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Threading advice.

Midnightlunchbox

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Hello folks,

I need a wee bit of advice about threading.

I bought a set of Crown chasers a couple of weeks ago and learning them is my next project, when time allows. However, I'm a bit confused on a few matters.

Tool/arm rest for cutting female threads, is it necessary? Is it different than simply setting the lathe tool rest? It seems unnecessary to me.

Lathe speed. Ever article and video I've watched have differing lathe speeds from around 150rpm to 300rpm, does the lathe speed differ depending on thread pitch and project size? Is there a formula to work it out?

When the chaser is initially presented to the wood, the tool is moved in an oval motion at a steady rhythm. Am I correct in thinking this rhythm needs to be the same for both the male and female threads or they won't fit?

I've prepared a couple of blanks to have a bash on but with my hollibobs over I'm back to the Fortress of Despair, er, sorry I mean work, tomorrow it might be a few weeks until I get some garage time so I have loads of time to suss it all out.

Cheers
Craig
 

Grump

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Why do you think I was happy to see them go?
I tried and tried to get a decent thread with em, I put them in the drawer for another day then tried and tried another day.
I often got them out and gave them a go and always ended up using a tap and die.
Armed with that knowledge I would go for the tap and die every time and not even attempt them bloody things.
I did send the booklet on when I found it, have you read that?
Of course you did that's why you're confused, so was I.

Have fun init?

https://www.youtube.com/watch?v=jslgNh5b-S8
 

Midnightlunchbox

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I'm keen to get going and try and perfect threading, I get a lot of requests for turnings where threads would be beneficial over a push fit or a separate fitting (such as a pool cue joint). I just like to have a clear picture in my head as to what's required. However I did get the threading booky, thanks, although it doesn't have enough cartoons in it for me?
 

Grump

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I gave in and never like a wooden joint anyway, to weak.
I got some cue joiners from eBay they work well nice brass ones.
Used em on sticks and all sorts of things that need joining, wish you luck with it.
 

monophoto

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Tool/arm rest for cutting female threads, is it necessary? Is it different than simply setting the lathe tool rest? It seems unnecessary to me.

Lathe speed. Ever article and video I've watched have differing lathe speeds from around 150rpm to 300rpm, does the lathe speed differ depending on thread pitch and project size? Is there a formula to work it out?

When the chaser is initially presented to the wood, the tool is moved in an oval motion at a steady rhythm. Am I correct in thinking this rhythm needs to be the same for both the male and female threads or they won't fit?

The arm rest tool is a convenience, not a necessity. The real advantage comes when you have made the male thread, and are cutting the female thread to match. Using an arm rest tool to hold the thread chaser means that you can keep your tool rest parallel to the bed ways, and don't have to move it each time to test the fit of the female threads against the male threads.

There is no single magic speed. If the lathe is rotating faster, the thread chaser will move faster. The challenge in chasing threads is removing the chasing tool at the end of each pass - if you don't remove the tool, you will wreck the threads you have cut. The slower you run the lathe, the more time you have to watch the chaser approach the end of the pass, and the more time you have to react to move it out of the threads.

The period of that oval cycle is fixed by the pitch of the threads you are cutting and the rotational speed of the lathe. All you are doing when you chase threads is hold the chasing tool in the threads it has already cut - let the tool and the lathe determine the period of the cycle.
 

Jim

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Another question on this, is it dependent on woods that is used or can threads be added to all hard woods?
 

Midnightlunchbox

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The arm rest tool is a convenience, not a necessity. The real advantage comes when you have made the male thread, and are cutting the female thread to match. Using an arm rest tool to hold the thread chaser means that you can keep your tool rest parallel to the bed ways, and don't have to move it each time to test the fit of the female threads against the male threads.

There is no single magic speed. If the lathe is rotating faster, the thread chaser will move faster. The challenge in chasing threads is removing the chasing tool at the end of each pass - if you don't remove the tool, you will wreck the threads you have cut. The slower you run the lathe, the more time you have to watch the chaser approach the end of the pass, and the more time you have to react to move it out of the threads.

The period of that oval cycle is fixed by the pitch of the threads you are cutting and the rotational speed of the lathe. All you are doing when you chase threads is hold the chasing tool in the threads it has already cut - let the tool and the lathe determine the period of the cycle.

Yes that makes more sense now, thank you. I suspected the arm rest was more of a luxury but the reasoning behind it is also methodical, I think I'll have a go with just the lathe tool rest first.

Thanks for your help.
 

Shaver

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Threads on all hard woods, NO. The main criteria you look for is dense and little grain timber, the more grain there is will cause the threads to crumble as you cut deeper. Using a higher TPI would help, as does soaking the thread area with CA glue to help support the wood. This being the main reason most folks when demonstrating use Box, African blackwood, Lignum Vitae, and similar woods.
 

Shaver

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In addition to the above, generally if the wood is too brittle, coarse to take a thread easily I normally insert a ring of Box, or Blackwood to take the threads. You can also use Alternative Ivory, that takes a good thread as well.
 

Woody

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Box is the best wood to chase a thread on the arm rest is very easy to make all you need ai a flat bit of steel and bend the end of it up speed depends on experience and the thread pitch if you want a perfect thread buy a shed load of boxwood and stand at the lathe practicing till you perfect it them practise some more that is the only way to perfect it to much advise is more confusing because everyone will tell you a different way and they all work so you only need one of them then do it your way
 

George Watkins

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I used to do a lot of thread chasing but haven't done any now for a few years

I learnt from this Allan Batty video and was lucky enough to meet him at an awgb seminar
https://www.youtube.com/watch?v=-0iEd0kD0S4&list=FL3vvUao9XJdoOxX9HLcfiqw&index=10

I found that lignum vitae was the easiest to thread as it has the natural oil which aids cutting, African blackwood next then boxwood.

my acrylic takes an excellent easy thread or pvc pipe
 

Midnightlunchbox

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Thanks for all the replies, it has given me some stuff to think about. George, do your box blanks take a thread? I have a really nice one I fancied threading.
 

George Watkins

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The resin takes an excellent thread but I've never tried the ozzy burr Craig, in theory it should as its heavy and dense but then it is a burr and the grain runs all over the place.... so maybe not?
 

Penpal

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Threading small boxes sounds exotic but in practice unless you have built up the skills using it first up with one og Georges blanks unwise in the extreme IMHO mate good advice given so far.

Peter.:fingers::fingers:
 
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