Change Gears Identification

Would like to have these gears identified please and to what lathe that they may belong.

They appear to be unused and very fine condition of fine grain casting of steel. I do have a SBL 9 B that does not have a set if change gears, these may be able to be adapted ?. SBL are 18 DP I think, don't have a gauge. your thoughts please, otherwise I will be considering a swap trade. Doug

It would be difficult to use gears of different DP or MOD sizes if the shaft spacing was fixed. I have changed the hard to obtain British Smart & Brown gears for similar tooth size metric ones only because the changewheel positions are adjustable to accept many combinations of gear tooth numbers. If you are thinking of using your spare gears in this context, you may be lucky. These 16DP gears will be slightly bigger for the same tooth counts than your lathes 18DP ones. There would be some measuring to do before committing yourself to making them fit the lathe. You might not have enough combinations of gears to make the change viable.

Smart and Brown used 16DP gears. The standard sets do not include some of the tooth counts shown, perhaps they are for BA pitches.

Martin C

Edited By Martin Connelly on 08/08/2021 23:51:09

If they are for BA pitches, then the tooth numbers would be 'stange' numbers, probably all odd numbers.

The ones shown form a nice sequence of even numbers 'by fours'. That might be a toehold into their identification: you can eliminate all machines that were supplied with gears 'by fives'.

The 46 tooth gear looks like the only odd one out on the ‘count by 4’ sequence?

Look like Logan. DP, Bore, Single Keyway, Four Holes all match

46T is one shown on their change gear chart, the rest being in steps of 4

The fact Doug is using a DP gauge from a Toronto company and has a South Bend suggests it may be he is not UK based so cutting BA is unlikely..

EDIT The 46T allows cutting of 11.5tpi which is used for NPT pipe threads so one more indication the lathe is from the US.

Edited By JasonB on 09/08/2021 10:13:25

Hello Doug,

Good to make contact again, several years have elapsed now since you helped me with gearbox information and photographs for my book; maybe I can return a favour.

To confirm your thoughts.

South Bend change gears are 18 DP. I'm sorry to say this collection will not mesh with the ones you have already and in particular the 24T pinion that is machined on the spindle, they will bump and grind doing no good to either component.

I can't help much in suggested which lathe they would be best suited to, but I wouldn't recommend them for your lathe.

Best wishes

Brian

.

… and the fact that Doug wrote “SBL are 18 DP I think, don't have a gauge.”

would seem to contradict that ^^^

[confused] MichaelG.

.

Are the photos perhaps from a Seller’s description ?

Edited By Michael Gilligan on 09/08/2021 10:43:51

I think Doug is saying he has South Bend gears but his gauge does not have an 18DP section to confirm the DP..

Andrew

Edited By mahgnia on 09/08/2021 10:54:44

.

Could be

… but he did also write:  “I do have a SBL 9 B that does not have a set if change gears”

So it could be either, or a bit of both

MichaelG.

Edited By Michael Gilligan on 09/08/2021 11:30:08

You need to 1) check if they have a profile giving approx location, 2) look at early posts, or 3) be lucky with a guess.

No. 2) solves the enigma, in this instance. First post - Canada.

Edited By not done it yet on 09/08/2021 11:45:19

The model M Smart & Brown used 18DP gears, but they are only likely to be this side of the pond.

Another way to check the teeth is an online calculator.

https://www.technobotsonline.com/gear-size-calculator.html

Edited By old mart on 09/08/2021 14:32:32

The gears are not Myford pattern, although the same 5/8" bore.

You can calculate the DP by measuring the O D of a gear and counting the teeth.

Add 2 to the tooth count and divide that by the OD in inches, the resulting number should be the DP.

i.e. a 20T, 20 DP gear would be 1.1" OD   (22 / 1.1 = 20  )

Unfortunately, there is no easy way of determining the Pressure Angle. But if the gears are of any age, they are likely to be 14.5, rather than 20 degrees, which is what seems to be the standard for more modern Metric Module gears.

Gears of the same DP but different Pressure Angles should not be meshed together. Both will suffer wear and not operate properly.

HTH

Howard

Edited By Howard Lewis on 09/08/2021 16:18:33

My Model M uses 16DP gears. I've just checked to be 100% sure and the OD of the 100 tooth gear is 6.375". This matches my HPC catalogue's data. However the same book has got the OD of 18DP 100 tooth gear as 143.93" on one page and 143.99mm on another page, oops by them I think.

Martin C

102 / 5.6666 = 18 Using metric dimensions for an Imperial size!.

102 / 6.375 = 16

Howard

.....Except by the 'span' measurement across a number of teeth!

Look up Ash Gear, Novi, Detroit for their excellent website which has a gear tooth span formula for calculating the pressure angle of a sample gear.

Martin

Smart & Brown used at least 3 gear tooth sizes on changewheels. Atlas have 12DP on the bull gear, I don't know what their change wheels are, though.

Edited By old mart on 09/08/2021 16:37:42

South Bend gears are certainly 18DP 14.5PA (for the smaller lathes). Im making some currently.

Thank you Gentleman for your technical input much appreciated, I think that Jason B may have nailed it as a couple of the gears have cast lettering on the reverse side, L A , 211, K6,on the 56T and the 64T LA, 213, and a K, the 24T has LA, 02, and K, very difficult to see using a Opti Visor.

No I had no intention of meshing the 16DP with the 18DP.

Brian good to hear from you, would certainly like to obtain your book, you have my email ?.

Brian also knows that I also have another SBL 9A, 4 1/2, with QC gear box , this I acquired soon after the SBL 9B that was in a very neglected state and no attachments as the 9A came with 90% of factory accessories and very good condition.

On this side of the pond Myfords are extremely rare, they were mostly brought in by British citizens, I picked up a ML10 at a Auction as no one recognize it, came with many extras, full set of change gears.

I thank you all once again for your help as I would like to pass these set of gears on to a member in the hobby that has the lathe without the change gears as I to have been assisted by members of the society.

Doug in Canada. B.C.

That will be Logan then, found a 60T with LA 212 which fits between your two quoted teeth/part numbers and the 24T is actually LA-202