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Posted by on October 29, 2008, 8:56 am
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OK, one for the practical machinists - no, I am not going to buy some
special tool costing zillions to get round this problem...
Turned a MT2 taper on the lathe, 0.5mm oversize. Used the topslide on
the lathe, set it up with a dial indicator for (virtually) zero
deflection along the length of a reference MT2 taper - which, BTW, was
pretty worn/crappy, it was a MT1 to MT2 adapter that had a hard life -
I used a ruler, sighted it lengthwise to get the "best" one for the
setup....
(An aside - the complication is that the school exercise to to grind a
MT3, I changed it to MT2 so it would fit my lathe at home - end result
will be a centre drill holder..)
So, booked the cylindrical grinder, got the tool set for it, the
instructor showed me how to set it, using the aforementioned MT2 taper
I had turned. Took a while, but eventually, using a finger gauge,
measuring the grinding side (important that, as I soon realised) set
it up to AFAIK bloody very close to PERFECT.
Ground the thing, it was out by ?? degrees. Blast, Oh Dear, - and
other appropriate words.
OK, obviously my lathe turned taper was out. Tried to set up the
grinder with the MT2 adapter I had used earlier. Had to move the
tailstock on the grinder as it was longer than my work piece. Set it
up, ignoring the bumps and variations on a worn adapter.
Feeling pretty good about how smart I was , reset the tailstock to the
workpiece. Immediately realised I had lost registration by moving the
tailpiece.
I then ran out of time, will do night class next week to sort it out.
So, good people - how do I set it up to do an MT2 taper? - there is a
degree scale at the end of the grinder bed (where the adjuster is) but
its not accurate enuff to set by, and besides, its an old grinder so
its probably out. By trigonometry - get the degree taper, construct a
triangle, work out offset by this - mm, yes - but how to transfer it
to the end of the bed. Besides it would need very accurate marking out
and measuring, and as there is no gauge on the horizontal travel of
the bed....
There is a dial gauge attached to the adjuster end, but stuffed if I
know how to use it for this setup.
Arrrgh! - help!!!
Andrew VK3BFA.
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Posted by Steve Walker on October 29, 2008, 10:21 pm
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vk3bfa@hotmail.com wrote:
> OK, one for the practical machinists - no, I am not going to buy some
> special tool costing zillions to get round this problem...
>
> Turned a MT2 taper on the lathe, 0.5mm oversize. Used the topslide on
> the lathe, set it up with a dial indicator for (virtually) zero
> deflection along the length of a reference MT2 taper - which, BTW, was
> pretty worn/crappy, it was a MT1 to MT2 adapter that had a hard life -
> I used a ruler, sighted it lengthwise to get the "best" one for the
> setup....
>
> (An aside - the complication is that the school exercise to to grind a
> MT3, I changed it to MT2 so it would fit my lathe at home - end result
> will be a centre drill holder..)
>
> So, booked the cylindrical grinder, got the tool set for it, the
> instructor showed me how to set it, using the aforementioned MT2 taper
> I had turned. Took a while, but eventually, using a finger gauge,
> measuring the grinding side (important that, as I soon realised) set
> it up to AFAIK bloody very close to PERFECT.
>
> Ground the thing, it was out by ?? degrees. Blast, Oh Dear, - and
> other appropriate words.
>
> OK, obviously my lathe turned taper was out. Tried to set up the
> grinder with the MT2 adapter I had used earlier. Had to move the
> tailstock on the grinder as it was longer than my work piece. Set it
> up, ignoring the bumps and variations on a worn adapter.
>
> Feeling pretty good about how smart I was , reset the tailstock to the
> workpiece. Immediately realised I had lost registration by moving the
> tailpiece.
>
> I then ran out of time, will do night class next week to sort it out.
>
> So, good people - how do I set it up to do an MT2 taper? - there is a
> degree scale at the end of the grinder bed (where the adjuster is) but
> its not accurate enuff to set by, and besides, its an old grinder so
> its probably out. By trigonometry - get the degree taper, construct a
> triangle, work out offset by this - mm, yes - but how to transfer it
> to the end of the bed. Besides it would need very accurate marking out
> and measuring, and as there is no gauge on the horizontal travel of
> the bed....
>
> There is a dial gauge attached to the adjuster end, but stuffed if I
> know how to use it for this setup.
>
> Arrrgh! - help!!!
>
> Andrew VK3BFA.
>
>
How accurate do you want to be, and how are you measuring the taper on
the ground part? The dial gauge is for reference purposes only, unless
you know the center distance from the table pivot to the dial gauge.
You cannot grind it right the first time on an unfamiliar grinder. (you
can get close)
If you know the center distance from the pivot point to the gauge, (in
the manual), you grind a sample, (same length as your part, so you don't
have to move the tailstock) as straight as you can. Then you can trig
out the amount to move the tailstock by using the dial gauge.
Otherwise, grind sample straight, then shift table taper about .100 on
dial gauge and grind sample again until full clean up. Measure taper on
sample, and you can calculate how much more you need to move dial gauge
to get your taper.
Record your measured taper angle after the .100 move and keep for
reference. You can back calculate the center distance of the grinder
with it.
Always move a little less than you need when creeping up on it, as
it's easier to take more off the small end than the big end.
Don't forget to ALWAYS back off dial gauge and move back to where you
want to be, to account for any backlash.
Use a good high pressure grease in the centers.
See here:
http://www.tools-n-gizmos.com/specs/Tapers.html
I used to grind gages at a gage shop, and used to be able to grind a
taper accurate to .000050 over 10 inches. It was a VERY good manual
grinder.
--
Steve Walker
Fusion640@verizonwallet.net (remove wallet to reply)
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Posted by DoN. Nichols on October 29, 2008, 11:23 pm
Please log in for more thread options > OK, one for the practical machinists - no, I am not going to buy some
> special tool costing zillions to get round this problem...
[ ... ]
> So, good people - how do I set it up to do an MT2 taper? - there is a
> degree scale at the end of the grinder bed (where the adjuster is) but
> its not accurate enuff to set by, and besides, its an old grinder so
> its probably out. By trigonometry - get the degree taper, construct a
> triangle, work out offset by this - mm, yes - but how to transfer it
> to the end of the bed. Besides it would need very accurate marking out
> and measuring, and as there is no gauge on the horizontal travel of
> the bed....
Do you know about the sine bar? A piece of steel, typically
about 5" long, ground to a very flat surface on top. On the bottom are
two cylinders bolted in -- *precisely* 5.0000" apart, and precisely the
same diameter.
Calculate the height of a stack of gauge blocks needed to get
one end of the sine bar jacked up the right distance to get the desired
angle. Normally, you look up the sine of the angle needed (hence the
name of the sine bar), but looking up Morse tapers, you will find the
tapers specified in inches per inch or inches per foot. Divide that by
two, and convert that to the inches needed over a 5" length. With good
gauge blocks, this will give you about as accurate an angle as you will
need. Look up the taper in _Machinery's Handbook_ -- or some other
reference source.
How you use this to set this up the cylindrical grinder depends
on what kind of reference surface you have to work with. I've never had
access to one to try. But also -- be very careful about the gauge
blocks and the sine bar around any kind of grinder. It is very easy to
damage either with the grit which is all around any grinder.
Good Luck,
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 Harold and Susan Vordos on October 30, 2008, 1:09 am
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snip---
>
> Arrrgh! - help!!!
>
> Andrew VK3BFA.
>
Read what DoN said, and work accordingly. One does not set angles on a
grinder using the calibrations provided on the machine. They are for
reference only, considering they are accurate only at the specified length,
and then only as good as the degree of precision in which the headstock and
tailstock are located. Grinders are meant to be adjusted for each and every
operation. Do not trust any of the markings.
The typical cylindrical (or universal) grinder pivots on the center of the
table. It is common practice to use a dial indicator (a DTI works
adequately) to set taper, be it a straight part or a tapered part. One
takes a light grinding cut to determine the status of the taper, then
adjusts accordingly. Considering the length of the part determines the
effect of offsetting the table, there is no hard, fast rule. Adjust the
table a given amount, determine the effect, then adjust accordingly.
Setting taper may require more than a couple attempts----and if you expect
to grind more than one piece, length is often critical, as is the size of
the center in the part.
Do *not* trust setting the angle by comparing to other devices. Unless you
are dead on center, and the part is perfect, you will introduce error that
will not be in your best interest. Use a sine bar or plate to inspect the
grind, adjusting accordingly. Insure that when you inspect the grind that
it is placed at a perfect right angle on the plate or bar.
Harold
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Posted by on November 1, 2008, 6:04 am
Please log in for more thread options >
> snip---
>
>
>
> > Arrrgh! - help!!!
>
> > Andrew VK3BFA.
>
> Read what DoN said, and work accordingly. One does not set angles on a
> grinder using the calibrations provided on the machine. They are for
> reference only, considering they are accurate only at the specified length,
> and then only as good as the degree of precision in which the headstock and
> tailstock are located. Grinders are meant to be adjusted for each and every
> operation. Do not trust any of the markings.
>
> The typical cylindrical (or universal) grinder pivots on the center of the
> table. It is common practice to use a dial indicator (a DTI works
> adequately) to set taper, be it a straight part or a tapered part. One
> takes a light grinding cut to determine the status of the taper, then
> adjusts accordingly. Considering the length of the part determines the
> effect of offsetting the table, there is no hard, fast rule. Adjust the
> table a given amount, determine the effect, then adjust accordingly.
> Setting taper may require more than a couple attempts----and if you expect
> to grind more than one piece, length is often critical, as is the size of
> the center in the part.
>
> Do *not* trust setting the angle by comparing to other devices. Unless you
> are dead on center, and the part is perfect, you will introduce error that
> will not be in your best interest. Use a sine bar or plate to inspect the
> grind, adjusting accordingly. Insure that when you inspect the grind that
> it is placed at a perfect right angle on the plate or bar.
>
> Harold
Thank you Steve, Don, and Harold. The progressive grind then measure
approach seems logical, and point noted re not setting up to a
reference taper. The Sine Bar - its a word at the moment, heard it,
but no idea how to use one. (But will find out)
Accuracy of taper to Don) - accurate enuff to be a good, non slip fit
in the socket. Its out to blazes now as I can wobble it in the socket
- when I get close, will blue it and then see how close it is. Don't
know how much I have to play with after the initial abortive grind,
the angle is greater than required so MIGHT be able to do it - may
have to start over again (bugger!)
Harold - measuring after each cut - can I leave the job on the
machine, use a micrometer to measure the major and minor diameters? I
note in the reference tables (thanks Steve) that the drawing shows a
fixed length, measured at each end. This does not agree with the ones
I have seen, some are longer than others. I would imagine (???) that
the big diameter
so long as it occurs somewhere along its length, and the small
diameter is the size at the length designated in the tables, then its
ok. I know mine is pretty short, just a few mm projecting out of the
socket (when its cut, of course - not at the moment)
So. Once again, thanks to the members here. The learning curve is
flattening out a little, but still has the occasional deviation to
vertical!
Andrew VK3BFA.
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> special tool costing zillions to get round this problem...
>
> Turned a MT2 taper on the lathe, 0.5mm oversize. Used the topslide on
> the lathe, set it up with a dial indicator for (virtually) zero
> deflection along the length of a reference MT2 taper - which, BTW, was
> pretty worn/crappy, it was a MT1 to MT2 adapter that had a hard life -
> I used a ruler, sighted it lengthwise to get the "best" one for the
> setup....
>
> (An aside - the complication is that the school exercise to to grind a
> MT3, I changed it to MT2 so it would fit my lathe at home - end result
> will be a centre drill holder..)
>
> So, booked the cylindrical grinder, got the tool set for it, the
> instructor showed me how to set it, using the aforementioned MT2 taper
> I had turned. Took a while, but eventually, using a finger gauge,
> measuring the grinding side (important that, as I soon realised) set
> it up to AFAIK bloody very close to PERFECT.
>
> Ground the thing, it was out by ?? degrees. Blast, Oh Dear, - and
> other appropriate words.
>
> OK, obviously my lathe turned taper was out. Tried to set up the
> grinder with the MT2 adapter I had used earlier. Had to move the
> tailstock on the grinder as it was longer than my work piece. Set it
> up, ignoring the bumps and variations on a worn adapter.
>
> Feeling pretty good about how smart I was , reset the tailstock to the
> workpiece. Immediately realised I had lost registration by moving the
> tailpiece.
>
> I then ran out of time, will do night class next week to sort it out.
>
> So, good people - how do I set it up to do an MT2 taper? - there is a
> degree scale at the end of the grinder bed (where the adjuster is) but
> its not accurate enuff to set by, and besides, its an old grinder so
> its probably out. By trigonometry - get the degree taper, construct a
> triangle, work out offset by this - mm, yes - but how to transfer it
> to the end of the bed. Besides it would need very accurate marking out
> and measuring, and as there is no gauge on the horizontal travel of
> the bed....
>
> There is a dial gauge attached to the adjuster end, but stuffed if I
> know how to use it for this setup.
>
> Arrrgh! - help!!!
>
> Andrew VK3BFA.
>
>