Change gears for 1893-1903 P&W 10 Inch Lathe

[John Stevenson]

If I were to forget about the 127 tooth requirement, I could use 21 pitch for a 32 tooth gear and still have a 1.5" root diameter.

Does this make sense?

Regards,

Brian

21 pitch is as rare as a Birmingham virgin.
Last known sighting of one was in 1924 on the Cadbury's works outing to Blackpool.

It was never recorded whether she still was one on the bus back.

.

[SGW]

If you think the diameter of a 127 tooth gear is likely to be a problem, there are several "close enough" substitutes, such as a 47/37 pair that works out to a 1.2703 ratio...dern close.

There are some others, too.

[lazlo]

Rif,

Measure the number of teeth and the circumference of the drive gear on the lathe, and we can tell you the DP. It's almost surely a 16 DP, 14 1/2° pitch angle.

If you want to save yourself some head-scratching, get "Screwcutting In the Lathe," by Martin Cleeve. He goes into great detail on the math of change gears, and compares the type of leads you can get with the various sets of change gears. While you're picking you're own change gear standard, you might want to consider getting a couple of metric conversion gears too.

Cheers,

Robert

[lazlo]

Perhaps it might help if you visit Marv Klotz' (a Senior member of this forum) utilities web site at:
http://www.myvirtualnetwork.com/mklotz/

From the readme file:

"Evan Williams, in Canada, is planning on building an orrery. "

Evan, Marv wrote that back in 2003 -- did you ever build your orrery?

[Rif]

IMO, 32dp is WAY too small for a 10" lathe. I'd expect more like 16dp for a lathe that size. My 10K South Bend uses 18dp gears.

And you really don't have a choice, anyway. You've got to use whatever the dp of the gear is on your spindle, because your change gears are going to need to mesh with it.

The gear on my spindle doesn't matter due to how the gearing is configured. The lathe already has the forward/reverse tumbler right under the spindle. After the tumbler gears there is another gear that turns the change gear/feed rod driving shaft. One end of this shaft sticks out of the left hand side and has a key on it for mounting a change gear. The other end of the shaft has a pulley on it for a flat belt that would connect to a shaft on the left-hand set of legs. This lower shaft sticks out the left hand side as well. On the end of this shaft is a cone gear that is used to drive the feed rod.

Since there is only a shaft, to mount the change gear to, I am not restricted to the same DP as the other gears.

Brian

[Rif]

Rif, that really is a project.

Congratulations on the conceptual thinking.

Perhaps it might help if you visit Marv Klotz' (a Senior member of this forum) utilities web site at:
http://www.myvirtualnetwork.com/mklotz/

And in particular his:
"Gear Zip": http://www.myvirtualnetwork.com/mklo.../File/gear.zip

I thoroughly recommend that you read this first - its a superb resource.

Then I'd suggest you have a look at:

"Gear Find":
http://www.myvirtualnetwork.com/mklo...e/gearfind.zip

"Gear ratio":
http://www.myvirtualnetwork.com/mklo...e/gearatio.zip

"Gear PA" (Pressure angle):
http://www.myvirtualnetwork.com/mklo...ile/gearpa.zip

"Gear Spur":
http://www.myvirtualnetwork.com/mklo...e/gearspur.zip

I hope this helps.

Thanks! I'll take a look at these monday, when I have a little more time.

Brian

[Rif]

If you think the diameter of a 127 tooth gear is likely to be a problem, there are several "close enough" substitutes, such as a 47/37 pair that works out to a 1.2703 ratio...dern close.

There are some others, too.

Actually, I was thinking about not worrying about the metric gears change gears and just doing the occasional metric threads on my Sherline lathe, for now. Then, it occurred to me that about half of my threading is metric.

The last thing I threaded was a metric nut for a Stihl chainsaw. It was a M 10x1 LH. That particular thread size isn't even listed in my copy of the Machinery's Handbook, so I figured that it was probably proprietary. My dad also looked for it at a hardware store and couldn't find it. (He said they actually had metric, left-hand nuts where he went; but, not that size.) Stihl no longer makes the part, either. So, I spent over 3 hours making a lousy nut on my mini machine tools.

Brian

[Rif]

21 pitch is as rare as a Birmingham virgin.
Last known sighting of one was in 1924 on the Cadbury's works outing to Blackpool.

It was never recorded whether she still was one on the bus back.

.

Yeah, I figured it was rare. I just threw it out there because it showed up as a possibility on my spreadsheet. Using that particular pitch would be probably be about as cruel as using 19TPI screws in a machine you are working on.

Around here, so I am told (I don't have any sisters.), the virgins run faster than their brothers.

I live in Perry County, PA. This particular county is the subject of many jokes.

Brian

[Rif]

I was thinking. Maybe I could do something like Sherline does. They have two pitches for their change gears. The metric conversion gears could have a different pitch. That way I don't have to cut as many teeth for the standard gear set.

Brian

[lazlo]

IMO, 32dp is WAY too small for a 10" lathe. I'd expect more like 16dp for a lathe that size. My 10K South Bend uses 18dp gears.

And you really don't have a choice, anyway. You've got to use whatever the dp of the gear is on your spindle, because your change gears are going to need to mesh with it.

The gear on my spindle doesn't matter due to how the gearing is configured.

You're missing the point Brian. You have to use the DP (diametral pitch) of the drive gear of the lathe. That's almost always 16DP, and for an old lathe like that, it's almost surely 14 1/2° pitch angle.

So you need to measure the circumference of the drive gear (or the leadscrew gear) and figure out the correct diametral pitch of the change gears.