I think it distributes the force slower and get's a better torque.
What do other's think?

Cheers,

Tony.

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PostPosted: Thu Jan 18, 2018 9:31 pm 
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Joined: Sat Oct 07, 2006 7:12 pm
Posts: 592
Location: Surrey
A finer thread will require less torque to achieve the same force through the puller than a course thread. So with a fine thread you can apply more force than with a course thread cut of the same diameter.

If you think about TPI :
10 TPI = 10 rotations to move 1 inch
20 TPI = 20 rotations to move 1 inch
The mechanical advantage is gained by having a higher TPI, which means less effort to split a taper joint OR your puller can deal with really tight hubs.

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