The gears in my head don't mesh

First, you need to figure if the gears that you have are diametral pitch ( imperial measurement) or module (metric), then you need to figure out the pitch and whether or not the gears are 14 1/2 degree pressure angle or 20 degree P.A. If your machine is made offshore it is likely that they are Module system. The OD of a gear is figured (in the case of D.P.) gears by the formula: N(number of teeth) +2 divided by D.P. = OD, The formula for Module is similar, but different. Your biggest challenge will be figuring out the D.P. or Module; for DP there are charts in the handbooks with profiles if the different pitches, Module may be harder to find --- But, if you were to give the OD of the 66 tooth gear and also the Root diameter of it, the Module could be deduced, otherwise you may look for a set of plastic templates of Module gear teeth and figure it that way, once you find the module, its all simple formulas.
 
Well isn't this a pretty little puzzle. From the looks of the gear chart, it's an Asian lathe. We will need the center to center dim for the shafts, call them C1 for the upper gear set & C2 for the lower. Assuming Module gears, module will be the same for all gears (of course), call it M. Number of teeth =T. Reference (pitch) diameter (Rdx) = M x T.
Once you have the center to center, you can solve for the module
For the upper set of gears:
Gear 1 = 66 teeth, Rd1=66M
Gear 2 = 55 teeth, Rd2=55M
C1=(Rd1+Rd2)/2
C1=(66M+55M)/2
2(C1)=66M+55M
2(C1)=121M
(2{C1})/121=M

.To calculate the OD,
OD (in mm)=(T+2) x M

Someone please check this, it's late.
 
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You don't need to measure center to center. If you have one gear, measure it's O.D. and count its teeth. You can calculate module if it's a metric gear or diametral pitch if its an inch gear from those numbers. The calculated result will come out an nice number, i.e., either 1.00, 1.25, 1.5,etc. for metric gear modulus. If the number is squirrelly, assume its an inch gear and calculate the diametral pitch. Diametral pitches are all whole numbers. If you get something like 15.7, it is a metric gear.

Typically, the calculations may be off slightly due to the O.D. measurement not being accurate but they will be very close to the ideal.
 
Common diametral pitches: 6, 8, 10, 12, 16, 20, 24, 32, 64
Common modulus values: .4, .5, .75, .8, 1, 1.25, 1.5 2, 2.5, 3

For smaller lathes, you are most likely to have diametral pitches in the 16 to 32 and moduli in the range of .8 to 1.5
 
The tooth count on that 95 gear might give a pretty good clue as to what can physically fit.
Assuming module gears. Module 1 95 tooth gear is 3.8189 O.D.
The mating 57 tooth module 1 gear is 2.3228 O.D.
So that takes up 6.1417 inches of room. If that's large or small go from there.
I think module 2 is popular on asian equip. that would take up 12.2835 inch
 
What's the make and model of lathe?
 
There is a program called Gearotic Motion that solves this problem easily, produces drawings etc. $120 though.
 
I have measured the gears on the lathe and I used it for reference for the change gears I want to make and it looks like the module are M2.0 if I use the information the members gave me. That being said, I can say this is a metric lathe so it makes sense that the gears would be Module and not DP. In the pic below it shows the gear configuration on the lathe as it is now.
20200403_153816-1.jpg
Now that I have the module,I will be able to work out the rest. If someone thinks I am missing something, please let me know, but I think I am ons the right course now.
 
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