Matt Harrington | 01/12/2015 11:23:11 |
![]() 212 forum posts 16 photos | 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 udall | 01/12/2015 16:03:06 |
2032 forum posts 41 photos | 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 Stevens | 01/12/2015 19:02:58 |
![]() 1779 forum posts 1 photos | That is, a steel finger, and not a small child's. Just to be certain ... Tim |
jason udall | 01/12/2015 20:17:04 |
2032 forum posts 41 photos | Indeed |
Matt Harrington | 01/12/2015 23:20:11 |
![]() 212 forum posts 16 photos | Thanks. Do you think the finger/needle is within some sort of collet? Interestingly the gimble is spring loaded in one direction. Matt |
Gary Wooding | 02/12/2015 13:31:05 |
1074 forum posts 290 photos | Here's a photo of a similar item in use. |
Ignatz | 04/12/2015 02:42:36 |
![]() 173 forum posts 102 photos | 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 Wooding | 04/12/2015 08:11:00 |
1074 forum posts 290 photos | 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 Harrington | 04/12/2015 08:57:16 |
![]() 212 forum posts 16 photos | 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 Wooding | 04/12/2015 10:24:48 |
1074 forum posts 290 photos | The needle can be moved back and forth when the knurled nut shown in the photo is loosened. |
Matt Harrington | 04/12/2015 17:24:38 |
![]() 212 forum posts 16 photos | I think I will make a collet and knurled closer similar to yours and see how we go. Matt |
Bernard Greatrix | 08/03/2019 21:20:22 |
32 forum posts 6 photos | 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 Connelly | 08/03/2019 21:50:29 |
![]() 2549 forum posts 235 photos | Easier to use a dti and spare centre as shown on this page. Martin C |
Nick Wheeler | 09/03/2019 00:00:37 |
1227 forum posts 101 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 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 Dayman | 09/03/2019 00:31:56 |
2356 forum posts 47 photos | 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 entwistle | 09/03/2019 10:59:00 |
1716 forum posts | If you heat the ball to red for a few minutes it should be soft enough to drill Roy |
Ian Hewson | 09/03/2019 12:31:55 |
354 forum posts 33 photos | Stainless steel balls are available on the net, use them for governor balls, drill ok without heating. |
Maurice | 09/03/2019 14:28:08 |
469 forum posts 50 photos | 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 Fury | 09/03/2019 18:30:44 |
![]() 446 forum posts 88 photos | 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..
|
JC54 | 09/03/2019 19:25:10 |
![]() 154 forum posts 14 photos | 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.. |
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