Looking for change gears for Central Machinery 12x36 lathe Part #33274

[turningwheels]

I bought a lathe a year or so ago from a woman who's husband had died. It was a great deal and I have loved learning how to use it and turn all sorts of things. Now that I want to start making threads, I have found that I am stuck with the 43 and 60 tooth change gears. It's stock gears for imperial threads is 40 and 40 which I have found from grizzly to be a match with their G4003 Lathe and have ordered them. But the rest of the change gears are different tooth count and it's proving difficult to find out what pitch, pressure angle and thickness I need. By the way, I do want to make metric threads and this is why I am looking for the 25, 26, 46 and 47 tooth gears. Any suggestions?

 

[brino]

First, Welcome to the group!

Some lathes are shipping new with plastic gears.

3D printing has opened up a new world of products including lathe change gears.
Here are some references:

https://www.hobby-machinist.com/threads/gears-for-my-oldtimer-lathe.82245/#post-715308

https://www.hobby-machinist.com/threads/gear-drawings-for-a-3-d-printer.84037/#post-742225

https://www.hobby-machinist.com/thr...iring-diagram-on-maximat-7.72271/#post-710924

If you find all the parameters and need the *.stl files generated I can do that for you.
Then you could print them yourself, or find a friend with a printer.

If you also need them printed (and are not in a huge rush!) I could also print them for you.......
Or you could try asking in the 3D-Printing forum.

-brino

 

[brino]

I did a search in our downloads are for "Central Machinery" and found a couple hits....

There is a manual here:
https://www.hobby-machinist.com/res...al-machinery-df1237g-and-similar-lathes.3236/
for Busy Bee/Rex-Cut DF-1224G, DF-1237G, DF1240G and DF 1340G.

and here:
https://www.hobby-machinist.com/resources/central-machinery-manual-newer-model-pdf.2294/
for a Central Machinery 7x12 model 97009.

You may need to be a supporting member here to download manuals.
It helps defray server costs......

Good Luck!
-brino

 

[DAT510]

Though Grizzly doesn't list the part # for the change gears, they do listed them in the accessories. Grizzly's customer service is very nice. I believe if you were to call them and ask to order the "Change Gear Set –26T, 27T, 35T, 36T, 45T, 50T, 60T" for the G4003 they would help you.

 

[turningwheels]

Though Grizzly doesn't list the part # for the change gears, they do listed them in the accessories. Grizzly's customer service is very nice. I believe if you were to call them and ask to order the "Change Gear Set –26T, 27T, 35T, 36T, 45T, 50T, 60T" for the G4003 they would help you.

The central gear on mine is an 80 and on the grizzly, it's an 84T, hence why the change gears are slightly different. Would I have to get the middle gear to the correct ratio? I talked tho them at length and their answer is that because the lathe is CM rather than Grizzly, they basically won't help me. I have to purchase the gears and try them out first, and if they fit, great, otherwise return them. But the challenge is the different center gear...

 

[turningwheels]

First, Welcome to the group!

Some lathes are shipping new with plastic gears.

3D printing has opened up a new world of products including lathe change gears.
Here are some references:

https://www.hobby-machinist.com/threads/gears-for-my-oldtimer-lathe.82245/#post-715308

https://www.hobby-machinist.com/threads/gear-drawings-for-a-3-d-printer.84037/#post-742225

https://www.hobby-machinist.com/thr...iring-diagram-on-maximat-7.72271/#post-710924

If you find all the parameters and need the *.stl files generated I can do that for you.
Then you could print them yourself, or find a friend with a printer.

If you also need them printed (and are not in a huge rush!) I could also print them for you.......
Or you could try asking in the 3D-Printing forum.

-brino

How much stress goes into the change gears? 3d printing would be great if the gears could take it...

 

[brino]

The central gear on mine is an 80 and on the grizzly, it's an 84T, hence why the change gears are slightly different. Would I have to get the middle gear to the correct ratio?

The answer is ..........it depends!

In a simple gear train, if a gear is both a driving gear and a driven gear then the tooth count ends up in both the numerator and denominator of the equation. Therefore it's tooth count cancels out and you could really use any tooth count gear in that location.

The only impact being the spacing between gear centres, smaller gears need centres closer and larger gears need centres farther apart.
Which is why the lathe banjos have slots to mount the gears so they mesh with the two adjacent gears.

However, if the gear in question is fixed to the axle of another gear _AND_ one is a driven gear and the other is a driving gear then any replacement gears would have to have the same ratio. This in known as a compound gear train. You could change both as long as you maintain the same ratio, but you cannot just change one.

Here's some diagrams of simple and compound gearing:
https://mechanicalmania.blogspot.com/2011/07/simple-compound-gear-train.html

-brino

 

[brino]

How much stress goes into the change gears? 3d printing would be great if the gears could take it...

Agreed!

I believe the forces on the gear depend on many things; the gear train, the gear size, the lead screw pitch, etc., the load (the depth of cut and the tool sharpness) will have an affect.

I have never run the numbers to calculate it and suspect it would be time consuming and involve numbers for friction that would be tough to characterize.

I do NOT have any plastic gears for my lathe, and so have no direct experience.
Perhaps someone here could provide first-hand review of 3D-printed lathe change gears.

What I can say is that
1) plastic gears are used by some people (some new lathes ship with them, and Thingiverse has printable files for many different lathes)
(https://www.thingiverse.com/search?q=lathe+change+gears&type=things&sort=relevant)

2) 3-D printing offers a range of materials, temperatures and print settings to try to achieve strong parts.

I have printed a few spur gears.
Two I used to connect a "turns counter" to my lathe for winding coils.
Another larger one I printed just to try the process. I set the infill to 100% so it is solid.

Most of my prints are in PLA plastic, but I have also tried ABS and nylon.

-brino

 

[middle.road]

Agreed!

I believe the forces on the gear depend on many things; the gear train, the gear size, the lead screw pitch, etc., the load (the depth of cut and the tool sharpness) will have an affect.

I have never run the numbers to calculate it and suspect it would be time consuming and involve numbers for friction that would be tough to characterize.

I do NOT have any plastic gears for my lathe, and so have no direct experience.
Perhaps someone here could provide first-hand review of 3D-printed lathe change gears.

What I can say is that
1) plastic gears are used by some people (some new lathes ship with them, and Thingiverse has printable files for many different lathes)
(https://www.thingiverse.com/search?q=lathe+change+gears&type=things&sort=relevant)

2) 3-D printing offers a range of materials, temperatures and print settings to try to achieve strong parts.

I have printed a few spur gears.
Two I used to connect a "turns counter" to my lathe for winding coils.
Another larger one I printed just to try the process. I set the infill to 100% so it is solid.

Most of my prints are in PLA plastic, but I have also tried ABS and nylon.

-brino

We ought to try a Nylon one, toss it on my Logan and do a stress test on it.
H-M Testing Labs . . .

I got that Flashforge that's been laying around here forever dusted off and moved down into the basement. Now I just have to clear a spot for it, and find some time. Oh and yeah, learn how to use it. Been dodging that wabbit hole.

 

[DAT510]

So Interesting.... It looks like the Central Machinery Lathe decided to use a single 80 tooth gear and different change gears to achieve the Metric Threads. An 80T Center Gear with a combination of 25T, 26T, 43T, 46T and 47T.

The Grizzly G4003 uses a of a 86T Center Gear and a 91T/86T ratio to achieve the same Thread Pitches. My guess is it was cheaper to use just a single 80T gear on the the Central Machinery Lathe, at the expense of Metric Thread Pitches that were not quite as accurate. Where as the Grizzly Machine with with the step down/up center gear and different change gears (26T, 27T, 35T, 36T, 45T and 50T)

Looking at both gear train diagrams, the Center Gear appears to be an Idler Gear. So it appears as long as the Diametral Pitch is the same, an 80 vs 84 tooth gear would work the same, as long as you used the Metric Thread Chart and Gears from the Central Manual.

If the quick change gears are the same with both lathes, then one could also the 91T/86T gear from Grizzly along with the Change Gear Set, an then use the Metric Threading Chart from the G4003.

Hope this helped.