Thread Chart help needed

[Jay_McDaniel]

Let me start by saying I am new to machining. Like many people, I have always had the interest, but just recently got the space and expendable income.

I bought a 1940's Sebastian lathe from a friend who hadn't used it in a few years. I have attached a before and after picture, just as an FYI. I've been pleased with its performance. But as you probably know, there is very little documentation for these old machines. I was able to find a user manual online, and a parts manual at DC Morrison. But there is still a bit of information I am unable to find.

On top of the quick change gear box there is a metal plate that has a ton of info on it. I assume it is called a threading chart. Please correct me if I am wrong. It got pretty beat up over the years when machinist would use it as a shelf. My wife and I have been able to determine most of the verbiage on the plate, but cannot be 100% sure we have documented it correctly. Is there a way to compare our notes to a known chart? I guess what I am asking is, is the chart specific to this model lathe, or are they somewhat universal? The lathe uses a 8 TPI lead screw.

 

[Conrad Hoffman]

What a great lathe! Can you post a photo of the plate? No doubt somebody here can decipher it or has one that's similar.

 

[redlee]

Not hard to confirm the numbers go thru and set the lathe at all the settings, rotate your spindle 360 deg and use a dial.
Will work for threads and feeds.

 

[snowshooze]

If you know the lead-screw ratio, gearing between the lead screw and drive gear.. you could back-figure.
Or worst, break out your dial,measure the travel of the carriage per revolution.
You will have several lead ranges, they are merely multipliers.
So, gear 1-10 will be your base leads... ABCDE will be your multipliers...
You understand, say A1 could be 4 threads an inch, A2 might be 6 thread, A3 might be 8 thread..
Really, an hour should generate it.
But, once you know that ratio, there will be another lathe with that ratio and the chart will be valid.

 

[snowshooze]

Not hard to confirm the numbers go thru and set the lathe at all the settings, rotate your spindle 360 deg and use a dial.
Will work for threads and feeds.

Ah yes... single lead screw.
I bet that thing could take some respectable cuts.

 

[plannerpower]

There is a picture of the threading/feed chart for a 12" Sebastian here;

Sebastian Lathe Details

and a picture of an older 12" Sebastian here;

Sebastian lathes

that seems similar to yours.

There is, of course, no guarantee that the chart in the first link is the same as yours but it might be of some assistance.

 

[snowshooze]

There is a picture of the threading/feed chart for a 12" Sebastian here;

Sebastian Lathe Details

and a picture of an older 12" Sebastian here;

Sebastian lathes

that seems similar to yours.

There is, of course, no guarantee that the chart in the first link is the same as yours but it might be of some assistance.

Awesome!
Good job on that.

 

[michiganbuck]

There is a picture of the threading/feed chart for a 12" Sebastian here;

Sebastian Lathe Details

and a picture of an older 12" Sebastian here;

Sebastian lathes

that seems similar to yours.

There is, of course, no guarantee that the chart in the first link is the same as yours but it might be of some assistance.

If that is correct you can copy paste it to your computer and then perhaps enlarge to print it

agree a very nice looking lathe.

 

[Jay_McDaniel]

There is a picture of the threading/feed chart for a 12" Sebastian here;

Sebastian Lathe Details

and a picture of an older 12" Sebastian here;

Sebastian lathes

that seems similar to yours.

There is, of course, no guarantee that the chart in the first link is the same as yours but it might be of some assistance.

Thank you for the link. I have looked at that page before and must have passed right over the chart.

Attached to this reply is what we have been able to determine so far. I think it's accurate, so I guess I need to stop obsessing about it.


Thank you to everyone else for the input. I think it'll get me headed in the right direction.

 

[Jay_McDaniel]

Here is the plate that was on the lathe. I think we were pretty lucky to be able to get as much info off of it as we did.

 

[plannerpower]

What a mess!

Enough of it is readable to show that, unfortunately, it's different to the plate shown in my link.

 

[EPAIII]

Why on earth would any manufacturer put a chart in a place where that can happen? Duhhhhhhh!

Here is the plate that was on the lathe. I think we were pretty lucky to be able to get as much info off of it as we did.View attachment 245843

 

[Jay_McDaniel]

Here is what we were able to create. I guess time will tell if it's accurate or not.

 

[iwananew10K]

edited- duplicate info.

cool old machine.