Wiggler wobbler call it what you like.......

[Jonny]

Used to use the wiggler type up to 12 year ago, got another one and never used it in 10 years.

Then went on to the digital light up type and never looked back. However dont use all the time for centring plate or bar etc a milling cutter works just as well. Great if you dont want to mark the outer edges if using a cutter.
Find they really come in to their own when aligning vices in conjunction with DRO or scales.
This vid shows a dfferent mechanical type and look very easy to use plus made well. Later in the digital but i have that exact same one plus another better one and both says do not spin. If you spin it and finding edge on aluminiums, it will pick up and gouge the job edge very quickly build up the tip and throw a wobbler scrapping it.

I did import one of these from California around 7 years ago may be more before they were well known.

Bought it around £60 tried it and never used again, ok for plate work centring above holes thats it. You have to zero them as well with three screws.

[Ned Ludd]

Hi Guys,
We are of course forgetting the other form of edge finder, which is the centring microscope like the one from Hemingway Kits; http://www.hemingwaykits.com/acatalog/Centering_Microscope.html. If I get around to finishing mine, that will be another couple of per cent off my tuit list.
Ned

[RichardShute]

Yeah, they were the one's I was originally looking at. But look at the one in the michael decker link I posted. It just looks like a 'proper' piece of engineering...

I reckon making one might be the way forward. I don't have a clue how they work, but I've got a few ideas that might be worth a shot. In particular I reckon with the use of modern sensors it might be possible to build an electronic version that is much shallower...

I came across the link you quoted a month or two ago and as someone (JS??) pointed out that supplier specialises in supplying research labs and similar academic bodies so inflate the price according to what they can get away with, not what's 'reasonable'. That said, they are not generally cheap, I just go very lucky on fleaBay.

The height from the bottom of the quil to teh tip of the probe is a minimum of about 3", depending on whcih probe you have selected. The mechanism is very simple. There is a plate about 3" long and 1" wide which is pivoted at the mid point of each end. The probe causes it to rock one way or the other depending on whether it is inside a hole or outside a bar or on a not-normal swashplate. There is disc as I recall, a bit bigger in diameter than the width of the plate resting on the top of it, so that irrespective of which side of the plate rises or the orientation of the rocking plate as you rotate the spinde, the disc always rises. This presses the DTI probe which is mounted in the non-rotating body of the tool.

There are some additional details including a friction lock for gross adjustment so that it can cope with diameters from zero up to about 12" and some internal adjustments, but essentially that's it.

As others have commented, most of the time I just touch one side then the other with something, (often the cutter if I'm going to machine the outer surfaces later anyway) and split the difference. As long as the witness mark is the same width on both sides, it doesn't even matter how deep it is. I haven't got DRO's, but I don't find it a major issue - don't miss what you've never had. Though no doubt if I did get them I'd be a convert.

Richard

[Corvus corax]

BTW. There were a while ago pictures and videos about Joachim Steinke“s edge finders in HMEM, in here
http://www.homemodelenginemachinist.com/index.php?topic=10633.0
They are just small ball bearings mounted to a bit of round steel. I "built" one, their simplicity is almost ridiculous. But the accuracy and ease of use are wonderful.
  

These work well and are quite popular around these parts.
I was introduced to them by a Hungarian machinist I used to work with. Conversely, he laughed at my use of cigarette paper for finding edges and height on the mill.
Said he had only ever heard of the British doing that.
Oh well I did come from one of the old colonies. ;-)

[picclock]

That bearing idea is great. I just bought a Starrett 827MB tpye finder, but found that it made marks on aluminium.

Also, it would be very easy to make several of the 'normal' sizes just using silver steel bars. Could engrave or mark them with the bearing diameter.

Not sure how they would be affected by the play in the bearing though.

great idea

picclock

[Stilldrillin]

That pip on the left has been put on the shaft using gauges, DRO, Joderell Bank telescope and a Kray computer so it's spot on.

The pip on the right has been put on after the axis has been moved sideways by 0.001" and you can see it's off centre.

Sooo the MK1 eyeball CAN work to a thou.

John S.

John.
Mine still does. Can't be bothered with all the faffin' about with unnecessary technology...... 

David D

[bry1975]

At our old machine shop we use to use a rizzla smoke wrappers works everytime. 

[John Rudd]

At our old machine shop we use to use a rizzla smoke wrappers works everytime. 

Used to use them for setting ignition timing on two strokes...

[Corvus corax]

At our old machine shop we use to use a rizzla smoke wrappers works everytime. 

As I said that's how we always did it.
I always used Rizzla red papers. Lately, all I can get are the blue ones.