Another thread question

[joe d]

Hi

I've been looking at the drawing of a boring head that I downloaded from another thread here that calls out a 1/2-20 UNS 2B LH

I get all of it except the designation UNS.. (UNF(ine) and UNC(oarse) are the ones I know)

Can any thread wizards out there tell me what this is?

Thanks, Joe

 

[paulj84003]

I have seen that designation on special taps like 1/4-48 but I believe it can also mean standard. Paul

 

[DickDastardly40]

I thought it was for 'special', hopefully a guru will chime in and put us straight.

Al

 

[gilessim]

Hey Joe, the S is in fact for standard, the 2b is the class of tolerance,internal to external, but since the LH must mean left handed (as you must have worked out yourself!) and you don't want to go and buy a tap and a die for what they would cost!, I imagine that you'll do the threading on the lathe and since the only difference between UNF,UNS and UNC is the thread form and you have the TPI, I personally ,for a one off, wouldn't worry too much about the thread form, if on the other hand, you are interested in the 10 billion or so different thread types out there, try and get a copy of Machinery's Handbook, I have a very old one and it's still mostly valid!. At 2500+ pages it makes a good bedtime read!, by now they must cost $100 or so but it's worth it and it'll last you a lifetime!....Giles

 

[Stan]

Out of curiosity, I looked up Machinery Handbook and I will patiently type it out:

UNS Threads.- UNS screw threads which have special combinations of diameter and pitch with tolerance to Unified formulation have the basic form designation set out first followed always by the limits of size.

Now aren't you glad you asked?

 

[joe d]

Well, it was really out of curiosity that I asked! Thanks for all the replies, now I know.

Joe

 

[Stan]

joe: Using the strict definition "special combination of diameter and pitch" that thread is not UNS but was probably marked that way because it is left hand.

Is there any chance this tool is an import, where there is frequently a problem with translating US standards into another language and then re-translating back to the end user?

 

[joe d]

Stan

This thread was called out in the drawings for a boring tool holder posted by Tattoomike 68 in the "Plans" part of this BBS.. apparently originally posted by IOWOLF over on HSM. I'm suspecting that you are right, it might just be the fact that it's left handed.

I've been snooping around on the web, I can get a tap and a die for less than $10 ea from Victor, so this might end up getting built after all. (I run a Taig micro lathe that is as yet not modified for threading... dang: another project).

It is for sure right that some day I need to get a copy of Machinery Handbook, probably should be required reading for us newbies!

Thanks, Joe

 

[mklotz]

The Machinery's Handbook material useful to folks like us hasn't changed much over the years so an older copy is as good as, and sometimes better than, the latest expensive copy.

Many local library systems have periodic book sales. Older technical books are often ridiculously cheap. Just recently I picked up a 15th edition for $3. Over the years I've bought at least five other copies, none for more than $5.