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Thread: thread cutting
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7th May 2007, 09:12 AM #1
thread cutting
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.Hafco AL320G Lathe
Toolex RF31 Mill/Drill
Saber Bandsaw
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7th May 2007, 09:01 PM #2Diamond Member
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- Australind , WA
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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?
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7th May 2007, 09:49 PM #3
I wonder if by starwheel he means the thread chasing dial normally on the right hand side of the saddle??
Have a nice day - Cheers
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7th May 2007, 09:52 PM #4
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!
'What the mind of man can conceive, the hand of a toolmaker can achieve.'
Owning a GPX250 and wanting a ZX10 is the single worst experience possible. -Aside from riding a BMW, I guess.
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7th May 2007, 10:19 PM #5
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?Hafco AL320G Lathe
Toolex RF31 Mill/Drill
Saber Bandsaw
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7th May 2007, 11:06 PM #6
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.
JoeOf course truth is stranger than fiction.
Fiction has to make sense. - Mark Twain
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7th May 2007, 11:32 PM #7
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.'What the mind of man can conceive, the hand of a toolmaker can achieve.'
Owning a GPX250 and wanting a ZX10 is the single worst experience possible. -Aside from riding a BMW, I guess.
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7th May 2007, 11:35 PM #8
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?'What the mind of man can conceive, the hand of a toolmaker can achieve.'
Owning a GPX250 and wanting a ZX10 is the single worst experience possible. -Aside from riding a BMW, I guess.
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8th May 2007, 06:24 PM #9
Ok then, not having do any threadcutting since I left my trade (25years ago) which methods do you guys use for catching the thread ??
Hafco AL320G Lathe
Toolex RF31 Mill/Drill
Saber Bandsaw
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8th May 2007, 06:59 PM #10
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."Outside of a dog a book is man's best friend ,inside a dog it's too dark to read"
Groucho Marx
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8th May 2007, 08:20 PM #11so I am also re-learning what I've forgotten.
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
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 ??Hafco AL320G Lathe
Toolex RF31 Mill/Drill
Saber Bandsaw
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8th May 2007, 08:30 PM #12Diamond Member
- Join Date
- Sep 2006
- Location
- Australind , WA
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I'm not ashamed I didn't know what a Star Wheel was now..... I also learn't something.
Good stuff.
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8th May 2007, 08:45 PM #13
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"Outside of a dog a book is man's best friend ,inside a dog it's too dark to read"
Groucho Marx
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9th May 2007, 03:06 PM #14
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.Hafco AL320G Lathe
Toolex RF31 Mill/Drill
Saber Bandsaw
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14th Sep 2021, 03:12 PM #15
Sorry to bring up an old thread, it was the first that seemed to pop up in a search.
I'm only new here and I'll add I'm not a machinist.
I think these 'gadgets' might have a few names ? In the book for my lathe, they call it a Threading Dial.
My post here related to the Dial I have on my Lathe (a Hafco CL-36 - had it 10 years now ) I only now found at has 4 or 5 different gears for it and on the dial there's 3 sets of numbers. It will do Metric and Imperial Threads though for the few threads I cut, they do tend to be Imperial.
Has anyone here got a guide as to how I'd work out what gear I should be running on it ? The one that's presently fitted I'm finding can indicate correct but not always, I haven't been able to measure how many combinations it will indicate 'correct' (when it's not) but appears to have 2 or maybe 3 'correct' indications, when in fact, only one is true correct.
I hope this isn't confusing how I've worded this.
Cheers guys
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