Something rare nowadays for the new guys, old guys will recognise these straight away

[Rickabilly]

Hello All,

Nowadays we think of thread cutting in a lathe and the first thing that comes to mind is probably single point cutting or maybe using a die holder in the tail stock, but how do you make thousands of identical parts? CNC of course.

The following images are of the "Production tool" used before carbide threading inserts and CNC control.

Behold; The Herbert "Automatic" Die box,
   
Held either in the Turret of an automatic lathe or "Capstan" attachment or sometimes in the tailstock or in a holder mounted on the back of the cross slide, the latter would ensure the device was centered with an indexing pin or similar.
Once set the tool would simply be applied to the rotating shaft and the thread cut as with a normal die holder, but with a difference. when the operator stops feeding the tool or when the shaft reached an internally set stop the threading cutters would spring back clear of the work.

       
The above photos show the tool in the "set" position with the cutters closed in ready to cut the thread and the "open" position with the cutters right back out of the way,
The short protrusion on the top of the barrel is the adjustment screw which allowed for the cutting of tight or loose screws and allowed adjustment for wear etc.
The longer lever is the arming or "closing" lever simply rotate this lever and it brings the cutters back to the previously set position.
The cutting tools were made to an extraordinarily high standard using the best tool steels available and sharpened using special fixtures that were sold to production shops allowing very precise resharpening of the tools in minutes per set, the sharpening was done on a basic tool and cutter grinder. it was not unheard of to get 500 threads out of a single sharpening of a set of cutters in steel and I heard an account of 5000 threads being cut in a particular job making brass thumb screws, the story went that after 5000 threads they sharpened the cutters despite the fact that they were still working fine.

I hope this brings something new to the attention of our less experienced machinists.

Regards
Rick

[TomG]

We know them as Geometric or Rubometric threading heads over here. They are/were commonly used on screw machines and were very pricey. They could sure thread a part in a hurry though and every one was exactly the same.

Tom

[PixMan]

Nice tools! They can be very useful, but a pain in the butt to set up to the right pitch diameter on different materials.

Do you have a turret lathe or a tailstock mounted tool turret?

[f350ca]

They look very similar to the Ridgid pipe threading heads. On them you set the depth of cut so one die would do a series of pipe sizes.

[Mayhem]

Interesting. Do you still use these Rick or did you just happen to stumble upon them?

[shipto]

I have one of these with m6 chasers, never used it!
wife works at a place where they supply/refurbish them along with other threading equipment apparently they sell quite a few.

[Rickabilly]

I looked up Geometric and Rubometric and yep same basic idea, in most Commonwealth countries it was all Herbert and Ward , to my knowledge the Rigid pipe threading heads on the other hand were pretty universal.

As far as the difficulty setting up pitch circle... I can't say that I agree, the Herbert system has a little scale on the side, you simply turn the knob to set the cutters almost like jaws of a self centering chuck set to the centre mark for mild steel normal fit tighter for hard materials looser for soft and so on,

Theres not a lot of point setting up the head for just one thread but any more than two or three and the time saving is worth it, of course expect to run a couple of tests to get it set up right, but that is production tool setting. If you are as lucky as I am and have enough to set them all up to all your common threads and materials it really is just like using a die holder with the automatic function meaning you can thread right up to a shoulder, I even have some cutters custom ground "plug tap style" so you can thread ultra close to a shoulder.

Unlike the Rigid head these ones use purpose ground cutters, so even if the pitch is the same, a different diameter will mean different cutters.

The other difference to a Rigid head is that not all Rigids have the automatic function, where to my knowledge all Herberts do.

And yes I still use these, I have an exhaustive range of cutters mostly "BA" and some smaller Pipe sizes but one set of Metrics M8 from memory and of course 0BA is also M6. I have to find it... but somewhere... I have a 3MT adaptor I wasn't able to locate it for the photo, I also have a small range of Box tools. I had loads back in Aus but they didn't make the trip, nor did my Mint condition Ward No 3a turret lathe with the lever operated collet chuck with hundreds of collets including square and hex bar stock ones for pretty much all common sizes, I had loads of box tools in that size but... whatever... move countries and some stuff stays behind.

One day I'll get around to making a turret head for one of my lathes they are just so much fun for little production runs, but for now it's just the single holder mounted in the tailstock.

Regards
Rick

PS Mr Shipto, I might need to get to know you

[shipto]

lol before you ask not sure what discount the wife can get
wouldnt hurt to ask though ;)

[Rickabilly]

hello Mr Shipto,
Whereabouts in England are you (and more importantly your wife and the die head folks)

Just kidding, I probably have more heads and parts than I'll ever need.

On second thought, If they deal in NOS(New Old Stock) I might have some cutters that they might like to swap for others that I have more use for. I have loads of BA stuff and I hardly use that any more, but it might be of value to someone else, for example, I'd give five sets of BA cutters for one good set of M10x1.5.

Anyway it's just nice to know how close by people are when you're chatting to them, I'm in Cambridgeshire now but I've lived in West Sussex and Milton Keynes, and I've traveled all over since moving to England.

Best regards
Rick

[the artfull-codger]

Tracey tools[uk] were selling sets of these cutters a few years ago ie only one cutter of each pitch with quite a nice handle to clamp them in to be used as chasers for finishing off threads they were from ''coventry die heads''
Graham.