Adler 4-10

[Jianis]

2 hours ago, DonInReno said:

I do not have any information - I’ve never seen one until yours.

It shouldn’t be too hard to find a gear to match, although sewing machines are famous for oddball gears and screw threads to prevent others from making spare parts so it might not be an exact fit.

There are three things you’ll use to identify the gear - the number of teeth, the relative size (diametrical pitch or dp), and the angle formed where the teeth meet (pressure angle or pa).

Spur gears in the US that were used on older machines are normally a 14.5 degree pressure angle, vs 20 degree pressure angle used on new machines.   I have no idea what type of gears were common when and where your machine was made.

The number of teeth can vary since all gears of the same dp and pressure angle mesh with each other, but most reducers are 3:1 and then there’s the reduction between the reducer and handwheel pulley, which can be up to 6:1.   All combined the reduction is something between 10:1 and 18:1.   If your main gear has about 50 teeth you’ll want a small gear and it probably won’t give enough reduction on its own and you’ll have to have a large pulley driving the small gear and small pulley on the motor.

For size (dp) it’s not going to be easy to determine other than comparing it to gears of a known size.

In the photo these are both dp of 8 and number of teeth are 20, but the one with squarish teeth is 14.5 pa and the other is 20 pa.  They somewhat mesh, but if used together it would be a very loud setup.  Just a wild guess, but it seems your gear is somewhat close to dp 8, but probably the larger dp 6 or even a dp 5.

The catch is, there is no requirement for them to follow these common gears and it might be a weird pa and nonstandard tooth shape.

This catalog somewhat describes the differences and commonly available inch (not metric) size gears from Boston Gear.

Thank you ! 
Lots o useful information.

thIt is a German machine so it should be metric.

I am a couple of thousand miles away from home so it will be some months before I can work on the machine again!

The gear has some 50 teeth.I can eventually calculate the number of teeth of the smaller gear measuring center to center between the the gear itself and the center of the back-gear bracket.  Then find out the kind of  gear and go further….

Jianis

 

[DonInReno]

Of course you’re right about the metric gears on your machine - it’s such an American thing to think everyone used d.p. on old gears!  Lol

I found this explanation of the similarities and differences between the metric and American designations that was just what I needed to better understand the gear modulus system.

Best of luck on it - that’s quite a nice machine.

https://qtcgears.com/tools/catalogs/PDF_Q420/Tech.pdf

Edited June 18, 2023 by DonInReno

[Jianis]

9 minutes ago, DonInReno said:

Of course you’re right about the metric gears on your machine - it’s such an American thing to think everyone used d.p. on old gears!  Lol

I found this explanation of the similarities and differences between the metric and American designations that was just what I needed to better understand the gear modulus system.

Best of luck on it - that’s quite a nice machine.

https://qtcgears.com/tools/catalogs/PDF_Q420/Tech.pdf

Thank you .

A lot of usefull information in one document.

Back in the 70s I had the theory in college and I even got a deviding head and 2 sets of gear cuting discs to experiment on my Myford lathe with milling attachment. At the time I made two gears on coper disks and then I forgot all about it.

Jianis