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Centre finder?

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FMES09/03/2019 20:05:09
602 forum posts
2 photos
Posted by Bernard Greatrix on 08/03/2019 21:20:22:

Hi

If this post isn't dead - does anyone have any simple plans for this device. The links to a similar thread appear to have expired

It has been suggested to me to help centre work in a 4 jaw chuck.

Snag is the old guy who described it to me said the hardest part was drilling a ball bearing.

I think he was having me on, but I can't be sure

Any comments welcomed

regards

Bernard

Edited By Bernard Greatrix on 08/03/2019 21:24:51

I used a phosphor bronze ball in mine.

Regards

Michael Gilligan09/03/2019 20:22:55
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15704 forum posts
687 photos
Posted by Bernard Greatrix on 08/03/2019 21:20:22:

Snag is the old guy who described it to me said the hardest part was drilling a ball bearing.

I think he was having me on, but I can't be sure

Any comments welcomed

.

I recently posted a link, on another thread, to this firm: **LINK**

https://www.animationtoolkit.co.uk/12mm-stainless-steel-ball-x-10/

... Might also be of interest here.

MichaelG.

Nicholas Wheeler 109/03/2019 22:15:45
314 forum posts
19 photos

Here's mine:

p_20190309_215151.jpg

and disassembled:

p_20190309_215238.jpg

The rose joint was bought from one of the odds&ends suppliers at an ME show for £3, and is 8mm bore. The mounting bar was clamped in the toolpost, and I used the lathe to drill and tap the hole for the rod end. The rod is 3mm silver steel turned to a taper on each end and hardened(in the gas stove) at the working end. There's a stop soldered on 1/5 along the rod, nearest the working end; this gives a 4:1 ratio and is plenty close enough for anything I do. The centre parts are 10mm steel, turned to a sliding fit in the rod end, and screw together with an M8 thread. The spring is from an assortment bought for just this sort of job; nothing technical, just 'springy'.

That was a productive 1/2 hour in the workshop, making it up as I went along.

Maurice10/03/2019 00:23:15
464 forum posts
50 photos

If the centre punch hole is not far out of true, you can nip an automatic centre punch, between the off centre dimple and the front of a half inch drill chuck in the tailstock, with the jaws retracted, and get the body of it running true with a DTI. Better still, make a spring loaded centre with a smooth body, and theother end with the a centre hole or a point, and use in the same manner. Not as instantly visible for truth as a long pointer, but worth bearing in mind perhaps.

Maurice

Howard Lewis10/03/2019 08:05:17
3267 forum posts
2 photos

If you want to use the "two centres" method, look at the front cover of No.28 in the Workshop Practice Series, by Tubal Cain. A very useful method.

Lacking a centre with a centre drilling at the back end, made my own.

I used a piece of Silver Steel, about 5/8 - 3/4 diameter, about 3 inches long, (so long ago, can't remember exact sizes, and too idle to go and check ) , clocked in a four jaw and centre drilled , and then turned it around, recentred it before turning a 60 degree taper on that end.

Howard

Hopper10/03/2019 08:59:16
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4530 forum posts
94 photos

I think this type of centering tool was popular back when dial indicators were expensive exotica beyond the reach of many home hobbyists. Fun to play with though.

duncan webster10/03/2019 11:11:15
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2588 forum posts
33 photos

I just have a bit of 3/16" rod about 12" long with a point on one end. Grip it in the tailstock chuck and poke the point into the centre punch mark and run your DTI on the outside. The point doesn't need to be concentric as the rod isn't rotating. What I do to keep the point pushed against the pop mark is arrange for the handle on the tailstock handwheel to be off balance to push the rod along the bed. Saves taking the chuck out to put the centre in. If I were to improve it I'd loctite a 1/2" diameter collar up at the pointy end, then you could use the dti with more eccentricity. The fact that I haven't bothered in all these years means that either I'm bone idle, or it wouldn't make that much difference

Bernard Greatrix12/03/2019 15:13:04
32 forum posts
6 photos

First apologies for appearing to ignore all your replies, I've been away on a long weekend.

I am greatly appreciative of all your comments and suggestions and went away inspired to make something.

I tried cooking a 1/2" Ball bearing (I don;t know what type of steel - it was 'rescued' from a dead ball race). I got it bright red hot and allowed it to cool slowly between the two firebricks that I'd cooked it in. Rather disappointed - the oxidation scale was rather heavy and it was still too hard to file a flat on.

I have - somewhere- a small double ended rose bearing, but have not been able to find it, so I'll put that on the back,burner for now.

So using materials that I had lying around I've a made a centre finder - al la Tubal Cain but found that until I get close to centre my dial indicator kept dropping off the side. I'll try again when I get some larger diameter material to add a collar, as suggested above.

I've made a gimbal model (see picture) which does work quite nicely. I just need to get some 3mm rod to complete the build. The photo shows just a piece of thin wire It's probably not as precise as I would have liked as I used odd pieces of material that I had and the smallest available screws are 6BA.

Again many thanks for all your replies

regards

Bernard

imgp3536.jpg

I've also ordered some 1/2" threaded balls off the net. They look too useful not to have any

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