Myford quadrant - too small, are larger ones available?

Trying to cut 11.5tpi on my Myford Super 7. According to the book, I need to drive a 75tooth gear from a 65tooth gear, but the slot in the
quadrant isn't big enough to allow this. Are there longer quadrants available aftermarket?
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Robin wrote:

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.
HTH
Bob
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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!
r
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Robin wrote:

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.
Regards, Duncan
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Thanks, Duncan, I'll try that. Had a brainwave last night and realised I could swap 2 of the gears over (so instead of:
40---A---55 65---75
I could use 40---A---75 65---55
But that doesn't fit either (can't get the "A" gear in). I suppose I could try 65---A---75 40---55
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!)
R
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Great software! Running it under DarWine on my Mac
R
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Managed to get it working with my existing gears. The book recommended: 40----A----50 65----75
But I've used:
40----75 65----A----50
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.
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Got it done:
http://i277.photobucket.com/albums/kk76/richardspandit/Pump/DSC_0758.jpg
http://i277.photobucket.com/albums/kk76/richardspandit/Pump/DSC_0759.jpg
http://i277.photobucket.com/albums/kk76/richardspandit/Pump/DSC_0760.jpg
http://i277.photobucket.com/albums/kk76/richardspandit/Pump/DSC_0761.jpg
http://i277.photobucket.com/albums/kk76/richardspandit/Pump/DSC_0762.jpg
http://i277.photobucket.com/albums/kk76/richardspandit/Pump/DSC_0763.jpg
Not perfect but it'll do. Used a spade bit to drill the ends as don't have a boring tool.
Robin
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http://i277.photobucket.com/albums/kk76/richardspandit/Pump/DSC_0763.jpg
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 coffee..............
John S.
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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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