Gallery, Projects and General > The Design Shop

Aciera F3, ER32 retrofit.

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David Jupp:
You could shrink on a collar, then machine the outside to ensure concentricity - has the advantage that it is reversible if things go badly wrong...

PekkaNF:

--- Quote from: NeoTech on October 04, 2012, 04:23:01 AM ---Addendum; there isnt enough material to machine the  cone into the collet holder itself. And i didnt buy a cheap chinese one. I went and bought an expensive one. (next time i buy the chinese... cause they are half he price  :doh:).

But been thinking, i could prolly tig some brass onto that shank and build up a machineable layer that could be machined to fit that cone and centrered on there.. could that be one way to go?

--- End quote ---

Uuh...If it is expensive I probably would not modify it but would leave it for future use. Need will come.

I would not weld or metalspray it, unless there is absolutely no other way. Usually material on these are not ideal for welding (not always too bad either), but any thermal schock will bend it one way or another and probably will do it long time unless preheated, stress relieved etc.. which all will require machining everything all over. Easier to buy 20-30 £ chinese one and machine it correct fit or make one from scratch

I still don't get it. I tought that you said it has W20 collet and your ER32 holder has OD20, lenght 50 mm cylindrical shaft on it. But your drawing and pictures shows a sleeve that has cylinrical extension? To knowledge Aciera F3 was produced only for W20 and ISO30 spindles.

You do have W20 not ISO30 spindle bore? What tooling and adapters come with it? Although if you got it from a "jobber" it might come with just about any part lookking tools (one individual tried to sell me once a lathe that has a lot of junk tooling that even did.t fit into it but looked good in the picture). I have heard that some were fitted for W25 or even R8, there might be enough meat in the spindle.

Do you know where this inaccuracy comes from? This is #1 priority. The error you are getting is excessive.
* What spindle nose/taper it is. I have been assuming it most common W20, but is it?
* Is the spindle (taper) itself true? Crashes do happen and machines are sold becuse of them.
* Did you deburr the key grove?
* Does the key bear on grove bottom?

If you pursue making the taper "collet" this information might help (providing it is W20):
http://www.nann.de/tl_files/NANN/Download%20EN/STANDARD_2011_EN.pdf
page 22 shows that collet tapper should a bit obtuse (15' on this example) it also shows pretty good where collet should bear on the spindle.

Do you have this spindle nose/collet form factor: 349E i.e W20 with ø 19.7 x 15G/`` thread, collet length of 70 to 73 mm (69 mm from end to apex) and tail end OD pretty close 20.0 mm?

Internet will reveal whole more accurate information about this collet with 349E or 349 E (German speaking nomeclature, more exact than W20, which is very generic name, more of a "style"  where thread, length, angle and key seems to vary).

Pekka

NeoTech:
yeah see my seperate thread about the machine itself under "tools".
But yes, the machine is a W20 spindle. I have some W20 collets but they are frickin expensive. So this was an attempt to work around that. Once i figured out that the inside diameter of the spindle is 20mm i figured a straight shank chuck would fit inside if with some modification. But i needed some way to center it in the  spindle so thats why i made those brass rings for it.

The original drawtube itself has a similar surface but its integrated with the tube. it has some play in the "upper part", but its not much. The lower end with the collet it self well that compresses into the spindle so it will center around the tool anyway. I figured i could mimick that..

Thats why the lower brass ring has the shape of a type-b collet (20mm collet) but  i didnt slit it i just made it slipfitted as noted.

When running the orignal drawbar and original collet, the runout is about 2/100. Measured on a piece of silversteel chucked in the 20mm holder.
When running the ER32 collet its..way off. But,  the upperpart of the drawbar isnt wobbling at all it plays about 1/100mm less than the orignal drawbar.
So i figure the play must be with the lower centering ring i made and the collet chuck itself.  I will know more this evening when i attack it again..

NeoTech:
So after made 2 attempts more..

One lower collet with a compression design slots in it. Didnt work. And one version where i pressed a piece of brass onto the 10mm shaft with a 10t shop press, and then turned the collet to the spindles sizes within 2/100mm, sitting on the shaft of the collet holder - it still wobbles 0.5mm sideways.

Let us say this was a bad idea and leave it at that. ;)

PekkaNF:
I didn't get excactly what you did and what you tested, but I'm sure you have reason and logic in your method.

Hmm.. :scratch:

Where does that error comes from?

1) Have you measured the spindle taper?

2) Have you measured any original tooling?

3) How does the spindle looks and feels when you put a original tooling into it?

0.5 mm is HUGE on that small parts. Sounds like your manufacturing methods are right, but the trouble is somewhere else.

Pekka

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