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| Gear parameters |
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| vtsteam:
A set of pitch gauges is what I use. As chipenter says, they are just straight sided rack form, so you could make a template and measure that. The worm is a straight rack at any axial profile. If you make your pitch gauge accurately out of tin sheet stock, and cut it out with tin snips, you can use it to check your cutter grind (for making the hob). The pitch gauge is handy to have in future. To make a really accurate template, do a rough one first, get its measurements, which will point to one standard pitch and angle (one hopes). Then lay out the proper measurements in CAD for that pitch, and print it. Paste that onto your tin sheet and cut out with snips to give you a gauge. If you then duplicate the worm on the lathe in drill rod (silver steel) and gash and harden you can make it into a hob to cut the gear. Making a tap is similar -- I did that in my new lathe build project, though I used Acme threaded rod, gashed, and hardened with Kasenit. |
| vtsteam:
Actually, there's an even easier way. With a scriber just lay out a doubled 14-1/2 degree (29 degree) angle on a piece of sheet tin, and cut it out to make a 14-1/2 deg pressure angle gauge. Since it comes to a sharp point, trim/grind that back until it just fits into your worm. If it's right, that's your gauge for making a lathe tool. If the angle looks wrong, do the same thing to make a 20 degree pressure angle (doubled) gauge. Now you have two useful gauges. Since you now need only the TPI (or metric equiv). to set your lathe for cutting the hob, just count the worm's threads per unit length, and Bob's yer aunt! |
| John Rudd:
Guys, I appreciate all the help here, I appreciate the DP and or MOD are the same for the gear and worm, but I am completely lost from then on...... :scratch: .........Just read Steve's 2nd post....I'm off to play and see what trasnpires.... |
| vtsteam:
Also, your hob needs to be the same diameter as your worm. So no need to calculate or look that up, either. Just measure it. |
| John Rudd:
Steve, The gear mates at right angles to the worm, the teeth are cut at an angle so its not just a straight cut gear...( which I could handle...) so I need to determine the angle at which the teeth are cut...,is that easy to do? |
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