Starrett wiggler/center-finder set is imperial. Ball diameter 0.250", disc contact 0.100".

Edited By Weary on 09/05/2022 12:55:50

Dave is probably right in saying that most wriggler sets end up in drawers.

But most wiggler sets are the collet held style which vary from total crap at the very cheapest E-Bay, Amazon, AiBaba end to sort of OK on a good day in the case of the over-priced Starrett and similar name brand versions.

The fundamental issue is excess friction in the holding collet. This demands a relatively large step over before the wiggler walks sideways. Its also pretty much impossible to repeatably set the collet grip sufficiently closely to get the same offset each time. So you can't simply calibrate it out. Which makes them pretty much useless when used as intended to detect a single edge.

If you have a high end version, eg Starrett, they may well be long term repeatable if you don't change the tip but the lower end aren't. My Draper set became a drawer queen for that reason.

I does depend on what accuracy you need. Mr Huffam states "for work where positioning accuracy of the order of 0.001" is adequate" and means it. I can live with that. Errors of 0.005" to 0.010". Fergedditt.

With a DRO you can work off both sides to determine the centre thus cancelling out most variation. By no means "silk purse from sows ear" but maybe "coarse sandpaper to hessian sack"!

My Huffams are silly accurate when used on opposite sides to determine centre. Down in the couple of tenths of a thou variation range. I imagine DRO, scale mount and general machine errors have more to say about that than the inherent performance of the Huffam. They are accurate to maybe half a thou, or possibly a bit less when I'm on a good day, in single sided mode. Surface friction, rotation speed and general operator performance at noticing when its just starting to move rather than waiting for a full walk are important in determining exactly what the error will be.

The old Draper manages to find centre to within a couple of thou if carefully used in side to side mode. In single sided mode better than 10 thou, maybe pushing towards 5 thou error is about as good as I can reliably expect.

Been meaning to scare out a clear day or so to analyse the repeatable accuracy of the Draper, Huffam and Hamier 3D Taster as compared to the conventional cylindrical edge finder. There are a couple of Heidenhain nanometer sensitive optical probes and readouts in the cupboard which might be good enough to resolve the issue.

Best thing to do with a cheap set is to make a new body with a narrow seat and spring loaded pusher for the swivel ball. Geo. H Thomas did a design back in the day which could easily be modified or take a root through my photo album for a disassembled Huffam to use as inspiration.

Clive

Edited By Clive Foster on 09/05/2022 14:06:52

Edited By Clive Foster on 09/05/2022 14:15:28

I tend to use mine on the CNC as it is more forgiving to jogging errors or simply using rapid when you meant to jog The point is also handy and less hassle than using a sticky pin. I think it was Soba but had it so long I can't remember

As I mostly work with the ctr of the work as my datum I find one edge and zero then the other edge and half the reading so any error due to it flicking off late is cancelled out.

As for metric or imperial I actually use a 0.2" electronic finder all the time on the manual mill and it's no problem to enter 0.1 or 2.54 depending on what I have the DRO set in at the time if I am working to a single edge. Wobble is 1/4" ball so again easy enough to enter 0.125 or 3.175

I used the parrslel shank Metric ones for years. Not used a real wobbler since I helped build the ark.

YES they do, or at least hybrids.

My Soba wiggler turned out to have a cylindrical probe, 0.100" diameter but a 6 mm ball! (Obviously a cock up )

Until I realised this, errors aplenty. Now, just have to remember whether to allow 0.050" or 0.118"

Howard