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Posted by on September 22, 2006, 7:38 am
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I've just got my first milling machine up and running. It's a
Dore-Westbury which I've been restoring/improving for the last 3 or 4
years.
The TIR on the spindle, measured using a DTI either on the external
Myford chuck register, or on the inside of the MT2 taper socket, is
just under a thou. This doesn't seem too bad (to me)
My question is what run-out is acceptable on a cutter?
I ask because I'm finding that on my machine it can be anywhere between
0 and 3 thou, the variability coming from how I fit my Modeloy milling
chuck into the spindle, and how I fit the cutter into the chuck.
I'm tearing out what little hair I have left trying to get consistent
results. Am I wasting my time?
All advice from the old hands much appreciated
Mike
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Posted by on September 23, 2006, 7:28 am
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mike.crossfield@virgin.net wrote:
> I've just got my first milling machine up and running. It's a
> Dore-Westbury which I've been restoring/improving for the last 3 or 4
> years.
>
> The TIR on the spindle, measured using a DTI either on the external
> Myford chuck register, or on the inside of the MT2 taper socket, is
> just under a thou. This doesn't seem too bad (to me)
>
> My question is what run-out is acceptable on a cutter?
>
> I ask because I'm finding that on my machine it can be anywhere between
> 0 and 3 thou, the variability coming from how I fit my Modeloy milling
> chuck into the spindle, and how I fit the cutter into the chuck.
>
> I'm tearing out what little hair I have left trying to get consistent
> results. Am I wasting my time?
>
> All advice from the old hands much appreciated
>
> Mike
Mike, hi, I have to declare straight away that I am no expert on
milling but I thought I would post a few experiences just to see if we
can stimulate some advice from the better informed.
Just out of interest I measured the runout on the 3MT spindle of my
RF25 mill, to be honest it is almost unmeasurable but at a guess
something like .0002". I only got this after a really good clean and
degrease of the socket which as far as I can see is undamaged; with the
uncleaned spindle I was getting figures of .0005" or so.
When using an Osborne screwed collet chuck and a variety of cutters I
got figures of between zero and .003". The best figures were obtained
with Presto/Clarkson/SKF cutters. The cheap import cutters I have are
all within .0015" and the .003" was a cheap long shank dovetail cutter.
Again to get any repeatable results everything had to be very clean and
I have not yet cracked how to ensure the centre locator is properly
positioned. I have cracked more than one small diameter endmill by
screwing it in too far.
When using a Vertex ER32 system (20 micron spec) the figures were
better but this is a new system compared to a 30 year old Osborn. I
also tried the ER32 with some new drill blanks and got consistent
results all within .0005" so they are all well within the 20 micron
spec. Best results were with the collet holding the max size it could
ie a 6-7mm collet holding a 7mm drill blank.
To be honest although these figures are interesting they don't mean a
great deal. In use the chucks are never that clean and I have not
experienced any problems milling with the import cutters which appear
to be the worst, in fact I thought they all cut fairly well and have
recommended them to several friends who also use them without problem.
I have experience problems with the dovetail cutter which very
obviously cuts on one side when trying to take a fine finishing cut.
I'm not sure if this helps at all Mike but with a bit of luck someone
with more experience will come along and tell us what we should be
getting.
Best regards
Keith
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Posted by on September 23, 2006, 2:03 pm
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jontom_1uk@hotmail.com wrote:
> mike.crossfield@virgin.net wrote:
> > I've just got my first milling machine up and running. It's a
> > Dore-Westbury which I've been restoring/improving for the last 3 or 4
> > years.
> >
> > The TIR on the spindle, measured using a DTI either on the external
> > Myford chuck register, or on the inside of the MT2 taper socket, is
> > just under a thou. This doesn't seem too bad (to me)
> >
> > My question is what run-out is acceptable on a cutter?
> >
> > I ask because I'm finding that on my machine it can be anywhere between
> > 0 and 3 thou, the variability coming from how I fit my Modeloy milling
> > chuck into the spindle, and how I fit the cutter into the chuck.
> >
> > I'm tearing out what little hair I have left trying to get consistent
> > results. Am I wasting my time?
> >
> > All advice from the old hands much appreciated
> >
> > Mike
>
> Mike, hi, I have to declare straight away that I am no expert on
> milling but I thought I would post a few experiences just to see if we
> can stimulate some advice from the better informed.
>
> Just out of interest I measured the runout on the 3MT spindle of my
> RF25 mill, to be honest it is almost unmeasurable but at a guess
> something like .0002". I only got this after a really good clean and
> degrease of the socket which as far as I can see is undamaged; with the
> uncleaned spindle I was getting figures of .0005" or so.
>
> When using an Osborne screwed collet chuck and a variety of cutters I
> got figures of between zero and .003". The best figures were obtained
> with Presto/Clarkson/SKF cutters. The cheap import cutters I have are
> all within .0015" and the .003" was a cheap long shank dovetail cutter.
> Again to get any repeatable results everything had to be very clean and
> I have not yet cracked how to ensure the centre locator is properly
> positioned. I have cracked more than one small diameter endmill by
> screwing it in too far.
>
> When using a Vertex ER32 system (20 micron spec) the figures were
> better but this is a new system compared to a 30 year old Osborn. I
> also tried the ER32 with some new drill blanks and got consistent
> results all within .0005" so they are all well within the 20 micron
> spec. Best results were with the collet holding the max size it could
> ie a 6-7mm collet holding a 7mm drill blank.
>
> To be honest although these figures are interesting they don't mean a
> great deal. In use the chucks are never that clean and I have not
> experienced any problems milling with the import cutters which appear
> to be the worst, in fact I thought they all cut fairly well and have
> recommended them to several friends who also use them without problem.
> I have experience problems with the dovetail cutter which very
> obviously cuts on one side when trying to take a fine finishing cut.
>
> I'm not sure if this helps at all Mike but with a bit of luck someone
> with more experience will come along and tell us what we should be
> getting.
>
> Best regards
>
> Keith
Thanks Keith, much appreciated. Good of you to carry out these tests.
Having spent some more time checking my set up, I've convinced myself
that the axis of the morse taper in my machine spindle is slightly
tilted with respect to the axis of the spindle. This error adds or
subtracts to the errors in the chuck and cutter, resulting in the
variation I'm seeing.
So the question now is whether to live with the run-out of up to 3
thou, or to attempt to re-machine the spindle to improve the Morse
taper accuracy.
Thanks again
Mike
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Posted by Andrew Mawson on September 23, 2006, 3:14 pm
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>
> So the question now is whether to live with the run-out of up to 3
> thou, or to attempt to re-machine the spindle to improve the Morse
> taper accuracy.
>
> Thanks again
>
> Mike
>
IIRC the Dore Westbury was a kit of parts to make at home, so you have
two possibities, either it was wrongly machined by the P.O. or it has
had a bash at some time that has given the spindle a 'permanent
offset'. Probably worth giving the spindle a very close examination,
and consider making a new one. The runout should be imperceptable as
the bearing seatings and taper should have all been machined at one
set up ensuring concentricity. Ultra high precision spindles would
have the socket ground spinning on the actual bearings to be finally
used in the machine.
That said, there isn't a milling machine in existance without some
runout, and all milling cutters will have a tooth that cuts first if
only by a small margin. Take consolation that it will be the first to
wear down <G>
AWEM
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Posted by Steve on September 23, 2006, 3:17 pm
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>
> jontom_1uk@hotmail.com wrote:
>> mike.crossfield@virgin.net wrote:
>> > I've just got my first milling machine up and running. It's a
>> > Dore-Westbury which I've been restoring/improving for the last 3 or 4
>> > years.
>> >
>> > The TIR on the spindle, measured using a DTI either on the external
>> > Myford chuck register, or on the inside of the MT2 taper socket, is
>> > just under a thou. This doesn't seem too bad (to me)
>> >
>> > My question is what run-out is acceptable on a cutter?
>> >
>> > I ask because I'm finding that on my machine it can be anywhere between
>> > 0 and 3 thou, the variability coming from how I fit my Modeloy milling
>> > chuck into the spindle, and how I fit the cutter into the chuck.
>> >
>> > I'm tearing out what little hair I have left trying to get consistent
>> > results. Am I wasting my time?
>> >
>> > All advice from the old hands much appreciated
>> >
>> > Mike
>>
>> Mike, hi, I have to declare straight away that I am no expert on
>> milling but I thought I would post a few experiences just to see if we
>> can stimulate some advice from the better informed.
>>
>> Just out of interest I measured the runout on the 3MT spindle of my
>> RF25 mill, to be honest it is almost unmeasurable but at a guess
>> something like .0002". I only got this after a really good clean and
>> degrease of the socket which as far as I can see is undamaged; with the
>> uncleaned spindle I was getting figures of .0005" or so.
>>
>> When using an Osborne screwed collet chuck and a variety of cutters I
>> got figures of between zero and .003". The best figures were obtained
>> with Presto/Clarkson/SKF cutters. The cheap import cutters I have are
>> all within .0015" and the .003" was a cheap long shank dovetail cutter.
>> Again to get any repeatable results everything had to be very clean and
>> I have not yet cracked how to ensure the centre locator is properly
>> positioned. I have cracked more than one small diameter endmill by
>> screwing it in too far.
>>
>> When using a Vertex ER32 system (20 micron spec) the figures were
>> better but this is a new system compared to a 30 year old Osborn. I
>> also tried the ER32 with some new drill blanks and got consistent
>> results all within .0005" so they are all well within the 20 micron
>> spec. Best results were with the collet holding the max size it could
>> ie a 6-7mm collet holding a 7mm drill blank.
>>
>> To be honest although these figures are interesting they don't mean a
>> great deal. In use the chucks are never that clean and I have not
>> experienced any problems milling with the import cutters which appear
>> to be the worst, in fact I thought they all cut fairly well and have
>> recommended them to several friends who also use them without problem.
>> I have experience problems with the dovetail cutter which very
>> obviously cuts on one side when trying to take a fine finishing cut.
>>
>> I'm not sure if this helps at all Mike but with a bit of luck someone
>> with more experience will come along and tell us what we should be
>> getting.
>>
>> Best regards
>>
>> Keith
>
>
> Thanks Keith, much appreciated. Good of you to carry out these tests.
>
> Having spent some more time checking my set up, I've convinced myself
> that the axis of the morse taper in my machine spindle is slightly
> tilted with respect to the axis of the spindle. This error adds or
> subtracts to the errors in the chuck and cutter, resulting in the
> variation I'm seeing.
>
> So the question now is whether to live with the run-out of up to 3
> thou, or to attempt to re-machine the spindle to improve the Morse
> taper accuracy.
>
> Thanks again
>
> Mike
>
Mike
If you contact the company below, I'm sure you'll get some sound advice.
MES no longer make the DW due to the low cost of Eastern imports, but you'll
get to the benefit of the designer of the later Mk2 version.
Steve
MODEL ENGINEERING SERVICES
PIPWORTH FARM
PIPWORTH LANE
ECKINGTON
SHEFFIELD
S21 4EY
Phone +44 (0)1246 433218
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> Dore-Westbury which I've been restoring/improving for the last 3 or 4
> years.
>
> The TIR on the spindle, measured using a DTI either on the external
> Myford chuck register, or on the inside of the MT2 taper socket, is
> just under a thou. This doesn't seem too bad (to me)
>
> My question is what run-out is acceptable on a cutter?
>
> I ask because I'm finding that on my machine it can be anywhere between
> 0 and 3 thou, the variability coming from how I fit my Modeloy milling
> chuck into the spindle, and how I fit the cutter into the chuck.
>
> I'm tearing out what little hair I have left trying to get consistent
> results. Am I wasting my time?
>
> All advice from the old hands much appreciated
>
> Mike