Cheap 60 degree tool or correct threading bit shape?

[cdhknives]

My 60 degree gauge 'thread fish' has rounded bottoms in the vee notches. When I round/blunt my threading bit tips to match, my threads look bad and are too tight, so I end up cutting too deep (per 3 wire measurement vs. 'book' dimension) to get a nut on. I'm beginning to wonder if the no-name gauge should have a relief in the tip. With a sharp bit the tip catches the radiused bottom before I can get the edges against the notch to really check my angles.

In the picture below I'm trying to build a 1/2-28 mandrel. To get the thread protector on, I had to cut to the point the thread measures .011" undersize...for a 2 hour to build paperweight!

Should I relieve the tip of the vee notch in my thread fish, or is that radius the proper tip geometry and I have another problem with my threading?

 

[Ulma Doctor]

a threading tool should be pretty sharp. some will have the smallest of radius at the tip- almost unnoticeable.
is the fish tail for UNC/SAE threads???

Whitworth threads have a pronounced radius in their threads and is at 55*v rather than a 60*v like the UNC/SAE

 

[Bishop]

Can you post a photo of your fishtail gauge.

 

[higgite]

The tool point isn't supposed to be shaped like the fishtail gauge cutout. The notch at the base of the cutout is so you can snug the tool up to the gauge to check the side angles without hitting the tool point and dulling it.

Tom

 

[Bishop]

The tool point isn't supposed to be shaped like the fishtail gauge cutout. The notch at the base of the cutout is so you can snug the tool up to the gauge to check the side angles without hitting the tool point and dulling it.

Tom

He mentions the tip of the tool hitting the bottom of the relief hole before the tool touches both sides of the v notch.

 

[Brandon1]

First obvious problem is the poor choice of beer.:rofl:

 

[higgite]

He mentions the tip of the tool hitting the bottom of the relief hole before the tool touches both sides of the v notch.

My bad. I misread it. In that case, I would cut a relief notch if there is none or buy a better fish gauge.

Tom

 

[NightWing]

The tool tip should have a radius of .125 times the pitch.

 

[mikey]

I'm with Ulma Doc - sounds like a British Whitworth fish tail.

 

[Bishop]

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?