Threading dial

[John Stevenson]

Yeerrrhoo,
Finally found me a Metradial.
This is like a threading dial but you have a small gearbox built into it and two or three spare drive pinions depending on the thread you need to cut.

In imperial mode on an imperial machine, you fit the imperial pinion, lock the gearbox and just use as per a normal thread dial.
Even number threads on any number, odd threads on 1 and 3 or 2 and 4,sily threads like 7-1/2 stick to one number.

On metric threads select the pinion and gearbox ratio according to a chart, swop the dial over to a single mark dial and you can now cut metric threads on an imperial lathe AND dis-engage the 1/2 nuts. Rewind, watch the dial and it re-engages back into mesh bang on the mark.

Woo hoo no having to wind back.

Getting a friend to colect it tonight and I'll get it towards the later end of next week.
Might have to make a couple of pinions to fit my lathe as it's a finer leadscrew but that's not a big job on the hobber.

These are like rocking horse s#~t to get hold of, been looking for ages and bugger me just like buses two come together, the friend who's collecting is having the other.

John S.

[dsergison]

hot-dang!

that would make a REAL project for the magazines. I might even re-up my subscription if you were to draw up plans and write an article on it.

could you post some pictures for us? thanks.

I think I can see it working in my head. just like the metric change gears, but backwards?

cool.

[Jim Hubbell]

John I would surely like to hear more on this dial. As you try it out please post the results. Would this be used on an imperial machine using a 127 tooth translating gear? Is the dial gear an odd number also? I have a hard time envisioning when the screw and spindle will coinside due to compounding, etc.
Thank you

[John Stevenson]

Can't tell you much more about it as I don't know.
All I do know is there is a small internal gearbox with 3 or 4 ratio's and you set the ratio to a pinion size for a given pitch from a chart.

Some years ago I tried to find more out and contacted Crawford Collets who had bought out Metradial but all they would do was supply a skimpy leaflet that explained nothing.

A while later I tried again and rang them and asked for a parts list as I had got one with some missing parts and wanted to order the bits.

No go, they wouldn't supply a part list but offered to take the unit, repair it and return it at a cost of a few hundred pounds.

From what I can gather their main customer was Harrison's and Colchester. They did suppy to others but these were the main customers.
I have only seen and heard of these for machines 12" or over.
I may be wrong but I have never seen or heard of a small one suitable for a 7" or 9" lathe

You do have to set the machine up to cut metric with the translation gears.

John S.

[aboard_epsilon]

is this it .

http://v3.espacenet.com/textdoc?DB=E...=US4218942&F=0

[John Stevenson]

Mark,
Similar from what i can remember but not as complex.
I was sure there were only about 4 ratio's
Might know better tomorrow when I can get Tim to describe it for me on the phone as he collected them tonight.
These were private sales not ebay so I don't have a photo. Just told they were new, still in the boxes.

Interesting is the date on the Southbend patent of 1980, I thought these were earlier than this.
I also thought that Metradial would have also had these patented.
Perhaps the secrecy was because they hadn't ?

Bugger it just done a search for a picture and found one sold about a week ago on Ebay.
http://cgi.ebay.co.uk/ws/eBayISAPI.d...tem=7502184834
Double bugger it as the guy selling it, Railroad Gin, lives about 1/2 mile away and owes me a favor or two, tripple bugger it another flat battery in the car park of life.

John S.

[Fred White]

>>You do have to set the machine up to cut metric with the translation gears.


From a PDF brochure I have on file:
*********************
AINJEST/METRADIAL
The Ainjest High Speed Screw cutting Attachment allows threads to be cut at
the high surface speeds applicable to Tungston Carbide tooling.
The Metradial attachment was introduced originally to enable both metric and
imperial threads to be produced easily on a centre lathe fitted with an
imperial lead screw. By combining Ainjest and Metradial it is now possible to
achieve an immediate changeover from high speed screw cutting of imperial
to metric threads.
***********************


The metradial sounds like something that could be made from electronic parts rather than gears.

[John Stevenson]

Fred,
I have seen something along these lines before.
There have been some in Model Engineer or Model Enginers Workshop and I think the Houston shop club page also has something along these lines but if I recall they are simple setups that only match the spindle to the leadscrew in one place.

Just contacts on a disk on the spindle and leadscre that have to be in line before a light comes on.

John s.

[John Stevenson]

Update,
Won't get this dial for at least another week.
me and the guy who has it have got to get a few things together and meet for a swop.
Trouble is both a bit busy and the moon is in the wrong phase

Good news is he's emailed me the sheet down and they are simpler than I thought.
Three speed only and it comes with two gears 16T and 20T, the others are extra's.



So it looks like 14, 18 and 22 are needed for the full set, although 22 is a bit of an odd one.
According to Tim A is direct drive and B is about 5:1, C is about 6:1

So far it's looking very do-able for a small machine.
I have an 8tpi acme hob so spare pickup gears are no problem on the hobber.

John S.

[Fred White]

There was an article in Home Shop Machinist sometime back about thread dials. The authors point was that going forward sometimes there were a LOT of spindle rotations to reach the correct point to re-engage the split nuts.

I also have an old reply by Forrest describing the same situation.

At some point, it appeared faster to stop the lathe and "rewind".

I will be anxious to hear how long it takes for the proper point to return.

[John Stevenson]

Fred,
That point also crossed my mind last night but I was thinking about it another way.

If you had a geared screwcutting dial that worked on imperial then you would be able to up the spindle revs to get a better finish / cut but still be able to engage in a reasonable way.

When you are doing course threads the speed of the dial to spindle revs is the deciding factor.

So if this metric setup is 5 times slower I can't see why in theory you can't up the speed ??

John S.

[Fred White]

John-

In theory, I guess you could. But that would mean that you would have to be more accurate in engaging the split nuts and disengaging them if you were coming up to a shoulder. Perhaps as an experiment, set your lathe to 5 times your normal threading speed and try to thread imperial threads.
( Try threading "air" first to watch things happen so you don't damage anything. )

Keep us posted.

[Fred White]

There was a good article about needing a counter on a thread dial in HSM...but now I can't find the date.

It is titled "On use of Treading Dials for Cutting Metric Threads" by Eugene E. Peterson.

I bought a copy of it from Village Press in 2002. Gave them my credit card number over the phone and they faxed me a copy. Instant gratification!

Another thread at another time from Forrest Addy said you have to rewind 127 revolutions to get in sync or go forward 3937 revolutions.

[JCD]

Does anyone have a design for one of these or something with the same function?
It looks like a good and useful project.
JCD