# Multi start threads on metal lathe



## MuddyWater

I'm looking at ways to make threads and know people have talked about either using triple start tap and dies or using a metal lathe.  I am looking at purchasing a metal lathe for various reasons.  I would like to be able to make some parts for pens and of course to cut thread for the pens I make.  I was reading in another thread, but can't find it now, that if you are going to use a metal lathe to cut threads that it must be capable of cuttinng triple start threads.

I don't know very much about metal lathes of machining threads, so I need some advice and a little education.  Are not all lathes capable of cutting multi start threads?  If they are not, then what would I need to look for on a lathe that would indicate it is capable of multi start threads?  I am looking at some of the Grizzly lathes at around the $1,000 price range and did not see anything on the website that stated they were capable of multi start threads.  But then again, I am not sure what to lookf for.  I would appreciate advice that anyone  might be able to pass along in recommendations.


----------



## Russianwolf

technically, yes, any metal lathe that can cut threads can cut multistart threads. There are a couple ways that it can be done that I can think of.

going to use the popular m12x2.4x.8 for the examples

1) set up the lathe to cut an m12x2.4 thread but only cut .8 deep. use the tool post slides to move the tool .8mm longitudinally and then repeat the cutting. adjust one more .8mm and you should end up with a m12x2.4x.8 thread. how good it is will depend on how finely you can adjust the tool post slides.

2) set up the lathe to cut an m12x2.4 thread but only cut .8 deep. disengage the gears and rotate the workpiece 1/3 of a turn and reengage the gears. repeat cut. disengage and turn another 1/3 and reengage to complete final cut. again you should have the m12x2.4x.8 threads. how good will depend on how close to the 1/3 turn the gears allow you to get when disengaging/reengaging.


----------



## skiprat

Any lathe that is capable of cutting single threads is also capable of cutting multistart threads. 
Be warned, it is a long hard road

I have found an excellent book on just that subject. I'll dig it out and post the ISBN number.

Got it...

ISBN-13:978-0-85242-838-2

Called; Screw Cutting in the Lathe

It is Number 3 in the Workshop Practice Series, written by Martin Cleeve.
Available in the UK for around £7


----------



## MuddyWater

Thanks for the replies and I'll have to check out the book that Skiprat recommended.  Your responses make me think that is why people are interested in the taps and dies they have recently been posting about in the group buys.  What does everyone else think?  Is it easier to cut multi start threads on the lathe or would you recommend the multi start taps and dies?


----------



## me2cyclops

I have a taig metal lathe, a pair of atlas 10" metal lathes and easy access to a monarch 10ee ....... I use a tap and die


----------



## BRobbins629

It is no doubt easier to thread with a tap and die whether single or multi start.  The disadvantage is the worry about wearing them out and each set can only cut a specific size.  
If you are serious about using the metal lathe to cut threads, look for one that is easy to change gears and the beefier the better.  It can be done on the small lathes but gear changing is a pain.  Also look to see that the gears will support the number of threads per inch, which is generally a low number when doing multistart - 3 start 8 tpi is common which will give the equivalent strength of a single start 24 tpi.
Personally I use a smaller metal lathe which I am very happy with and use the multistart tap and die, but know many others you cut their own threads.  It does take some practice, but those who have accomplished the task seem to be able to do so repeatedly.


----------



## Paul in OKC

Hey Steve, sent a couple of pm's your way, just thinking out loud!


----------



## skiprat

Got 'em. Thanks Paul:wink::biggrin:

Getting back to the book I mentioned. I can't recommend it highly enough.
It covers EVERY aspect of cutting threads. It has at least 6 ways of cutting any type of thread on any lathe with either a metric or TPI leadscrew. It dispels many of the myths too. It has a great section on understanding why the gears are the way they are and even shows how to sharpen the cutters.


----------



## furini

Thanks for the link, Skiprat - was looking at this book last week wondering if I should buy it...I now have!
Cheers
Stewart


----------



## skiprat

Yeah Stewart, it's a great series of books. I wish I had all 41 of them, but I've got a couple and ordered a few others. I have to admit that a few are a bit old fashioned though and are reprints of stuff Noah used to build the Ark, but most are excellent.:biggrin:


----------



## Blind_Squirrel

skiprat said:


> Yeah Stewart, it's a great series of books. I wish I had all 41 of them, but I've got a couple and ordered a few others. I have to admit that a few are a bit old fashioned though and are reprints of stuff Noah used to build the Ark, but most are excellent.:biggrin:



Is there a drawing of Ed beside Noah in there as a young lad? :biggrin:


----------



## Darley

Steve does Martin Cleeve explain inside threading as well or is just for srew cutting?


----------



## skiprat

Darley said:


> Steve does Martin Cleeve explain inside threading as well or is just for srew cutting?


 

Screw cutting, both internal and external. 

I dunno if the guy is even alive anymore, but I should send him a note and tell him I want commission:biggrin:


----------



## BigShed

skiprat said:


> Yeah Stewart, it's a great series of books. I wish I had all 41 of them, but I've got a couple and ordered a few others. I have to admit that a few are a bit old fashioned though and are reprints of stuff Noah used to build the Ark, but most are excellent.:biggrin:




They're now up to #43, which is on the Mini Lathe.


----------



## Kaspar

I take it that multi start threads are really three or four independent thread cuts that interlock or really fall in the spaces left by the previous thread cut?   Which would mean you could not have a very flat, compact thread cut for any one of them?  (I'm not sure of the terminology yet...)


----------



## KenV

I have been thinking that CNC mill with a thread mill was the practical way to cut inside and outside threads (thread mill can be described as a tap with only one tooth remaining)


----------



## skiprat

Kaspar said:


> I take it that multi start threads are really three or four independent thread cuts that interlock or really fall in the spaces left by the previous thread cut?   Which would mean you could not have a very flat, compact thread cut for any one of them?  (I'm not sure of the terminology yet...)



Yes to the first question. 
And I think the term you were looking for is the Helix Angle. It gets steeper the more threads you have. But they should be as 'compact' as any other thread as you can't get any more compact than each thread coming to a point and touching the adjacent thread:biggrin:


----------



## Kaspar

IOW, multi-start threads are comprised of multiple cuts (two, three, four or more, as per the required number of starting points), while a multi start tap would do them all at once?


----------



## Russianwolf

Kaspar, multi-start threads are the end product. The pen caps on all the Fountain kits are multi-start, meaning that you can screw the cap on in multiple locations (Barons have four starts and Jr's have three starts for example)


You can cut multi-start threads either on a lathe or with a tap and die (or if you are VERY adventurous, a file could be used ).

Going back to the example I mentioned in the first response. If you had a 13.6mmx2.4mm tap, you could use the tap to make conceivably make a 12mmx2.4mmx.8mm triple start thread with some serious practice. You have use the tap three times, but it is conceivable.


----------



## Kaspar

Yes, I get that, but what I'm asking is: does the multi start tap do all the threads at once?  (Whereas the lathe requires a quarter turn reset of the initial position and then you cut the second thread, and so forth.)


----------



## skiprat

Kaspar said:


> Yes, I get that, but what I'm asking is: does the multi start tap do all the threads at once?  (Whereas the lathe requires a quarter turn reset of the initial position and then you cut the second thread, and so forth.)



Yes


----------



## Kaspar

skiprat said:


> Yes



I think I'll fetch some practice materials, and have a go.


----------



## PTJeff

Kaspar,
i practice on this 
http://www.usplastic.com/catalog/va..._name=21315&product_id=21166&variant_id=44603
it's cheaper


----------



## Kaspar

Except for the shipping charge (that I DON'T pay for Grizzly products since I live in Springfield, MO) and the time lost waiting for it, you'd be right.  :biggrin:


Actually, thanks.  That looks quite useful.


----------



## workinforwood

I ordered the book too Steve.  I'll email the author and have him cut you a cheque for being such a good salesman!


----------

