Hercus 260 lathe Collets & Adaptors
I have been reading about "Anorak Bobs" experiences with Tool Post grinding set ups.
Today I drove out an hour or so & visited "Pipeclay" & we were talking on a similiar subject & his work in machining adaptors to take E.R Collets.
The search for increasing accuracy is something we all seem to seek.
I like collets for their repeatable accuracy, & in particular for holding small parts for second operation work.
Some years back I purchased a Burnerd Collet set (see photo) & found it very accurate, except for its limitation in not being able to hold short workpieces, I think a rule of thumb with that type of collet was workpieces no shorter than 3 times the workpiece diameter.
This was a limiting factor,in its uses. When I purchased the 260 Hercus lathe from Hercus S.Aust 20 yrs back I did include with it some 4C collets & a 4C headstock spindle adaptor.These worked fine.
Recently on Ebay I got hold of a Hercus Indexing head as shown in the photo.A great little gadget........But then I needed more 3C collets. One cannot have enough tools.
So I purchased a whole bunch of them from "Tools4Cheap" in the USA as shown in the photos. At the same time purchasing a 4 morse to 3C collet adaptor from Hercus S. Aust.
The first one I got was not accurate enough, so they swapped another to me. It was a bit better but not totally concentric in the front tapered section that supports the collet.
The rear end of the adaptor with its key (The parallel portion) was concentric, so I decided to set an Air Die Grinder with a mounted point up in the lathe toolpost clamped by a toolmakers clamp.
The compound slide was set to the required angle & the mounted grinding point dressed by a single point diamond.
It took a short time to grind out the error in the hardened adaptor & just let it spark out.(There were some slight vibration marks but they were not measurable after grinding)
Now it is truly concentric, & to ensure that the adaptor goes back in the same location I have marked it with a Texta pen accordingly (See photo)
A half thou dial indicator hardly shows any movement in the needle.So I would say it is wthin tenths of a thou.
Since getting all of the 3C collets I find them very useful for a range of work long or short & the gripping power is excellent.At high speed there is minimal vibration, unlike larger chucks, & they are safer to work with.
I thought this may be of interest,
regards
Bruce
Abratool:)