Centre Finding Round Bar with Edge Finder – Big Deal?

[EmgeeParticipant @emgee]

+1 for the same method used by Ramon and Paul, not as easy as the Haimer but spindle to job dictates what can be used.
I also use an electronic edge finder to locate bore centres but if total concentricity is needed I always use the spindle mounted indicator revolved in the bore by hand.

Emgee

See the set-up here https://youtu.be/KRiiEywpzZk

 

 

Edited By Emgee on 30/11/2020 13:49:42

[Dr_GMJNParticipant @dr_gmjn]

Thanks all.

I'm just wondering what, in practical terms, accuracy difference we're talking about here, between a coaxial centre finder and an edge finder, and even if it's relevant? By the time I've set the coaxial thing up, I doubt there's much time saving – not that saving a minute (or even an hour) or so is important either way.

I mean, as you can see I faced the stock in the lathe, and found the centre in the mill with the edge finder. It looked spot-on coincident with the machining marks using a pointer in the chuck, so I went ahead and offset it for the throw.

Once it was replaced in the 4 jaw, apart from any cylindricity error in the stock itself, there will be an error in centering the offset, another error turning it, clearance in the eccentric strap, slop in the valve mechanism…etc etc, all of which may add or detract from any edge finder error.

At the end of the day, just how accurate does it need to be for the things I'm building? As I mentioned, the drawings aren't toleranced. I found the suggestion of "just buying the right tool" (at a cost of £60-odd) to be a bit stupid to be honest.

[Howard LewisParticipant @howardlewis46836]

It is too easy to buy a tool, only to find eventually, that it was used just for the one job. (Witness a couple of gear cutters and a few Taps in my keeping! )

Wherever possible, I have the Vee Block against the moving jaw, so that the wiggler can contact the fixed jaw. Knowing the diameter, the table can be offset (after locking the Up and resetting the Zero to accommodate backlash ) to bring the job centre under the centre of the spindle.

Howard

[Ramon WilsonParticipant @ramonwilson3]

In my time I've used Starret wigglers – still have them, cylindrical edge finders – still have them, just never use them at home. Used Renishaw probes and light emitting electronic edge finders too.

Having nice posy kit is one thing – paying out for it is another. Alternative?

Packet of 5 6mm dia x 60mm Hardened and Ground dowels – eBay – £1.85 £3.65  Packet of green red or blue ciggy papers – pence!

Draper DTI – in constant use – In the drawer is a Swiss Compac .002mm DTI – ( Hmm I paid a lot of money for that for use at work) never use that either

Does me fine for what I do and I do work accurately – well, I'm quite happy to think my results confirm that

It really is "Pays yer money etc" the main thing is just to get on with the job

 

Regards – Ramon

 

 

 

Edited By Ramon Wilson on 30/11/2020 17:04:49

[Anonymous]

The Haimer Centro shown in my previous post claims ±0.003mm centring accuracy for shafts and holes. The Haimer Zero Master claims ±0.01mm accuracy for axial and radial probing. I've got a wiggler set somewhere but have never used it. I don't have a mechanical edge finder. In the past I used fag papers and either the tool in use or a piece of silver steel. Accuracy was probably ±0.04mm at worst. I still use fag papers on a regular basis and it's my go to method for centring on a horizontal shaft for cross drilling.

I've learnt two things today by reading the Haimer manuals. The Centro can be used to check perpendicularity. I'll use that next time I tram the Bridgeport. The Zero Master manual gives a procedure for centring on a shaft or hole, which is a truncated form of Osborne's Maneuver.

Andrew

[BazParticipant @baz89810]

Hailer are ok if you have a spare four inches headroom and can afford about three hundred quid, I think I will stick to my wobbler after all we are not trying to split atoms, at least I’m not, most of my fits are more rattling than precision.

[duncan webster 1Participant @duncanwebster1]

I've just tried a centre finder as used by OP on a bit of 30mm bar and a flat. It didn't seem to 'flick' as much on the round bar. I suspect smaller bar would be even smaller flick.. Despite my misgivings it gave the same answer within 0.01mm. Important to get it on the X axis centreline.

Edited By duncan webster on 30/11/2020 17:34:47

[Jeff DaymanParticipant @jeffdayman43397]

"

It really is "Pays yer money etc" the main thing is just to get on with the job

Regards – Ramon"

My sentiments exactly. Most things I build do not need accuracy anywhere near the capability of Haier centre finding, and most times a cigarette paper between tool and work is plenty accurate for the job at hand. Zig Zag white ones are still available locally. Apparently popular too with the local hemp head practitioners. Never lit one on fire on purpose here in my shop though, just use 'em for setup.

For round work in a vise, picking up the vise jaw (by any method) is so much easier than using a wobbler on the round bit, and is pretty foolproof, so I have no idea why anyone would bother fooling with a wobbler on the round bit. It just adds locational uncertainty, it does not improve any skill in particular.

To the OP, again, Just make stuff, don't stress on the details for the last thou. The more you do the better and more accurate you will get. To quote Stewart Hart "a little clearance never got in the road."

[Dr_GMJNParticipant @dr_gmjn]

Posted by duncan webster on 30/11/2020 17:33:13:

I've just tried a centre finder as used by OP on a bit of 30mm bar and a flat. It didn't seem to 'flick' as much on the round bar. I suspect smaller bar would be even smaller flick.. Despite my misgivings it gave the same answer within 0.01mm. Important to get it on the X axis centreline.

Edited By duncan webster on 30/11/2020 17:34:47

Thanks Duncan. Must admit I don’t notice any difference with mine, it’s a definite flick whatever it touches, and it’s repeatable as proved by the DROs. However I don’t recal ever trying it on an inside diameter.

What did it give the same answer as? Did you mean you tested it against the round, and also against a vice jaw that it was clamped with? Whatever it was, I can’t ever see 0.01mm posing me any issues whatsoever!

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