Chatwin polygon box

[CrabtreeengineerParticipant @crabtreeengineer]

Hi there, I have just latched onto a Chatwin Polygon box. Does anybody out there remember how these things are to be driven? It has some sort of dog on its front face that could be driven from the work piece, but it also needs to slide. Bearing in mind these are a production tool, there must be a standard & indeed quick method to drive them. Any ideas? Regards R

[CrabtreeengineerParticipant @crabtreeengineer]

Drive mechanism

[Michael GilliganParticipant @michaelgilligan61133]

Try here for starters

Edit: not much help, but there's a Chatwin advert in this.

MichaelG.

Edited By Michael Gilligan on 21/02/2015 08:28:35

[JasonBModerator @jasonb]

Video on the makers site, think they need a cam driven off the lathe backplate

[Michael GilliganParticipant @michaelgilligan61133]

Just found this neat 3D animation of something similar.

MichaelG.

[Robert DoddsParticipant @robertdodds43397]

I recall the Chatwin polygon box from the 60's using it to produce brass stuffing boxes for hospital 1/4 turn taps.
It was fitted to the turret of a Ward 2A and requires a drive peg on both turret tool and the headstock spindle to create the drive. The hexagon part was produced by the tool sliding in and out driven by a camring specific to each profile.

The latest design seems to cover several sizes but my recollection is that each size required a different cam and even then the shape was a compromise as sharp corners were a NONO.
There may have been other versions intended for auto lathes with power driven tailstock spindles so eliminating the driving dog arrangement.
Bob D

[CrabtreeengineerParticipant @crabtreeengineer]

Hi Bob, thanks for that at least you have confirmed my thoughts. I intend using it on a coventional manual capstan lathe so it seems to me I need to rig up some sort of corresponding spigot on the main spindle to match up & latch onto the dog on the front face of the polygon box. It needs to be adjustable, allow for forward movement & be easiely swung out of the way so that other turret based tools can be used without clashing with the chatwin drive. Thanks again & regards R

[MuzzerParticipant @muzzer]

Quicktime claimed it had installed correctly but then refused to play the Wheeler vids. Oh well.

I found this after playing the vid MichaelG linked to. Rather like a 4th axis. Groovy music too – bonus.

Murray

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Muzzer on 21/02/2015 12:17:32:

I found this after playing the vid MichaelG linked to.

.

Wow …That's impressive machining.

MichaelG.

[mark costello 1Participant @markcostello1]

Would the straight appearing surfaces actually be straight as checked with a common scale, or slightly curved?

[martin perman 1Participant @martinperman1]

I worked for a machine tool agency as a service engineer and the company sold WERA Profilators, initially the tool was geared to the chuck to cut shapes internally and externally, they then progressed to using CNC and we installed machines at the Leyland plant at Longbridge to manufacture the synchro gears for the gearboxes, I still find it hard to see hows its done even though I worked on the machines.

The flat surfaces are flat but when checked there are slight curves.

As a machine tool fitter I used to work on Wickman multi spindle lathes which were fitted with what we refered to as pecking units which were also geared to a spindle to cut hexagons on diesel fuel injector bodies and a cam fed the tool into the job.

 

Martin P

Edited By martin perman on 21/02/2015 17:19:57

[BazyleParticipant @bazyle]

Can we have some detailed pictures of this thing please. They would be th only ones on the web.

There used to be a polygon box that came up on ebay for about 18 months with no takers. Not seen it recently though.

[martin perman 1Participant @martinperman1]

Bazle,

Here's one for a Wickman multi spindle http://www.autoturn.biz/catalog/wickman-flat-generating-thread-milling-rolling-ball-slots-attachment-b50.htm

Martin P

[jason udallParticipant @jasonudall57142]

Re the link of muzzer….
That thing can also part of
…

[Ady1Participant @ady1]

Makes a heck of a racket to do its job. It looks like they use fancy rotary geometrics combined with specific tooltips and linked variable speed headstocks to crank these parts out by the thousand

There used to be a polygon box that came up on ebay for about 18 months with no takers. Not seen it recently though.

I watched it for a while but the price never dropped under 100 quid and it looked too simple and compact to be the guts of a hexagon system. I think it was only a cross cutting tool to cut one hex flat while the positioning of the workpiece would be done by the main machine

Didn't stop me wondering if it did the whole ballgame though

I now think you need the full sized lathe, the polygon box and the right timing program to make these things work properly

That polygon box may even have been made for a specific pre-programmed task on a specific machine

Edited By Ady1 on 22/02/2015 12:42:13

[martin perman 1Participant @martinperman1]

The actual principle is dead simple, take two gears one has a 120 teeth and the other has 20 teeth, for every complete turn of the 120 gear the 20 gear rotates six times, now mount a chuck on the 120 gear and a single point tool on the 20 gear, if you then refer to your school days and draw the above out, using Loci, you will see that as the the tool passes the chuck it will create a straight line, this it will do six times and you have machined a hexagon.

Change the gear ratio's and the number of flats can be changed, the latest machines use electric motors which are in synch and are controlled by a PLC but the principle is the same.

 

Martin P

Edited By martin perman on 22/02/2015 12:47:20

[BazyleParticipant @bazyle]

There is a distict difference between power driven units and the OP's device which sounds like it is driven off the chuck. I seems ot have a lot in common with a profiling head in that it is the complement, mostly making hte male part..

[martin perman 1Participant @martinperman1]

The original machines I worked on were driven by the chuck spindle to get the correct timing, also the wickman multi spindles lathes drove the tool via the chuck spindle, the electric modern machine still work to the same principle.

Martin P

[Robert DoddsParticipant @robertdodds43397]

The 1960's Chatwin box was a million miles away from the concepts of the Fast Cut machine featured in the video link above from Muzzer. It really was little more than a cam ring with the required profile on the inside, driven by the headstock and with a single point tool to follow the chosen cam profile. One major shortcoming was large amount of relief angle under the cutting edge that was required to ensure that the tool could plunge as it went round the external corners. Something like 35 degree clearance was needed and that only worked by virtue of leaving a slight chamfer on the corners of the hex / polygon

I'm still a bit befuddled as to how they create the end slots and universal joint part on the Fast Cut but the Schwanog site does have a diagram showing how the basic hexagon shape is achieved on their modern machines. Try this link

**LINK**

Bob D

[Neil WyattModerator @neilwyatt]

Looked at the schwanog site and a bit of faffing around in CAD and it's true, if two circles rotate so one turns twice as fast as the other, a point on the circumference of the faster circle draws straight chords across opposite sides of the other circle, so a tool with N cutting edges will produce a 2n sided polygon.

best thing is, it seems to be independent of diameter as long as the cutter is somewhat larger in proportion to the polygon required so as log as you can lock the two spindles in a 2:1 ratio while varying their separation you could probaly achieve this using home made cutters.

Using a single poit tool and a 60:30 gear pair would allow indexing round a 60 tooth gear for several types of polygon.

K3WL!

Anyone going to have a go and write it up for me?

Neil

[martin perman 1Participant @martinperman1]

Neil,

I'm sorry to say this but all of the posts following mine give me the impression that I'm either being ignored or not believed as I described exactly what you have now written as have others.

Martin P

[Robert DoddsParticipant @robertdodds43397]

Martin P,
Please don't get offended. Your post was read and noted but the eyes glaze over sometimes at the thought of drawing loci and the like so the pictures that Schwanog put out by way of explanation were a quick solution to understanding the methodology of this type of tooling.
Meanwhile no one is telling me how the Fast Cut machines can machine slots in the end face of a bar!
Bob D

[jason udallParticipant @jasonudall57142]

Unless I am over looking some thing in the fast cut video.

Many cnc lathes have full C axis control and mill capable live tooling..

With C axis and control of X and Z..the tool path can be taken anywhere you like..the trick becomes on the real world tool radius…

Milling polygons in end working is common practice…
As are face and perimeter milling/engraving.

Polygon TURNING.. now that is a differnt fish…
But was included in the demo from a 1980’s machine we once had…

Again just a matter of controling C and X and Z..at say 1000 rpm…
Its just a matter of machine agility and stiffness…oh and computational power…but thats cheap…and not realtime.

[jason udallParticipant @jasonudall57142]

So simply put…draw your desired grove.
Across the bar face.

Now calculate as many points as you desire (you know how flat a slot you need)…..these points in C and R..polar coordinates…
These
Coords are programmed?Into a move say..G01 C180.34 X 20.345 Z -3.0..
And so on for the other points….as many as you see fit…
And in modern controls “conversational ” programming even does the arithmetic for you.

[Lionel TitchenerParticipant @lioneltitchener]

If you think of the C axis as the same as the Y axis on a mill, it's easier to visualise how it's programed.

The C axis will allow just about any shape to be made. The X axis just moves in and out as the spindle turns slowly converting the degrees to the Y movements.

Working on the face is OK, slots on the outside surface have a curved bottom as the spindle turns, It will slot OK on centreline with driven tooling, but when the slot needs to be off centre you get the curved base.

[Author]

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