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SM change gears - Imperial 1120 for metric gears

8

88hillman

Member
(I had a typo in the title. It should have said 'Imperial 1120 for metric threads')

I've started using my old Standard Modern Series 2000 lathe again recently and one of the tasks I was going to perform was making metric threaded parts. Being an imperial machine I would need change gears. I purchased a copy of the original manual years ago and it states the gears that I need by tooth count and I've mostly figured out the pitch and PA.

So the first question is whether there is an easier source than making them? I've considered making them from scratch or buying from Boston Gear, etc and modifying them to fit.

The manual states that I should use change gears with 127, 80 and 50 teeth to achieve the 1.0 and 1.25 metric pitch I'm looking for. My guess is that these were originally 24DP with 14.5 degree pressure angle. Since these only mesh with one another and not the main gears (16DP) they only need to physically fit the space. Module gears seem to be much easier to find...

Second question, does anyone actually have SM change gears to get dimensions from? I've already measured the headstock, idler and input gear that are on my machine.
 
If you have access to a 3D printer you could draw them in Fusion360 and print them. They are in a low-stress environment so they last well.
 
88hillman said:
My guess is that these were originally 24DP with 14.5 degree pressure angle.
Click to expand...
That is what the factory used originally. I’ve made mine to those specs.

88hillman said:
Since these only mesh with one another and not the main gears (16DP) they only need to physically fit the space. Module gears seem to be much easier to find...
Click to expand...
For sure.

The difficult one is the 127T transposing gear. I could not find it off the shelf at the time for reasonable $$s.

Here is the link where I made change gears for my SM1340.

canadianhobbymetalworkers.com

SM1340 Change Gears

My Standard Modern 13X40 lathe is all metric. I want to be able to cut inch threads as well. It did not come with the change gears. Called SM to see if they are available: YES. Great, how much? $$$$$$$$s! OK thanks, I'll pass for that price. Off I went to make my own. This time I had my mill and...
canadianhobbymetalworkers.com canadianhobbymetalworkers.com
 
127/50 is the standard conversion ratio all lathes. It's derived from 2.54 Centimeters = 1 inch. 2.54/1 = 254/100 = 127/50. Change gears from other lathes not just SM may also work?
 
The instructions for the 1120 are really simple and list 127, 80 and 50 teeth change gears, in tandem with the quick change gears, to achieve the thread pitches I was looking for. Those three need to be combined as either 127/80 or 127/50 meshing.

Either pair will compound (stack) with 48t. One of the 48t is already on the machine as the input for the feed gearbox. I'll need to source another. There is also the small matter of the banjo. The banjo layout looks really simple to fabricate. Of course if anyone has a sample I could copy, that would certainly be appreciated!

Cheers
 
I also have a dividing head. Of course no 127 role ring on the plates, but I could make a rough 127 hole plate for the dividing head which would reduce the errors by the ratio of the dividing head gearing.

If I take a twist on @DavidR8 'S idea and make the gears out of plastic it would be really easy going. Aluminum would only be slightly more effort.

This is seeming quite realistic...

I also just found a set of change gears for a mini lathe that includes the 80T, 50T plus the other pairs needed to cut any common metric pitch. These are M1 so only slightly smaller than 24DP so it might work.
 
88hillman said:
(I had a typo in the title. It should have said 'Imperial 1120 for metric threads')

I've started using my old Standard Modern Series 2000 lathe again recently and one of the tasks I was going to perform was making metric threaded parts. Being an imperial machine I would need change gears. I purchased a copy of the original manual years ago and it states the gears that I need by tooth count and I've mostly figured out the pitch and PA.

So the first question is whether there is an easier source than making them? I've considered making them from scratch or buying from Boston Gear, etc and modifying them to fit.

The manual states that I should use change gears with 127, 80 and 50 teeth to achieve the 1.0 and 1.25 metric pitch I'm looking for. My guess is that these were originally 24DP with 14.5 degree pressure angle. Since these only mesh with one another and not the main gears (16DP) they only need to physically fit the space. Module gears seem to be much easier to find...

Second question, does anyone actually have SM change gears to get dimensions from? I've already measured the headstock, idler and input gear that are on my machine.
Click to expand...

Another 1120 owner following the conversation with interest.....

D :cool:
 
Tecnico said:
Another 1120 owner following the conversation with interest.....

D :cool:
Click to expand...
Ideally we need to find someone with an imperial 1120 and the conversion gears on the machine! I haven't found a dimensioned drawing of the banjo yet, but it may be out there somewhere.
 
Brent H said:
Give me a bit and I will see if my CAD files still have it. You will need to verify measurements. I drew it up several years ago when contemplating making the gears. I aquired a metric Utilathe and didn’t keep going on the change gears.
Click to expand...
Thanks, Brent!

Is the banjo different on the Utilathe? I've never seen any of these banjos in person but the images all seem different if you have a metric machine and want to cut imperial gears, or don't have the 1120/1334.
 
88hillman said:
Ideally we need to find someone with an imperial 1120 and the conversion gears on the machine! I haven't found a dimensioned drawing of the banjo yet, but it may be out there somewhere.
Click to expand...

Sounds like a plan!

FWIW, my 1120 presently is configured with an imperial box and metric cross and compound. I think it could have been an "upgrade" model for a trade school machine during metrication. I'm plotting a conversion to full imperial but ideally I still want to be able to do metric threads.

Doing a 127 tooth gear on a dividing head has my wheels turning too, I have a DH but not the differential gearing add-ons. I think I'm going to provoke some discussion on a different way to do that in a separate thread just to see what comes up.

D :cool:
 
@Brent H did a lot of leg work on this one. He’s mentioned a CAD file a few times for not only the gears but the different bracket that the modified change gears mount to. I am eagerly following this thread as well. If anyone gets CAD files, please make sure I’m included on the list of recipients, as I have a 1230.
 
I believe the gear specs will work across the range of old SM machines, but as I said above, I think there are various banjos. I'll look through what I've collected to give an example.
 
This is the 'swing bracket' for the 10" Utilathe:

1710305162534.png


This is from a the reproduction paper copy I have for the 1120 and 1334:
(note that it looks like a horizontal rectangle under change gear A and B)

1710305743359.jpeg


One thing that confuses me about the setup above is the centerline of the 36T headstock gear and 83T idler aren't vertically aligned. They are aligned in my machine and there does not seem to be any provision to offset it this way that I can see. The idler for my imperial machine rides on a dowel in a vertical bar secured by 4 cap screws. Does this piece need to be replaced as well? It may be the above diagram is actually for the 1334, and my 11" is just different because of the center height. As it is, the 36T, 83T and 48T on my 1120 are all engaged as the small diagram in the lower left of the image below:

1710306637393.jpeg


Cheers!
 
IMG_1920.png
The “End Gear Train” diagram is from an SM 1334 Lathe and I don’t believe applies to the Utilathe or Series 2000 lathes

The Utilathe and Series 2000 are virtually identical. Pretty much just a rebrand of the Utilathe to Series 2000. The parts are interchangeable and you will note that the back gears are the same (even same part numbers). The 10” Utilathe and 11” series 2000 have the 48 tooth feed train gear and 83 tooth idler and the 12” Utilathe/13 series 2000 use 2 x 54 tooth idler gears to accommodate the 2” clearance between lathe models.

The banjo for the 10/11 series will/should be the same. The 12/13 will be different due to the double idler but will be similar. There is a YouTube video of this guy changing the bearing on the back of a 12” Utilathe. This lathe has the metric gearing but he doesn’t focus on anything other than the bearing and his overall explanation is poor. I wrote him way long ago with no reply. I will dive back into my files as I have quite a bit of this information all worked out already.
 
Here is what I made up in Auto Cad - I have to find the actual drawing yet. I was working out the gear placements and the tooth profile. One issue I had was finding the 14.5 and 16 pitch cutters to match the number of teeth required. The 14.5 I think is the harder cutter set to locate (at least for me)



10 inch Utilathe metric gear assembly.jpg

Gear test fit 10 inch.jpg


Here is a screen shot of the lathe (a 12") that I got from the Youtube video and you can see the banjo and the way the assembly would look in place. This was the only place I was able to get a decent idea of the fitment. Buddy has his finger on the 127T gear. Sadly he is not explaining this assembly and how it works.
Metric Gears bracket.jpg


Once gears are made this is the Thread chart:

Metric Tread Transpose Gear TPI Setting
0.35 70 127 40
0.4 80 127 40
0.45 90 127 40
0.5 80 127 32
0.6 60 127 20
0.7 70 127 20
0.75 90 127 24
0.8 80 127 20
1 80 127 16
1.25 50 127 8
1.5 60 127 8
1.75 70 127 8
2 80 127 8
2.5 75 127 6
3 60 127 4
3.5 70 127 4
4 80 127 4


I will stay on the hunt but have to go tile the laundry room and powder room right now......
 
DavidR8 said:
If you have access to a 3D printer you could draw them in Fusion360 and print them. They are in a low-stress environment so they last well.
Click to expand...
X2. I printed out an entire metric set for my south bend along with the transposing gear.

I also read some people leave one plastic gear in the set just in case so I decided it was a good idea to figure out the durability.

I've had a plastic gear installed for the last couple months and have been using it lots with no issues, printed with PETG. Makes everything a little quieter as well and hopefully in the unfortunate event of a crash it would be the piece to give.
 
Johnwa said:
I don’t know if you could make these work but the prices aren’t bad. I’ve ordered from RDGtools and was happy with them.

SC4-CG127 Change Gear 127T - Arc Euro Trade

127 Tooth cast iron change gear. ø129mm x 8mm wide. Hub width: 10mm, bore: 16mm, Keyway: 4mm.
www.arceurotrade.co.uk www.arceurotrade.co.uk
Click to expand...
John, RDGTools sure have a good selection of gears for the Myford lathes! I could pretty much buy every gear I need but they are DP20 so the 127T gear would be larger by a little more than an inch in diameter.

I'm really starting to like the idea of machining at least some of the gears from a softer material, plastic or aluminum. While my scrap supply is very small, I do have a chunk of aluminum round about 6" diameter that should be large enough for either a 127T Mod 1 or DP 24 gear. I also like the idea of making a fly cutter rather than buying a whole set of gear cutters to get the 1 or 2 that I need (Mod 1 I would need #6/7, DP 24 would be #2/3).

If a set of gears fell in my lap at a decent price, I wouldn't look that gift horse in the mouth though!
 
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