shoulder depth vs barrel rotation ?

K

Kirk Ethridge

Guest
I've lost my notes, and don't remember the math,

Question for 18tpi , how much to cut off the shoulder to rotate the barrel 90 degrees?

also, on 16 tpi.

Thanks!

Kirk

ps, i've searched for 30 minutes and can't find it, though i know its here somewhere. seems like Gene Beggs posted this previously.
 
Last edited by a moderator:
Try this

For 18 TPI:

360º = 1/18
180º = 1/36
90º = 1/72


For 16 TPI:

360º = 1/16
180º = 1/32
90º = 1/64

Hope this helps.

A. Weldy
 
Now that you have the answer the math is;

X = Degrees you wish to turn
Y = TPI
T = CUT

T = ( 1 / Y ) / ( 360 / X )

Ie; for 18 TPI at 90d
-----------------------------------
1 / 18 = 0.05555 (Inches movement in one turn – Rounded off)

360 / 90 = 4

0.05555 / 4 = 0.01389”
 
Or, you could simply...........

Ken_Rieck said:
Now that you have the answer the math is;

X = Degrees you wish to turn
Y = TPI
T = CUT

T = ( 1 / Y ) / ( 360 / X )

Ie; for 18 TPI at 90d
-----------------------------------
1 / 18 = 0.05555 (Inches movement in one turn – Rounded off)

360 / 90 = 4

0.05555 / 4 = 0.01389”
Click to expand...


Or, you could simply...........

Divide the number of threads per inch into the number one.

-Dave-:D:)
 
I think Lucky Shooter has the simple method, which does in fact come out exactly as the others.

20TPI, hmm, well one thread (rotation) will be 1/20th of an inch....pretty easy to figure out what 1/8th, 1/4, etc... of a turn will be from there and how much to cut off to turn the barrel a set amount....


I know Ken's math is correct and essentially the same, but even with a lot of college alg and calc years ago, this is simpler to figure out when I'm doing it at home.
 
I got dizzy looking at those formulas. If you got 18 TPI, 1 divided by 18, divided by 360, times the degree you want to turn. Works out real easy with a calculator.
 
Remember when you were in High School and your math teacher told you to, "pay attention, some day you will need this?" Well that day was today.:rolleyes:

Ray
 
Jkob said:
I got dizzy looking at those formulas. If you got 18 TPI, 1 divided by 18, divided by 360, times the degree you want to turn. Works out real easy with a calculator.
Click to expand...

T= (( 1 / 18 ) / 360)D Its all good.

I keep all that type of stuff in a spread sheet. You could make a spreadsheet up for all your common formulas so you just plug in the numbers even if your cutting a 5.5 TPI thread.

I tend to think formulas are easier to understand for some reason - I guess it's just me.
 
Cheechako said:
Remember when you were in High School and your math teacher told you to, "pay attention, some day you will need this?" Well that day was today.:rolleyes:

Ray
Click to expand...

Mine actually said that if I didn't pay attention I would spend the rest of my life digging ditches. She was right!
However some days I made more than she did in a year.
 
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