Threading Gear ratios and other what nots..

Gallery, Projects and General > How do I??

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NeoTech:
This is why i love this forum. ;)

Pete, i run a my Optimum D320x920 lathe, its a metric lathe - "gunsmith" lathe or what they are usually refered to.

Bill Todd, how did you do the math for that?! Im interested in being able to calculate that myself next time i find myself doing something that is waaaay over my knowledge and skill leve.. =)

:mmr:

rhankey:
NeoTech, If your leadscrew has a 3mm pitch, and you need a 1.6666667 pitch, the ratio you need is computed simply by dividing the two pitches - e.g. 3 / 1.666666667 = 1.8. Then all you need to do is figure out what combination of gears you have that will arrive at 1.8. In this case a 54 / 30 = 1.8.

BillTodd:

--- Quote ---Bill Todd, how did you do the math for that?
--- End quote ---

No maths involved just the ability to use a calculator

lead screw pitch = 3
you need 1.667 (which is almost certainly a rounded fraction) hence why I said 1.6666666666......

3 divided by 1.66666...... is 1.8

So, each turn of the spindle moves the lead-screw 1/1.8 turns, slightly more than a half-a-turn - It's always work having a rough estimate in you head as it can save errors later)

if we multiply the pair to get nice whole numbers we get 10/18 i.e. 10T on the spindle and 18T on the lead screw (remember we needed something like half speed at the lead screw so we know the gears are the right way 'round) , but that's a very small gear so multiply the pair by 3 or 4 or what ever to get a sensible sized pair of gears (The Idler gear doesn't matter so just pick one big enough to fill the gap between the others)

Bill

NeoTech:
Well, and its seems like i cant disengage the norton gearbox.. so wouldnt that need to be taken into account in that formula then.. if i set it to like 1.5 that is usually 60/120/60..

BillTodd:
If you can't disengage the threading gearbox then just set it to do a 1.5mm pitch, then calculate the change gears as if you have a 1.5mm pitch lead-screw

1.5 / 1.666666... = 0.9 = just under 1, so the "lead screw" (input to the gearbox) is going to be going faster than the spindle.

multiply by ten to get whole numbers = 10T on the spindle 9T on the lead screw

multiply by, say, 4 = 40T on the spindle and 36T on the lead screw

Bill

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