View Full Version : Centre Finder

John Stevenson
05-05-2003, 07:39 PM
I have 12 bearing blocks to do out of rectangular stock. These need to be identical and are offset in the bar stock.
I have marked them out with a vernier hight gauge and spotted them with an optical punch so these are spot on. The first one I setup with a sticky pin and dial gauge. Didn't take long but I wanted to speed it up a bit so I went into the shop tonight and made this centre finder up.

Not saying this is unique, not much is, but it's something I cobbled up in about 30 minutes.
Pic at:-

The body is a bit of hex bar about 6" long in total. No reason for the hex, it could be round but I had three design changes between the saw and the lathe http://bbs.homeshopmachinist.net//biggrin.gif
About 1 1/4" is turned down one end to about 1/2 so it can fit in the tailstock chuck. This part is drilled and reamed 1/8" for 1 1/2"
It's then turned round and drilled to meet the 1/8" hole to about 1/2" diameter. This is only clearance so it doesn't matter about size.
Next a bit of 1/4" plate was welded on to form an ear for a clock to bolt to.
Last bit is a piece of 1/8" drill rod or silver steel with one pointed end and the opposite end held in the reamed hole with a small grub screw.

Method of operation:
Put atachment in chuck, offer up to the centre punched mark and rotate the lathe by hand. Any run out will be shown on the clock. Adjust the 4 jaw as per normal using only one pair of jaws at a time.
Got the second one setup in just less than 30 seconds.

I make no apologies for the state of the attachment. This was a rush job and needs play a greater part than shiny surfaces. It works and it's quick.
Feel free to make or modify as it suits.

John S.

Forrest Addy
05-05-2003, 08:38 PM
When I was an new apprentice and when I was sure my trade instructor was an ogre instead of a harsh talking softie, he put me in the school shop to make a dozen center finders similar to those you made.

He had me cut 8" pieces of 1/4 drill O-1 rod, hand forge the end flat 1/4 wide x 0.050 " x 1 1/4 long and make an upset bend 90 degrees to the side. Following McBride's sketch, I made a U-bend 180 degrees on a 3/16" radius so there was a springy tab in line with the drill rod axis.

Then I coned the opposite end 60 degrees and drilled a #3 center hole in the tab concentric with the ground diameter of the drill rod.

Set the cone in a center punched hole and nudge the tailstock center in the center holes of springy tab and you have a centering thingy with limited spring accomodation of axial movement.

It served the same function as the gadget you show. I still have one someplace. Wish I could post a picture.

Herb Helbig
05-05-2003, 09:05 PM
John -

Neat gadget! Neat picture. I guess if you have an alternative way to hold the clock, you could just put the drill rod directly in the tail stock chuck. Or am I missing something?


05-05-2003, 09:32 PM
Pretty neat John.. My magnetic base would work too? We used to line up couplings with two dial indicators, check the weeble and wooble.

What I am still learning, all the set up can be ruined by one lil chip in under the morse taper or in the kwik switch tool holder.

Thanks for the post.

05-05-2003, 09:50 PM
John Stevenson:
Looks quite usable to me - Bodging at its best!

BTW - you have nice flat stock, must be British Steel! http://bbs.homeshopmachinist.net//biggrin.gif We had a British Steel distributor here and their stuff was beautiful too - even the Cast bar 20" in diameter. http://bbs.homeshopmachinist.net//eek.gif

05-05-2003, 09:51 PM
Ideal made a similar item for their mechanical indicator years ago. It combined the spring loaded type wiggler with a holder for the indicator. Patent has long since expired.
I prefer the Starrett gimbal center finder for quick setup. Can get as close with that as with most indicators in no time at all.

John Stevenson
05-06-2003, 03:50 AM
I just wanted something that was permanant.
This was an old clock off a redundant test rig so I can leave it setup and just pop it in as needed.

John S

Paul Gauthier
05-06-2003, 07:02 AM
Nice and quick I like that. Good job.

Paul G.

John Stevenson
05-06-2003, 08:48 AM
Mark 2 released.
Ok quick mod this morning before I stared on the other blocks.
Took the dial gauge clamp off and just put a simple 2 holes link on to tilt the dial gauge so it can reach the end of the 1/8" rod.
Works a lot better this way.


John S

G.A. Ewen
05-06-2003, 09:02 AM
Very nice. There will be on in my tool box before long. http://bbs.homeshopmachinist.net//wink.gif