orthogonal"twist" in a screw 1

[BraunP]

Hello all,

Is there a equation or reference that can state the orthogonal "twist" allowance of a screw through a hole depending on the material thickness? The picture hopfully helps. The material is .5" thick, and that is a m6 threaded rod with a m6x1.0-6h threaded hole.

Is there a chart or an equation that will help depict how much it will rotate orthogonal. It might just be I would have to figure out the tolerance between the screw and the thread, see the room there, and assume it pivots at the center point of the threaded part. take into account the OD and root of the rod and go from there.

Thank you for your time.

 

[racookpe1978]

Basically, yes, that would be the theoretical process.

To reduce the flexing, go to a longer threaded length, use a fine thread, use a higher-precision cut thread and rod.
Clamping the plate tightly will eliminate the flexing completely, but then the threaded rod itself will be what is resisting the bending moment.

Recognize that testing the plate will be most accurate. You will see some flexing of the rod.

A 1/2 inch plate (12-13 mm) with 6 mm (1/4 inch) rod is not very stiff.

 

[BraunP]

The application is the screw moves the plate for adjustment, I will have to look into acme threads or more higher-precision. I am trying to keep the cost down on the part.

I also take it, there really is not a equation or a chart I can referance to tell me the angle the metal will pivot to or anything like that.

 

[Tmoose]

Could the plate be part of the component being adjusted, and take advantage of its stiffness/guidance?
How hard must the adjuster tug on the component?

Longer thread engagement would limit "twist" quicker than screw precision I believe.

Welding a "coupling nut" to the plate would get up to 20 mm of engagement pretty quick.
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http://rsfinc.us/images/rod 3.jpg

 

[Dougt115]

As mentioned the angle is determined by the thread clearances and the depth of the threading.

Pretty much the angel is the arc tangent of the diametric clearance over the thickness of the plate, atan(clearance/thickness). You can either get better threads, a thicker plate (longer threading) or use a locking nut to take up the clearance.

I think the locking nut may be your cheapest option.

Oh and your rod may still bend.

 

[BraunP]

Ok, thanks for all the information. It would be nice to be able to predict the angle that will happen. What can I say, collage has taught me to love equations. =). and charts, we like the charts

 

[Tmoose]

CHART showing range of clearance of M6-1 threads at pitch diameter.

http://www.katonet.com/article/imgpedia/PitchDia4.jpg

 

[BraunP]

Tmoose:

That is extremely useful THANK YOU =)