ScrewCutting Star Lathe

[tommyc87]

Hello all,
I inherited an 1918 Seneca Falls Star Lathe that I need to cut some 10 tpi threads on 3/4 stock. I've searched the web and forums on how to cut threads on this particular machine and haven't had any luck. So I was hoping if one of you guys could help me out on how to do that on this lathe.It also has a quick change gear box by the way. I've tried to post pics but for some reason I get error messages.

Thanks, Tom

 

[Joe in NH]

My usual "go-to" on cutting most "standard" threads (like 3/4-10 NC) is to "start" the thread using the lathe, and then "finish cut" using a die. Of course you may not have the die or die-stock.

But your problem may be more fundamental? Most of the pix of Star (Seneca Falls) lathes at "Tony's Lathe site" (Seneca Falls Lathes) show the lathe WITHOUT a so call "thread dial." If that is what you don't have - then you have to take "special steps" to cut a successful thread.

First with no thread dial - once you engage yourself to the lead screw - NEVER DISENGAGE. Instead when you reach the left end of your cut - stop the lathe and wind it BY HAND to the end of the cut (As you get better you may be able to "anticipate" the coast down of the lathe and reach the end of cut by power alone.)

Then back off the tool. Then "back" the ENTIRE lathe, pulleys, head stock spindle, and all without disengaging from the lead screw.

Then restart your cut as before, but advance the tool a little to increase the stock removal. Your tool is FORCED to cut the same path as before by the lead screw.

Rinse and repeat - use a nut as your "proof check" on size as the thread starts to appear "finished."

It is possible with certain thread pitches that match or are multiples(or divisors) of your lead screw to disengage and then re-engage the feed as you might with a thread dial - but a lot of this depends on the vagaries of the lathe - better not to go there and keep it simple for your first try.

Also, you don't say and I'm not exactly sure of your level of lathe acumen. You don't want to engage your feed via the apron clutch feed AND the lead screw via the hand lever at the same time. To do so will probably break the lathe, or at least severely challenge it.

Best would be to look at a few books to brush up ahead of time. My go-to myself for lathe refreshment is Robert H. Smith's "Advanced Machine Work" printed in 1916 usually. Seen online at Text-book of advanced machine work : Smith, Robert H. (Robert Henry), 1852-1916 : Free Download & Streaming : Internet Archive and available for usually $20 from used books places like abebooks.com or new from Amazon. You may find some of the woodcuts show your lathe?

Anyway, do some homework and give it a try.

Welcome to our board.

Joe K

 

[Andy FitzGibbon]

Pictures would help a lot. Later Seneca Falls machines sometimes did have thread dials.

Andy

 

[projectnut]

I guess I don't know where you are as far as experience single pointing threads. I have cut hundreds if not thousands of threads on my 1916 Seneca Falls Star #20 lathe without a thread dial. The key is as Joe in NH describes. Once you engage the lead screw don't disengage it until you're finished.

A little more rudimentary question is do you have the proper profile on the threading tool, and are you presenting it properly to the work piece? A simple tool to check both is a thread gauge like this:

Starrett Thread Center Ga 6�-Degree American - MPN: C391

The point of the tool should match the V in the side of the tool perfectly. Remember this is a mirror image to the thread you are cutting. Any space between the gauge and the point means you won't be cutting enough material off for the nut to thread on. If the tool is too wide to fit in the gauge you'll be cutting off too much material.

When positioning the cutting tool in the tool holder place the gauge against the work piece with the V opening facing the tool holder. Align the tool so it fits perfectly in the V.

Once you have the tool facing the work piece properly adjust the height. This can be done by simply trapping a 6" rule between the point of the tool and the work piece. If the top of the scale leans toward the operator the tool is low. If it leans away from the operator the tool is high. Back the tool away from the scale and adjust in the proper direction. Recheck and repeat as necessary until the scale is perfectly vertical.

I always thread at the lowest speed using the back gear. On my machine that's about 40 rpm. I also make sure the cutting surface is well lubricated. As Joe mentioned after a few practice runs you'll be able to tell how far the tool will coast after the power is removed.

It's difficult to cut a thread to a shoulder so the best thing to do is put a relief groove in the stock between the section you intend to thread and the shoulder. Here's a link to an example:

https://i0.wp.com/rifleshooter.com/wp-content/uploads/2014/01/DSC_0044.jpg?ssl=1

 

[michiganbuck]

QT:[It also has a quick change gear box]
Is the problem the QC is not numbered for thread selection?
or the lathe does not have a drop in half nut thread dial ?
Agree keep it engaged if having no thread dial.
Just and 10 thread screw is a thread pitch gauge..agree you need a fish gauge (post 4)
keep engaged is good advice. (as per Joe)

 

[tommyc87]

I've been trying my darndest to post some pictures but this site won't allow it for some reason. But no, the lathe doesn't have a thread dial.

 

[tommyc87]

Your correct in the lathe has no thread dial, and yes my problem is very fundamental as I don't know much at all about using the machine and all of the controls. For example, the brass tag on the lathe says for 10 threads: Stud 48 out and knob 1. What is stud 48 out mean? And what is knob 1? And what controls on the apron should I engage or not? I wish I could post pictures but the site isn't allowing it for some reason. I did download the book link for Advanced Machine Work so I'll go over that.And thank you all for sharing your helpful knowledge!
Tom

 

[Joe in NH]

Typically a lathe comes with 13 gears. This to cut all the commonly found sizes of thread usually from 40tpi up to perhaps 12tpi. By following the chart and placing gears in their locations, one can cut the desired thread.

Quick change gears have all the gears, but get rid of the arithmetic of calculating gear trains - the work has been done for you.

On your lathe with its developmental quick-change, apparently there is a stud (intermediate) type gear which can be moved in or out? Also a multi-position selector which among other choices says "10" somewhere? Also probably three knobs, or a lever with positions 1, 2, 3?

On my Flather No. 715, I had a two position stud type gear which could be shifted "in" or "out." Also a quick change box with perhaps 11 different possible positions to be placed. Also a lever handle on top of the quick change with left-center-right. And a chart above the 11 position selector indicating "Left-center-right" so that each of the 11 positions actually had 3 possible TPI associated with it or 33 total. A small note on the selector chart said "gear out - double the thread count." So the lathe actually could cut 66 different TPI.

I don't think I ever used the stud gear "out."

You can set the selector on "10", pick the associated lever position, and engage the lead screw. Turning the spindle over by hand 10 revolutions SHOULD yield a movement of the lathe carriage of 1 inch.

That is if that stud location gear is properly set up. Otherwise you might get 1/2 inch - or 2 inch?

Pix will help. Go advanced - scan down the page to "manage attachments." From there screens blow up and guide you into "browse" and "upload." Just don't forget what you're doing is adding to a file from which you can "click & carry" a pix into your thread as attachment. The pix stay behind in your file in case you want to use them again.

Good luck
Joe in NH

 

[projectnut]

I've been trying my darndest to post some pictures but this site won't allow it for some reason. But no, the lathe doesn't have a thread dial.

There are several Seneca Falls lathe catalogs available from the vintage machinery.org website:

Seneca Falls Manufacturing Co. - Publication Reprints | VintageMachinery.org

Take a look at them and see which machine is most similar to yours. With that information it will be a bit easier to give you some more accurate information.

 

[michiganbuck]

from here it looks like A on the AB lever
3 on the 123
and 2 1/2 om the gear change
To get a 10 thread ...
Does that seem logical with looking at your lathe controls?

and with no drop in half nut must keep engaged and travel back to a starting position..I know I don't like doing that going toward the head stock.Guess I would flip the bit and go away..

With not having a thread pitch gauge I would use a 10 pitch screw. Just a 3/4-10 bolt or measure for .100
Good to have a broom stick segment to test thread pitch

looks like about ,075 feed at 30* with a .013 nose flat.. but best to try a good nut or check with wires.