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Using the sliding headstock thread chasing assembly on 19th century lathe

SpeechlessCalm

Plastic
Joined
Mar 29, 2023
Many years ago I inherited an old lathe, I set her up during early COVID lock-down, and have been experimenting since. She’s a fairly basic treadle-drive ‘ornamental’ style from ?mid 1800s. I cannot confirm a manufacturer - there are no markings at all - but the main headstock spindle is Holtzapffel #3 threaded (which I only recently learned here).

The lathe has a sliding headstock type of thread chasing assembly, and I am trying to find information on how – exactly – to use it to cut threads. I'm wanting to build an adapter to allow me to fit the eccentric chuck mount (photo 1) to my modern wood turning lathe.

My question, relating to how this assembly is used, is primarily whether the thread is cut with a single pass or, if not, do the multiple passes rely simply on the follower / master engagement geometry to ensure subsequent deeper cuts align perfectly with previous cuts.
Even better, does anyone know of contemporary manuals / instructions for this – not so common – type of screw cutting assembly?

p.s. I'm sure you have worked it out from my question but I am not a machinist at all. I hope what I am asking makes sense.

Photo 1 shows the headstock assembly with eccentric chuck attachment foremost and thread chasing assembly to the rear/right.

1680227887532.png

Photo 2 shows the thread chasing assembly. Rotating the lever releases the main spindle and brings the threaded ‘star’ follower up to engage the master threaded ‘drum’. That engagement drives the headstock spindle laterally as it rotates. Each of the two stars has 7 concavities, six threaded and one blank. There are 12 drums, one matching each thread on the stars, that can be fitte
1680227978440.png

Photo 3 shows the threaded follower stars elevated so as to engage the appropriate master-threaded drum.
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john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
So ,the star/thread guide stays stationary and the spindle advances through the bearings?.........lots of production lathes used the idea of a threaded drum on the end of the spindle and a follower ...but normally the follower is the moving element......never the less ,I see no difficulty cutting threads with it.............obviously ,there is no need for any kind of indexing or thread pickup as the "leadscrew" is the same pitch as the thread being cut.
 

SpeechlessCalm

Plastic
Joined
Mar 29, 2023
So ,the star/thread guide stays stationary and the spindle advances through the bearings?.........lots of production lathes used the idea of a threaded drum on the end of the spindle and a follower ...but normally the follower is the moving element......never the less ,I see no difficulty cutting threads with it.............obviously ,there is no need for any kind of indexing or thread pickup as the "leadscrew" is the same pitch as the thread being cut.
yeah, the star follower only moves up and down and the master barrel is attached to the main headstock spindle and moves along its axis at a rate in keeping with whichever follower and master thread pair are being used.
Your final sentence, have I got this right? If I start with everything much the same I can make consecutive deeper cuts easily enough by just moving the cutting tool a step deeper ... and the cut will start ('pickup') at the same place?
 

Rob F.

Diamond
Joined
Aug 5, 2012
Location
California, Central Coast
Your final sentence, have I got this right? If I start with everything much the same I can make consecutive deeper cuts easily enough by just moving the cutting tool a step deeper ... and the cut will start ('pickup') at the same place?
Yes that is what he meant. This is because it is using a pattern to cut the threads and the pattern and the part you are cutting are both the same threads so they have no other option than to line up.
Be sure to lubricate everything, you dont go to the store and get new parts....
 

SpeechlessCalm

Plastic
Joined
Mar 29, 2023
Yes that is what he meant. This is because it is using a pattern to cut the threads and the pattern and the part you are cutting are both the same threads so they have no other option than to line up.
Be sure to lubricate everything, you dont go to the store and get new parts....
Thanks, yeah I just checked AliExpress and ... nothing! Would you believe that?
I suspect I'll have done a squillion dry runs before the carbide meets the steel ... hell I have to find the right cutting bits from the boxes (50degrees damn their individuality) :-)
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
What kind of tool holding arrangenent is there?......old lathes often had a rocking or tilting mechanism to feed the tool into the work .........shouldnt be difficult to cut a thread using such a mechanism .......if ,for instance you are cutting brass,then possibly increase the cut by 2 thou (002) each pass .
 

SpeechlessCalm

Plastic
Joined
Mar 29, 2023
What kind of tool holding arrangenent is there?......old lathes often had a rocking or tilting mechanism to feed the tool into the work .........shouldnt be difficult to cut a thread using such a mechanism .......if ,for instance you are cutting brass,then possibly increase the cut by 2 thou (002) each pass .
A fairly simple two-axis flat sliding assembly that accepts a number of types of 'heads' which in turn hold the tool or the (smaller) tool clamped into a holder ... if that makes sense. Nothing tilting and nothing particularly complex.
1680252320916.png 1680252363974.png 1680252479865.png
 
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john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
I doubt the assy shown is half the age of the lathe,if its 1800s .....anyhoo,with that setup ,you can even feed the tool in at an angle ,as is commonly done in thread cutting.
 








 
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