Screw Gauge Pitch: Length of Main Scale Division?

[gautam_cool88]

In a screw gauge, the pitch is defined as the distance traveled in one rotation. Is it also equal to the length of one main scale division?
If the length of one main scale division is not given, then can we take it to be equal to the pitch? Or do we take it as equal to some other default value.

 

[FredGarvin]

The pitch can also be thought of as the distance from peak to peak or crest to crest of adjacent threads. Now, when you say "one main scale division" what kind of thread gauge are you referring? I am used to seeing the types of gauges that you physically hold against a fastener to compare the thread engagement (similar to attached pics). What scale are you referring? It also helps to know what kind of screw thread type you are referring to.

http://www.mcfeelys.com/images/prodimages/dg-0014.jpg

 

[gautam_cool88]

reply

hey i m talkin bout dis type of screw gauge.

 

[Cyrus]

What is a 'main scale division' ? The pitch is the measured distance between two consecutive threads for a single threaded screw. Is that what you are asking?

 

[gautam_cool88]

reply

The screw gauge which I m talkin bout (image attached) has a circular scale and a main scale. By main scale division I mean the distance between two marks on a main scale.

 

[Cyrus]

I can't view your image yet. Pending approval.

 

[shankara]

I can't view your image yet. Pending approval.

I guess, your are right. Ridges of helix around a cylinder( as in screws) can give a linear movement for rotational movement. But, I am not sure about the magnitude of linear displacement for one complete revolution. I think it depends on the screw gauge. I will search for any generality or standard in the manufactures and comment again. Please oblige.

regards
shankara

 

[MATLABdude]

What you have is a micrometer screw gauge, or just plain micrometer (as opposed to screw or thread gauge, which usually refers to the thing that FredGarvin posted):
http://en.wikipedia.org/wiki/Micrometer

If I understand your question correctly, then the main scale (and the Vernier as well) indicate the length of the jaw opening, and not the distance travelled--that's left up to you and/or your calculator, though I imagine that the digital ones (and probably some higher end mechanical ones) have this ability.

EDIT: I totally didn't answer your question (I'm posting this from my iPhone and couldn't see your original post). I'm not sure if my answer holds in general, but for all the ones I've seen, if there's a Vernier scale then the divisions on the main scale will be the pitch, since it takes one rotation of the dial to wrap the Vernier scale around and move from one division to the next.