21\2 inch 6 tpi uns thread caculations

[azzrock]

hi all. can some one please help me out and give me the
the minor dia for an internal 4 1\2 6tpi uns thread.

I haven't got any of my books here. I'd like to make a test ring.
for the thread on some L0 safety taper backing plates i have to make/
making.
have fun
aaron

im not shore how i got that wrong so ive edited above post its 4 1/2 not 2 1/2 uns 6tpi.
hopfully phil or some one notices.

[Steamwhisperer]

Hi Aaron,
The minor Diameter is 2.2834" for general purpose and
2.3016" for close tolerance

Phil

[Bryan]

I got a slightly different answer from here: http://theoreticalmachinist.com/Threads_UnifiedImperial.aspx
That being 2.32 - 2.35 ish. If I did it right.

[Steamwhisperer]

I got a slightly different answer from here: http://theoreticalmachinist.com/Threads_UnifiedImperial.aspx
That being 2.32 - 2.35 ish. If I did it right.

Apologies Bryan, I was editing.:D

Phil

[Ueee]

Shopcalc gives 2.365" for a 75% contact. Thats as a sugested "tapping drill" size.

Ew

[azzrock]

hi again. plil bryan and ew thanks.
the last few times I've cut internal threads. i wasn't happy with the result.
a bit like a c**k in a shirt sleeve.
So i think ill go for close tolarance size. Its meant to be a thread gauge of sorts
so a close fit would be appropriate.
thanks again
aaron

[Steamwhisperer]

Apologies Aaron,
I have given you external thread minor Diameters.
Close tolerance internal thread will be 2.3196" :-

Phil

[KBs PensNmore]

Hi Aaron, the only thing I can find is a formula for drill sizes for thread cutting taps.

........................................................................... ......% of full thread
Drill size = basic major dia. of thread 4.5" minus .0130 X ---------------- = Drill size
................................................................................ .threads per inch
example: to find tapping drill size
for 1/4"- 20 with 75% thread
........................................75
Drill size = .2500 - .0130 X --- = .2010 inches
.......................................20
This is taken from the Engineers Black Book 1st edition
Hope this helps
Regards
Kryn

[azzrock]

im not shore what formulas ive been using and haven't been able to find
a suitable online calculator.
kb pens thanks for that one but it doesn't seem to be right
i get 59.83 ????
ill have another look
bryan that calculator only goes to 4"
aaron

[easymike29]

I've written a spreadsheet for thread calculations. If anyone is interested I'll attach it for downloading.

Gene

[Ueee]

This is what i have been using, will go as big as you want. http://home.scarlet.be/mini-draaien-frezen/engels/program-01.html

Ew

[azzrock]

thanks guys. ive got a mac.. thanks gene.
aaron

[pipeclay]

Try 4.284"

[Ueee]

I think if Aaron bores to 4.284" then threads the for May be just a tiny bit too loose.....
But what would I know, my answer came from a computer program.

[Techo1]

From Machinery's Handbook - 4.320 to 4.3396 for class 3B.
All you have to do is use dimensions for any 6 tpi UN thread.

Lex.

[pipeclay]

That could well and truly be correct for the thread diameter you worked on but it has changed.

Mine could be a bit tight

[Steamwhisperer]

Try 4.284"

I must have missed something.
I thought Aaron was after specs for 2 1/2" 6 TPI.
But then I am having a lot of senior moments lately lol.

Phil

[Ueee]

I must have missed something.
I thought Aaron was after specs for 2 1/2" 6 TPI.
But then I am having a lot of senior moments lately lol.

Phil

Aaron has edited his post, had me confused too. Its 4.500" not 2.500".

Ew

[Steamwhisperer]

Thanks Ew,
Now, to cancel one senior moment...

[azzrock]

thanks pipeclay,ew ,phil,lex and every one.
ya i messed up the size its 4.5 not 2.5.
as far as class of fit if im going to use this as a thread gauge
for up coming jobs what class would be best to make this?

aaron

[Steamwhisperer]

Hi Aaron,
not sure if I am too late or not but,
basic dimensions for minor diameter of an internal 4 1/2" 6 TPI thread is 4.3196".

Phil

[azzrock]

may of been phil but i didn't have any thing to measure internally last night.
plus my out side mic the right size is not here either.
so thanks.
how do i figure out the minor dia or doc.
aaron

[Techo1]

Aaron, your bored hole IS the minor diameter, the theoretical Major diameter is simply the nominal size, in this case 4.5". So the depth of cut will be 4.500" minus 4.320" to 4.3396" divided by 2.

Regards, Lex.