Cheap 60 degree tool or correct threading bit shape?

Bishop said:
What I don't get is if the OP is using the gauge to check the threading tool and his grind, how is it bottoming out before touching both sides of the gauge?
Click to expand...


Three possibilities that I see: 1) it's a crappy gauge with no relief in the bottom of the V, 2) the OP is grinding a 30 degree tool, 3) as said above, it's a Whitworth gauge.
 
If your root width of your thread is coming out too wide. Just chase the thread with a die nut to finish out the root. I used to have to do this almost every time cutting fine pitch threads. Now, I have a good selection of pre-formed threading inserts that do a pretty good job cutting threads. I still use die nuts once a while when needed. I have cut 1/2-28 thread before without any issues.
 
I have el cheapo fishtails from China n they have the relief. I'm betting you're right about it being a whitworth gauge.
 
Thanks guys. The gauge is not marked with anything except the measurement data...not even a manufacturer's mark. There is no relief at the tip, just a radius at the bottom of a vee notch. Hopefully it isn't a Whitworth...you've got me worried now because isn't Whitworth a 55 degree thread? It was what they had at the local Rex Supply. If so my threading bits are ground to the wrong angle too.:angry: I used the thread fish to scribe alignment lines on my grinder to set the angle.
 
Unless it's mismarked, it is a standard 60* gauge, not a Whitworth gauge. Just a cheap one.

Tom
 
That is not a Whitworth fish tail gauge. It has a 60 degree included angle so it is meant for standard Imperial threading. Whitworth threads have a 55 degree included angle and a pronounced round profile at the bottom of the thread.
 
You need to get a better gauge. You don't need a Starrett, Just one that looks like this.
71Hsbp8p6FL._SL1500_.jpg

71Hsbp8p6FL._SL1500_.jpg
 
You must log in or register to reply here.
Back
Top