- Aug 18, 2020
I made this diagram that should clear some things up. As you can see, the proper profile is not obtained until the V-point threading insert is fed in an extra bit.Yeah. Pretty sure the Machinery's Handbook gives the MAX diameter for the root of an O.D. thread.
OP, I'm another that doesn't understand your problem. The pitch diameter determines fit. You have a pitch mic. The only time the insert radius has an affect on fit is when it gets too large. The no-go gauge will go while the go-gauge won't when that happens. You don't even have to look at the insert to know it is time for a new corner. If you only have a pitch mic and wires, then I can see you getting into trouble at some point.
Once I get the thread where I want it, I use an optical comparator to measure root diameter, and change my X-value to that and the P-thread height in the program to reflect the actual thread height. (I'm using canned threading cycles. Mostly G76 cuz we mostly have Fanuc controls.) Sometimes you have to lie, but that is for another post.
Yes this is a better way to describe it. So this ratio is universal? In other words when we use these tools we need to increase the thread depth by a factor of 1.4? I think we added 7 or 8 thou on this one, I am curious to see how close that is to the output of the formula.I think you mean to say, "the minor diameter comes to a sharp point because we are using V inserts, and this means that the pitch diameter is not correct."
As stated above, you do need to cut deeper, by a factor of 1.4. In other words, if the formulas tell you to cut 1mm deep with a correctly-flatted tool, you would need to cut 1.4mm deep with the sharp tool.