I can see how a tool may be ground/honed to cut the proper profile for the bottom of a BA thread, but how is the radius of the crests done--on the lathe? Al Messer --- Jeff Dayman <jeffdayman@xxxxxxxxxxxx> wrote: > Hi Rich, > > The -2A and -2B is the thread class (fit) and the > *.75 probably means 3/4" > deep full thread. > > The thread class doesn't mean much for hobby work, > it's used in commercial > work to designate fit quality only if required. If > you've got taps to suit, > they may or may not have the class marked on them. > If not, they'll probably > cut normal commercial quality loose threads, fine > for hobby stuff. > > The UNC does not mean UNCa Jesse Livingston needs to > come and make yer > threads, much as he might like to. > > Cheers, Jeff Dayman Waterloo Ontario Canada > > > ----- Original Message ----- > From: "R.L. Roebuck" <rlr20@xxxxxxxxxxxxxxxx> > To: <modeleng@xxxxxxxxxxxxx> > Sent: Thursday, October 20, 2005 9:29 AM > Subject: [modeleng] Off topic a bit: UNF and UNC > threads > > > > Hi there All, > > > > I'm used to what I would call 'normal' UNF and UNC > thread designations, > > such as 1/2"*20 UNF, but I've got a few things on > a drawing that don't > > make sense to me - I wonder if anyone could shed > some light on them. > > > > I have a stud marked as being threaded 1/2-20 > UNF-2A > > > > I have another stud marked as 3/4-16 UNF-2A > > > > I have a hole marked as 1/2-13 UNC-2B * .75 > > > > Does anyone know what the stuf after the UNF or > UNC refers to? > > > > > > Yours, > > > > > > Rich. > > MODEL ENGINEERING DISCUSSION LIST. > > > > To UNSUBSCRIBE from this list, send a blank email > to, > > modeleng-request@xxxxxxxxxxxxx with the word > "unsubscribe" in the subject > line. > > > > MODEL ENGINEERING DISCUSSION LIST. > > To UNSUBSCRIBE from this list, send a blank email > to, > modeleng-request@xxxxxxxxxxxxx with the word > "unsubscribe" in the subject line. > __________________________________ Yahoo! FareChase: Search multiple travel sites in one click. http://farechase.yahoo.com MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.