The saga continues... Thursday evening once again I tried to get the
aluminum system extension table aligned to the dovetail rails on my
BF6-31. I must have spent another hour on it. Unfortunately, despite
positive thinking, the same result: a depressingly consistent 1-degree
sag. If I adjust the screws for perfect alignment and use a goodly
amount of clamping pressure, it is fine until the slightest weight is
applied. Then, it sags to the same 1-degree position and rests solidly.
Strangest thing.
So, just for a change of pace, I decided it would be worthwhile to
align the cast-iron extension - it needed aligning anyway. Piece of
cake! It only took a few minutes and it is spot-on with no sagging
despite heavy weight. I was impressed with the results and curious as
to what could be different!
OK... so I figured something was wrong with the aluminum extension
table. Could it be the dovetail angle? What if the dovetail was
slightly steeper on the new extension table. That would create the
result I was seeing: precise adjustment, careful mounting, and heavy
clamping pressure would secure the table flush, but only the tip of the
dovetail would actually be clamping onto the table rail. The slightest
weight on the table would cause the aluminum dovetail to pivot away
from the rail dovetail, and the table would come to rest at the point
the two dovetails mated against their full faces.
So, with that theory to go on, I started checking dovetail angles. The
critical one as I see it is the angle between the dovetail and the
table surface. This should match precisely on both the rail and the
extension tables so the dovetails mate solidly across their full bevel
faces. My tools were admittedly crude: a Stanley sliding bevel, a flat
metal rule, and a plastic protractor from an artist's supply house.
With the dovetail facing up (extension tables upsidedown), I positioned
the steel rule on the bevel of the dovetail, then used the sliding
bevel tool from the side to copy the angle between the bevel and the
table surface. I traced this angle with a fine drafting pencil onto a
squared block of maple. I could then use the protractor to read the
angle. The results were consistent within 1/2 a degree or better over
several re-measurements.
My '97 BF6-31's dovetails are all about 29-degrees in relation to the
table surface. The cast iron extension that came with the machine is
also at 29-degrees. This extension aligns perfectly and solidly.
The new aluminum system extension table (F and S couplings) has a
30-degree dovetail. Aha! That would explain why the table wants to
consistently lock down with a 1-degree sag regardless of the adjustment
bolts. They can't compensate for that much difference.
I talked to Felder today, and they are looking into this. I would be
very interested to hear what other 6-series machine owners have for
dovetail angles. Maybe it was changed at one point, or possibly I have
an incorrectly milled extension table.
Well, that's the theory for now. I don't think the aluminum extension
table should be any more difficult to align precisely and solidly than
the cast iron extensions. Something is definately different about it,
and even with my crude measuring devices, it seems to be the dovetail
angle.
At least the F-coupling works very well so I can use it on the sliding
table.
I'll let you all know how this turns out.
..Geoff
nibs-@... wrote:
original article:
=85
I don't know if I have any special hints in adjusting the aluminum
extension
table. It did take me some time and quite a bit of fiddling, but I
got it to
fit right and it doesn't sag. I think if you hold it up by hand so
it's
flush with the machine table and then adjust the screws it may help.
Seems
to me that's what I did ..but it was over a year ago and I don't
quite
remember. Good luck!
Larry
