I almost fell asleep watching the 'video'!

Presumably its not a cheap device but they have skimped on the brochure (spelling errors) and the video is appallingly bad.

I dont quite see how it works but at best it can only adjust for zero runout at one point so potentially even a perfectly parallel slot drill might cut a dovetail shaped groove.

I'm not a potential purchaser.

Ian

Ahem! ER collets don't hit the specified run out until they are torqued up properly. Which is a lot. 70 ft lb or so I think for ER-25. Nipping up by hand as shown won't do it. Nor will it hold the tool or whatever properly. That skinny ring and adjuster screws will do sweet FA if the thing is tightened up. As shown all its going to do is push the cap around so that the slack collet is square in the taper before you lean on the spanner. Very theoretically it might encourage things to settle squarer than they would if left to their own devices but in a practical world just pulling up tight does just fine unless there is a fault in collet or holder.

ER collets are, by design, aligned by the rear taper so there is sufficient clearance in the cap threads et al to allow front to follow back. Which it will do just fine provided the component being held is rigid enough not to crush and inserted far enough to fully support the fingers.

Clive

Hi All

I think I can see how it works. From the video you can see the first part is a screwed ring being attached to a standard chuck body I will call this the backing ring for want of a better name, Then the actual collet closing ring is attached. It appears to be made from two parts. First what appears to be a standard collet closing nut that may have had a shoulder turned on and then a press fitted ring bedded firmly on the shoulder. This ring is drilled and tapped then fitted with radially disposed hex grub screws. These screws bear against the previously attached "backing ring".

On first look you would have to wonder how this actually makes a difference; clearly the back taper not the nose taper is what aligns the tool, it should not make a difference?

I think the answer lies on the inherent flexibility of an ER collet. Let us first consider if the collet was composed of separate wedge segments that you placed around a tool in the holder and drove them in to clamp the tool. You would have to drive them in evenly or the tool would not be cantered in the holder.

ER collets are not separate pieces but with so many saw cuts they are quite flexible. by using this device attached to the nut working against the backing ring (Which would need a slight Clarence fit between the collet closing nut and the holder to allow it to rock slightly) The nut could be canted forming a micro swash plate that forces the wedge segments of the collet in unevenly and the tool slightly out of alignment. thus the device is able to correct small errors. correcting a few tenths or even a thou or two would appear to be quite feasible.

It is also a tool that would be fairly easy to make on a small lathe on the small lathe, ideally starting with a commercial nut.

Cheers

John

Edited By John McNamara on 24/03/2013 13:39:32

Johns theory is interesting but improbable give the forces involved. The micro misalignment if the back taper isn't entered dead true probably does occur but doing the cap nut up properly removes any such effect. Probably more likely with cheaper sets with lesser attention to taper and finish tolerances. Many years back I did some exploratory tests with my Vertex branded set after being told how important it was to do things up properly. Hand or light nip tight would sometimes leave a small runout, memory says thou or two, which would always disappear once something approaching book tightness was achieved. The effect didn't seem to be especially repeatable but appeared to be most likely towards the bottom end of the holding range. Assuming my judgement of hand / light nip torque was reasonably reliable its defensible to assume that greater closure uses up a greater portion of the applied torque in collapsing the collet leaving less for alignment and grip so errors were more likely.

Despite the slits an ER collet isn't all that flexible and there are mutual alignment forces from the interaction curved walls on the male and female tapers. Closing onto the tool also helps drive towards accuracy for similar reasons. Might be interesting to do a proper analysis of the forces and deflections involved with special attention to how the errors purported to be fixed by this device could arise and whether or not its actually strong enough to work as advertised.

Clive

I can't find them in their ebay shop, but they sell some esoteric stuff although THIS seems to bear a strange resemblance to a deburring tool!

Joey