checking dies

[Bob Culver]

The front stub nut does not have to (and should not) be very tight. Feeding a fixed die or dienut over wonky thread often cuts a new one in the wrong place. Damage is usually due the end burred or the split pin been deliberately sheared. Can often sort by reducing the length of stub and tidying thread with a small diamond section riffler file. 3 corner file not suitable for BSF.

[JonE]

Thanks all. All good learning. I found this thread from 6 years back!
David's item much less expensive than Tracey (so a nobrainer), but knowing the rarity just ups the ante to try and find one in a pile too!
http://pub25.bravenet.com/forum/static/s...1&cmd=show

I'd still like to know what the approximate difference with a UN 5/8 16 would actually be in terms of feel?
In the old thread, Chris Garner's die was unidentified at the time (so could have been in either WF or UN camp). And presumably others will be used similarly.

[AustinWood]

I have a set of thread files which work well for cleaning damaged and rusted male threads.

[JonE]

there are many thousands of pages on the mini forum whose crank uses the good ol' 5/8 16tpi. Someone did a CAD comparison as the UNS and W F seem to be interchangeably used by various sectors of mini race engine builders! Here is the comparison. (Interestingly, for mere clean up, there is a chinese UNS tap and die pair on ebay for under 9 quid...  
  Whitworth_UNS_Profiles.jpg (Size: 189.13 KB / Downloads: 147)
dklawson's notes from Mini Forum:

"The JPG shows what you see if you superimpose the two thread forms. Note that there is minimal interference between the two due to the way their geometries overlap. A 5/8-16 UNS tap would barely cut the major diameter of the female threaded hole... hence, almost no swarf would be removed if the UNS tap is run in a Whitworth form threaded female hole. Owing to manufacturing tolerances, I'd say that the UNS tap will only cut material when the MINOR diameter of the female threads have been damaged.

EDIT: Note in the JPG that the UNS thread is shown in blue in all instances and the Whitworth form in grey. The UNS thread form has the flat crests. The root radius/bottom of the UNS thread is not defined by any standards I've seen. While I show potential interference there, it's not likely to exist as it's probably removed by the tap drill for the Whitworth form tap.

EDIT2: I went back and took some information from KC's earlier emails. He mentions that the tap drill is called out on the drawings as 0.557"diameter. Superimposing the tap drill on the section view details in the picture below... there's virtually no contact between either tap's minor diameter and the tap drill hole. The only interference will be the minor amount occurring at the crest of the threads."

[JonE]

I have a set of thread files which work well for cleaning damaged and rusted male threads.

thanks Jim - I asked about these on the closing down day and came away with two cubic 9" lengths which each have 4 different tpi "files" on each end, for a few quid each. Never seen such a thing before - will be interesting to see how they work.