Simple threading job turned complex

Off topic, I realize, and no intention of hijacking the thread. At some point you start to wonder where some of these thread forms come from. Some engineer comes up with a ”better” answer, even if new tooling must be developed. Or marketing thinks it would drive the customer back to them for parts. You can kind of hear the meeting, or the committee, ”you know, if we had a 53 degree thread,, sort of Whitworth, but metric pitch, with a head at 1/32 increments , that would be soooo much better”. It will revolutionize the industry and we will make billions. Wars suck, but good things have come from them at times. WWII did create the standards we enjoy today.

I guess it depends on creating a useful tool, a restoration, or scrap. If you can convert to something standard, it would be usable. A restoration to hang on a wall, most anything (JB Weld?) would create an attachment. Screw it up completely, not out much since it didn’t work before. My choice most always, if it isn’t going to a museum, make it functional and enjoy using it. But, your mileage may vary.
 
How are you measuring the original?
If you’re using a thread pitch gauge, did 24 TPI or 1mm fit better? What did the major diameter of the threads measure?

Can you turn the adapter threads, or do you have to use a tap?

Sorry for all the questions. This sounds like a fun one to solve
 
I had an issue today with two different tooling adapter threads, could not get a fit, though they both measured almost exactly in thread pitch and diameters. I tried the sample threads at Fastenal, I finally realized they were in fact measured correctly, but they were left hand threads. Ouch, since the day before I had a problem like that with the spindle nose cap on my Bridgeport clone.
 
Frank, with the greatest of respect you need to measure far more accurately than you appear to have done ! 3/8" & 10mm ??? there is 20 thou difference !! Measure the OD with a micrometer, ensure the thread is really clean, use a fine wire brush and a solvent etc. Use a good quality thread pitch gauge -- Starrett or M & W not one of the Far East units they leave much to be desired. Use a magnifier or use the app on a phone or better a microscope to be certain of the pitch & thread form.
I have over the years made many "specials" for vintage guns, fishing reels etc and many of the threads are far from any standard - sometimes close but no quite probably due maybe to worn tooling ???
Hope this helps and good luck, John
 
Bi11Hudson said:
It is rare these days to cross Whitworth,
Click to expand...

I just purchased a Chicom boring head arbor for making a ball turner. 1" shank with a 1/2" drawbar hole. It looks course, but a 1/2-13 won't thread in. And it's truly 1/2", not metric. Turns out it's 1/2-12, Whitworth. Grumble.
 
RandyWilson said:
I just purchased a Chicom boring head arbor for making a ball turner. 1" shank with a 1/2" drawbar hole. It looks course, but a 1/2-13 won't thread in. And it's truly 1/2", not metric. Turns out it's 1/2-12, Whitworth. Grumble.
Click to expand...
Hi Randy, how long a draw bolt do you need and what head style?
 
RandyWilson said:
I just purchased a Chicom boring head arbor for making a ball turner. 1" shank with a 1/2" drawbar hole. It looks course, but a 1/2-13 won't thread in. And it's truly 1/2", not metric. Turns out it's 1/2-12, Whitworth. Grumble.
Click to expand...
1/2-12 seems to be common on Chinese tooling. Seems they are more superstitous about the number 13 than most folks, hence 12 TPI. Seeing something with Whitworth threads is less common, but there was a very strong English influence in Hong Kong until recently. So I guess Whitworth is still in use in some places. I won't speculate on English motorcycles, but it is plausable. My idea for that problem is to scare up a tap for 1/2-12 with Unified 60 degree threads and re-do it. Taps for that thread are readily available. Save your making a special threading tool.

.
 
redgrouse said:
Hi Randy, how long a draw bolt do you need and what head style?
Click to expand...

This is going to be a ball turner. The drawbar thread is going to be used to attach the handle.... once I get it designed. I have no trouble single point cutting whatever I need. It just caught me out that the thread wasn't 1/2-13 as expected.

Bill, now that I know what the thread pitch is, it's not a problem. Whitworth 55 or UN* 60 doesn't really matter, as this is a very low stress application. I single point cut a test thread and it fit just fine.

I'm very familiar with British equipment from the 50s through the 80s. Whitworth to UN* to metric. It was common to change the thread sizing and pitch to the system de'jour only when redesigning a part. Sometimes on a per-bolt basis.
 
RandyWilson said:
I just purchased a Chicom boring head arbor for making a ball turner. 1" shank with a 1/2" drawbar hole. It looks course, but a 1/2-13 won't thread in. And it's truly 1/2", not metric. Turns out it's 1/2-12, Whitworth. Grumble.
Click to expand...
That’s crazy. Grr is right.
 
You must log in or register to reply here.
Back
Top