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Posted by Michael Koblic on September 28, 2008, 10:36 pm
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The dealer in the next town had a magnetic base and an indicator combo on
sale for $30. So I decided to make like a real machinist and bought one to
see what my various turning implements are doing.
First of all, I do not have a clue about differing qualities of indicators.
However, all the tests were done with this one, so hopefully if not
accurate, at least repeatable. I understand that using an indicator is not
straightforward but I tried to be careful to have everything clamped down
tight, the arm at 90 degrees to the surface etc. and I even tried different
positions of the indicator with similar results.
I tried my new drill press first. I put the indicator on the outside of the
chuck first and there was no more than 0.001-0.002" runout. Then I chucked
my biggest and bestest drill bit (3/4") and tried again. This time I got as
much as 0.015" runout. I tried rotating the drill in the chuck a quarter
turn at a time (re-chucking by tightening all three holes but not
excessively). The run-out varied between 0.010 and 0.015". I tried
differrent drill bits with very similar results, down to 1/8". I should say
that I tested by rotating the spindle manually holding the pulley.
I found I could bend the chuck 0.007" ether way without any tremendous
effort on my part.
I then tried the same but abbreviated test in my old cheap drill press - the
runouts were of the order of 0.007".
The reason I tried the drill bits is that I do not have anything round that
I am confident is machined to a close tolerance.
So a number of questions:
1) What is the expected stiffness of a drill press spindle? Is bending arc
of 0.014" to be expected? What would you expect in a mill? Or a lathe?
2) What are the expected tolerances of drill bits? Is 0.010" out of round
usual?
3) What are the expected tolerances of Jacobs 5/8" chucks? Is 0.010-0.015"
reasonable? I understand that 3-jaw chucks on lathes are not as good at
centering as manually adjusted 4-jaw chucks. Is this about the order of
things?
4) Given that the runout was of the same order throughout the testing would
you say that it is predominantly due to the chuck rather than the drill bits
being out of round?
Thanks,
--
Michael Koblic,
Campbell River, BC
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Posted by Michael Koblic on September 30, 2008, 12:42 am
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> 1) What is the expected stiffness of a drill press spindle? Is bending arc
> of 0.014" to be expected? What would you expect in a mill? Or a lathe?
> 2) What are the expected tolerances of drill bits? Is 0.010" out of round
> usual?
> 3) What are the expected tolerances of Jacobs 5/8" chucks? Is 0.010-0.015"
> reasonable? I understand that 3-jaw chucks on lathes are not as good at
> centering as manually adjusted 4-jaw chucks. Is this about the order of
> things?
> 4) Given that the runout was of the same order throughout the testing
> would you say that it is predominantly due to the chuck rather than the
> drill bits being out of round?
>
This seems to be a part of the answer:
http://www.jacobschuck.com/images/products/Pro%20Keyed%20Updated%20(ENG)-1.pdf
The question is if the runout would be cured by buying a "name" chuck to
replace the existing People's Liberation Army one...At a cost which almost
equals the drill press as a whole.
BTW has anyone tried the hitting-it-with-the hammer adjustment (as
recommended on a couple of forums)?
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Posted by Jim Wilkins on September 30, 2008, 5:31 am
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>
>
> > 1) What is the expected stiffness of a drill press spindle? Is bending =
arc
> > of 0.014" to be expected? What would you expect in a mill? Or a lathe?
> > 2) What are the expected tolerances of drill bits? Is 0.010" out of rou=
nd
> > usual?
> > 3) What are the expected tolerances of Jacobs 5/8" chucks? Is 0.010-0.0=
15"
> > reasonable? I understand that 3-jaw chucks on lathes are not as good at
> > centering as manually adjusted 4-jaw chucks. Is this about the order of
> > things?
> > 4) Given that the runout was of the same order throughout the testing
> > would you say that it is predominantly due to the chuck rather than the
> > drill bits being out of round?
>
> This seems to be a part of the answer:
>
> http://www.jacobschuck.com/images/products/Pro%20Keyed%20Updated%20(E...
>
> The question is if the runout would be cured by buying a "name" chuck to
> replace the existing People's Liberation Army one...At a cost which almos=
t
> equals the drill press as a whole.
>
> BTW has anyone tried the hitting-it-with-the hammer adjustment (as
> recommended on a couple of forums)?
Drill bits are probably good to a thousandth. Dowel pins are cheap and
very accurate.
The better Jacobs chucks are worth it on a milling machine, probably
not on a cheap drill press. Twist drills are flexible anyway and
center themselves on the punch mark, so runout in the chuck doesn't
matter all that much.
The one Enco keyless chuck I have is pretty good, too, although it's
on the tailstock of my lathe where I can't quickly measure the runout.
For small holes they are handier than keyed chucks, for larger ones
they have a problem with slipping.
A good chuck isn't really wasted on the drill press, you can move it
to a better machine later.
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Posted by DoN. Nichols on September 30, 2008, 7:41 pm
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> Drill bits are probably good to a thousandth. Dowel pins are cheap and
> very accurate.
Agreed.
> The better Jacobs chucks are worth it on a milling machine, probably
> not on a cheap drill press. Twist drills are flexible anyway and
> center themselves on the punch mark, so runout in the chuck doesn't
> matter all that much.
Well ... that depends. Yes, a typical half-inch Jacobs chuck
can't *directly* hold a drill bit much below 1/16th of an inch, and
0.007" runout is probably tolerable with a 1/16" drill bit. However, if
you are using one of the sensitive drill adaptors, and a #70 or #80
drill bit, your runout is going to be on the order of the drill
diameter, and that is likely to break the drill bit once it gets deep
enough into the workpiece. Even more so if you are using solid carbide
bits for drilling printed circuit boards. They are very brittle when
exposed to side loads.
> The one Enco keyless chuck I have is pretty good, too, although it's
> on the tailstock of my lathe where I can't quickly measure the runout.
> For small holes they are handier than keyed chucks, for larger ones
> they have a problem with slipping.
Hmm ... a real Albrecht is good at self tightening, so it tends
not so slip.
> A good chuck isn't really wasted on the drill press, you can move it
> to a better machine later.
Agreed -- and if the drill press and the lathe tailstock have
the same Morse taper (or the lathe tailstock is larger so you can use
an adaptor sleeve), you can move the same chuck back and forth at need.
(Granted, it is nicer to have them each have its own good chuck. My
lathe currently has a Polish clone of the Albrecht in the 5/8" size, my
drill press has a Jacobs (close of the Albrecht, though looks a little
different), and my little Compact-5/CNC lathe has three chucks -- a 1/8"
Albrecht, a 1/4" Albrecht, and a 3/8" Rohm, which is a good clone of the
Albrecht.
A worn Albrecht with a large bit can self-tighten to the point
where you need a strap wrench to loosen it.
Enjoy,
DoN.
--
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
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Posted by Michael Koblic on September 30, 2008, 7:43 pm
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"Drill bits are probably good to a thousandth. Dowel pins are cheap and
very accurate.
The better Jacobs chucks are worth it on a milling machine, probably
not on a cheap drill press. Twist drills are flexible anyway and
center themselves on the punch mark, so runout in the chuck doesn't
matter all that much.
The one Enco keyless chuck I have is pretty good, too, although it's
on the tailstock of my lathe where I can't quickly measure the runout.
For small holes they are handier than keyed chucks, for larger ones
they have a problem with slipping.
A good chuck isn't really wasted on the drill press, you can move it
to a better machine later."
***I was thinking along the same lines. I have actually found a real Jacobs
chuck in my possession. I think it is this one:
http://www.jacobschuck.com/images/products/JC-003%20Multicraft%20Series%20No%20Crops.pdf
Cost less than $20, but the specs are about the same I am getting now. And
it is, of course, smaller. It was just an interesting exercise.
BTW what TIR would you expect on a, say, 3-inch 3-jaw chuck in a lathe? What
sort of improvement do you expect going to 4-jaw chuck? When you are
mounting a chuck, are most of the mounts self-centering (The Advanced
Machine Work says they just screw on to the spindle but that is surely not
the case in every instance)? Can you center the chuck by using the indicator
on the periphery of the chuck or do you need to chuck something demonstrably
round and center on that?
--
Michael Koblic,
Campbell River, BC
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> of 0.014" to be expected? What would you expect in a mill? Or a lathe?
> 2) What are the expected tolerances of drill bits? Is 0.010" out of round
> usual?
> 3) What are the expected tolerances of Jacobs 5/8" chucks? Is 0.010-0.015"
> reasonable? I understand that 3-jaw chucks on lathes are not as good at
> centering as manually adjusted 4-jaw chucks. Is this about the order of
> things?
> 4) Given that the runout was of the same order throughout the testing
> would you say that it is predominantly due to the chuck rather than the
> drill bits being out of round?
>