Centre finder?

[Matt HarringtonParticipant @mattharrington87221]

[Matt HarringtonParticipant @mattharrington87221]

Hi,

I was given this tool the other day:

It is more than likely a centre finder (?) but does anyone have a similar tool and able to tell me what bits are missing? (It is made by J Whitworth & Co)

(There are a few more photos in an album I have just created)

Matt

[jason udallParticipant @jasonudall57142]

It is indeed a centering aid…
A finger fits through the gimbled bit…a point on either end..one short ( near the gimble)..wjich is engaged with the center mark of the stock..the other end wobbles around describing a much larger circle ..the stock is adjusted in the (four jaw) chuck until this wobble is minimised. ..with a typically five to one ratio a very small error can be detected…

[Tim StevensParticipant @timstevens64731]

That is, a steel finger, and not a small child's. Just to be certain …

Tim

[jason udallParticipant @jasonudall57142]

Indeed

[Matt HarringtonParticipant @mattharrington87221]

Thanks. Do you think the finger/needle is within some sort of collet? Interestingly the gimble is spring loaded in one direction.

Matt

[Gary WoodingParticipant @garywooding25363]

Here's a photo of a similar item in use.

Sorry for the typo, for sring read spring

[IgnatzParticipant @ignatz]

Does a centering finger like this have to run off of a center-bored hole (as in previously-turned item) or would it also work pressed into a center-punched witness mark on new, not-yet-turned work?

[Gary WoodingParticipant @garywooding25363]

Posted by Ignatz on 04/12/2015 02:42:36:

Does a centering finger like this have to run off of a center-bored hole (as in previously-turned item) or would it also work pressed into a center-punched witness mark on new, not-yet-turned work?

Yes, that's what it designed to do.

I'm afraid that my photo was created in a hurry and, to save time I just stuffed something in the 3-jaw. In practise, the workpiece would be in the 4-jaw independent with a centre-punched mark that needs to be centred. The pointed end of the finger follows the centrepop as the chuck is rotated, and if its not truly centred the other end wiggles even more because of the difference in the lengths either side of the support.

[Matt HarringtonParticipant @mattharrington87221]

Thanks Gary,

In your centre finder is the pin fixed or does it slide along and the knurled part used to fix the pin in situ? I'm obviously missing parts here and I still cant see how the small attachments (stored in the body) are used on it.

Matt

[Gary WoodingParticipant @garywooding25363]

The needle can be moved back and forth when the knurled nut shown in the photo is loosened.

[Matt HarringtonParticipant @mattharrington87221]

I think I will make a collet and knurled closer similar to yours and see how we go.

Matt

[Bernard GreatrixParticipant @bernardgreatrix61453]

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

[Martin ConnellyParticipant @martinconnelly55370]

Easier to use a dti and spare centre as shown on this page.

**LINK**

Martin C

[Nick WheelerParticipant @nickwheeler]

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

It's easier to make one using a spherical bearing(rose joint). I'll sort a photo of mine in the morning, but it's not something I've used very much as I rarely use the four jaw chuck

[Jeff DaymanParticipant @jeffdayman43397]

Kozo Hiraoka described a nice simple version of this type of tool in his "building the Shay" book. Found a link in a different place to it, here:

https://thehobbyistmachineshop.com/cms/workshop/kozo-s-wliggler

The ball in his version is brass, I believe.

[roy entwistleParticipant @royentwistle24699]

If you heat the ball to red for a few minutes it should be soft enough to drill

Roy

[Ian HewsonParticipant @ianhewson99641]

Stainless steel balls are available on the net, use them for governor balls, drill ok without heating.

[Maurice Cox 1Participant @mauricecox1]

I have one of these, similar to the photos. The collet that holds the pointer is spring loaded to allow the pointer to move endwise if the centre hole is wildly out of adjustment. I can't tell it the photographed one does this, but it would seem to be desirable.

Maurice

[Fowlers FuryParticipant @fowlersfury]

Many years ago in one of the ME mags, it was suggested that you could dispense with gimbals etc and just cut a thin slice of india rubber (= pencil eraser) and fix in a frame. The pointed rod was simply pushed through to provide the magnified "wobble". I remember trying the idea and after cutting a slice from an eraser about 1/16th thick (?) it worked well enough for setting up in a 4 jaw.

Much later, the gimbal below was removed from a broken lab item. The gimbal looks easy enough to make, probably more so than drilling steel balls..

[JC54Participant @jc54]

Another simple method is to cut a short piece of box section (10mm) that will fit in the toolpost fill with silicon sealer then push a long "needle" through it. Same idea as FF. This makes a very quick cheap wobbler..

[FMESParticipant @fmes]

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 GilliganParticipant @michaelgilligan61133]

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.

[Nick WheelerParticipant @nickwheeler]

Here's mine:

and disassembled:

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.

[Maurice Cox 1Participant @mauricecox1]

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

[Author]

Posts