I am trying to calculate the centre distance of a worm and worm gear and al though I have looked lots of formulae on line I am, as usual, confused!
The worm gear has 40 teeth and the OD at the largest point of the gear is 4 .375?. The worm OD is 1.167? and it is a three start worm, if that is important.
Could somebody explain in words of one syllable how I do this calculation a nd what answer I should get?
I need the easy to understand method of calculation as I know I will need i t again in the not too distant future.
I would be tempted to mount the worm and wheel on some suitable adjustable mount, and tweak for a nice running fit, then measure. Rather like I understand clockmakers use a depthing set up.
The chuck of the lathe could carry the worm on a suitable arbor, and the wormwheel could be mounted in the toolpost again on a suitable arbor. (or vice versa) using the cross slide dials for measurement.
although I have looked lots of formulae on line I am, as usual, confused! T he worm gear has 40 teeth and the OD at the largest point of the gear is 4.
375?. The worm OD is 1.167? and it is a three start worm, if that is im portant. Could somebody explain in words of one syllable how I do this calc ulation and what answer I should get? I need the easy to understand method of calculation as I know I will need it again in the not too distant future . As usual, thanks in advance. John H
Thank you Mark, your calculations have sorted out my understanding of the f ormulae that I have read.
As I said, I will be doing this type calculation again. Hopefully now I sha ll be able to, but with a few less decimal places!!
although I have looked lots of formulae on line I am, as usual, confused! The worm gear has 40 teeth and the OD at the largest point of the gear is 4.375?. The worm OD is 1.167? and it is a three start worm, if that is important. Could somebody explain in words of one syllable how I do this calculation and what answer I should get? I need the easy to understand method of calculation as I know I will need it again in the not too distant future. As usual, thanks in advance. John H
formulae that I have read.
be able to, but with a few less decimal places!!
Andrew's suggestion of trying it for fit and measuring is the optimal solution if it's at all possible. I discovered this when I made a load of gears to replace the clapped out ones in a gearbox and then found that mine were a few thou oversize!
Hut that's for a different reason, and is to locate the transition point between the hypocycloidal and the epicycloidal curves. There won't be the same effect with involute teeth because all that the happens is that there is a change in the effective pressure angle, a dodge sometimes used to cut different numbers of teeth on the same notional pitch cirlce diameter.
although I have looked lots of formulae on line I am, as usual, confused! The worm gear has 40 teeth and the OD at the largest point of the gear is 4.375?. The worm OD is 1.167? and it is a three start worm, if that is important. Could somebody explain in words of one syllable how I do this calculation and what answer I should get? I need the easy to understand method of calculation as I know I will need it again in the not too distant future. As usual, thanks in advance. John H
formulae that I have read.
be able to, but with a few less decimal places!!
I needed some small custom worm and worm gear sets and decided to use a tap as the hob. I made a few different sets, measured the parts, calculated center distances, and still had to adjust more than I thought I would need to. Measuring over the gears with the worm nested in the worm gear gave me much better results, so I think I goofed a little on the math. The best part though was how easy it is to make small worm gears with a high spiral tap held in a collet in the lathe. In fact, it was so much fun that I made extra sets of different sizes that I didn't need and now just sit around as show and tell parts on my desk. Eric
although I have looked lots of formulae on line I am, as usual, confused!
what answer I should get?
again in the not too distant future.
A high spiral tap should really be called a low angle helix flute tap. In my opinion. But anyway, instead of having straight flutes like most taps the flutes wrap around the tap. If you were to try to hob a worm gear with a regular tap, using the tap to turn the work, it wouldn't work too well because the tap would not be constantly engaging the work. A high spiral tap will always have teeth engaged in the work. And the purpose of the taps is to eject chips out of the hole, not push them ahead like a spiral point or let them pack the flutes like a hand tap. See this link:
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