Calculating Thread Depth

[Sam.B]

Hello all!

I am having a bit of trouble figuring out the proper and universal method of calculating thread depths.

I have always thought that counting number of revolutions, and dividing the revolutions by threads per inch was correct, and based on the math, I think it is.

Y/X=Z

Variables:

Y=Number of revolutions

X=Threads per inch

Z=Depth of threads

However, in every Machinery's hanbook I've gone through, they only ever calculate by dividing 1 by threads per inch, to find pitch, then multiplying it by the number of revolutions. 

Y(1/X)=Z

 

Technically:

Y(1/X)=Y/X

And they should be interchangeable, but I can't find anything verifying this, as everyone just uses Y(1/X)=Z.

Is there any real difference between these two equations? or is there a special rule that makes it so?

I would love to know!

 

 

[dolphin1]

is your reference for inspection or programming

[CEMENTHEAD]

I always did pitch * turns.

1/2-13

1/13=.0769

10 TURNS OF BOTTOMED OUT GAGE * .0769 = .769 THREAD DEPTH.

[AHarrison1]

4 minutes ago, CEMENTHEAD said:

I always did pitch * turns.

1/2-13

1/13=.0769

10 TURNS OF BOTTOMED OUT GAGE * .0769 = .769 THREAD DEPTH.

Way back in the day effective thread depth was 1-1/2 x thread diameter

which the above equates to plus a little less than one turn.

[Sam.B]

1 hour ago, dolphin1 said:

is your reference for inspection or programming

It is for inspection.

[Sam.B]

2 hours ago, CEMENTHEAD said:

I always did pitch * turns.

1/2-13

1/13=.0769

10 TURNS OF BOTTOMED OUT GAGE * .0769 = .769 THREAD DEPTH.

Yep as do most people. My main question is why add the extra step of dividing 1 by 13 when you can just do 10/13.

(1/13)*10=.7692

10/13=.7692

Why include the extra step of math? Is there any situation when doing the latter would be ineffective?

 

[AHarrison1]

47 minutes ago, Sam.B said:

Yep as do most people. My main question is why add the extra step of dividing 1 by 13 when you can just do 10/13.

(1/13)*10=.7692

10/13=.7692

Why include the extra step of math? Is there any situation when doing the latter would be ineffective?

 

I guess there is no reason really, apart from individual preference. For instance when converting imperial to metric or vise versa i use

25.4 as my conversion factor. My manager uses 0.03937, different factors and opposite multiply/divide but same result.