Machining Thin Wall Ring Strategy

Hi all,

I have some thin walled Ali/bronze rings to machine. The drawing is below.



The material I have to work with is a premachined spuncast pot with dimensions - 189mm OD x 176mm ID x 250mm long.

Currently we only get 6 rings from this material when we could get 7. This is because the process we use at the moment is supposed to be idiot proof. However I would really like to get an extra ring out of this material.

NOTE: we currently do these in batches of 18 spuncast pots (so 108 individual rings)

Currently we do as follows:

OP1

Grip one end of the pot in soft jaws with the ID of the pot supported by a jaw boring spider so not to crush the pot.

We then bore out the opposite end to 177mm dia, 20mm deep.

OP2

we hammer a tight fitting bung into the 177mm counter bore and grip on the OD with the same set of soft jaws (hydraulic chuck @ 18bar).

We then machine a ring, part it off, and use a macro prgram to shift the datum in by the width of the part + parting off tool width(3mm).

This give use 6 rings and a waste ring that is 35.5mm long. However this is a stable process that the very low skill on our shop floor can handle.

HOWEVER,

This really annoys me as there is another ring in that scrap material.

Does anyone have any suggestions on how to improve this process?

THANKS

You are trying to save the ring that the bung(Squeeze plug) is in?

Is the material expensive?

Try pi jaws with thin squeeze plug
Try vacum fixture
Try pi jaws with squeeze ring
Try bolting material to a plug

There are other ways too.

Yes, machine soft laws in to a dovetail, with a matching DT on the end of the casting you can get away with 2 to 2.5 mm for one ring, (AS LONG AS YOU DON'T GO MAD!) .........turn the rest as you normally would then grip the 1offs by the dovetail.

Theses are wood turning chucks but the ideas the same dovetail chuck jaws - Google Search

Alternatively bore the whole length and put the last one on an expanding mandrel to machine the OD - like this PTG Workholding

Limy Sami said:

Yes, machine soft laws in to a dovetail, with a matching DT on the end of the casting you can get away with 2 to 2.5 mm for one ring, (AS LONG AS YOU DON'T GO MAD!) .........turn the rest as you normally would then grip the 1offs by the dovetail.

Theses are wood turning chucks but the ideas the same dovetail chuck jaws - Google Search

Alternatively bore the whole length and put the last one on an expanding mandrel to machine the OD - like this file:///C:/Users/Mark%20Figes/AppData/Local/Packages/Microsoft.MicrosoftEdge_8wekyb3d8bbwe/TempState/Downloads/brochure.pdf

Click to expand...

Thanks for the advice, although your last link isnt working

vettedude said:

You are trying to save the ring that the bung(Squeeze plug) is in?

Is the material expensive?

Try pi jaws with thin squeeze plug
Try vacum fixture
Try pi jaws with squeeze ring
Try bolting material to a plug

There are other ways too.

Click to expand...

Yes i am trying to save that material. The material costs about £40 per ring.

Im open a completley new strategy if anyone has an idea.

Fixed it (I hope ) Give this one a spin PTG Workholding

Edge Precision on Youtube demonstrates dovetail on a 4-jaw with a part that struck me as remakably long (the video is short)
Boring Dovetial Jaws - YouTube

Limy Sami said:

Yes, machine soft laws in to a dovetail, with a matching DT on the end of the casting you can get away with 2 to 2.5 mm for one ring, (AS LONG AS YOU DON'T GO MAD!) .........turn the rest as you normally would then grip the 1offs by the dovetail.

Theses are wood turning chucks but the ideas the same dovetail chuck jaws - Google Search

Alternatively bore the whole length and put the last one on an expanding mandrel to machine the OD - like this PTG Workholding

Click to expand...

With the dovetail ideal do you put 45 on both or do the jaws have a slightly "sharper" dovetail to ensure when clamping under pressure it deflects and sets with a full line contact?

Why not just get two sets of aluminum pie jaws. After all the cutoff rings are done, take the ends and put them on the male pie jaws. Turn the od's. Then bore the other set of pies female. Put the turned rings into the female set and bore. Set both sets of pie jaws aside for next time.

Viola ?

Yeah, pie jaws is also my suggestion. Don’t clamp on points but on large surfaces.

SeaMoss said:

Why not just get two sets of aluminum pie jaws. After all the cutoff rings are done, take the ends and put them on the male pie jaws. Turn the od's. Then bore the other set of pies female. Put the turned rings into the female set and bore. Set both sets of pie jaws aside for next time.

Viola ?

Click to expand...

Seems a bit long winded to me..

Nerdlinger said:

With the dovetail ideal do you put 45 on both or do the jaws have a slightly "sharper" dovetail to ensure when clamping under pressure it deflects and sets with a full line contact?

Click to expand...

I dont thinkthe dovetail jaws should deflect much to warrent doing this as the front face of the dove tail jaw wil lock against the back face of the part being gripped, as well as on the tappered dovetail face.

Watch the edge precision video and you will understand.

Kristian30041995 said:

Watch the edge precision video and you will understand.

Click to expand...

Have you guys with your dovetail jaws ever actually machined anything like this ? Did you look at the print ?

I used to make some wear plates that were similar. They were more like 10" o.d. and had a leg coming down on one edge, maybe an inch and a half, like an L in cross-section.

If the jaws did not support the part everywhere - can't even have a half-inch gap between jaws - and if they were not flat on front and round to within a few thou of the size of the ring, then the part looked good on the machine but came off like a potato chip. There's no way in hell tapered jaws are going to work on a part like this, with only 3/16" wall.

The other tricky part was, no way I could do it in a power chuck. I ended up bolting a 12" manual chuck to the front of a 15" power chuck. Even clamping it was a bit tricky - too much pressure and sproing ! too little and it would spin.

This ain't a 1" thick piece of cast iron.

I think if waste is the issue your trying to solve...cause I'd most likely run like your doing...

I'd do as others mention...but machine that first parts OD to size before inserting holding plug. Then
Face, turn OD and part off.

Flip and insert in pie jaws...
Face and Turn ID

I can understand tossing the drop.. Seems you would spend almost as much time getting 1/7th of
the parts as you would making 6/7ths of the parts.

The problem I see, and what it seems everyone sees.. Its THIN wall (not real thin, but thin
for its size), and the problem is its hard as hell to hold (FROM THE ID or OD) without f'n it all up.

I'd be tempted to face the drop to length after the 6 parts come off.. Then put it to the side until
you get a big pile (108 of them for the next order??).. Then either on the lathe or the mill. Simple fixture,
one for OD, one for ID.. But don't clamp on the ID or OD.. Clamp on the length, the 33ish mm dimension, then
you don't have to worry about turning it into all different kinds of funny shapes. I don't see a concentricity
call out on the print, so if its off, ID to OD, a few thou, who cares.

vettedude said:

You are trying to save the ring that the bung(Squeeze plug) is in?

Is the material expensive?

Try pi jaws with thin squeeze plug
Try vacum fixture
Try pi jaws with squeeze ring
Try bolting material to a plug

There are other ways too.

Click to expand...

this is the way we run some Ø4.78" flanges, for Smith. Our wall is a little thicker, but the process is the same.
Insert a plug (OD= the nominal ID of the tube) and insert the tube into some bored Pie jaws. You can probably get away with 0.2-.3" grab length; although, there will be some process control experiments/ time.

Doug.

Turned rings of diameters up to six feet, forged and non forged steels, on CNC frontal lathes. Boss advised me to clamp radially on eight points which worked but at times I felt the urge to have more points or bodies instead. Better still is when you can clamp axially with stops to the ring to prevent it from moving.

Kristian30041995 said:

Thanks for the advice, although your last link isnt working



Yes i am trying to save that material. The material costs about £40 per ring.

Im open a completley new strategy if anyone has an idea.

Click to expand...

Take Limy Sami's idea... bore thru or switch to tubing if you can GET it in that alloy, see the bit about the "last one" and do the entire lot on a CUSTOM expanding mandrel... one with grooves in it to clear the parting tool. Very THIN blade on that parting tool, too. ELSE live tool it with a slitting saw.

Worked for 18K white gold wedding bands, the material not being exactly "cheap".
Scale it up.