On Oct 15, 7:36 am, RayV wrote:
My latest project requires me to rip some 1 1/2" Maple so I deicded to
check blade alignment.
Good idea. Like cherry, maple is prone to show scorch marks and any
closed grain wood will make blade marks more obvious.
I cobbled together a jig similar to thishttp://www.newwoodworker.com/dilindjig.html
to check my setup
That will do the trick for blade and fence alignment.
My alignment, which I think is OK, is 0.001". Not bad considering I
used this method to align my bladehttp://www.woodmagazine.com/wood/story.jsp?storyid=/templatedata/wood...
(whoever came up with that technique is a genius)
I'm wondering why you think the alignment is this close. See my
comments below.
Is the "Ray Vojtash" of the Wood Mag article the same as "RayV" of
this posted message? I'm not sure why you think the technique is
special or better than any other "feel the rub" technique. It doesn't
matter if you hold the stick (or bevel gauge blade) against the miter
gauge or screw it onto the bar, it's the exact same technique.
The runout measuered on the body of the blade is 0.003". I think this
is too much but it could be the 'silver' coating on the Avanti blade I
just bought.
It is a bit high, but not outrageous. It's probably not the silver
coating on the blade (unless this coating is thick paint). This
brings up the alignment question I mentioned above. How can you be
sure of your alignment accuracy when the blade runout is three times
higher? Did you mark a spot on the blade and make all your
measurements on that spot (rotating the blade)? Or did you just run
the indicator stylus along the surface of the blade?
Is 0.001" alignment close enough?
Yes. In general, anything less than 0.005" is good enough. I've done
a lot of testing with various blades and woods. Even with
magnification, I could not detect any improvement in the quality of
the cut surface for alignment error below 0.005"
Is 0.003" blade runout too much?
It means that your cut surface will have ripples in it that are 0.003"
deep. The size and shape of these ripples will depend on how high you
raise the blade and how fast you feed the stock. This sort of defect
can easily be seen and felt on exposed surfaces so expect it to
require some extra cleanup. Good quality modern glues don't generally
have any trouble filling 0.003" gaps between mating surfaces.
You need to determine if this runout is due to blade warp or an arbor/
flange problem. You can easily use your setup to check both the arbor
and the flange. You will want to tilt the arbor so that the dial
indicator can meet the surface of the flange at 90 degrees. You will
want to leave the arbor at 0 degrees to check arbor runout. Hopefully
there is a spot along the surface of the arbor where you can avoid the
threads. You should see less than 0.001" runout on both of these.
Is it OK to have the dial indicator angled so the measurement can be
taken closer to the table or does it need to be 90deg?
The best practice is to keep the dial indicator plunger at 90 degrees
to the surface being measured (zero degrees tilt). When the dial
indicator is tilted at an angle it introduces error into the reading.
The error is going to make the reading look higher than actual changes
in the surface being measured. It will also exaggerate any
instability in your dial indicator fixturing.
(as seen here, but not my site)http://home.comcast.net/~kvaughn65/dial_indicator.jpg
You can calculate the actual geometry from the dial indicator
reading. It is equal to the dial indicator reading times the cosine
of the tilt (away from 90). The cosine of zero degrees is 1 (best
situation). If you are tilting your indicator by 30 degrees, then
multiply your readings by 0.86 to see what it would read if there were
no tilt.
Tilting the indicator is a better alternative than using one of those
flat blade replacement plates. Apart from the monetary savings ($40
or more), and the time you save not needing to swap out your blade,
you won't be introducing a reference surface with unknown errors. The
specs on one popular plate seen in catalogs and online are +/-0.003".
You could think that you've aligned your saw properly when all you
actually did was align it to match the warp in the blade replacement
plate.
Feel free to ask questions.
Ed Bennett
http://www.ts-aligner.com
Home of the TS-Aligner