View Full Version : small I.D. threading
09-18-2001, 10:57 AM
what is a common method for threading small diameter internal threads. In particular, a fine thread one. Tap not readily available at my local supplier.And in small, lets say
3\4 on down.
09-18-2001, 11:25 AM
using a good tap grind all the teeth off but one near the end and use it like a boring bar
09-18-2001, 11:27 AM
I like to single point internal threads. That way I am sure they are concentric. Something you can't always count on with a tap! I use internal thread inserts when I can, and grind tool bits when the size is to small. 1/4 is about as small as I've single pointed, then I do use a tap. Always cut a relief groove in a blind hole, or turn the chuck by hand if you must have the thread to the very end!
I nearly always use a tap. MSC, Travers, etc. seem to sell just about every possible tap one would ever want. Your local hardware store won't, but the maiorder suppliers have them. I once got a 10-56, for instance, for a special nut I had to make for a fishing reel.
Use the tailstock to align the back end of the tap wrench so the tap starts squarely with the work. I have a piloted tap wrench, but even regular tap wrenches I've seen have a center hole in the top that one can put a center into to align it. Trying to turn the tap while advancing the center as the tap advances gets tricky though...which is why a piloted tap wrench is easier.
09-18-2001, 05:47 PM
I got me one of those miniature threading kits from Enco. A bit pricey at $135 but 'twill cut threads all the way to the bottom of a blind hole as small as 7/16". Uses replaceable 60* inserts with 3 cutting edges per.
09-19-2001, 01:28 AM
Taps and dies are generally used if fit is not critical - as is usually the case.
Where concentricity or accuracy is required you must use the lathe or a CNC Mill with thread milling capability.
For most internal threads I use a Sharp 60* Laydown Threading insert in Valenite threading bars - they produce lovely threads!
09-19-2001, 07:20 AM
I was not clear on the problem but if you grind all the threads off but one and hold it in some form of "V" by the shank you should be able to rotate the tooth to centre hight