I've not seen one for sale.
When I needed one, it was a relatively simple build from 3/8 aluminium
alloy plate screwed onto a boss with a pinch clamp.
Aluminium is quite strong enough to light hobby use and easy to machine.
Not having a mill it might be easier to buy the necessary gears
(38,55) and rigging the quadrant the other way (which I initially
avoided as it needed the purchase of 2 gears as supposed to 1).
Thanks again, Bob!
Robin, you might want to try my ML7GEAR software which is quite good at
working all this stuff out, either with the gears you have or run free
to give you some ideas on which gears to buy.
Your ideal is 16/23 which is not available, or 32/46 which is - this
will give you an exact 11.5 TPI, but neither 32 or 46 come with the
standard gear set.
BTW, the standard gear set will not ever give you 11.5 TPI, only
approximations, the nearest of which is 11.500529 TPI. For most
practical purposes this will do the job.
You can grab the software (it's free) from
http://metal.duncanamps.com/software.php It won't try and load things
onto the quadrant that won't fit.
Thanks, Duncan, I'll try that. Had a brainwave last night and realised
I could swap 2 of the gears over (so instead of:
I could use
But that doesn't fit either (can't get the "A" gear in). I suppose I
but I doubt that would work. I'll see what the software will come up
with, otherwise I'll buy the 38 and 55 tooth gears (turning out to be
an expensive little project, this one!)
Managed to get it working with my existing gears.
The book recommended:
But I've used:
A test cut (before I destroyed the workpiece! Don't worry, it was
scrap) showed the threads to be correct, or at least close enough. The
male thread my adaptor will be fitting too is fairly poorly made, so
I'm not too worried about precision. It's only PVC I'm cutting so
there'll be a bit of give anyway. I'm bound to need a load of PTFE/
plumbmate to make it watertight anyway.
Next time wind in to clear before withdrawing tool <g>
[ Only some one who has done this will recognise the distinctive
scrawk mark ]
Hands in pockets, nonchalantly whistling and goes to make a cup of
My threading tool only just fits in the hole, there's not enough space
to fully withdraw it (the other piece I made was released from the
chuck to make removal easier) - I was hoping that nobody would notice
that! :D Going to look for a smaller tool (despite what all my spam e-
mails say...) as would be nice to be able to make these things
commercially. Can one buy hexagonal PVC rod, or should I invest in a
vertical slide to mill some flats on them?
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