thread cutting

[Oldhack]

Can anyone tel me whats involved in making a starwheel to fit my lathe ?
want to do some threadcutting, and would prefer not to have to use the reverse method.

[Sterob]

I'm ashamed to say I don't know what a starwheel is.
I tried to find out but Google was no help. Have you got a pic of one you can show us?

[Wood Butcher]

I wonder if by starwheel he means the thread chasing dial normally on the right hand side of the saddle??

[Article99]

You're not referring to a thread chaser dial by any chance are you?
Whilst it might be a little raising of the blood pressure when approaching shoulders on delicate materials, such as brass, the stop method of cutting a thread is much more accurate than relying on a chaser dial. The dial will get you close, but not bang on.

Edit: Lol. Beat me to it while I was googling a pic of one!

[Oldhack]

no a threadchaser and a star wheel are too different things

I have some info from a trade manual in pdf format, but its bigger 1.66mb, not sure how else I can post it?

[joe greiner]

US patent No. 4,419,797 contains phrases "star wheel" and "thread cutting."

http://www.uspto.gov/patft/index.html
Boink "Patent Number Search"
Enter 4419797
Boink "Search"

From text display, Boink "Images." You'll need to plug-in a viewer to see images. USPTO has guidance for this.

The star wheel is part number 36. I have no idea how this contraption works.

Joe

[Article99]

Ah... a starwheel we're talking old school tricks, now...
(Have been told about them, but never actually seen one for real.)

The star wheel, fig.160, is a wormwheel, not more than 6mm thick, that meshes with the leadscrew. It is attached to the saddle by means of a bracket, on the right hand side of the carriage. A pointer is also fixed to the bracket and chalk marks are made on every second or every third, etc, tooth, according to the particular requirements; when these marks coincide with the pointer, they show the momemt for engagement of the split-nut.

If two star wheels are made, one having 35 and the other 36 teeth, these will satisfy the requirements of almost any lead, the 36-tooth wheel being a multiple of 2,3,4 or 6 revolutions of the leadscrew before engaging the split-nutsl while the 35 tooth wheel, being a multiple of 5 and 7, can be used for threads requiring 5 or 7 revolutions of the leadscrew.

Example- It is required to cut a screw-thread having a 10mm lead in a lathe having a 6mm leadscrew. What star wheel should be used and how many teeth should be marked?

Solution:

(D/F) = (L.W/L.M)
=10/6
=5/3

The numerator of the ratio, in this case 5, represent the least number of revolutions of the leadscrew before engaging the split-nut. Therefore, the star wheel divisible by 5 must be used. (35 teeth.) and every fifth tooth must be marked.

Example 2 - If a 9mm lead is to be cut in a lathe having a 6mm leadscrew, what star wheel should be used and how many teeth should be marked?

Solution:

D/F = L.W/L.M = 9/6 = 3/2

In this case, the numerator being 3, the 36-tooth star wheel would be selected, and every third tooth marked.

[Article99]

To be honest, I'm really not sure. I suppose making a pair of star wheels should be possible. How accurate they'd be, I couldn't answer, however. Something like that'd most probably be ground or done on a horizontal milling machine with a gear cutter.

However the concept of this bugger is very much before my time. Perhaps Graeme has encountered them before in his travels on the different lathe sites?

[Oldhack]

Ok then, not having do any threadcutting since I left my trade (25years ago) which methods do you guys use for catching the thread ??

[Woodlee]

Ok then, not having do any threadcutting since I left my trade (25years ago) which methods do you guys use for catching the thread ??

Never seen or heard of a star wheel did my trade as a fitter and turner late 60"s early 70's.
This must be some device preceeding the chaser dial.I have used lathes built as early as 1902 and never seen a star wheel fitted to one..

I've always used the thread chaser dial for thread cutting as I was taught.

If you want to pick up a thread that is already cut and get the cutting tool in sync with it ,set the lathe gearbox to the correct pitch of the thread and on its slowest speed ,engage the thread cutting lever & take note of the position on the chaser dial and adjust the tool post and tool with the compound and cross slide slide until the tool lines up in the valley of the thread.

Reading back through the thread again , it looks to be a device that is similar to the function of the thread chaser dial on more modern lathes .Just a simpified version,or maybe the original version. The starwheel in the modern device is the gear that drives off the lead screw and turns the dial

To make a star wheel you would need a dividing head to get the teeth spaced correctly on the diameter of the wheel ,actual machining could be done on a lathe or a milling machine.
I've been out of my trade for a long time as well ,just aquired a lathe so I am also re-learning what I've forgotten.

[Oldhack]

so I am also re-learning what I've forgotten.

My problem is that I think I've forgotten more than I new

If you want to pick up a thread that is already cut and get the cutting tool in sync with it ,set the lathe gearbox to the correct pitch of the thread and on its slowest speed ,engage the thread cutting lever & take note of the position on the chaser dial and adjust the tool post and tool with the compound and cross slide slide until the tool lines up in the valley of the thread

Problem is my lathe doesnt have a chaser dial.

although i did see on a site somewhere recently where someone had fitted an indexed wheel to the tailstock end of the leadscrew.

would that serve the same purpose ??

[Sterob]

I'm not ashamed I didn't know what a Star Wheel was now..... I also learn't something.
Good stuff.

[Woodlee]

My problem is that I think I've forgotten more than I new



Problem is my lathe doesnt have a chaser dial.

although i did see on a site somewhere recently where someone had fitted an indexed wheel to the tailstock end of the leadscrew.

would that serve the same purpose ??

What brand of lathe do yo have ?
You maybe able to adapt a Myford chaser dial to your machine or an after market chaser. .
http://www.myfordmachinetools.com.au/

or Minitech in Brissy ,they are the agents for Myford,pretty sure you can get the chaser dial set up as a spare part .It should be easy to adapt ,it only has one moving part and a bracket fixed to the end of the saddle should do it .The Myford spares manuals are viewable from that site .You would need to make sure the lead screw as the same tpi as yours though.

http://www.myfordmachinetools.com.au/page%2016.jpg here is a image of the chaser dial

[Oldhack]

Lathe is the one in my signature Hafco AL-320G.

The book tells me its a metric leadscrew, but doesnt say what the pitch is.