|
|
Sliding Miter Sled
The following is a short
discussion and description of a table saw sliding miter sled in its
various configurations.
Cross-cutting on the table saw very often demands high precision. The miter gauge provided with most table
saws can be very limited in its versatility. There is little bearing
surface provided for the piece being crosscut,
and there is friction created by moving the piece and miter gauge across
the table saw top. This friction can
often reduce precision with much of your effort concentrated in keeping
the piece from sliding left or right and
from rocking. A sliding miter sled addresses these issues by providing a
secondary surface to which you can
rest the piece being crosscut. Once you have locked the piece against
the fence of the sliding miter sled,
it is left only to move the sliding table past the blade to perform a
very accurate crosscut.
Below is an overhead
view of the sliding miter sled with attached adjustable fence and to the
right of the blade
a fixed auxiliary table.
The auxiliary table serves to keep any offcuts from falling onto the
table top and possibly
binding the saw blade
causing kickback. The sliding miter table and the auxiliary table both
have hardwood
runners attached which
are sized to the length of the table saw miter left and right miter
slots, therefore serving
to align both sides of
the miter sled parallel with the saw blade. Having both the sliding
table and auxiliary table
in close proximity
to the blade also serves as a zero clearance setup for your cuts.
Below is a view of the far
end of the sliding miter sled fence. The fence itself is a 2 inch high
by 1.5 inch thick
laminated slab of hard maple. Any stable hardwood will make a good
fence. The dark hardwood cocobolo
block serves as an adjustable stop block along the 24 inch length of the
fence. The stop block slides along
an aluminum T-track which has been epoxied into a groove in the hardwood
fence. A vertical fence locking
knob is also visible. This locking knob is attached to a 2.5 inch long
cap screw which screws into a blind nut
embedded into the miter sled base. To the right is the adjustment knob
and mechanism to tune and maintain
the fence perpendicular at 90 degrees to the saw blade.
Below is another view of the
sliding table fence horizontal adjustment mechanism. The mechanism
consists of the
4 in. wide cherry block, a 2.5 inch long, 5/16 inch carriage bolt with
nylon washer and a 2.5 in. diameter knob.
The carriage bolt is threaded into a 5/16 inch sized blind nut pressed
into the cherry block and locks with the large,
plastic star knob. The fence pivots very close to the blade end of the
sliding miter sled, whereas the adjustments
are performed at the opposite end pictured below. The advantage to this
setup is adjusting the fence angle as
far from the fence pivot point dramatically increases the accuracy of
the adjustment.
Below is an overhead view of
a block of wood set up to be crosscut to a certain length. The block of
wood is held
against both the fence and the stop block. The sliding table is then
pushed past the saw blade performing the
cut while the piece of cherry is held against the fence. A small offcut will
remain on the auxiliary table after the
cut is complete. The sliding table is then pulled back and the cherry
block removed. The pivot point for the fence
consists of a 3/8 inch carriage bolt through a precisely bored 3/8 inch
hole in both the hardwood fence and the
sliding table base. There is a 7/8 inch counter-bore in the underside of
the table for the carriage bolt head.
The carriage bolt is locked in place with a nylon lock nut and washer.
It is always advisable to stand to the left
of the blade for this operation to reduce any possibility of being
injured from possible kickback.
A second view of the block
of cherry being crosscut to a precise length. Here the cherry board is
just entering
the saw blade. The blade guard above the saw blade has been raised for
clarity, it is normally 2 inches above
the fence of the sliding miter sled. The auxiliary table to the right of
the saw blade is held firmly in place with
4 (1/2 inch diameter) rare earth magnets and cups embedded into bored
holes on the underside of the auxiliary
table. The auxiliary table can easily be popped on and off the saw table
top and the magnets are sufficiently
powerful to keep it from sliding forwards or backwards. A hardwood
runner on the underside of the auxiliary table
for the table saw miter slot, serves to keep the table aligned and to
keep it parallel with the saw table.
Below the crosscut is
complete and the sliding miter sled is at the far end of its travel. The
offcut created by the
cut is left in place on the auxiliary table. The auxiliary table also
keeps the offcut piece from falling onto the
saw table top possibly preventing a kickback. It should also be noted
that the combination of sliding table and the
auxiliary table automatically create a zero clearance kerf for the saw
blade. This zero clearance kerf greatly
increases the safety of the crosscut as it removes any risk of a small
piece being trapped to the right of the blade.
Below the sliding miter sled has been pulled
back and the cherry block will be removed once the saw has
been powered down. Once the saw has been powered down, the offcut can be
safely removed. The sliding
miter sled increases the safety ,ease and speed of making similar, exact
wood parts. Each piece of wood
will be crosscut to the similar, precise length as the previous piece.
Below an overhead view of a piece of cherry having a miter crosscut
performed at 45 degrees. This sliding miter
sled has been set up with fence locks at both 90 and 45 degrees, the
most often used angles. For other angles
such as 30 degrees, it is a matter of swinging the fence to 30 degrees
from perpendicular or 90 degrees.
A 5/16 in. hole is then drilled through the base to fit a blind T-nut
for the locking knob and cap screw. The locking
knob hole in the fence itself can easily be used as a a drill guide. An
adjustable protractor can be used to
determine any angle other than 90 degrees.
Below, another view of the
small cherry block being crosscut at 45 degrees. Notice the small relief
angle cut into
the pivot end of the fence, this provides clearance for the fence end
when cutting 45 degree miters. The aluminum
T-track has also been offset 1/2 inch in its groove to provide for this
clearance in the fence. The sliding table is
guided past the saw blade and pulled back after the cut. The auxiliary
table remains in place to provide a
equally tall base for the offcut which is generated. Any small offcut
pieces are unlikely to bind with the saw blade
as the tight kerf created by both the miter sled and auxiliary table
against the saw blade prevent this.
Below is a close view of the
adjustment mechanism for the fence at 90 degrees. A 2.5 inch (5/16 inch
diameter)
carriage bolt is threaded into a blind T-nut pressed into the hardwood
cherry block. The hardwood block is
located at the furthest point from the pivot point of the fence. The
pencil lines are a guide to setting the fence
exactly at 90 degrees to the saw blade. The carriage bolt head sits
against a small screw set into the fence.
Any adjustments performed at this end of the fence serve to micro-adjust
the fence along its length,
since we perform this 19 inches from the pivot point. . The hardwood
block is attached to the sliding table
base with two screws counter sunk into the underside of the base.
Below is the front view of
the fence angle adjustment mechanism with the 2.5 inch diameter star
locking knob.
This adjustment block is located as far to the left of the fence pivot
point as possible (19 inches) to benefit from
the micro-adjust feature of this distance along the fence. Also visible
is the screw and recessed washer located
along the fence as part of the microadjust mechanism.
Below is a view of the underside of the
sliding miter fence. The sliding miter table has been assembled with
a baltic birch piece approximately 3/4 inch in thickness and 21 inches
wide by 20 inches deep. The width and
length are customized to the saw top left area including wing. The miter
sled is 2 inches wider than the saw top
to the left of the saw blade. The length is long enough to be able to
safely complete any 24 inch deep crosscuts.
The hardwood runner is also visible. Any hardwood can be used for this
runner. It is important to have the
hardwood runner tight in the saw miter slot with next to no sideways
movement. The runner is inserted into a
3/4 inch dado groove in the underside of the sliding table to a depth of
3/16 inch. The blind T-nuts for both the
90 and 45 degree settings are also visible along with the head of the
pivot carriage bolt. Every hole drilled in
the underside is either counter bored or countersunk to prevent the
screw or bolt head from dragging on the
saw table top. The sliding miter table is initially approximately 1/4 to
1/2 inch wider to the right of the saw blade.
Once the sliding table is inserted onto the saw table top, this 1/4 to
1/2 inch piece is trimmed with the saw blade
and the result is a perfectly aligned, zero clearance sliding miter sled
table edge parallel to the saw blade.
Below is the underside of the auxiliary
table. There are four rare earth magnets embedded into the left and
right of the hardwood runner. These magnets serve to keep the auxiliary
table locked on to the saw table top
fixed in place and to prevent it from sliding forwards or backwards
along the table top. The runners are sized at
3/4 inch wide by 3/8 inch deep for the miter slots in this particular
saw table top. The auxiliary table is also
initially oversized by 1/4 to 1/2 inch along the saw blade side. This
piece is then trimmed by the saw blade to
create a zero clearance gap between the edge of the auxiliary table and
the saw blade. The dimensions for this
auxiliary table are 18 inches wide and 24 inches long.
Below a view of most of the hardware
necessary for a sliding miter sled such as described. Any or all
of these individual components can be replaced with equivalent parts.
Other variations of this sliding miter
sled exist with different features. The sliding miter table can have as
many or as few features as necessary.
Some other features might include a longer fence, a sliding extension to
the fence for much longer boards.
All
rights reserved | Tous
droits réservés
© 2010 Refined Edge Design
Ottawa Ontario ON K0A 2P0 CANADA
Phone: (613) 821-5160 E-mail:
studio@normanpirollo.com