Multi-start threading

[Ruaidhri]

I was having a chat b/c with Ron about his and I remembered an old article (Oct 1936!) I thought might be of interest to anyone wanting 2, 3 or 4 start threads (eg for caps).

 

Basically it goes (example sizes used) :

 

To cut a two start 12 tpi thread (24 'threads per inch')-

• Put a 24tpi chaser in the toolpost
• Set your screw cutting gear train for 12 tpi
• Cut as normal

Similarly for a three start 12 tpi thread (36 'threads per inch') -

• Put a 36tpi chaser in the toolpost
• Set your screw cutting gear train for 12 tpi
• Cut as normal

Obviously by varying the gear train and chaser, various multi start sizes can be readily cut, without the hassle of pick-up

 

A quick and cheerful alternative is to simply use (eg) a 36 tpi chaser and chase the thread by hand, but it won't be multi-start and will need three times as many turns for the same travel when capping the pen! The hand chasing also takes just a tiny bit of practice

 

Regards,

Ruaidhrí

[goodyear]

I have a sudden longing to understand all this strange code.

 

But no! I can't investiagte another hobby!

[Ruaidhri]

I have a sudden longing to understand all this strange code.

 

But no! I can't investiagte another hobby!

 

You may well be right - some of the bits & bobs are a tiny bit pricey and eat into the pen budget

 

On the other hand it is the most relaxing way to spend one's time

 

Regards,

R

[OldGriz]

The hand chasing also takes just a tiny bit of practice

 

Regards,

Ruaidhrí

 

Look Boss, you know damned well I fully respect your abilities on a lathe.... you have far more experience than I do with fancy turning...

BUT to out and out lie to people about that amount of practice it takes to learn hand chasing on a wood lathe is just wrong

[Ron Z]

On the other hand it is the most relaxing way to spend one's time

 

Regards,

R

 

And I might add, entertaining. There's something very satisfying about watching the material spiral off of a work piece.

 

Also fun to make something useful. My son left for college this weekend - and just a couple hours before departure announced that the knob AND shaft of the volume control on his TV had snapped off. The life long expectation of "just fix it dad!" surfaced.

 

Dad obliged, making a knob out of hard rubber that could be made to conform to the flat sided volume control shaft to keep the knob from spinning. A little shellac to hold it in place, and off he went.

[Ruaidhri]

Look Boss, you know damned well I fully respect your abilities on a lathe.... you have far more experience than I do with fancy turning...

BUT to out and out lie to people about that amount of practice it takes to learn hand chasing on a wood lathe is just wrong

 

Seriously Tom, if someone starts out with a chaser - somewhere around 16tpi or finer it is well doable.

For what it's worth I practiced years ago using candles (not a tech term - wax candles )

Sounds a bit daft but like riding a bike, once you hit on the knack it is easy enough. Be prepared to practice though

 

I should be drafting up an article for PT shortly on the subject of hand chasing (an old promise to Lex) and once it's up there I'll post it here as well.

Sounds disloyal - but a promise is a promise

 

Cheers,

Ruaidhrí

 

[Ruaidhri]

On the other hand it is the most relaxing way to spend one's time

 

Regards,

R

 

And I might add, entertaining. There's something very satisfying about watching the material spiral off of a work piece.

 

Also fun to make something useful. My son left for college this weekend - and just a couple hours before departure announced that the knob AND shaft of the volume control on his TV had snapped off. The life long expectation of "just fix it dad!" surfaced.

 

Dad obliged, making a knob out of hard rubber that could be made to conform to the flat sided volume control shaft to keep the knob from spinning. A little shellac to hold it in place, and off he went.

 

There's something in the way the Daaaaaaddddd????????? is pronounced that let's you know immediately that they aren't looking to give you money :D

As you say, though, there is a lot of satisfaction in being able to do the fixing

 

Enjoy the threading

 

Regards,

R

 

[bgray]

Maybe I'm not understanding.

 

Are you chasing threads by hand, or on a metal lathe?

 

What material?

 

Post some pics

[Ruaidhri]

Maybe I'm not understanding.

 

Are you chasing threads by hand, or on a metal lathe?

 

What material?

 

Post some pics

 

Sorry if I'm a bit confusing - there's a lot of 'stuff' going on at home here.

 

I'm doing both

 

Materials range:

Woods from African Blackwood through to Zebrano (with a few lumps of bog oak in there as well).

Various plastics, incl synthetic ivory, MOP, tortoise shell etc

Various metals (but have not tried Titanium - that's for another day).

Add in antler, bone, horn, stone and whatever else can be chucked & you're close

 

The lathe depends on what's happening at any time - often the workpiece will ramble from Record to Myford to Carbatec and back for different operations

 

For single threads it is often quicker to chase by hand on the wood lathe than be bothered setting up a gear train on the Myford.

 

Regards,

Ruaidhrí

 

 

 

[Ruaidhri]

Here are a few of pics of a desk pen tail in the works, BTW - this was NOT Bambi

http://i3.photobucket.com/albums/y59/ruaidhri/1.jpg

Chucked for roughing out (Chuck is Axminster with O'Donnell jaws, Lathe is Record No4)-

http://i3.photobucket.com/albums/y59/ruaidhri/2.jpg

Testing for fit

http://i3.photobucket.com/albums/y59/ruaidhri/3.jpg

Phew! - next to decide on shape -

http://i3.photobucket.com/albums/y59/ruaidhri/4.jpg

Some of the chasers (there are teeth on the bottom pair, just at 36 tpi they don't show in the pic) -

http://i3.photobucket.com/albums/y59/ruaidhri/Chasers-1.jpg

 

More anon

 

Regards,

Ruaidhrí

 

Note: The antler came from one of the herd of Fallow Deer in the Phoenix Park in Dublin - you can read about them here (should you wish)

here and here

 

 

[Penturner]

Some day I'm going to learn to use those 'chasing' tools. Right now I can't see how they would cut anything but a concentric ring around the shaft.

[Rick Krantz]

I guess I need some explanation as to how the chasers work. I have been stumbling about trying to figure out triple lead threading for some time. If there is a reasonable way of doing it, I have a lot of interest to know. Right now, I am working on setting up a Dunlop/Atlas/craftsman metal lathe (one of those smaller benchtop models from the late 30's early 40's) I have change gears, and all of the tool holders, etc.... my thoughts to cut triple lead threads was to just index the work 120 degrees per cut, thread at 12 tpi, or something. If there are hand chasers, and I can try this by just setting the threading speed, I would probably want to experiment this way, first. I have yet to start the lathe, need to do some motor work, yet, but really would like to try my hand at making a pen. MY material of choice would be acrylic/plastic of some type.

 

taps and dies are too costly to purchase, for me anyway.

 

I could really use some pointers on multi lead threading, if anyone wants to share. I have been talking about pen making for ages, now it is getting time to start doing.

[George]

I have been talking about pen making for ages, now it is getting time to start doing.

 

 

When you do make some nice Chilton repros out of HR and such, I hope that you have some test pens, ya know, just to see how good they are *nudge*

[Ruaidhri]

I guess I need some explanation as to how the chasers work. I have been stumbling about trying to figure out triple lead threading for some time. If there is a reasonable way of doing it, I have a lot of interest to know. Right now, I am working on setting up a Dunlop/Atlas/craftsman metal lathe (one of those smaller benchtop models from the late 30's early 40's) I have change gears, and all of the tool holders, etc.... my thoughts to cut triple lead threads was to just index the work 120 degrees per cut, thread at 12 tpi, or something. If there are hand chasers, and I can try this by just setting the threading speed, I would probably want to experiment this way, first. I have yet to start the lathe, need to do some motor work, yet, but really would like to try my hand at making a pen. MY material of choice would be acrylic/plastic of some type.

 

taps and dies are too costly to purchase, for me anyway.

 

I could really use some pointers on multi lead threading, if anyone wants to share. I have been talking about pen making for ages, now it is getting time to start doing.

 

Rick,

 

Give us a shout when you have it up & running. Used handchasers in excellent condition can be found fairly readily. Most of mine cost around £8 each ( you'll need inside and outside obviously), unhandled, but that was a few years ago

Chasing multi-start threads by hand can be done (I have done a few) but NOT with reliable accuracy most times - it's a VERY hit and miss.

Single start threads by hand are merely a fair bit of practice and some very rude language

 

When I have a few moments (things are hectic here at home at the moment) I'll bang up a few rough sketches which may clear things up.

 

Regards,

Ruaidhrí

 

BTW - I'm sure I mentioned this before, but just in case:

Check the thread on your own spindle nose and get chasers this size - you can make tons of cheap add-ons for your machine. If your thread is less than about 16tpi it is better to practice first on 16 upwards before going down to eg 8tpi which is a lot faster.

[btboone]

I thought that you just input 3 when the CNC lathe asks how many starts you want. Works for me.

[richardandtracy]

Basically it goes ...

• Put a 36tpi chaser in the toolpost
• Set your screw cutting gear train for 12 tpi
• Cut as normal

Ruaidhri,

 

Please, for a novice machinist (only 6 years of diy metalworking) who's not long been cutting threads, can you describe how to cut multi-start threads with a screw cutting lathe without a thread chaser.

The way I'd go about it would be to cut the first thread; Mark a fixed point on the chuck, disengage the screw drive, turn the chuck through the required angle for the next thread and re-engage the screw drive at the nearest tooth engagement.

Is this a practical way of doing it?

 

As an alternative, I've just got room to mount my rotary table on the face plate, then fit a 4 jaw chuck to the rotary table. Then use the rotary table to turn the work relative to the faceplate when wanting to cut the other threads. However this all seems a lot of faff.. Attempting to centre it all would mean that it would probably be quicker to make several threads the other way and throw out the ones that don't work.

 

When cutting a multi-start barrel thread do you make a tap and use that, or do you cut a multi-start internal thread? If that's the case, oh dear. All my attempts at boring so far have led to slightly tapered holes, and I don't see that a thread would be any different.

 

Regards

 

Richard.

 

 

 

[Ruaidhri]

Basically it goes ...

• Put a 36tpi chaser in the toolpost
• Set your screw cutting gear train for 12 tpi
• Cut as normal

Ruaidhri,

 

Please, for a novice machinist (only 6 years of diy metalworking) who's not long been cutting threads, can you describe how to cut multi-start threads with a screw cutting lathe without a thread chaser.

The way I'd go about it would be to cut the first thread; Mark a fixed point on the chuck, disengage the screw drive, turn the chuck through the required angle for the next thread and re-engage the screw drive at the nearest tooth engagement.

Is this a practical way of doing it?

 

As an alternative, I've just got room to mount my rotary table on the face plate, then fit a 4 jaw chuck to the rotary table. Then use the rotary table to turn the work relative to the faceplate when wanting to cut the other threads. However this all seems a lot of faff.. Attempting to centre it all would mean that it would probably be quicker to make several threads the other way and throw out the ones that don't work.

 

When cutting a multi-start barrel thread do you make a tap and use that, or do you cut a multi-start internal thread? If that's the case, oh dear. All my attempts at boring so far have led to slightly tapered holes, and I don't see that a thread would be any different.

 

Regards

 

Richard.

 

Richard,

 

I'll come back to this in a few days when things have settled down a bit on the home front.

 

Before going further - do you use a built in gearbox, or do you set up your own gearing on your machine?

Does your lathe have a thread dial indicator?

 

Have a think about the chasers - then have a think about taps and dies.

Then have a think about making (eg) an internal chaser from a bottom tap with some bits ground back

 

Much more anon.

One quick thought - given the sizes we are dealing with, there is possibly a little 'spring' in your internal tool. Taking a few cuts at each setting will often sort this out, and in some case can be a decided advantage.

 

Regards,

Ruaidhrí

Not being mysterious - just up to .... in stuff

[richardandtracy]

...

Before going further - do you use a built in gearbox, or do you set up your own gearing on your machine?

Does your lathe have a thread dial indicator?

...

One quick thought - given the sizes we are dealing with, there is possibly a little 'spring' in your internal tool. Taking a few cuts at each setting will often sort this out, and in some case can be a decided advantage.

Ruaidhri,

 

I use the selection of gears provided with my machine. Or not provided.. (I use a Warco WMT300, and Warco didn't give me all the gears they specify in their manual - 2 are missing & I certainly haven't lost them, but I've had the lathe 6 years now so I can't go back to them about it.) Also some of the specified gear ratios only give LH threads - something tells me Warco haven't really thought it through, particularly when I contacted Warco & they categorically told me the lathe can't do LH threads.

 

The lathe does not have a thread dial indicator, however that's not a problem as it doesn't have a half nut either!

 

I think there is some spring in my internal tools as I particularly notice the taper when taking 'heavy' cuts of 0.5mm on large diameter deep holes (65mm dia x 90mm deep on one casting I made). I use, at the moment, TCT tipped 12mm dia shank boring tools (the sort that come in sets of 9 lengths for about £20) but feel I should experiment with sharper HSS tools. I do usually take multiple cuts at the same diameter when boring and this usually reduces the taper to maybe 0.02mm every 25mm, but doesn't eliminate it. Whenever boring a through hole, I try to cut on the return feed too, however I don't seem to get a tapered hole from each side for some reason.

 

Regards

 

Richard.

 

[Bruno]

If you can cut a single point thread on your metal cutting lathe, you can do a multi-start thread. Using trig (or basic geometry), you can reset the tool for each lead by adjusting the compound and cross slide 0 points.

 

[That's the very short explanation... details depend on the capabilities of the lathe and specific threads being cut.]

 

-Bruno

Edited September 3, 2007 by Bruno

[Ruaidhri]

If you can cut a single point thread on your metal cutting lathe, you can do a multi-start thread. Using trig (or basic geometry), you can reset the tool for each lead by adjusting the compound and cross slide 0 points.

 

[That's the very short explanation... details depend on the capabilities of the lathe and specific threads being cut.]

 

-Bruno

 

Bruno,

 

I'm afraid I don't understand you post. Is there any chance you could expand on it a little when you have time please - it sounds interesting.

 

Richard,

 

If you have a look at GandM Tools they often have chasers quite reasonably priced (I paid about £8-£10 for some of mine)

They may not have anything on their site but if you ring Digger he may be able to help (super guy )

 

Usual disclaimer etc.Regards,

Ruaidhrí

 

Back to this later - need to scribble a few sketches