Wiggler or edge finder?

I have just been looking at arcEuroTrade and they have two types of edge finder.

There is the wiggler with its ball ended rods and there is a more solid looking type with a spring loaded end.

I understand how they work, but I dont understand the merits of each type.

Any thoughts?

Adrian

Both, plus a decent 3D tester, they all excel in different ways.

There is also the simple bearing edge finder.

**LINK**

Agree with Nick both wigglers and edge finders excel in different ways. A 3D Taster is a wonderful instrument but I pretty much don't use mine.

In practice there is a lot of overlap what they do and where they are used so its best to make one type your preferred device and get really good at exploiting it for most jobs and fill in with the other types when appropriate.

I'm a wiggler person because I like the very clear and very consistent indication that a good wiggler gives. In particular the ability to see what its doing from a significant distance. The latter has become particularly important with increasing age. As Bridgeport X-axis handles are on the ends of a relatively long table, I'm often too far away to have totally sharp view of the centre finding device unless I switch glasses.

My wiggler is a Huffam, somewhat more expensive than the Arc Eurotrade offering but better engineered. The Huffam supports the pivot ball via a spring loaded nylon pad giving a very consistent and low drag. Hence it reacts very quickly and is very repeatable.

The collet style sets as sold by Arc Eurotrade tend to be a bit stiffer in action and sensitive to the exact tightness of the collet.

I'm quite happy to use the Huffam in single sided fashion to find an edge directly and simply offset the found dimension by the probe radius on all but very precise work. In contrast I feel the collet type are best used in centre finding mode where you touch off both sides of the work and calculate the centre. So easily done with a DRO that it should probably be your standard method if you have one. Touching off both sides automatically compensates for any slight variation in offset due to collet setting changes.

Realistically the Huffam is probably good to half a thou or so single sided whilst the collet type can be more like 2 or 3 thou unless you take great trouble setting them up.

My collet set, an OK brand whose name I have long forgotten, is now permanently fitted with the pointed probe used for picking up on scribed lines. Helped by a magnifier in my case. Great for that job as a bit of extra stiffness in the pivot is exactly what you need to ensure it stays spinning true once you have dressed it into position. I use my thumbnail but sensible folk use something a bit more resistant to impalement should the sharp point go berserk. For example the thick ruler out of a combination square set, preferably the one that came with that cheap alloy one you regret buying not the nice Starrett, M&W or other good brand you actually use.

Sticky pins are so "between the wars" period.

Clive

Edited By Clive Foster on 19/07/2019 22:38:24

Edited By Clive Foster on 19/07/2019 22:38:48

Hello, i have had all sorts of these gadgets. Electric ones which light up, wigglers the ones that come in sets with things you can not work how to use, a simple piece round bar 6mm diameter which i use with a 2 thou feeler gauge, and a wobbler the best of all.

You set the head rotating and move it slowly up to the work piece until it runs true then going a little further makes it run off to one side. Bingo your on the edge by a know distance. I am lucky i do have DRO's on my milling machine which makes things easy.

I hope it helps.

Bri

Mine is like the second from the left.

**LINK**

brian

I personally really like the Borite Machinist's Mate electronic edge finder. Had mine for more than 15 years.

**LINK**

Just my $0.02 worth.

Bri

Assuming you are referring to sets like the Arc Eurotrade one the purposes of the various things are :-

Ball ended rod is for picking up nominally vertical edges. Kicks sideways at half ball diameter from edge (plus a small offset related to joint stiffness).

Disk, actually small cylinder, ended rod is for picking up the sides of rods, round bars and curved edges. Align it with the diameter and it kicks sideways when it hits. Being a cylinder gives you some vertical tolerance when hitting the diameter. I don't like this type with the short cylinder of smaller diameter than the ball. Huffam sets have cylinder probes of the same diameter as the ball about two diameters long. Makes picking up the centre line of a rod dead easy. Theoretically the small end version as sold by Arc can get into smaller spaces but I've yet to find a need.

Needle point is for picking up on scribed lines as described in my previous post.

Last (bent) one is an indicator holder. Use it with a lever type indicator, such as a small Verdict, to find the centre of a circular part standing on end. Adjust the angle of dangle in the collet to bring the setting error within the indicator travel. Another one I don't like as they tend to sag under the weight of the indicator unless done up very tight which probably isn't good for the collet. Realistically anything heftier than the smallest Verdict is going to be a bit much. I have a suitable Verdict indicator and tried the one in my set once. Underwhelmed so I spent £50 on a import co-ax (Blake knock-off) indicator 40 odd years back and never regretted it.

Huffam sets only have ball and cylinder ended probes plus an extension piece for the shank.

From the link your "wobbler" is a standard edge finder. I've never been tempted by a set like that as using the various pointed probes doesn't make sense to me.

Clive

Edited By Clive Foster on 19/07/2019 23:23:37

The type c edge finder uses a lot less daylight than the wiggler, in fact with a round column machine I found the wiggler nearly impossible to use as you had to shift the head to get back to using a cutter. I've got a machine with a knee now, but more often than not I just turn the cutter to an appropriate angle, shine a torch into the gap and watch from the other side as I bring the job into contact. Not as accurate, but a lot faster

I'm with Jeff and use my PEC electronic one 99.9% of the time, with a wobbler on the other odd occasions.

I must admit that when I worked in a toolroom we always used a 'fag' paper !

By strange coincidence ... this mystery object is under discussion: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=143610#2474485

MichaelG.

Excellent point from Duncan about the extra daylight needed between workpiece and spindle by a wiggler in comparison to a type C edge finder.

My answer was to put the wiggler in a collet and use Clarkson screwed shank cutters. The Clarkson holder pretty much made up the difference. OK this was with a Chester Lux style large square column bench mill rather than a round column one but the big and heavy square head took a deal of winding up and down with the short handle provided so I preferred not to move it too much os, in principle, similar issues. With that machine the extra room between head and workpiece provided by the Clarkson chuck was welcome because otherwise it could be quite difficult to see round the head when using short cutters with everything close down on the job.

The short type C has the opposite disadvantage when picking up to drill larger holes as being too short to reach the job. Generally a rather rarer problem than the "wiggler is too long" issue.

As ever there is no perfect answer. My view is that the inexpensive wiggler sets are good for starting out as they can manage an acceptable job at four tasks for not much money. When the need for increased precision means you outgrow the set it still remains useful as a dedicated holder for the sharp pointer. Given the low price its arguable that buying two sets makes sense. One dedicated to the ball ended edge finder and carefully set up for maximum sensitivity the other to be tightened down on the pointer or indicator holder as needed.

I'd not bother with the disk/cylinder probe for horizontal rounds. A simple truly parallel rod in chuck or collet trapping Davids 'fag' paper or, if you want to be "engineering" about it, a one thou feeler gauge works fine. So easy to feel when it just nips up.

I'm uncomfortable with the electronic breed as they generally don't have any sort of over-travel indication so its easy to make a mistake by going a bit too far. Possibly better used in reverse, light going out rather than on, mode as you are relying solely on the switch characteristics which ought to be a bit more reliable. Easy to forget how tiny a movement a thou, or less, is and how challenging reliable detection can be.

Really don't like stationary systems. Rotating edge detectors find the centre of rotation minimising intrinsic errors. Stationary ones just add or add and subtract any fundamental insertion errors. Doesn't take much. A thou here, a thou there and soon things won't fit. Typical Model Engineer and Home Shop Worker pockets are no way deep enough for the super precise kit that goes back into exactly the same place exactly on centre every time. The shed isn't exactly the best place to use such anyway.

Modern affordable DRO boxes have made a huge difference in how easy it is to compensate for budget equipment limitations on mill work. Certainly the first place to direct your hard saved instrumentation budget once you have the basics.

Much as I'm impressed with my 3D Taster I have to admit that its largely wasted money with my manual machines. Exploiting the DRO with more basic kit pretty much lets me cover its advantages. Be a different story if I ever get that CNC VMC that has been on my wish list for so long!

Clive.

I bought a set many years ago & couldn’t figure out why I kept getting inaccurate results, so the set has stayed unused in a drawer ever since. I presume the ‘small offset’ was the reason.

How does one know or work out what that offset is? Surely without having a figure, the whole exercise is a bit pointless.

Brian

Mine's the one on the far right. I don't think I've ever used the pointy end - I'm not sure how it would work to datum off an existing hole, but the more I think about it, the more I think I should try it. The parallel end is very good - consistent within less than a thou. It was a cheapie, maybe from Arc - can't remember - well worth the tenner or so it cost.

Brian

After struggling with the offset variability on my collet holder set I calibrated it by trapping a one thou feeler gauge against an accurately vertical face with a dead straight silver steel rod of same diameter as the ball. After a bit of practice I could repeatably locate where the feeler gauge was just trapped enough to have some resistance to being pulled out. Watching the dials and recording the scatter gave me a good education in just how small a thou' is and just how much we take feed screw accuracy for granted.

Reference was probably the edge of my old Brown & Sharpe T slotted indicator carrier which has a nice 1/4" (ish) deep ridge each side decently clear from the main body but I really don't recall what I used. Long time ago.

So the calibration gave me the spindle centre line offset as half the rod (ball) diameter plus one thou. As I recall it first effort with the set gave a rather variable stiction error of around ten thou'. With a bit of playing around I think I got it down to a reliable 5 thou or so when simply assembling the thing. If I wanted to take extra trouble I think I could get a reliable 2 or 3 thou offset out of it.

Which is why I suggest that if you intend to make serious use of one you should take the time to get it working just so and leave it assembled.

Obviously these devices can never be intrinsically super precise. Although as with everything mechanical "Inspector Meticulous" types taking their time can do better than book.

The instruction leaflet for the much more expensive Huffam device with its intrinsically far lower friction and much smaller stiction offset, only claims it to to be useful "in the vast majority of cases where an accuracy of the order of 1 thou is sufficient and a jig borer is not available". The leaflet goes on to say that an unskilled operator "should be able to locate the relationship between the machine spindle centre line and datum face to within half a thou by the run off method and to within two tenths of a thou by the line of light method". Which I find fair comment but said unskilled operator needs a bit of practice to get the hang of things and to be fairly careful type to boot.

If I roll up my sleeves and concentrate I'd reckon to halve those values on a reasonable day.

Line of light method won't work with a collet type. They are just too stiff. Even with a Huffam its fairly frustrating at the best of times.

If you have a decent DRO system then working off opposite sides of the workpiece and using the centre finding function is a much better way of going about things as you only need consistent, albeit still small, stiction offset. The error cancels. I've never bothered to really test a collet based system used like this but I'm confident that within one thou accuracy is perfectly reasonable expectation if its sensibly assembled for smooth, easy movement. I did try my imperial Huffam against a 3" gauge block and, with care, the results are approaching unreal. Almost certainly better than you can easily measure with vernier or micrometer. Pretty much down to ± a single last digit shift on my Sino DRO and I'm unsure that is trustworthy right down there.

Out in the real world I'm confident that my Huffams get me to within a thou single sided. Once you get below a thou there are so many other potential sources of small errors that life is just to short to worry unless it has to be precise.

Clive

Edited By Clive Foster on 20/07/2019 20:43:57

Edited By Clive Foster on 20/07/2019 20:44:33

I bought a Vertex electronic edge finder years ago, it has a 20mm shank, and a 10mm spring loaded ball. The shank size will be too big for smaller machines, but if you can manage that size, it is recommended. They are not intended to be used with the machine running. Identical versions are available cheaply on ebay, see listing 263808616504.

If you have a DRO, try approaching a block of known size from both sides. The difference between your measured width and its true width is twice the error.

I have a Starrett edge finder and swear by it. Use it all the time. I have a cheaper one but its not as good. if you have a look at the sururban tool channel on youtube , they do a test of the various types, the edge finder wins it i think.

Here's another twist. From an estate sale, I got a 'General' (General Hardware Mfg. Co., Inc., USA) 'Universal Wiggler and Center Finder'. It's of the spring chuck / collet / multiple probes type in appearance, but is intended to be used differently.

Its instructions state: 'Insert the large ball of attachment into spring chuck. With the spindle turning, make the ball run true by holding any blunt object against it. Apply a thin coating of layout blue on the ball and feed the work up to it until the blue is barely wiped.' Note, layout blue is specified. I suppose you're supposed to use a small brush, and ensure the probe is not deflected. No alternative method of use is given.

The chuck can be tightened, but, even at its slackest, it holds the probe fairly stiffly and 'roughly', and it's not suitable for use with the usual wiggler kick-off technique. How one is supposed to get the ball to 'run true' accurately, by the suggested method, is beyond me, but, since the thing is surplus to my requirements, I've never bothered to try seriously. I find it difficult to believe that this method is used, if for no other reason that one needs to be able to have a very good, close-up view of the probe in action. Anyone ever come across this method in use?

I have a flaky memory of GHT commenting on a 'stiff' wiggler that didn't kick-off consistently. He considered it useless, until someone pointed out to him that it was not supposed to kick-off. Memory thinks one was supposed to look for disappearing light between probe and work, so the probe had to be set running true, as above. Could be mistaken - memory nearly full, and stuff is being dumped to retain a little capacity...

The 'General' set also contains a cranked 'probe', intended to hold an indicator, which can be held stiffly enough by tightening the chuck. Perhaps those sets containing such a 'probe' are intended to be used as above, and not to 'kick-off'.