Thread: Hercus Repetitive Turret & Stops

Here is a more detailed photo of the die head used in the Turret or Tailstock.
Its a simple design.
The die is presented to the rotating workpiece.
The threading then takes place, until the die reaches a preset stop.
The die continues cutting until it disengages from its holder (see photo of the 2 unbrako screw heads that do the driving.)
The lathe spindle is then reversed & the die unscrewed from its workpiece.
Turret head is then rotated to the next stop position in readiness for next operation.
A proven system that worked in repetitive operations for many many years before the advent of CNC.
regards
Bruce
ps Of course a nice Coventry style diehead with its individual chasers is even better than the above method.

Nice work Bruce. How do you find time to fit an afternoon kip into your busy schedule?

I like the Burnerd collet chuck. Larger capacity than the 3Cs you have I imagine which makes me ask why you would bother with the latter? The releasing die holder is neat and simple.

What are the parts for?

BT

Originally Posted by Anorak Bob

Nice work Bruce. How do you find time to fit an afternoon kip into your busy schedule?

I like the Burnerd collet chuck. Larger capacity than the 3Cs you have I imagine which makes me ask why you would bother with the latter? The releasing die holder is neat and simple.

What are the parts for?

BT

Bob
There are no afternoon naps, only blokes approaching 60 ish like, your good self might need a rest, older blokes seem to be able to press on
The Burnerd collet chuck is excellent for those repetitive parts, because its quick to undo & retighten & its very accurate.It does not have a large OD which is nice for a lot of work from a space saver, aspect.
The only disadvantage with this type of collet chuck is its not good for holding short length workpieces, whereas the 3C & 4C collets can grip very short pieces, & can be used for work, like you recently did with your Sherline Chuck. 2nd operation work.
Yes, the releasing Die holder, is very simple. I have adaptors to use it in the Turret 3/4" dia parallel or a no 2MT for the standard Hercus Tailstock.
The parts made were arbors for an Air Tool, one of those small paying jobs, a remnant from when I had my business.
regards
Bruce

Hi Bruce, nice work

Maybe I'm a bit thick but could you please explain how you adjust that die head to disengage at the required depth ?

thanks, john

Originally Posted by shedhappens

Hi Bruce, nice work

Maybe I'm a bit thick but could you please explain how you adjust that die head to disengage at the required depth ?

thanks, john

John
The problem in understanding this Die head & its disengagement is its so simple its hard to understand.
Like all good designs that have stood the test of time & have been put aside for more complicated versions, is its simplicity.
I will try to explain
The knurled barrel that holds the Threading Die is free to spin in its holder.
The Holder is clamped in the Turret head or in a 2MT tailstock in the conventional Hercus set up.
The only thing that stops Knurled Die Head spinning are the 2 Unbrako Screwheads,
they could be 2 dowels or steel pins, their sole purpose is to stop the die head rotating or spinning while the threading operation is taking place.
Once the threading depth is preset,(disengagement of the drive pins or screwheads in this case) threading ceases & the Die head is allowed to spin until the lathe spindle is reversed the Knurl is gripped by hand & presto die head ubscrews from the workpice.
OK in the case of the Turret head a preset stop is made on the Turret.
In the case of the unit being used with a conventional tailstock the thread depth would be set by presetting the lathe saddle so that the tailstock was free to slide on the lathe bed.
Once it strikes the carriage, the die head feeds on until the 2 screw heads, or in some cases steel dowels or steel pins ( whatever is used in the construction of the head)
disengages.
I hope this offers an explanation.
regards
Bruce

Thank you Bruce,
I could see that the Unbrako's worked as a dog clutch, I suppose that I just wasn't looking beyond the die head (I was probably mesmerized by it) and didn't didn't jerry that the adjustment was not actually on it, it has now pierced my thick scull and thanks for your reply.

When I finish my current project I am going to make one of them, it's a ripper.

Do you have a similar tap holder ?

thanks, john

Very nice indeed.

Originally Posted by shedhappens

Thank you Bruce,
I could see that the Unbrako's worked as a dog clutch, I suppose that I just wasn't looking beyond the die head (I was probably mesmerized by it) and didn't didn't jerry that the adjustment was not actually on it, it has now pierced my thick scull and thanks for your reply.

When I finish my current project I am going to make one of them, it's a ripper.

Do you have a similar tap holder ?

thanks, john

John
I am glad that the picture is now clear.
So simple isnt it?
The design is shown in some old books on Lathes & Capstan - Turret tooling.
Yes, I do use the same head for tapping.
That is the reason for the "Outrigger" support arm on the holder.
Because of the high torque in tapping I found the 3/8" dia Outrigger arm stops unwanted rotation & slippage. I set it up so that it rests on a support arm out of the lathe Toolpost.I have machined up a few 1 1/2" dia OD pieces (The same dia as the Dies) with a centre hole to accept the threading taps. At the rear of the insert, a couple of grub screws make contact with the flat on the tap shank, & hold it firmly in place.
Great for repetitive tapping operations.
I have communicated, with BT "Anorak Bob" on this subject, as I have found for repetitive tapping, with very low torque, a Spiral fluted tap works best.
The Americans like Gun Taps or fluted point Taps & I am yet to try them.
regards
Bruce
ps If a photo of the tap holder is required , please lets know.

"ps If a photo of the tap holder is required , please lets know."

Thanks for the info Bruce, I think I can work it out from there, and I reckon your right about the spiral fluted taps.

When I tap something held in the vise the tap feels like it winds in fine, but when I use the same tap in the same sized hole with something held in the chuck on the lathe the torque required to tap the hole seems to double so I think will look at getting spiral fluted taps.

I think that tapping head could also be made to work in a mill or drill.

john

Originally Posted by shedhappens

"ps If a photo of the tap holder is required , please lets know."

Thanks for the info Bruce, I think I can work it out from there, and I reckon your right about the spiral fluted taps.

When I tap something held in the vise the tap feels like it winds in fine, but when I use the same tap in the same sized hole with something held in the chuck on the lathe the torque required to tap the hole seems to double so I think will look at getting spiral fluted taps.

I think that tapping head could also be made to work in a mill or drill.

john

John
I have never tried the Tapping head in a vertical position, as the free spinning piece, holding the Tap, would just want to drop out of its holder.
However, if it was held by the hand to stop it dropping out then I guess it would work well, with the stop on the drill press or mill preset.
regards
Bruce

Very nice indeed.
Sometime soon I will be want to begin tapping on my lathe and you have
provided a very elegant solution.
When you reverse the lathe do you have any problem with the unbrako
screws disengaging?

Originally Posted by GSRocket

Very nice indeed.
Sometime soon I will be want to begin tapping on my lathe and you have
provided a very elegant solution.
When you reverse the lathe do you have any problem with the unbrako
screws disengaging?

GS Rocket
No Problem, with reversing the Lathe rotation, as the Unbrako screws have already disengaged.
After the Tapping or Die Head threading Operation is completed (That is the Tailsock has slid along the bed & met its carriage stop) The threading Operation continues slightly, fed along by the srew thread being formed, until the Unbrako Screws lose contact with each other. ( A bit like a Dog Clutch) then the knurled head spins, the Lathe spindle is put into reverse rotation, & the Tap or Die unscrews off the workpiece.
One has to think about it to get it clear in the mind, as its just too simple
But it all works very well.
regards
Bruce