It’s a thread Jim, but…

[JasonBModerator @jasonb]

As has been mentioned earlier if you want to run at speed and don't think you can stop in time work at the rear of the work with the lathe running in reverse and you have got until you hit the tailstock to stop the machine. Think I diod this at 4-500rpm

[CirclipParticipant @circlip]

Please assist and advise what I'm doing wrong. 50mm long M42x4mm pitch thread using HSS tool ground once? Set over topslide, 4 way toolpost with shimmed tool and slide dials.

Do I need to change to CNC and carbides?

Regards Ian.

[Neil WyattModerator @neilwyatt]

Posted by Circlip on 21/11/2018 10:22:15:

Please assist and advise what I'm doing wrong. 50mm long M42x4mm pitch thread using HSS tool ground once? Set over topslide, 4 way toolpost with shimmed tool and slide dials.

Do I need to change to CNC and carbides?

Regards Ian.

Depends what problems you are having. Can you give more detail?

Historically, people used to cut far larger threads than that with HSS, if your tools are blunting or failing just reduce the rpm and don't try and remove too much material in one go.

Carbide will work faster and with longer tool life if you have a lot of threads to cut, but if you only need a few threads you can get the results you need with HSS, if you take things steadily.

Neil

[Alan VosParticipant @alanvos39612]

Posted by JasonB on 21/11/2018 07:06:19:

As has been mentioned earlier if you want to run at speed and don't think you can stop in time work at the rear of the work with the lathe running in reverse and you have got until you hit the tailstock to stop the machine. Think I diod this at 4-500rpm

Is that a standard internal right hand threading tool, or a special for external right hand threading running in reverse ?

[JasonBModerator @jasonb]

Standard Internal.

Neil, I think Circlips question was directed towards Jon who said HSS would not do the job.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 21/11/2018 18:39:37:

Standard Internal.

.

Please forgive my naivety on this matter, but how do you accommodate the difference in truncation?

P/4 vs P/8

https://en.m.wikipedia.org/wiki/ISO_metric_screw_thread#/media/File%3AISO_and_UTS_Thread_Dimensions.svg

MichaelG.

 

Edited By Michael Gilligan on 21/11/2018 19:28:34

[JasonBModerator @jasonb]

It's a partial form insert so does not create the true crests and valleys, think of a HSS tool ground to a point. Needle file over the crests to ease them and make the other part to fit. This would apply to using a external partial form insert as well as the external.

[Neil WyattModerator @neilwyatt]

Tip radius is a maximum not a minimum, and is actually the width – a flat is allowable..

To quote the article:

"In an external (male) thread (e.g., on a bolt), the major diameter D_maj and the minor diameter D_min define maximum dimensions of the thread. This means that the external thread must end flat at D_maj, but can be rounded out below the minor diameter D_min. Conversely, in an internal (female) thread (e.g., in a nut), the major and minor diameters are minimum dimensions; therefore the thread profile must end flat at D_min but may be rounded out beyond D_maj."

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 21/11/2018 20:21:03:

It's a partial form insert so does not create the true crests and valleys, think of a HSS tool ground to a point. Needle file over the crests to ease them and make the other part to fit. This would apply to using a external partial form insert as well as the external.

.

That's O.K. then, Jason … Sorry, I thought it was full-form

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 21/11/2018 20:28:42:

Tip radius is a maximum not a minimum, and is actually the width – a flat is allowable..

To quote the article:

"In an external (male) thread (e.g., on a bolt), the major diameter D_maj and the minor diameter D_min define maximum dimensions of the thread. This means that the external thread must end flat at D_maj, but can be rounded out below the minor diameter D_min. Conversely, in an internal (female) thread (e.g., in a nut), the major and minor diameters are minimum dimensions; therefore the thread profile must end flat at D_min but may be rounded out beyond D_maj."

Neil

.

Quite so, Neil … That's why [*] I was struggling.

MichaelG.

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[*] when I wrongly assumed that Jason was showing a full-form insert

[Alan VosParticipant @alanvos39612]

Posted by JasonB on 21/11/2018 18:39:37:

Standard Internal.

Which means, when I came to cut a simillarly proportioned blind internal thread, I could have used my existing external tool, under power, in reverse, rather than buying an internal tool and turning the chuck by hand to avoid a crash. Every day is a school day.

As for inserts and high rpm, that was a hand turned chuck, with an insert threading tool, cutting (probably) EN1A. The thread came out fine. New sharp tool. Free machining material.

[Martin ConnellyParticipant @martinconnelly55370]

Might not be enough bottom rake on an external tool to do an internal thread.

Martin C

[JasonBModerator @jasonb]

Posted by Alan Vos on 22/11/2018 18:44:37:

Posted by JasonB on 21/11/2018 18:39:37:

Standard Internal.

Which means, when I came to cut a simillarly proportioned blind internal thread, I could have used my existing external tool, under power, in reverse, rather than buying an internal tool and turning the chuck by hand to avoid a crash. Every day is a school day.

As for inserts and high rpm, that was a hand turned chuck, with an insert threading tool, cutting (probably) EN1A. The thread came out fine. New sharp tool. Free machining material.

Don't know how you would get the usual external holder inside the hole as they tend to be at right angles to the lathes axis

[Robin GrahamParticipant @robingraham42208]

Well, to report back on suggestions, I've now tried upping the speed (250 rpm instead of 65), using EN1A instead of EN3B and taking spring cuts. Still in badger's ar*e territory. I'm reluctantly forced to think that it must be the 'poundland' inserts – **LINK**

I don't understand the codes for inserts – can anyone point me to a source of decent inserts which would fit this holder?

Robin

[EmgeeParticipant @emgee]

Robin, measure the side of the insert, it will be 16, 11 or 8mm, the tip code will have that dimension included in the code number along with an E for external, an I for internal and R or L for right hand or left hand threads.

Emgee

[John ReeseParticipant @johnreese12848]

Another weapon in your arsenal: sulfurized cutting oil. It is almost universally used by plumbers when threading pipe. I prevents tearing in really gummy steel.

I am not going to get in the debate of HSS vs carbide. I use both. HSS does give you the option of varying the top and side rake to suit the material.

Flank feed is preferred to plunge cutting. When plunging there adr chip impinging from two directions and tending to jam on top of the tool.

[JasonBModerator @jasonb]

From the Bangood link you need a 16mm, External Righthand, 60 Degree , Partial form insert = 16 ER AG60 for a mid range try JBcuttingtools which is likely to be Kennametal.

[robjon44Participant @robjon44]

Hi all, if I may make a point (geddit) regarding some of the 'heftier' pitch threads mentioned say 3mm & above, the manufacturers recommend roughing out using 55 or 60 degree V point throw away tipped tools to save wear on the rather expensive larger pitch threading tip (and its holder?). Just a thought.

Bob H.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Neil Wyatt on 21/11/2018 11:05:28:

Posted by Circlip on 21/11/2018 10:22:15:Do I need to change to CNC and carbides?

Regards Ian.

Depends what problems you are having. Can you give more detail?

Neil, I think Ian's post was tongue in cheek. He has been around on this and other forums for many years.

Russell

[CirclipParticipant @circlip]

And there was me thinking that Neil's posting was his tongue in cheek reply to my tongue in cheek reply to Jon's???

Russell don't give the game away. His late Sir Highness would have had a birthday with this one. Think it may have actioned his catch phrase to the O/P – – – C B

 

Regards Ian.

Edited By Circlip on 23/11/2018 11:46:37

[Neil WyattModerator @neilwyatt]

Fortunately, Ian and I have our tongues firmly in our own cheeks

Neil

[Robin GrahamParticipant @robingraham42208]

Posted by JasonB on 23/11/2018 07:15:26:

From the Bangood link you need a 16mm, External Righthand, 60 Degree , Partial form insert = 16 ER AG60 for a mid range try JBcuttingtools which is likely to be Kennametal.

Thanks Jason. Your link is actually to the NR (N=iNternal?) insert, but  obviously they do ER (presumably External Right) as well. However, following Emgee's advice to measure the edge of the insert I'm still confused – which edge? This is one on the Kkmoon inserts:

 

I can't find any dimension close to 16mm. Maybe I should just buy the JB tool and inserts and write this off to experience?

Robin

 

Edited By Robin Graham on 23/11/2018 22:36:45

Edited By Robin Graham on 23/11/2018 22:37:34

[pgk pgkParticipant @pgkpgk17461]

I understood the size dimension was the diameter of the inscribed circle the insert would fit into. Without doing the math i'd guess the example above is 16mm.

(edit.. looking at that again I probably mean 12mm???)

Compared to most guys on here my thread cutting experience in limited but i find it odd that you get such poor results whatever quality of insert you are using. So far I've cut my threads with both an off-hand ground HSS and also using cheapo triangular inserts – with results satisfactory for my purposes (and way better than your first pic).

I had reason to cut a 1.5mm thread to a shoulder recently and it was only 4-5 turns long 38mm diameter and that was done just pulling the chuck around with a chuck key using the HSS. That particular unknown bar gives me a matt finish when turned at any speed/depth of cut or feed-rate I've used with inserts

Are you sure there isn't something else going on like a loose toolpost or poor fit on a quick change tool holder or way too much stickout?

 

pgk

Edited By pgk pgk on 24/11/2018 00:14:48

[JasonBModerator @jasonb]

Its the length you would get if you carried the edges on until they meet at a point. not the inscribed circle." L" on this drawing.

Link should have been to ER  which I thought I had done.

Edited By JasonB on 24/11/2018 07:11:15

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 24/11/2018 07:07:54:

Its the length you would get if you carried the edges on until they meet at a point.

.

Rather like Apple's way of describing the screen-size on the latest iPad Pro …

[quote] The 12.9-inch iPad Pro display has rounded corners that follow a beautiful curved design, and these corners are within a standard rectangle. When measured as a standard rectangular shape, the screen is 12.9 inches diagonally (actual viewable area is less). [/quote]

… but, of course, related to a triangle !!

MichaelG.

.

Ref. https://www.apple.com/uk/ipad-pro/specs/

Edited By Michael Gilligan on 24/11/2018 08:26:20

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