Another workholding problem

Hi

I need to make this part shown in the drawing below and whilst I have never made a part like this before I would have machined it and then parted it off of a bar. However I happen to have this ring of gunmetal that is big enough to have the part in it but is only 0.3 inch thick. Question is how do I hold this and machine it to get the part out? I can only think of machining the bore then trying to hold it on the bore and get it squared up somehow then do the outside. I have all the usual lathe tooling etc.

Any ideas would be great as I only have the one piece and don't want to mess it up if I can avoid it.

Thanks in advance.

By the way off to work in a bit so wont be able to respond until at least 7pm.

Any merit in gluing it to a sacrificial substrate, mounting substrate on the faceplate, center workpiece and level, turn the profile you want and then remove finished article from the substrate. This process has been discussed on this forum more than once I believe.

HTH

Martin

Buffer

As Martin suggests for finish turning but to get there many other methods may suit, my method as follows.

1.Mount the blank in a 3 jaw chuck and face the surface, only remove enough to clean up.
2.Turn job around and face other side, Drill, bore and ream a 1" hole through the part.
3.Fit a known accuracy 1" mandrel to the lathe and secure the blank with a large diam turned washer and nut.
4.Turn OD to 2.990" diameter.
5.Turn the 2.630" diameter to leave .070" thick outer flange.
6.Use the topslide set to suit the 25 deg angled cut and turn the taper.
7.Face off where possible to leave .022" thickness to part.
8.Remove job from mandrel and mark out and drill the holes shown in the flange.
9.Fix the part via the holes in the flange to a piece of ply/MDF bolted to a faceplate and faced/bored to suit the flange diameter to prevent movement.

If no faceplate available:
If absolute concentricity is not required hold the work by the flange OD in a 3j SC chuck and bore to 2.360" diameter, don't overtighten the jaws or the diameter will be distorted.

Alternatively for good concentricity of the bore use a 4jIND chuck but risk of distortion still present.

Emgee

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I do hope that inches are specified somewhere on that drawing ^^^

if not, then you have an interesting ‘watchmaking’ job ahead of you

… and plenty of spare material.

MichaelG.

Emgee, the blank is a ring, no material for a 1" hole.

I'd consider holding the blank concentric on the OD, bore 2.36" and face.

Turn a stub of, say, 3" dia material, (steel, LA?? ). to 2.36+" dia for 0.2"+ length.

Mount on the mandrel. Heating or loctite / super-glue will provide secure fit.

Hold the OD with a 3 jaw chuck. Machine the inside bore undersize and leaving a lip. You can then use this inside lip to clamp the part to a faceplate or other flat plate. Machine the outside features and the holes. Then use the outside lip to hold it on a suitable plate to bore out the centre to size.

Martin C

Hi Clive

Yes I missed that, should have read it twice and seen the 2nd picture.!!!!!

Emgee

Drill the holes first and bolt it to a faceplate?

I was going to suggest machining rear face, and bore b before drilling the bolt holes.

Then turn up a plate, If worst comes to worst, drill and tap the Faceplate.to match the ring of bolt holes in the W I P.

Bolt W I P to plate.

Clock bore to centralise (Clearance on bolt holes should allow this. )

Machine front face,and taper.

As J S would have said "Job's a good 'un"

Howard

Aside from the units of measure … another thing surprises me a little:

Only one of the circles is specified by its Radius

… this is the circle that we would typically reference as a Pitch Circle Diameter.

MichaelG.

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If it’s your drawing, Buffer … No criticism intended !

Thanks guys for all your help with this. I knew a bit of brainstorming would come up with solutions and you've all been most kind taking the trouble to help.

I have had a good read through and they all seem like good ideas, however I don't fancy drilling into my faceplate when there is another idea. So I am going to do what Clive Brown has suggested and slide it over a mandrel with a bit of loctite then break it off with a bit of heat. In the past I have glued bits together to save on waste and then turn up finished components. Once I broke the loctite bond by taking too deep a cut and getting it too hot, so I don't know why I didn't think of this. It just proves to me yet again how hard it is to think clearly and generate options when you jump to conclusions.

Thanks everyone, I will try and do it tomorrow and post a picture if the kiddies don't play up.

Michael yes my solidworks drawings are a bit poor but for some reason that one just came out like that and I couldn't be bothered trying to change it. And as it wasn't meant to be seen by anyone I thought sod it it'll do.

Buffer.

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Good attitude

MichaelG.

All done.

Buffer

Nice job, very crisp machining.

Emgee

Good morning, Buffer

Having just looked at another thread : **LINK**

I feel obliged to withdraw my comment about your pitch circle

The drawings on that thread also show Pitch Circle Radius, in a scheme that is otherwise predominated by diameters.

MichaelG.

Edited By Michael Gilligan on 22/12/2021 08:16:23

Turned out well, if it were me I'd have used the soft jaws which are ideal for thin work and being they grip over a large part of the circumference less likely to distort or mark the part.

If you are set up for 5C collets you can use a5C pot chuck.