Calculating force required to seat self tapping thread?
Calculating force required to seat self tapping thread?
(OP)
Evening,
My general question to the forum is stated in my title. I am using a self-tapping thread to hold a to objects. One has a clearance hole and the thread is cut into the 2nd piece. I am having issues seating the screw properly and require more than one attempt. I work in a high volume manufacturing facility and this effects the efficiency, thus cost of this assembly. I am using pneumatic drivers and want to verify the force or torque I am using is adequate for the process.
Thamks...
My general question to the forum is stated in my title. I am using a self-tapping thread to hold a to objects. One has a clearance hole and the thread is cut into the 2nd piece. I am having issues seating the screw properly and require more than one attempt. I work in a high volume manufacturing facility and this effects the efficiency, thus cost of this assembly. I am using pneumatic drivers and want to verify the force or torque I am using is adequate for the process.
Thamks...





RE: Calculating force required to seat self tapping thread?
Any calculation will have a bunch of assumptions built in to it.
Test.
RE: Calculating force required to seat self tapping thread?
-b
RE: Calculating force required to seat self tapping thread?
But, B I will use your trial and give an update regarding the results.
RE: Calculating force required to seat self tapping thread?
If so, that sounds more like a tooling problem than a torque problem. That would suggest that you should either pre-tap the holes with a bit that has the same threads as the fasteners. The bit would be held in a chuck, and should always tap true. The other choice would be to have some sort of constraint on the fastener, to keep it from rotating, a seemingly more difficult problem.
TTFN
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RE: Calculating force required to seat self tapping thread?
One would think there should be only minimal force pushing on the fastener, only enough to maintain mechanical contact long enough for the thread to catch in the material.
TTFN
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RE: Calculating force required to seat self tapping thread?
What material is being tapped?
Which screw thread type? (forming or cutting)
Sizes involved?
RE: Calculating force required to seat self tapping thread?
Have you asked if the design is appropriate for your assembly?
Paul
www.ostand.com
RE: Calculating force required to seat self tapping thread?
I would imagine a lot. That may compound your problem
in finding a solution.
RE: Calculating force required to seat self tapping thread?
I would like to address the comment on design. This application is on a small magnetic motor armature and this tap is spot welded in place and holes drilled for the self-tapping screws. The material is a mild steel. Cost is a major consideration in our operation and that was one of the reasons self-tapping screws were used. The operations I laided out previously are done in an automated piece and adding the tapping operation would mean handling the pieces additionally.
This evaluation I am currently undertaking will address the cost of rework and the additional operation.
Thanks again for the input.
RE: Calculating force required to seat self tapping thread?
If you need torque, then it is simply the normal force times the radius of your tap, i.e. half the major diameter of the threading.
I use this on our NC machines in order to figure out if we're going to bend small size drills during tapping operations. Works to about 2.8% error, pretty bang on for scientific error acceptability which is 5%.
Hope this helps.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Calculating force required to seat self tapping thread?
I think thread lengths over 1.0 are kind of rare for a reason for self tapping screws, and each manufacturer claims the other guys' thread forms are problematic, but these guys make pretty nice screws.
http://www.camcarsolutions.com/taptite2000.asp
RE: Calculating force required to seat self tapping thread?
Again all ideas and suggestions appreciated.
RE: Calculating force required to seat self tapping thread?
You might consider if it's possible to make a combo drill bit, bottom part drill, upper part tap to automate the tapping process. I assume that the drilling takes place on a drill press, at least, and isn't done by some guy holding a portable drill?
TTFN
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RE: Calculating force required to seat self tapping thread?