flexispeed lathe/chuck problem

1/2 UNF is 20 tpi. Finer than 16 tpi

1/2 UNC is 13 tpi, Coarser than 16 tpi

AND both are a 60 degree thread form, not the 55 degree of the BSF and BSW.

so 1/2 BSF being 16 tpi is in between.

STUPID question

The Die isn't 7/16 BSF is it? That would not fit on the spindle. You said that it wouldn't fit the 1/2 BSF Tap.

Core daimeters 1/2 BSF is 0.4200,, 7/16 BSF core dia. is 0.3665. Might be worth checking the die with a bit of bar turned down to those sizes.

Howard

Hi baz,

the first die i got was a 1 inch closed round, and i then got a 2 inch split die, and a week later got a holder/tool for it, so that's taken care of.

Again i was carefull not to start a new thread when testing and all fit back together as normal afterwards so that's all good, having said all this, I'm sure it'll get to the bottom of the "great flexispeed thread mystery( a lot of time on my hands due to lockdown)

The first thing i ever turned in my life was a mahogany table lamp, on a HUGE metal lathe in primary boarding school, 9 or 10 YRS old if i remember rightly (47 now) , (before the health and safety bods got involved).

The second thing I'll turn in my life will probably be a metal pen on this really quite pretty little flexispeed,

I really am starting at the bottom, so again guys, thank you all so much for all your timer,help and advice.

Jason

Howard, this demonstrates my last messege (starting form the bottom), I even read a chart wrong... i have a lot to learn, but thank you.

Jason

Jason, You won't be the first, or the last, to misread a chart, or set up a machine wrongly.

The man who never made a mistake, never made anything.

The main thing is to learn from our mistakes.

"Experience is what allows you to recognise the mistake the next time that you make it"

At some time, we have all set the spindle turning in reverse, or inadvertently cut a REAL odd ball thread and then wondered why it won't fit! (My last one was 0.964 mm pitch, or 26.4 tpi; ALMOST 1 mm pitch, but out by a factor of 120/127 )

If you can get some sets of thread gauges, Whit, Metric and Unified. At various times they will allow you to recognise a thread, by its form, or pitch. But you will come across some "specials" Myford 1.125" x 12 tpi Whit form, 2.250" x 8 tpi Whit form on my lathe Filters for cameras are often 0.75 mm pitch although the sizes may differ, for instance.

It may be extra expense, but assuredly "will come in handy one day"

Howard

Hi there, all,

My apologies for being a bit late to the party.

I just thought it might help to mention that the old Imperial electrical conduit threads were 16 tpi (Whitworth form), certaily for the ¾" and 1" sizes - I'm not sure if that's also true for ½". Conduit threads were 'borrowed' by some machine builders, e.g. my Coronet Minor woodworker mandrel was ¾" conduit thread.

And I seem to remember that British Brass thread was 16 tpi while some (Imperial) cycle threads are also 16 tpi though one or both might not be Whitworth form.

Best regards,

Swarf, Mostly!

Just to clarify:

BSBrass is Whit form, (55 degree ) usually 26 tpi, where Cycle thread is also 26 tpi but 60 degree form.

But how are things progressing on sorting out the Die cut thread in comparison to the Thread on the mandrel of the lathe?

Any checks on core diameter of the Die, for instance?

Howard

thanks Howard and Swarf, and a happy new year to everyone

Update and a resolution.

It turns out that the 2 inch split die does in fact open to a point of giving a PERFECT THREAD MATCH.

I do however feel slightly vindicated as i took it to a mechanic close by and it turns out that the setting/splitting screws in the cheap die holder were deforming and the heads were starting to strip out before the die could open enough. Once he replaced them with some propper bolts the die worked great.... note to self be careful of cheap equipment...

you guys have been so helpful and i've picked up more from your replies than just an answer to this specific issue

THANK YOU ALL

Jason

Excellent result, Jason ... Thanks for letting us know

MichaelG.

That makes a good start to the New Year. Now things can only get better.

Thanks for telling us that you have solved the problem., and how.

Howard