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Any sources for coarse 1/4" thread other than 1/4-20?

Zip

Aluminum
Joined
May 25, 2007
Location
Champlain, NY
Considering a project that will require a stationary part to move left and right from center with less than one revolution of the screw head. Just tried 1/4-20 but it only travels about 80% of the travel needed, any ideas for a screw and tap source?

Thanks
 
Considering a project that will require a stationary part to move left and right from center with less than one revolution of the screw head. Just tried 1/4-20 but it only travels about 80% of the travel needed, any ideas for a screw and tap source?

Thanks

WoW.....let's put some real numbers here..."About 80%"...:nutter:

What travel doo you want, for each revolution of the leadscrew ?
 
Or, have someone make a thread with whatever pitch you want, just be mindful of how weak it becomes when the minor diameter gets smaller and smaller.

Regards.

Mike
 
Last edited:
A 1/4-20 thread travels .050” in a full revolution.
The OP needs to tell us the distance required then figure out the fraction from there.
20 TPI = 1/20 = .050”
If my math is right and 20 TPI is 80% of the travel then 16 TPI is 100% of the travel. Or very close at .0625”


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Acme ...

McMaster-Carr

Or, have someone make a thread with whatever pitch you want, just be mindful of how weak it becomes when the minor diameter gets smaller and smaller.

Regards.

Mike

As DavidR8 points out if 20 TPI gives 80% then 16 TPI gives 100%. Anything courser than 16 TPI will give more than 100%.

Re "... whatever pitch you want, just be mindful of how weak it becomes when the minor diameter gets smaller and smaller." (unless I misunderstand you) a finer thread is not only stronger but is better at withstanding vibration.

1/4-20 is UNC. If you want less than 20 TPI (for example 16 TPI) you'll have to go up in diameter. Post #2 might be a solution.
 
Re "... whatever pitch you want, just be mindful of how weak it becomes when the minor diameter gets smaller and smaller." (unless I misunderstand you) a finer thread is not only stronger but is better at withstanding vibration.

I think you do ;). Larger pitch, e.g. 16 instead of 20 >> smaller minor >> weaker fastener.

Regards.

Mike
 
I'm surprised no one has mentioned a two start 16 pitch, giving you 16 pitch but the strength of 32 pitch. Play with whatever numbers you want. Make you own tap or have one made, screw is pretty easy to cut on a lathe.
 
I e never seen one in person, I'd love to get my hands on one just to check it out.

You've seen them, you just don't know that you've seen them. The screws that hold the cover on a circuit breaker panel are just one example of double lead screws. They go in fast because the thread is steep but can still grip thin sheet metal.
 
I e never seen one in person, I'd love to get my hands on one just to check it out.

Just about every one has seen them. Milk jugs, Gatorade bottles, blah blah blah. Not only are they faster by they "prevent" cross threading. The average joe would cross thread their caps all the time if it wasn't for multi start threads.

There are several different ways to cut them and lots of good info out there. Depending on the pitch and lathe you can sometimes do it with the thread dial, if you have a D1-# mount that is divisible by your start number then you can take the chuck off and index it. Several other ways but obviously a CNC turning center is the ultimate solutions. :smoking:
 








 
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