# 16er inserts?



## Munty Scruntfundle (13 May 2022)

Hi folks.

I’m a bit new to thread cutting, I’ve only had a small lathe up until now that just wouldn’t handle it so I used taps and dies instead. I’m moving up a size or two now and need to pick up some holders and inserts. 16er seem to be the right size for what I’m going to be doing, but I don’t understand the 1, 1.45, 2 etc. Do I need different inserts for each thread pitch? I thought the lathe decided the pitch, not the insert? Or does this number mean something else?

Sorry to sound dim. But I can’t find any reference with my searching, of course I could be searching for the wrong terms.

Many thanks.


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## Dalboy (14 May 2022)

ER collets are for holding the work instead of a chuck they have a very limited holding range each one is marked 1.5-2 for example that is the diameter they can hold you buy they individually or as a set. They have nothing to do with the pitch.
As far as I know there is not one marked with 1.45.

Arceuro sell them.

What lathe do you now have


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## J-G (14 May 2022)

Munty Scruntfundle said:


> Hi folks.
> 
> I’m a bit new to thread cutting, I’ve only had a small lathe up until now that just wouldn’t handle it so I used taps and dies instead. I’m moving up a size or two now and need to pick up some holders and inserts. 16er seem to be the right size for what I’m going to be doing, but I don’t understand the 1, 1.45, 2 etc. Do I need different inserts for each thread pitch? I thought the lathe decided the pitch, not the insert? Or does this number mean something else?
> 
> ...


I'm just off out to an all day choir rehearsal but I'll respond with fuller discussion later


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## Lorenzl (14 May 2022)

16er = 16 insert size, er external right hand there should be another number for the pitch and letters for form e.g. W, UNF, ISO often metric don't have a letter as it is implied.

With thread cutting especially in the olden day's people used a simple tool ground to the correct angle mostly 55deg.

As you say the lathe sets the pitch and with a simple tool you could cut any pitch or size of thread as long as the tool was big enough. As it was a simple tool you had quite sharp edges unless turned the maximum diameter down. You could then paper it to remove burrs and sharp edges.

Now if you buy thread inserts they are formed to shape so there is a rad in the bottom and a rad at the top of the tips leaving a nicer and stronger thread. Obviously as this is the case you need to have each tip match each thread so you have a lot of tips.

They are made out sintered carbide, ground an sometimes coated so as long as you take care of them they can last a long time.

Tip manufacturing process video:


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## Munty Scruntfundle (14 May 2022)

Dalboy said:


> ER collets are for holding the work instead of a chuck they have a very limited holding range each one is marked 1.5-2 for example that is the diameter they can hold you buy they individually or as a set. They have nothing to do with the pitch.
> As far as I know there is not one marked with 1.45.
> 
> Arceuro sell them.
> ...


16ER inserts. Not ER16 collets.


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## Phill05 (14 May 2022)

ER16 are collets the designation 1.5 - 2 means it will hold round bar between 1.5mm and 2mm it has nothing to do with thread pitches. what lathe do you have and does it have a chuck?

Edit: just re-read you are after 16er thread cutting inserts then yes you need an insert for each thread pitch.


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## Munty Scruntfundle (14 May 2022)

Lorenzl said:


> 16er = 16 insert size, er external right hand there should be another number for the pitch and letters for form e.g. W, UNF, ISO often metric don't have a letter as it is implied.
> 
> With thread cutting especially in the olden day's people used a simple tool ground to the correct angle mostly 55deg.
> 
> ...


Ahh ok, I know a fair bit about general turning inserts and hss, just not threading. So in theory I could use a larger number insert for any lesser thread, but the internal radius would be incorrect?


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## Lorenzl (14 May 2022)

Munty Scruntfundle said:


> Ahh ok, I know a fair bit about general turning inserts and hss, just not threading. So in theory I could use a larger number insert for any lesser thread, but the internal radius would be incorrect?


You might get away with it but you would have to go deeper due to the larger tip rad so causing a loser thread.

I thought there may be tips without rads and there are but check before you buy - Partial Profile


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## J-G (14 May 2022)

Most has been said - and correctly so - but hopefully I can add my two-pen'erth 

So much depends upon what thread form/standard you want to cut. If you are only interested in (say) Metric threads then using a single point tool may be possible - in reality you do need separate tools for each pitch though since the width of the flat at the root is proportional to the pitch - 0.25P is the norm - the crest flat can be left to fend for itself so when you have cut the thread to the correct depth it will be 1/8P IF the OD is 'nominal'. To some extent Unified form is the same, though the UN standards do allow an optional radius of 0.108P in the root.

Whitworth, BA & BSCycle each have their own radius at both Root & Crest so a 'single point' tool cannot be used for these. 

The 16er Tips are not 'single point' tools, they have the correct root & crest geometry for each Pitch (or TPI) so measuring the OD which has been cleaned up by using these tips will mean that the 'Effective' diameter is correct - using single point tools requires a more sophisticated method to measure the effective diameter! (3 wire)

So --- yes you do need separate tips to cut each different 'pitch' - for Metric that would be (full set) 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.6, 0.7, 0.75, 0.8, 1.0, 1.25, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5 & 6 mm. Of course you can cut a 6 x 1, 8 x 1, 10 x 1 etc. with the same 1.0mm pitch tip though only the first two of those are 'standard'.

With Whitworth & Unified the tips will have a 'TPI' designation (but are different 'Forms') so you need tips for each form and each 'TPI' - pretty much anything between 80 and 2.5 TPI.

If you wish to send me a PM with your full name & e-mail address I'll make my '3Wire' program available for you to view which details many different 'Forms' and shows the 'Standard' OD/TPI-Pitch combinations but also shows the depth of cut you need to take when using the top slide set over at the appropriate angle - not just for 'Standard' threads - - - any.


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## ChaiLatte (14 May 2022)

Most of the major cutting tool manufacturers have documentation on threading. E.g.

https://usercontent.azureedge.net/Content/UserContent/Documents/021367.pdf (Seco)
Threading | MITSUBISHI MATERIALS CORPORATION (Misubishi)
https://cdn.sandvik.coromant.com/fi.../global/technical guides/en-gb/c-2920-031.pdf (Sandvik)

It would be wise to assimilate the information from the horse's mouth rather than from half truths such as that posted above. For home workshop-type stuff, you do not need one insert per pitch.


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## guineafowl21 (14 May 2022)

J-G said:


> Whitworth, BA & BSCycle each have their own radius at both Root & Crest so a 'single point' tool cannot be used for these.


This is certainly news to me. I’ve cut loads of Whit (and some BSC) threads with a single point tool, and they seem to work just fine. Perhaps your advice applies to more critical parts than I make.


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## J-G (14 May 2022)

ChaiLatte said:


> It would be wise to assimilate the information from the horse's mouth rather than from half truths such as that posted above. For home workshop-type stuff, you do not need one insert per pitch.


I'm sorry you consider my sincerly expressed TRUTH to be erroneous. I may not be a commercial manufacturer of such tips but I do have knowledge of thread standards and 'Threads' were my 'bread & butter' for many years.

Nothing I've stated (here and elsewhere) is 'half-truth' but I will conceed that I'm only concerned with creating accurate threads rather than what will 'Do' in a hobby environment.

I would appreciate your detailed critique regarding which part of my post you consider a 'Half Truth'.


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## Lorenzl (14 May 2022)

Your post @ChaiLatte is of no help what so ever and just argumentative. Some people have been in engineering their whole life and know what they are talking about.

Anyway If you want a nicely formed thread you will need a carbide tip to match each thread specification and pitch. But you can get a carbide tip that will cut any pitch thread of the same thread angle using a "Partial Profile" tip but it will not be fully formed.


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## ChaiLatte (14 May 2022)

If the idea of part profile inserts offends you both so much, kindly advise why every manufacturer under the sun makes and sells them into an industrial market.

I would very much hope that anyone who has been in engineering all their life has learnt that there are numerous standards which can be applied to any piece of work and that it is not good advice to someone who is both a beginner and not working in a commercial environment to say that they need an insert for every pitch they want to cut. Most of the time, near enough really is good enough.

Perhaps if the documents to which I linked do not provide good information for the OP, you might suggest alternatives which take account of "I'm a bit new to thread cutting" and "I can’t find any reference with my searching".


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## Lorenzl (14 May 2022)

Did you actually read my posts:


Lorenzl said:


> Now if you buy thread inserts they are formed to shape so there is a rad in the bottom and a rad at the top of the tips leaving a nicer and stronger thread. Obviously as this is the case you need to have each tip match each thread so you have a lot of tips.





Lorenzl said:


> I thought there may be tips without rads and there are but check before you buy - Partial Profile


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## Phill05 (15 May 2022)

Chailatte: telling someone "Most of the time, near enough really is good enough." is just not on we should ALL stride to do the BEST, that kind of attitude is why we have a big mess in this country.


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## evildrome (15 May 2022)

OK, so here's a left field idea... thread cutting... how about Coventry die heads?



Really they're a production tool from a bygone era (CNC did for them) but now, 2nd hand, they're cheap and you still get a production standard finish when using them. Better than any single point tool, even full profile carbide tips.

If you're canny you can get die sets for £3 (usually by buying a whole lot at one time).

Over the years I've built up a collection of around 200 sets. A lot of it is weird (left hand UNS for example) but I have got most of the metric threads up to 24 and any number of BSW, BSF, GAS, etc.

I'm very rarely stuck for a thread. 10mm x 1 buttress comes to mind but that's properly weird (Levin collet drawbar).


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## J-G (15 May 2022)

evildrome said:


> OK, so here's a left field idea... thread cutting... how about Coventry die heads?
> 
> I'm very rarely stuck for a thread. 10mm x 1 buttress comes to mind but that's properly weird (Levin collet drawbar).


Oddly enough, I was involved in the developement of the first Coventry Diehead that was able to cut 'Undercut Buttress Threads' and for some time had the very first successful 1" x 5TPI sample produced - some 8" long IIRC - on my desk.

You do have to take care with Coventry Dies though - to make sure that you select the correct set for the material being cut - Cutting Steel with type 'B' would produce poor threads, and for Buttress, ACME etc. you would need 'Holozone' - - - Ah.... memories


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## J-G (15 May 2022)

Lorenzl said:
I thought there may be tips without rads and there are but check before you buy - Partial Profile
======================================
'Partial Profile' simply means that the CREST of the thread is not formed. The root radius or flat IS correctly profiled so each different 'pitch' or 'TPI' will be different.

For Metric & Unified forms this is of little consequence but any form that should have a Crest Radius will either have to be truncated (making the O/D undersize) or will be 'tight' in a standard 'nut'.

Yes you could cut different pitch threads with a 'Partial Profile' tip (or a single point tool for that matter) but you would need to cut larger pitch threads deeper - thus weakening the thread - such that the width of the root flat is still 'clear'.

[EDIT] There is a way to maintain the correct thread depth using a Tip (or single point tool) intended for a smaller Pitch but it requires great skill and good depth of knowledge - I'll see if I can write an explanation . . . . .

PS - Can we have the previous [Editing] options back please!! The 'Preview' option is OK but the ability to 'insert' comments within a previous posting Quote was/is more important.


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## J-G (15 May 2022)

Right - - in an effort to dispel any suggestion that my comments are 'Half-truths' I've created drawings of the 'Screw-cutting' process.

First, the most important dimension of any thread is the 'Effective Diameter', the OD and Root are both secondary - as long as they are not wildly beyond the 'norm'. ie. if the OD is truncated, the thread will generally still be OK - as long as the Effective Dia. is within tolerance.

It should be borne in mind that Screw-Cutting is one of the most demanding operations in lathe work and there are two major methods by which threads can be 'Screw-cut' - the least demanding is by setting the top-slide over at half the thread form included angle (30° for Metric, 27½° for Whit. etc.). 
*!!!!! - the 'Editor' now precludes the inserting of 'special characters' using the [Alt] keypad !!!!! I had to resort to "copy'n'paste" to get '°' Grrrrrrrrr.........!*
The more demanding is feeding the tool in perpendicular to the work - this causes material to be removed from both side of the thread causing a conflict with the swarf folding in on itself.

However, life is a compromise and if you wish to use a threading Tip (or single point tool), which is designed to cut (say) a 1mm pitch but the thread being made is 1.5mm pitch then the second option would allow you to make the lateral adjustment to maintain the root flat width without having to feed too deep.

Pictures speak much louder than words, so :





This shows a single point tool (or 'Partial Profile' Tip) (Blue) being used with the top-slide at the half-angle. Feeding deep enough to maintain the correct Effective Dia. takes the depth into the Magenta region. If you were to stop at the correct depth of thread (the shading pink area) you would then have to make a 'lateral adjustment' to remove the 'grey' area but with the top-slide at the half angle and the need to maintain the 'saddle' in correct mesh ( with the lead-screw) that becomes quite difficult.

If you take the compromise (Green), with the top-slide at zero deg., then lateral adjustment is possible.

The drawing shows an extreme example where the tip used is very much smaller than would normally be considered - just to make the example more obvious.

If you now consider a thread form which has a rounded crest & root (such as Whitworth), I'm sure you will appreciate that there are many more difficulties :





Here, again, using a Partial profile or single point, without 'truncating' the OD (pale blue section) you can see that the green section would interfere with the internal mating thread. To create a thread with the correct Effective dia. the cut depth would have to extend into the magenta section. Lateral adjustment is even more complex to figure out in this case (though not impossible).

I do accept that for many applications threads can be successfully produced with both single point tooling and partial profile tips but if you are 'Screw-Cutting' it is usually because you are dealing with 'Special' threads (outside the Standard OD/Pitch combinations) or you want the best possible thread under your absolute control.


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## guineafowl21 (15 May 2022)

I see what you mean about getting the Whit form just right.

In amateur use, and there are far better amateurs on here than me, I find that taking a few spring cuts, and maybe running a file over the crests or even some scotchbrite, will achieve a ‘decent’ fit, especially if you can keep trying the internal thread on until it fits nicely.

One more thing - and this is from the book ‘the amateur’s lathe’ - I thought the compound slide should be set over to one degree under half the angle, ie 29deg or 26.5deg for metric/American and Whitworth respectively. This is apparently to avoid steps on the trailing edge of the thread.


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## J-G (15 May 2022)

guineafowl21 said:


> One more thing - and this is from the book ‘the amateur’s lathe’ - I thought the compound slide should be set over to one degree under half the angle, ie 29deg or 26.5deg for metric/American and Whitworth respectively. This is apparently to avoid steps on the trailing edge of the thread.


Ah.. Well done for spotting my 'short cut'  

There are (at least) two schools of thought about that. One is that there should be a 'clearance' between the tip and the Right hand Thread Flank, the other is that there should be a small 'interference' such that the Right Flank will always be 'skimmed'. I'm in the second camp, since I think that the first method is more likely to leave a 'stepped' finish. 

I wouldn't go anywhere near 1° though - - - at most I'd consider a 0.1° interference acceptable. 

One thing I didn't mention is that it is imperative that the Tip (or single point) is mounted EXACTLY at 90° to the workpiece - (unless cutting some pipe threads but that is taking the complications too far even for a pedant like me) - I use a Thread Angle Gauge held against the work to achieve this.


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## TFrench (15 May 2022)

J-G, thanks for those explanations. Makes a lot of sense, and explains why I've had trouble getting metric threads to cut nicely in the past.


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## Scruples (16 May 2022)

I use a hand stock and die to cut threads. I've always thought that machine thread cutting is more for mass-production.


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## guineafowl21 (16 May 2022)

J-G said:


> I wouldn't go anywhere near 1° though - - - at most I'd consider a 0.1° interference acceptable.


A bit tricky using the scale on my little Boxford! It seems the best I can do is approximate a Whit or whatever thread form with a single point tool. But with careful fettling and checking, that approach seems adequate for the odd custom piece that I need. Thanks for the explanation.


Scruples said:


> I use a hand stock and die to cut threads. I've always thought that machine thread cutting is more for mass-production.


I tend towards the opposite - single point for a custom thread that I don’t want to buy a tap/die for, but if I need 10 bolts made I’ll buy a die. Mainly because single-pointing them would take forever. 

Best example was a brewing gas fitting, 5/8” (14 tpi) BSPP both ends, but one end needed to be taken down to 21.8mm, but still with 14 tpi that had to synchronise to and deepen.

I doubt I could have found a die for this strange b’stard M21.8/14tpi Whit form thread for a sensible price.


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## J-G (16 May 2022)

Scruples said:


> I use a hand stock and die to cut threads. I've always thought that machine thread cutting is more for mass-production.


Hmmm... Mass production would call for a 'Die Head' - whether that was a 'Coventry', 'Namco', 'Fette', 'Versotool' etc. or specialist machine (Flat Thread Rolls) would depend upon many factors though.

Screw-cutting would generally be done where prototypes with 'Special' threads are being developed or, of course, in the 'hobby' workshop where 'one-off Specials' can be the 'norm'.


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## chaoticbob (17 May 2022)

First I'd like to thank J-G for explanations / graphics - in the past I was as perplexed about thread cutting as the OP is now, researched, but never came across anything as clear (for a beginner) before, despite having been on many engineering sites.
Second, to the OP, I think you might be trying to run before you can walk in a way. You've got a nice lathe but maybe it would be better to worry about tooling and technique when you need to make something specific, rather than trying tool up for perfect thread forms at any pitch your lathe can make. Which will be very expensive and likely unnecessary.
Myself, I mostly single point with a V ground tool if over 12mm or a strange pitch. That leaves a stress raiser at the root, but I'm not making F1 engines!
Bob.


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## J-G (17 May 2022)

Unless you wish the threads that you make to be capable of mating with other peoples work, there is no real reason why you have to stick to any [Standard].

You could simply decree that YOUR threads will be YOUR standard which may well mean that the width of the flat at the root (and/or crest) will be (say) 0.5mm (or 0.020" if you wish) irrespective of the pitch - though naturally that might make a 1mm pitch thread somewhat weak and preclude the use of 0.5mm pitch or below. You could even decide that you would prefer a 40° or 50° form. 

You would of course then have to create the 'nut' as well


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