The head end is square cut but of a much greater diameter that the wrong end or extensions just slide in without thread contact.
Lower on the order page Simon answers “are all threads the same? I.e. can I buy any color for my al7? Even the ones labeled for M3? Can choose any color, red best option as per me”.
Ah, you’re right. I don’t know why he doesn’t just correct the listing. :person_facepalming:
I’m looking everywhere on that listing, but could someone to point out Simon’s response to L6 colour?
I actually found the Q/A on the tube extension page here just past the review section.
Thanks! Going bonkers there.
But that isn’t Simon responding. It’s the Q & A from any buyer.
Simon’s English doesn’t have those syntax errors.
So I see the M3 head diameter is larger than the extensions or the L6/L7.
My basic interest was with the tail end. And as per the pictures, either silver/gold fit the L6/L7 as well as the red/purple.
To conclude, the extensions would be 32mm in diameter with square-cut threads.
Either some error crept in production batches and since changed. Or something else escapes me.
When I inquired:
But this getting too convoluted, I’ll order some and see what the thread forms are.
I have a couple gold and one red from the first batch. They are different.
But they are similar enough that they seem to interchange with my M3C and L2 just fine.
I measure 1.2525 OD (about 31.8mm)
Square thread form as near as I can tell. Under magnification it looks ever so slightly trapezoidal, maybe, and root v crest measurements might indicate so, but it was hard to measure those accurately. Could just be the shape of the cutter used causing the root to be narrower.
1.75mm pitch (edited to correct earlier mistake…said 2mm but it’s 1.75mm)
The female end on the gold has a considerably thinner outer lip/wall than the red by around thirteen thou. The pocket depth on the gold is also a bit shallower than on the red. I assume this means that if interchanging between models that there could be a small gap on one. Screwing the gold onto the red works fine - screwing the red, with its thicker wall, onto the gold won’t work unless you remove the o-ring.
OAL is the same within several thou, which I would probably attribute to finishing rather than design.
OD on the head end of the M3C battery tube is 1.3912 (call it 35.3mm). Same threads near as I can tell.
Empirical data – now that’s a turn for the best.
Gold and red are very closely identical, the red having the lower fit internal tolerance (why it doesn’t thread fully onto the male gold end with the “O” ring). This, along with the product picture, disproves the original listing as silver/gold for one model flashlight and red/purple for another light.
And the thread is 32mm (nominal) x 1.75 pitch - square thread. Male end.
Presumed the same on the female end of the extender.
A few engineering tips:
- As the male end of a threaded form is readily measurable, it is the reference.
- The female is either said to fit onto or the male fits into.
- Pitch is determined with a ruler alongside the thread profile; the number of complete threads over a given length and then calculated per unit. Metric or inch is determined by this criteria. With some experience, the math works out within the second try of # threads per ‘x’ length.
- The diametrical measurement plus 1/8th of the pitch (max) should fall to a rounded number (metric) or a multiple of 16 (lesser than 1 inch) or multiple of 8 (sizes greater than 1 inch). This is the nominal size. [barring American small screw sizes]*
- Trapezoidal threads have a 30º inclusive angle, which is a 15º flank from the perpendicular of the threaded long axis.
- Square threads are 90º from the long axis.
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Thread profile determined against a white background. Focus on crescents, then form in darkened foreground.
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Small screw diameters: # x .013” + .060” | eg. #10 screw = .190” (~3/16”) nominal diameter