Thread: Ball Centres

Is this a crazy idea?

Nope,but you arent the first if thats what you're thinking.

Stuart

p.s. I have a book some where thats has a little about them but I dont seem to be able to find it just now

Nope, they use ball centres for tapers cut using the off set tail stock method and also the boring head in the tail stock set up.

Dave

Probably not however it would depend on the weight being placed upon the triangle and the material being used.

Thanks guys. I didn't really think I was the first to think of it. Seems pretty obvious once you start offsetting your tailstock. Which I'm doing a lot. But a quick search online found very little. Just a short thread on PM.

Dave, the ones you've seen, where they fixed on one side or a floating ball like my sketch? Below is the pic from the PM thread. But not having a ball turner and not wanting another tooling project, it seems so simple to drill two holes and trap a ball. I also don't really like the way those neck down so much.

Scott, do you think my revision below would be safer?

Stuart if your book ever turns up I would be interested to know what it says. My TAFE book doesn't mention them.

I wonder how hard it would be to get hold of tungsten carbide balls to silver solder into a socket.

Like this? Ballstungstencarbide - Small Mechanical Parts And Components

Looks expensive, although one is $12.95, I expect you'd need one at least 10mm diameter to give enough strength to stay soldered in place.

Bryan,

1. A photo of a selection of ball centres - can you pick the origin of the threaded shank balls?

2. A John Stevenson photo of ball centres used in conjunction with a boring head turning a taper.

Frank.

Added Later: I tried to replace the John Stevenson set up photo with a larger, clearer version, but can't find out how to delete the photo already in the post. If anyone would like to see the higher resolution photo I will post it separately.

Later Again: Thanks to Stuart, I have been able to substitute the better photo, which now appears below.

Frank.

Hi Bryan,
I'll have a look

Hi Frank,
when you go into edit, click "go advanceed" then scroll down a little "manage attachments", there should be a "remove" button next each file name.

Stuart

Originally Posted by franco

1. A photo of a selection of ball centres - can you pick the origin of the threaded shank balls?

They remind me of spherical joints, like you see on linkages, eg car gear shifts.

Added Later: I tried to replace the John Stevenson set up photo with a larger, clearer version, but can't find out how to delete the photo already in the post. If anyone would like to see the higher resolution photo I will post it separately.

I would like to see that. Thanks Frank. It looks like he's cutting a fairly steep taper - compared to a Morse anyway. I wonder just how far you can trust this setup?
And now I'm confused about terminology. Is a large included angle called steep or shallow?

Originally Posted by Stustoys

Hi Bryan,
I'll have a look

Hi Frank,
when you go into edit, click "go advanceed" then scroll down a little "manage attachments", there should be a "remove" button next each file name.

Stuart

Thanks Stuart. The original photo is now replaced with the higher definition one.

They remind me of spherical joints, like you see on linkages, eg car gear shifts.

Hi Brian, they are actually tappet adjusting screws from an old pre-hydraulic valve tappet engine, in this case 1927 Chevrolet.

Not too sure about the taper description - I think it would be a steep taper, but I am open to correction.

Regards,

Frank.

Hi Bryan,
Sorry found one but it adds nothing to whats been said already. There might be another but I dont think it adds a lot more. Of course you'll use a tool that directs most of the cutting force along the bed not across it.

Stuart

Frank, are the Chevy centres yours? If so how do you find using them? In particular, have you ever had anything get away from you? What would be the approx ball dia? How deep would you normally set them?

Stuart, thanks for that. Don't spend any more time looking.

Originally Posted by Bryan

Scott, do you think my revision below would be safer?

Hi Bryan,

Safety, as such, wasn't on my mind. I was thinking more along the lines of the stress on the points of the angle(s) which you've addressed in the second plan. Without doing the maths and knowing what sort of stresses will be placed upon the model, it looks a better now