Collet Chuck (Part 2)

On Sat, 05 May 2007 07:48:11 +0100, Chris Edwards
You could always use the trick that they use at the garage up the road
from me to keep the crap off their hands - wear surgical gloves.
Alternatively, there are "barrier creams" (based on Lanolin usually) that you can work into your hands before you start getting them coated in muck - the layer of grease on the skin helps with later removal. Not tried it myself, but said to be useful.
Regards, Tony
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wrote:

road
coated
For year I've been using powdered latex gloves, but only recently found that I get a rash after a few hours use. I've gone over to using the blue nitrile powder free ones find find them much better. They are not quite as sensitive to the touch as latex, but far tougher. I tried vinyl ones but found them far too stiff and awkward.
AWEM
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On Sat, 5 May 2007 11:37:22 +0100, "Andrew Mawson"

Andrew
Have you tried more than one brand of Vinyl? I used to get the blue nitrile ones, my part-time helper has a latex allergy, but actually prefer the vinyl plus they're *much* cheaper <g> Oh, and lots of places stock them now, which isn't true with the nitrile. Not impressed with vinyl gloves from RS, though.
Tim
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wrote:

usually)
removal.
using
are
tried
<g>
Tim,
I bulk bought through my department store (eBay !) and it works out at 3.6 p per glove
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item 0100918124
So far I've almost got through 1 of the 10 boxes I bought 5 weeks ago so my lot of 10 should last about a year.
AWEM
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writes> I don't think I'll make my own

See my post about a borax/soap mix. It also is good for cleaning sinks!.
Steve R.
--
Due to high levels of spam, all email sent to this account is being auto
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wrote:

Only one answer, Sell your machines and take up knitting, at least it keeps your hands clean. Part of my business also means meeting people and shaking hands with them. Only difference is they now also have black hands.
Three pints of Newcastle Brown takes the taste away, after twelve you couldn't give a rat's arse.................. -- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:- http://www.homeworkshop.org.uk /
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"Steve W" <steve> wrote:

OK, so why not fix the backplate? Put it in a 3 jaw chuck, align, face off a tad, lick over the centering cone. DO NOT unchuck, but take the whole setup (chuck and backplate) off the spindle and reverse it to see how well the backplate fits. Repeat if necessary.
That should work, unless I misunderstood you.
Nick
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The C6 spindle has a cylindrical spigot not a cone mounting Nick.
Regards
Steve
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"Steve W" <steve> wrote:

Oh, then I'll pass along a trick I have read (but do consider it more a hack than a repair). With a center punch, punch some dings quite near (1mm or so) the "cliff". It will extend the material a bit and thus make the bore a tad smaller. It then either fits or can be bored to the right diameter.
Don't know why this is coming to my mind: "Never use force, just go for a bigger hammer"
Nick
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Dad taught me the same trick when I was little as a way of stopping bearings spinning in a crancase, - thanks for the memory!
Steve
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On Sun, 22 Apr 2007 18:17:31 +0100, "Steve W" <steve> wrote:

If you're fitting a new collet chuck it is wrong to use the runout of a test bar as the control measurement. This runout test cannot distinguish between chuck error, collet error and test bar residual error.
The fundamental test is the concentricity of the chuck internal taper. This needs to be internally clocked at two widely separated diameters - these should both clock within tenths. Two equal (in both amount and angular position) runouts shows parallel displacement. Unequal runouts indicates skewed mounting.
Pallel displacement is the most likely problem and easily fixed by using a loose fitting register. With the fixing bolts lightly tightened, gently tap the chuck into concentricity before final tightening.
For final checks with individual collets, dowel pins are convenient accurate test bars.
Jim
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Thanks Jim. The runouts are equalt in an angular sense, but not in size. Taking care to have DTI working at the same spot on its travel the runout difference is less than 0.01mm but I suspect you were speaking of 10ths of a thou.
Repeatability onto the spindle is an issue - at least 0.04mm on re-mounting the backplate.
Steve
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On Apr 28, 7:27 pm, "Steve W" <steve> wrote:

Steve
Unfortunately you seem to be chasing your tail with this collet chuck and you have lost me as to what exactly you have done. As Jim says the test on the internal spindle excludes the collet and test bar as an error but very much leaves both the backplate/spindle and chuck body/ backplate as possible errors. If you have machined the backplate register on the machine and obtained zero rainout then that should have eliminated the spindle/backplate interface, but ONLY if that fit is repeatable. One of the issues I had with these things in the past is that you fit the backplate and get it running as accurately as possible, machine the required register and mark where the backplate fits. The problem then is that you have no face on the backplate to use the DTI on when the chuck body is fitted so no way to "tap" to the original position if that is necessary. When I cut the register on the backplate I then also take a light cut off the outer diameter of the backplate that is visible when the chuck body is bolted on. This way I have a face to check on with the chuck bolted up. Without this you have no way of telling if the backplate is exactly as it was when you cut the register. If as you say yours has a loose fit then it is a lottery as to what error you will get.
The figures I posted for my setup in your original question were with the components assembled as supplied. While mine were not bad, after fitting properly to your own machine you should be able to get an apparently zero runout on the collet seating taper. Unless of course you are using a very, very expensive DTI. After fitting on mine, the backplate reads zero runout on the register outer diameter, flat face that the chuck butts against and the outer diameter for checking. As long as I keep the threads and contact faces very clean this is repeatable on backplate removal/refit within the resolution of my Starrett DTI. With the chuck fitted to backplate I again get no apparent runout on the collet taper but with collets fitted I can get a variation on the test pieces of maybe 0.0002-3" depending on the particular collet being used. My idea of no runout is that my 0.0005" Starrett doesn't move more than the needle width so most likely it is within a couple of tenths of a thou.

displacement between backplate and chuck body. While cutting the backplate register/outer diameter I also check on the flat face the chuck body contacts to ensure that it also has zero runout, if not (often the case) I take a light facing cut off this surface. This ensures the backplate rear face (to spindle) and front face (to chuck body) is absolutely parallel at the fitted position. Another possible cause of the angled chuck is again the register, if that is not entering the chuck body fully it can hold it off minutely at an angle. Many people make this fit quite loose so that it can again be tapped into final position before the bolts are fully tightened. I have found on many occasions that the chuck body internal register may have a burr on the outer edge which needs removing.
Steve, I'm sorry about the length of this post but I'm not good at elegant prose. My main point would be that you have to sort this out methodically and eliminate each cause of possible error in sequence. If you cannot get the backplate to spindle fit to repeat accurately (even if you need to tap and test with the DTI on every fit) then the runout at the collet is going to be a complete lottery. Apologies if this is "teaching granny".
Best regards
Keith
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On 29 Apr 2007 02:11:37 -0700, jontom snipped-for-privacy@hotmail.com wrote:
SNIP

SNIP
Keith has given you lots of useful advice. A few extra comments may help.
I was brought up on Imperial units so tenths of a thou is my natural measure - it somehow seems a lot less clumsy than 1/400 of a mm!
With two unequal runouts at the same angular position.
You have both parallel displacement and cockeyed mounting (i.e the backplate mounting is not quite square to the spindle axis).
Tap the backplate until one runout is zero. The runout on the other test plane shows the amount and direction of the angular error.
Repeatability of re-mounting the backplate to the spindle nose is of prime importance. Until you've reduced this to a satisfactory level you'll be chasing your own tail in correcting the chuck position. At this sort of level absolute cleanliness and burrfree mating surfaces is vital
Jim
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snipped-for-privacy@yahoo.com wrote:

1/1,000th of a mm, or a micron, is a useful measure too.
Of course it doesn't look as good when you measure something and it's only accurate to three or four (or twenty) of them rather than one, but still ...
Good electronic micrometers will measure to a micron, and even if you are using a 1/100th mm device like a digital caliper, you just have to add a zero on the end.
And "Accurate to 3 microns" does sound okay :)
--
Peter Fairbrother


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Much less clumsy than 0.000118110236 inch too ;)
Tim
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wrote:

Is that larger or smaller than a Gnat's left bollock ?
. -- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:- http://www.homeworkshop.org.uk /
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On Sun, 29 Apr 2007 12:40:33 GMT, John Stevenson

Depends which side the gnat dresses <G>
Regards, Tony
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On Sun, 29 Apr 2007 12:01:04 +0100, Peter Fairbrother

I suppose it's inevitable that my preference for Imperial measure would not be supported by the metric minded. I can well understand that, brought up on the metric system, Imperial units can seem to be outdated and irrelevant.
However there are a few occasions where Imperial numbers just fit better.
With the average home workshop tools it's not too difficult to achieve one thou accuracy. One tenth thou marks a different region. It's close to the limits of standard mics and small lathes and beginning to call for the use of gauge blocks and grinding/lapping techniques.
On this basis "a few tenths" is a conveniently vague term for an accuracy that's reasonably achievable in the home environment.
"Accurate to 3 microns" implies an accuracy that does not exist.
"Within a few times 3 microns" echoes the clumbsiness that gave rise to my original comment!
Jim
P.S. For the professional community I of course agree that the the micron is the natural small unit - 1 thou is far to big!
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snipped-for-privacy@yahoo.com wrote:
<snip>

Hello All
I have a friend who is a professional turner and is young enough to have been educated entirely in metric.
I find "a fortieth of a millimetre" translates well.
Russell
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