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square thread forms

square thread forms

(OP)
hello - i have been told to use square threads on a new design - i know that square threads are harder to manufacture & have been replaced by acme threads but i have to use them - the part i need to thread is approx. 6" in dia. - i cannot find any tables of data for square threads & what i have found only goes up to 4" dia. - also the pitch of the thread seems very large for any large dia. - any help or data for designing these threads would be very appreciated - thank you

RE: square thread forms

Could you give us a hint of what this thread is doing?

The size of the thread pitch will have an impact on what process can be used to make the thread. If you want to single point the thread the clearance on the cutting tool will have to be greater the the pitch angle. The external thread will be easier to make than the internal thread. I would recommend you consider another type of thread such as a stub acme or a buttress thread if the loading is only in one direction.

Bill

RE: square thread forms

(OP)
hello - i have suggested using acme but have been told this is what i will use - it is for a power screw & nut which will see loads in both directions - i have been told by our manufacturing that it will be single point cut & it is no problem for them to make these parts - i just need some type of directioin or data as to how to determine the fits of the threads, size etc. -

RE: square thread forms

We can't tell from here who the players are, or what the play is about.

If your shop says square cut threads are easy >because they have done them before<, then there should be a record of what they did, and there should be some retained tooling, or spares in inventory, from which you may infer some of the shop's actual capabilities.

If your shop says square cut threads sound easier to make than Acme threads >but they have never cut either<, then they are speaking from ignorance, and will be climbing a steep learning curve, after which they will understand why Acme threads exist.
Some people cannot learn any other way.
There is no way to change that.

If your boss is bullying you based on misinformation from the shop, or based on his or her own misunderstanding, you have to tread gently and comply, while leaving a written record, polite and factual of course.

Again, if your outfit has never made square thread power screws, then I would fight fairly hard to not start. On the other hand, if they _have_ made them, there should be some company standard or other records that can be helpful in setting up your operation.

Mike Halloran
Pembroke Pines, FL, USA

RE: square thread forms

http://img.photobucket.com/albums/v157/MikeBurdick...

Have a look at this. Square thread is not a very standardized thread form and rarely used. I have a feeling that the person telling you that square thread "will" be used doesn't know a helluvalot about threads or machining.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: square thread forms

(OP)
hello again & thanks so much for all your help - i have tried to get both my boss & the head of the shop to change but it seems in our organization our shop "head" has the last say so i am stuck using this for my design - our shop resides overseas & after past experience w/ their so called "experts" i believe we are headed down the road to trouble w/ this one -
our company doesnt believe in standards - i have been fighting that battle for close to 2o years now w/ no luck - i trust all the professionals here on this forum more then i trust my fellow workers - i will post back when this is all said & done - wish me luck - i will need it

RE: square thread forms

The only thing I have seen them on is large force testing/calibration machines.

If you call around to the places that have or build million lb + testing machines, they may be able to point you in the right direction.

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