How should I make this?

What lathe and what type of spindle nose ?

-- Regards,

John Stevenson Nottingham, England.

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Have you got a pipe center? I' thinking about boring the centre portions from bar stock then turning the outer with a 3-jaw and a pipe centre. I'm very much a starter at this sort of thing but it looks quite do-able to me.

Chris

As you`re limited by the spindle bore it would be better to get cut blanks about 47mm long. Grip in the chuck and rough bore the hole. Do them all to that stage. Grip in the bore with your three jaw and turn and finish the OD all over. Bore a set of soft jaws and grip on the OD and finish bore and face off flange. Mark.

Can you make soft jaws?

Do the hole and that side of the flange.

Flip it over and grip from the inside with the soft jaws; do the outside.

1970's AUD 5" Boxford, standard screwed nose.

Ian

In that case as you can't use expanding 5C mandrels then your best bet is a set of soft jaws and turn down so you can hole on the inner diameter which you turn first.

If in stainless get sawn blanks, let them cut them and wear their saw out .

-- Regards,

John Stevenson Nottingham, England.

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Several folks have suggested something like that. As the actual item is not as robust as the sketch would suggest, is there a danger that it will distort when held by the bore?

Henry

Soft jaws sounds a good idea but I don't have any.

Ian

I suppose that is why I wanted to grip it with something that expands equally all round. I have considered Loctite'ing it to a mandrel then heating it after machining to loosen the bond.

Ian

Do you have any old jaws for your chuck ? If so you can weld some lumps of mild steel on and machine those down.

Sounds horrible and it is but it works.

-- Regards,

John Stevenson Nottingham, England.

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Why not do _all_ the turning and boring with the over-length stock held in the chuck. Then part off 20 thou over length. clamp the parted off part to a faceplate using the top-hat rim and face the parted off end to length. You waste 1/2" of stock per part. Use it to make washers with :-)

This does not seem to be a complicated part.

I would cheat and do the last operation on the surface grinder or shaper, but turning will work just as well.

Starting from sawn blanks 48mm diameter and 45mm long with some machining allowance on both dimensions.

1) Hold in 3 jaw with a few mm sticking out and drill/bore the hole to 42mm dia and 43.5mm depth. Check depth of bore and face off the bottom flange. 2) Turn round in chuck and face off the top flange. Part is now at finished length and i/d. 3) Now make a "pushing button" for use with a running centre - 44mm diameter bit of aluminium or mild steel about 30mm long. Stick the biggest centre drill you have into one end to fit over the nose of the running centre. 4) Chuck some scrap with 45 to 50 mm sticking out and turn that to a 41.95mm diameter plain mandrel. Chamfer the end. You can counterbore the end lightly to a diameter of 35/36mm if you're concerned that the bottom of the bores in your top hat bushes aren't perfectly flat or have a pip in them. Then it will just register around the outside of the end of the mandrel on a rim about 3mm thick. 5) Fit the bored blanks over the mandrel and press back hard with the pushing button and running centre in the tailstock. From now on you'll just be using friction to hold the piece while you turn the o/d and flange.

I use friction to hold more jobs in my lathe than I do chucks. I'm always surprised that no one else ever thinks of using it or realises just how hard you can machine into something held this way before it slips. The same people presumably also won't give a thought to the fact that the only thing connecting the engine in their car to the gearbox and wheels is the same principle transmitting 100 plus bhp.

A llllllll llllllll B lllllllllllllllllllllllllllllllllllllllllllllllll llll llll D llll C llll llll lllllllllllllllllllllllllllllllllllllllllllllllll llllllll llllllll

Whilst I like Dave Bakers option it seems to ignore bore "C"

I would

Buy cut blanks at 47 long Chuck in the "A" area as little as you are comfortable with Rough allparts at "B" and "C" within .5mm of finished OD and ID Turn around, chuck on "B" and complete roughing of "B". Rough out Bore "D". Rough diameter "A". Mark jaw 0 on part to allow putting back up with minimum error. Do all parts Finish bore "D" end face and diameter "A". Main problem now is holding to finish "B" and "C" Make a mandrel as follows

R S T U

111111111111111111111111 111 1111111111111 1 1 1 11 1 1 1 1 1 Drill 10 1 1 1 Tap 10 1 1 1 11 1 1 111111111111 1 1 1 1111111111111111111111111 111

The "R" diameter and length is to allow chucking. "S" will be a slip fit in bore "D". A thick "O" ring will sit on diameter "T" and be compressed with washer "U" clamped up with a piece of 10mm studding through the spindle.

The parts previously roughed and part finished can now be loaded to the mandrel with the "A" face on the chuck jaws and finished on "B" and "C".

Some may say too much picking up and putting down, but the above tends to differentiate between roughing and finishing and the associated tool changes.

Thats what I would do, but I have "all the time in the world".

Oops. Just looked at my post, mandrel should really look like this - (View in fixed font)

R S T U

111111111111111111111111111111111111 111 1 1 1 11 1 1 1 1 1 Drill 10 1 1 1 Tap 10 1 1 1 11 1 1 1 1 1 111111111111111111111111111111111111 111

Use a Fixed Steady to hold the 50mm diameter stock.

Here's a really simple design for an expanding mandrel. You will need a suitably sized socket head cap screw and a nice long socket key - one that will reach the mandrel from the outside end of the headstock spindle. A piece of hex-rod and a spanner would do the job. A

1st-taper tap and tapping drill to match the screw. Make the mandrel out of any suitable material you have, slightly oversize, and drill a hole right through with the tapping drill. Tap a thread from the headstock end of the mandrel until the end of the tap protrudes a little from the mandrel - this ensures that the thread is not cut to full depth at the end. Make two axial saw cuts in the end of the mandrel, at right angles to each other Insert the screw finger tight, put the mandrel in the lathe chuck and skim it to final size, and the job is essentially finished. The following link should make it all clear. the workpiece on the mandrel and tighten the screw from within the lathe spindle, which will expand the mandrel because of the tapered thread and grip the workpiece securely.

You could, of course, use a long threaded bar instead of a socket screw and long key.

The part is described as a "top hat" so one would assume it doesn't have a bore C and isn't meant to be viewed in fixed font.

There you go, my error. I must admit I always assume ASCI art is based upon fixed pitch font, and my reader is setup this way because of problems in the past, however incorrect in this case.

I therefore like your option even more! The "O" ring option that I described is useful though. ;-)

They're only about £20 for common chucks and well worth having. If you can weld you can make them by grinding down an old set of jaws and tacking lumps of mild steel on. You can hold on as little as 1mm of depth with a freshly turned set of soft jaws. I use mine occasionally for making thin washers.

A pro would do your job in two ops by holding the blanks with a few mm sticking out of the chuck, boring the i/d and turning the o/d of the flange part then holding on the flange with soft jaws and turning the rest. Total machining time on a cnc lathe would be about 5 minutes in a nasty material like stainless. You'd use a big F/O carbide insert drill with through coolant to rough the hole out in a single pass, finish with a boring bar, fit the soft jaws, turn the part round and turn the o/d.

On a manual lathe with conventional tooling figure on several hours per part and lots of burnt out tooling. Stainless is a pig. You'll probably start trying to drill the bore with successively bigger HSS drills just to get something you can get a boring bar into, shag them all and wish you'd never started the job.