How would you make these

[Ian ParkinParticipant @ianparkin39383]

How would you go about making 2 matching versions of this finial?

I have turned pieces threaded the base so i can hold it in a fixture but how on earth do i turn the small features?…hand held gravers perhaps like woodturning

Ian

[Ian ParkinParticipant @ianparkin39383]

[David Standing 1Participant @davidstanding1]

I would rough it out with pieces of purpose fine ground HSS, then finish with small files, emery paper and Scotchbrite type abrasive pads. Fiddly, but easily doable.

[egaParticipant @ega]

What is the material and have you got plenty of it?

If you have enough to practise on then you will probably end up with two that are sufficently alike – I am assuming the use of miniature hand-manipulated tools, although the main features could be established with a conventional parting tool.

[David Standing 1Participant @davidstanding1]

I'd assumed by the patina it is bronze.

[Martin KyteParticipant @martinkyte99762]

Definitely a hand turning job if you feel up for it. I recently made George Thomas's hand truning rest for the Myford and I use it all the time. You don't need to go to such elaborate lengths as that but I am sure that once you have seen how usefull and above all quick it is to freehand turn features you will get sold on it.

regards Martin

[Mick B1Participant @mickb1]

I'd do it with 3 or 4 carefully-ground form tools in 3 stages – mushroom point and front hemisphere, back taper to waist, and base flange/stem.

I've used hand-held tools for wood, but don't think I'd be happy trying it on something this small.

[JasonBModerator @jasonb]

Same as Mick. a couple of form tools then touch up with files and hand graver as needed.

The other option is to draw it out in CAD and then produce a set of co-ordinates at even spacing along teh length of the part so you can feed a tool into the set diameter then blend with file and graver. That show I did these couple of decorative bases. Just thought I could have entered those as candle stick holders

[Neil WyattModerator @neilwyatt]

That's a long cut on a small piece for a form tool, so with my new-found skills I might lost-PLA cast it then carefully finish it in the lathe using emery supported by a stick.

Neil

[JasonBModerator @jasonb]

That is why we suggested more than one form tool, a wise man would also use tailstock support when taking a big cut with a form tool

[Ian ParkinParticipant @ianparkin39383]

I’ve just done some testing on the sample of brass that i’m Using

I remembered that i have a 20 degree pointy tool so i measured the original to a set of co-ordinates from base and diameters and using the dro just plunged in to get the diameters and then a quick smooth with emery and a scotbrite pad and job looks good

The originals were brass just heavily tarnished

[Mick B1Participant @mickb1]

Posted by Neil Wyatt on 07/12/2017 16:15:10:

That's a long cut on a small piece for a form tool, so with my new-found skills I might lost-PLA cast it then carefully finish it in the lathe using emery supported by a stick.

Neil

I wasn't thinking to form the back taper – do that single point on the compound with a radiused tool. I'd need to play about to see if the flange could be done with the same tool.

Do the point and ball-nose first with minimal chuck protrusion, then feed a bit more out for the back taper and maybe the flange, then a bit more for the shank. It'd be tedious to make half a dozen that way, but Ian only wants 2.

 

Edited By Mick B1 on 07/12/2017 17:16:18

[David Standing 1Participant @davidstanding1]

There is so little meat in the waist of that, I would first try by parting it off to length + 2mm or so, turning down the shank, then use a fine centre drill and fine point rotating centre in the tailstock to support it (or even a well lubricated half dead centre), do as much work as possible between centres, and face off the last 2mm or so and lose the centre drill hole towards the end.

If the flange above the stem is the same diameter as the widest point near the top, and collets are available, for the last operations on the tip after it is taken out of the centres I would slide the finial back in the collet so the main part of the body is supported.

It will be tight to do between centres, but the whole job will be fiddly regardless of how it is approached.  I fear done without centres it will just snap at the waist if any lateral cutting pressure is put on.

 

Edited By David Standing 1 on 07/12/2017 17:33:17

[Mick B1Participant @mickb1]

Posted by David Standing 1 on 07/12/2017 17:30:40:

There is so little meat in the waist of that,

…

Edited By David Standing 1 on 07/12/2017 17:33:17

I was thinking of a succession of cuts with a sharp tool, only coming down toward final waist diameter on the last couple of passes. Get the front part of the taper close to the ballnose close to size first, so that you're not applying side pressure any distance away from the narrow waist. You might need to divide the taper into 2 or 3 lengths working back.

[David Standing 1Participant @davidstanding1]

Posted by Mick B1 on 07/12/2017 17:59:34:

Posted by David Standing 1 on 07/12/2017 17:30:40:

There is so little meat in the waist of that,

…

Edited By David Standing 1 on 07/12/2017 17:33:17

I was thinking of a succession of cuts with a sharp tool, only coming down toward final waist diameter on the last couple of passes. Get the front part of the taper close to the ballnose close to size first, so that you're not applying side pressure any distance away from the narrow waist. You might need to divide the taper into 2 or 3 lengths working back.

Mick

I think you could be right. Everything but the last bit of the waist first, and finish off there – with the advantage that is the bit nearest the chuck.

[John ReeseParticipant @johnreese12848]

I was thinking of turning freehand using gravers. An experienced turner could probably pull it off. I certainly could not.

[Michael GilliganParticipant @michaelgilligan61133]

Ian,

You will presumably recognise this pair:

Looking at the machining marks, rather than the polish and wear: I would say that 'beyond all reasonable doubt' they were turned by plunge cutting with a form-tool.

MichaelG.

[Mick B1Participant @mickb1]

Posted by Michael Gilligan on 08/12/2017 18:21:16:

Ian,

…

Looking at the machining marks, rather than the polish and wear: I would say that 'beyond all reasonable doubt' they were turned by plunge cutting with a form-tool.

MichaelG.

…but that doesn't necessarily mean it'd be practical for a home machinist to make 'em that way. They look like maybe stair-rod ends, turned in thousands with circular form tools, possibly with rear support, on Swiss-, cam- or multispindle autos.

[EmgeeParticipant @emgee]

Major diameter 19mm, M6 thread.

Emgee

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Mick B1 on 08/12/2017 18:37:15:

…but that doesn't necessarily mean it'd be practical for a home machinist to make 'em that way.

.

I never suggested it would be, Mick

… It was merely a point of reference.

[and a more detailed image of the item in question]

MichaelG.

.

Major diameter approx. 8.6mm

Edited By Michael Gilligan on 08/12/2017 19:17:45

[Michael GilliganParticipant @michaelgilligan61133]

Question:

Now you've seen the shape in some detail …

Can anyone suggest a practical way for Ian to make a pair of these ?

Difficult as it may be to produce and use: The form-tool looks an increasingly attractive proposition to me.

MichaelG.

Edited By Michael Gilligan on 08/12/2017 20:19:18

[JasonBModerator @jasonb]

See my post at 15.53 yesterday for two practical methods, one Ian has already tried and got good results on a test piece.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 08/12/2017 20:24:27:

See my post at 15.53 yesterday for two practical methods, one Ian has already tried and got good results on a test piece.

.

Sorry, Jason … I'm confused

The first of your suggestions was to use form-tools.

Are we in 'violent agreement' or am I missing your point ?

MichaelG.

.

P.S. for the avoidance of inviting any gratuitous pedantry … In this instance, I see no significant distinction between using a single, complex, form-tool and using multiple simple ones.

[JasonBModerator @jasonb]

I think we are in agreement that a form tool or tools would do it and should also ensure a matching pair.

My only worry about a single tool is that you can't support the end and form the whole shape in one without risk of snapping at the lower waist. I would go for two tools easily filed up from a bit of 1/8" gauge plate, first tool from top to largest dia of the pear shape. Then draw a bit more bar out of the chuck and using a female center in the tailstock do the rest with a second form tool. Finally draw out some more and use a parting tool to do the bottom parallel section before parting off.

If cross slide readings are noted the second one should match the first. Do any polishing or refining before parting off as it is easier to hold while still on the rod.

J

[Michael GilliganParticipant @michaelgilligan61133]

That's OK then, Jason

MichaelG.

.

Incidentally … Do you remember Pop-it Beads ?

https://theloveofvintage.wordpress.com/2012/07/29/popits/

I remember my Dad making some special Brass components that 'popped' into these.

Much less complex shape than Ian's finials but also much smaller.

… these balls, on very slender necks, were successfully produced in a single plunge.

Edited By Michael Gilligan on 08/12/2017 20:54:08

Edit: corrected typo Poppit Pop-it

Edited By Michael Gilligan on 08/12/2017 21:00:42

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