Accurize Your Tablesaw

Have you had these problems?

Accurizing your saw should solve one or more of these aggravating problems.
With the blade set at 90°, your rip cuts may be burnt (A). On the other
hand, your boards may pull away from the fence (B). Wide crosscuts may
tail off, out of square (C). But even if those cuts are perfect, you might have
similar problems with the blade set at 45° (D).

Before you begin the accurizing procedures, make sure your fence lines
up perfectly with the miter-gauge slot. In addition, check your miter gauge.
It should be exactly set to 90° and shouldn’t wobble in the slot.
These fixes could solve all your problems
right away.

Trunnion brackets are the answer.

The mechanism under a contractor saw is relatively
simple (see photo, below). Two trunnions, connected by
long tie rods, allow the blade to tilt. The trunnions have
semicircular raised ridges that ride in grooves in the trunnion
brackets. This mechanism allows the blade to tilt.

The trunnion brackets are bolted to the table through
oversized holes. Loosen the bolts and you can move the
brackets back and forth more than 1/8″. Vibration can
cause the rear bracket to move, which skews the blade out
of alignment. The solution to this problem is to move the
bracket back to its proper position. That only solves half
the problem, however.

Your blade can be perfectly aligned at 90° and still
be off at 45°. How does that happen? When you tilt the
blade, you also tilt the motor, which is cantilevered off
the back of the trunnion tie rods. Over time, vibration
and the motor’s weight may cause the rods to twist
in relation to each other, so they’re not in the same
plane. This shifts the rear trunnion and skews the
blade. Moving or lifting the saw by the motor may
have the same effect.

You can solve the 45° alignment problem in
two ways. I prefer to lower one or both trunnion
brackets with shims. It’s slow-going,
but controlled and precise. You can also
untwist the rods. To do this, you loosen
the tie-rod nuts at the motor end, insert
a lever between the rods and pry. I’ve
tried this method, but I found it too
awkward and hard to control the
results.

If you could look through the table of a
contractor’s saw, here’s what you would
find. The trunnion brackets are bolted to the
underside. Loosening these bolts allows you
to move the brackets, which realigns the
blade to the miter slot.

Align the blade at 90°, then 45°.

Aligning your blade is a two-step process. First, you set
the blade at 90° and align it parallel to the saw’s miter
slot (Fig. A). Second, you tilt the blade to 45° and check
its alignment again (Fig. B). Each alignment procedure requires shifting the trunnion brackets in a different
way. You can’t reverse the order; you must perform
the 90° alignment before moving on to the 45°
alignment.

Fig. A

To align the blade at 90°, shift the rear trunnion bracket
left or right until the blade is perfectly parallel to the
saw’s miter slot.

Fig. B

To align the blade at 45°, lower one or both trunnion
brackets by inserting shims under the table. This brings
the blade back into alignment.

PALS simplifies alignment.

Aligning your blade can be fussy work, but
a precision alignment and locking system (PALS)
makes the job a lot easier (see Sources, page 4). PALS
includes a few pieces of precision hardware that fit on
your saw’s rear trunnion bracket. Believe me, it’s the
best $20 you can spend on your contractor’s saw. After
your saw is trued, PALS prevents it from creeping out of
alignment again.

When your tablesaw blade needs aligning, you have
to shift the saw’s rear trunnion bracket side to side to
put things right. The low-tech way to do this is to tap the
bracket back and forth (see “90° Alignment,” page 4,
Photo 3). Inevitably, you smack too hard and overshoot
the mark. The PALS method is more sophisticated and
much quicker. To move the bracket, you turn a pair of
opposing screws. In effect, you dial in the adjustment.

Installing PALS is easy and doesn’t require special
tools. It fits most contractor’s saws. First, you replace the
rear trunnion bracket’s bolts with studs. (You don’t have
to remove the bracket to do this.) Then you install an
L-shaped bracket with an adjusting screw on each stud.
The PALS hole precisely fits the stud, unlike the oversized
holes in the bracket. The adjusting screws bear
against the bracket’s ends. Turn the screws and you
precisely move the bracket.When the screws bear against
both sides of the bracket and their nuts are tight, the
bracket isn’t going anywhere.

The PALS adjusting screws also make the complicated
45° alignment procedure much easier (see page 5). With
PALS, you can loosen and lower the rear bracket without
losing its correct position.

90° alignment

I use a dial indicator to measure the blade’s alignment
(see Sources, below), but you can also use a combination
square. I installed the PALS system before beginning the
alignment procedure, but it isn’t absolutely necessary
(see “PALS Simplifies Alignment,” above).

1. Position the blade. First, unplug the saw. Tilt the
blade to 5°. Gently rotate the handle back toward 0°.
This relieves any strain from overtightening the tilt
mechanism that might have distorted the readings.
Raise the blade to its full height. Lower it one-quarter
turn to remove strain.

2. Remove play from the miter-gauge bar. If the
bar wiggles in its slot, insert paper or packaging tape
between the bar and slot. You can also push the miter
gauge right or left when you take a reading, so it
always butts against the same side of the slot. Place the
miter gauge in the saw’s right-hand slot.

3. Mark the blade. Remove the throat plate. Locate
a tooth at the blade’s front that’s at or just below the
table. Make a mark on the blade’s plate immediately
below this tooth.

4. Zero the indicator at the blade’s front. Clamp the
indicator’s base to the miter gauge (Photo 1). Adjust
the indicator so its spring-loaded ball foot touches the
mark. Clamp the indicator so its plunger is depressed
halfway. Set the indicator to zero.

5. Rotate the blade. Move the indicator to the
blade’s back and relocate the ball foot on the mark
(Photo 2). If you get a positive reading more than
.004″, the back of the blade is too close to the mitergauge
slot. To align the blade, the rear trunnion
bracket must be moved away from the slot. If the
needle moves in a negative direction and you get a
reading more than .004″, the bracket must be moved
toward the slot.

6. Shift the rear trunnion bracket. From behind the
saw, slightly loosen the bracket’s bolts (Photo 3). (You
may have to remove the saw’s rear rail for access.)
If you’ve installed PALS, turn its adjusting screws to
move the bracket left or right. If you don’t have PALS,
drive the bracket left or right using a hammer and a
pointed stick or dowel. A small tap will make a big difference,
so take it easy.

7. Measure again. Repeat Steps 4 and 5 to see where
you are. When the two readings are .004″ or less apart,
you should be good to go. Tighten the brackets’ bolts
and measure one last time. On the PALS system,
tighten both adjusting screws against the bracket to
lock it in place.

1. Accurate measurement with a dial indicator
makes realigning your saw’s trunnion brackets
much easier. Clamp the indicator to your
miter gauge and zero it on a spot you’ve marked at the blade’s
front.

2. Rotate the blade, slide the indicator forward
and measure the same spot. A negative
reading indicates the blade’s back is skewed
too far from the miter slot. A positive reading
indicates the opposite. Ideally, the difference
between the front and back measurements
should be less than .004″.

3. Shift the rear trunnion bracket by slightly loosening its bolts
and gently tapping left or right with a hammer and a pointed
stick. The blade moves with the bracket. This crude method
works OK, but you’ll find installing a PALS system makes this
adjustment much easier (see “PALS Simplifies Alignment,” above).

45° alignment

Before starting this procedure, make sure your
blade is aligned at 90°.

8. Measure the alignment. Repeat Steps 1 through
5 with the blade tilted away from the indicator
(Photo 4). Adjust the blade to 44° to remove strain.

9. Identify which bracket to lower. See the chart
below. To shim the front bracket, go to Step 10. To
shim the rear bracket only, skip to Step 12.

10. Shim the front trunnion bracket, if needed.
Remove the motor and turn the saw over. Install two
5/16″ washers under each bolt (Photo 5). Tighten
the bolts. Turn the saw back on its feet and install
the motor. You shouldn’t have to turn the saw over
again.

11. Check 90- and 45° alignments again. Repeat
Steps 1 through 8. You should get a positive reading
in Step 8, which means the rear bracket must now
be lowered. Move on to Step 12 to fine-tune the 45°
alignment.

12. Shim the rear bracket. Use scissors to cut
U-shaped shims of various thicknesses. Brass shim
stock works best (see Sources, below). The shims’
correct thickness can only be determined by trial
and error. Start with .006″ shims. Slightly loosen the
bracket’s bolts and insert one shim around each bolt
(Photo 6).

13. Repeat the 90° alignment procedure (Steps
1 through 7). It’s no fun, but you must correct for
any side-to-side movement in the bracket whenever
you’ve loosened it. If you have installed the PALS
system, chances are the rear bracket will not have
moved, but it’s still worth checking.

14. Check the blade’s alignment at 45°. Repeat Step
8. If the readings are within .004″, you’re done. If the
reading is positive and more than .004″, use thicker
shims. If it’s negative by more than .004″, use thinner
shims. Then measure again.

45° alignment for left- or right-tilt saws.

4. Measure the blade’s alignment at 45°. Repeat the same frontand-
back measuring procedure you used to align the blade at
90°. This time, the blade is tilted away from the dial indicator.

5. Place two washers under each side of the front trunnion
bracket if it must be lowered. This requires turning the saw
over. Washers will overcompensate, so you don’t have to turn
the saw over a second time. Fine-tune the alignment by shimming
the rear bracket, with the saw upright (Photo 6). This bracket
is easily accessible.

6. Place thin metal shims under each side of the rear bracket to
align the blade. You’ll have to experiment with different thicknesses
to make the alignment spot-on. It may seem odd, but a
paper-thin shim can shift the blade quite a lot.

Sources

(Note: Product availability and costs are subject to change since original publication date.)

In-Line Industries, in-lineindustries.com, 800-533-6709, Contractor saw precision alignment
and locking system (PALS).

Little Machine Shop, littlemachineshop.com, 800-981-9663, Dial indicator set,
#1782.

Lee Valley, leevalley.com, 800-871-8158, Brass shim stock sampler pack, #27K07.50.

This story originally appeared in American Woodworker October 2006, issue #124.

Purchase this back issue.