Weller Branding Iron Thread Size

[Robbo3]

I have just made myself an iron for using the Weller WHK30UK Wood Burning Kit. I posted about it, along with a photograph, in the woodturning section.
The tip threads are 4mm in diameter, 32 TPI & 0.8mm pitch. Measurements were taken with dial calipers & thread gauges & even though I'm a bit of a duffer I'm pretty sure they are correct.
Is this a standard thread?

 

[J-G]

...The tip threads are 4mm in diameter, 32 TPI & 0.8mm pitch. ...Is this a standard thread?

No. The standard pitch for 4mm dia. is 0.7mm. 5mm dia. is 0.8mm.

What the 'real' size is really depends how you measured the dia. - I am assuming that you used a thread gauge to measure the pitch - so even if it was an imperial gauge, 32 tpi is in fact 0.79375mm so is 'close'. If you measured the dia. with a steel rule then the 4mm could be closer to 4.8 which wouldn't be unusual for a nominal 5mm thread.

 

[Robbo3]

I measured across the threads with both dial calipers & a micrometer. Both read 4mm, whereas if I measure a 4mm machine screw it reads 3.8mm.
As I said, I'm pretty sure my measurements are accurate using the (metric - no imperial) tools at my disposal. To my mind 0.79375mm is closer to 0.8mm than I can measure. If I try with the 7.5 or 8.5 gauges, they are way out so I'm happy to accept that the pitch is 0.8mm.
Although I'm measuring everything in metric, is it possible that it's an imperial thread?
Thanks.

 

[AES]

I THINK (rpt, only think) that Weller brand originates in the USA (though they seem to be widely available), in which case an "Imperial" thread is likely. The only trouble is that (assuming your measurements are correct, and I'm not doubting) I've looked a UNC, UNF, SAE, BA, and ME "standard" threads and none in my (fairly extensive) collection of lists match exactly with your dimensions, sorry.

Can only suggest an on-line search, or an E-mail to Weller.

Good luck.

 

[Robbo3]

I couldn't find anything that matched those dimentions either. Just thought that it might be a standard but uncommon thread.
They sell sets of tips separately but it was the flat circular plate to make another brand that I thought I might be able to make. I'm probably just about capable of making a new insert for the iron with threads of my own choosing.
Thanks for your help gents.

 

[J-G]

I hadn't considered the possibility of an imperial (American) thread but now that has been posited I suspect that it is a N° 8 UNC . The basic major dia. of that is 0.164" or 4.1656mm and the pitch is 32 tpi. Knowing that most commercial threads are smaller than the nominal major dia., 4mm would not be out of place for a cut or rolled thread.

It is not unusual either for manufacturers to use non-standard threads where the possibility of future sales of consumable components is likely but a thread being only 6 thou undersize seems to negate that.

I'm fairly certain that a N°8 UNC nut will fit that tip - and yes, that is a 'Standard' so Taps and Dies are available, try Tracy Tools Ltd.