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.
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.
On Sat, 5 May 2007 11:37:22 +0100, "Andrew Mawson"
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
Not impressed with vinyl gloves from RS, though.
I bulk bought through my department store (eBay !) and it works out at
3.6 p per glove
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.
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
Visit the new Model Engineering adverts page at:-
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
That should work, unless I misunderstood you.
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"
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
For final checks with individual collets, dowel pins are
convenient accurate test bars.
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
Repeatability onto the spindle is an issue - at least 0.04mm on re-mounting
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".
On 29 Apr 2007 02:11:37 -0700, jontom email@example.com wrote:
Keith has given you lots of useful advice. A few extra comments
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
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
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 :)
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
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
On this basis "a few tenths" is a conveniently vague term
for an accuracy that's reasonably achievable in the home
"Accurate to 3 microns" implies an accuracy that does
"Within a few times 3 microns" echoes the clumbsiness
that gave rise to my original comment!
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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