Change gear help

Here's a little program, gearspec, that is really helpful when working with gears, whether making them or measuring them to find out what you got.
This one LatheGears gives combinations that may not be listed and also tells you what is needed without spending 1/2 hour with a calculator or pencil & paper.
Also have a look at what your feed rates are, in the fine pitches sometimes one will be what you need or so close that it can be used in a pinch for some work.
 

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RJSakowski said:
There is a difference Inch gears measure diametral pitch whereas metric gears measure mod (modulus or module). The relationship between diametral pitch and mod is diametral pitch = 25.4/mod, the 25.4 being the number of mm in 1 inch. There will always be a difference in tooth spacing between metric and inch gears. For example, my Grizzly 602 has a mod 1.5 spindle gear. A B & S timing gear from a lawn mower engine has a diametral pitch of 16. Converting the latter to mod, the modulus would be 25.4/16 or 1.5875. It is close enough to mesh the two gears but the mesh would be imperfect and the gears would wear rapidly.

Actually, diametral pitch = number of teeth/pitch diameter. Diametral pitch = (number of teeth + 2)/ outside diameter which, as I recall, is exact. The diametral pitch would be 72/4.25=16.94 and the mod would be 25.4/16.94 = 1.502. The gear is a metric mod 1.5.
Click to expand...

So I was right it is a mod 1.5 metric gear. If I were to try and find a replacement gear are there any other parameters I need to figure out?
 
Another question while were here, This lathe uses a belt drive for feed other than threading, in the feeds chart it also shows to use the 127 tooth gear to get mm/rev.
289859
Am I correct to assume that the 5 columns with a number in the Z row are mm feeds and only the 6th column under the pic of the belt is in inches?
Here is the belt drive.
289860
 
bpimm said:
So I was right it is a mod 1.5 metric gear. If I were to try and find a replacement gear are there any other parameters I need to figure out?
Click to expand...
The other parameter is the pressure angle. Typically, it is either 20º or 14.5º. It can be tricky as gear profile changes with the pitch diameter so you can't necessarily do a direct visual comparison. This should help.
www.grobinc.com

How to Reverse Engineer Spur Gears • Custom Cold Rolling | Grob Inc.

A question we get quite often is whether Grob can reverse engineer spur gears for a customer. Many times a customer may not know the exact parameters of the gear they need, but they do have a sample part in front of them.
www.grobinc.com www.grobinc.com

Aside from that other parameters are gear width, and material, along with the obvious number of teeth. I have purchased gears for my lathe from http://www.sdp-si.com/products/Gears/Index.php.
 
bpimm said:
I'm seeing the possibility that I have 3 different combinations to get a 1mm thread pitch, Am I reading this right I could use a 40 and 127 with II-X selected or an 80 and 127 with II-XI selected or in the Mod section (I don't even know what that section is about) I could use 48 and 97 with I-X selected, if that's the case I can cut the thread.
Click to expand...

You answered your 1st question right there.
 
I just found this thread via Google. I'm over the pond in Austria and I am looking at a relatively cheap Urpe-type machine, it's the bigger 1660 model but the gears are missing. Buying the metric gears with module 1.5 and and a pressure angle of 1.5 isn't the problem, the full set would cost about 600 euros and require some additional machining, but it's manageable. Normally, the pressure angle is 20 degrees, but I wonder if you could confirm that.
 
OK, am I missing something here? This lathe looks to be missing the gear on the outboard spindle and all the gears from the banjo (which probably would have included the 120/127 tooth gear pair.

It looks like maybe someone ripped out all the change gears and fitted it with a custom belt drive. Maybe to make power feed quieter?
 
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