110154042.pdf

Miter-Saw

Tune-up

iter saws are showing up more and more in cabinet- and

furniture-making shops. Although some of the early-

miter saws weren't reliably accurate, the current gener-

ation has evolved into tools capable of furniture-grade precision

for joinery and trimwork. One big advantage of a miter saw is that

you can get a cleaner cut—especially on long lengths—than you

get with a tablesaw miter gauge because you're moving the blade

into the stock, not the other way around. The result is less wobble

when the cutting edge meets the workpiece. To get consistently

clean cuts with one of these machines, whether you own a chop-

saw or a sliding compound-miter saw, you first have to tune it up

and then carry out periodic maintenance.

Keep your chopsaw or

sliding compound-miter saw

in peak form

JOHN

WHITE

John White is a contributing editor.

START WITH A THOROUGH CLEANING

Begin a tune-up by removing dust and

chips from the base of the saw. You can

safely use compressed air to blow out

the crevices under the saw's table,

but don't use it to clean off the rods

of sliding saws because the blast of

air can force dust past the seals to the

bearings. A shop vacuum is the better

choice. Take off the blade and clean out

the inside of the blade housing and the

guard, removing any pitch buildup

that may interfere with the guard's

motion. Spray penetrating oil, an effi-

cient pitch solvent, on a clean towel

and use It to wipe down the guard

mechanism and the guide rods for the

sliding mechanism. Don't leave excess

oil on the rods; wipe them with a dry

towel once they are clean. Use light ma-

chine oil to lubricate the pivot points

where the head rotates when the saw is

pulled downward.

Lubricate with two different

kinds of oil. Use penetrating

oil on the sliding mechanism

and light machine oil on pivot

points for the head rotation.

MAKE SURE THE FENCE IS FLAT AND SQUARE

Most miter-saw fences consist of an aluminum casting with a

large semicircular segment connecting the left and right

halves of the fence. The circular part of the casting is a weak

spot that can get bent, throwing the two faces of the fence

out of line. Check the fence with a straightedge. The left and

right sides should be in perfect alignment. If the fence is

bent, you have two options to correct the problem: You can

try to straighten the casting, or you can add wood shims to

the front faces. To straighten the casting, remove the fence

from the saw and set it up across two blocks on the bench-

top. With the high side of the fence uppermost, press down

on it with moderate pressure for just a moment, then recheck

it for straightness. Don't use a lot of pressure because most

fences are not that stiff, and you can easily overdo it.

Start with a flat fence. Slightly

bent fences may be pushed back

into alignment. White checks the

fence with feeler gauges.

SQUARE THE FENCE TO THE TABLETOP

The face of the fence should sit square to the tabletop, but

for most types of cuts a small discrepancy won't matter with

this tool. If you have to use the saw to make miter cuts on

large moldings, you can add a wood face to the fence and

shim it as needed to square it to the tabletop. Masking tape

makes a convenient shim material because it's thin enough

for making small adjustments, and it'll stay in place as you

screw the wood face onto the aluminum casting.

The fence should sit square to

the tabletop. For most tasks

these saws perform, this is not a

critical condition. Slightly out-of-

square fences can be shimmed

into alignment with the addition

of a new wood face.

TEST FOR ACCURATE HORIZONTAL ANGLES

gages a series of notches under the

table. The notches can't be repositioned,

so you're depending on the manufacturer

to have properly located them when the

saw was made. Make test miter cuts

with the turntable swung both to the

right and to the left to discover if they're

both accurate. As a final test, cut one

miter with the turntable in each location.

This last test is a good indicator, be-

cause in day-to-day shop work, most

miter joints are made from this combina-

tion of cuts. After sawing, butt the cut

ends together on a flat surface and

check the resulting corner with a square

placed on the outside corner of the joint.

Ideally, you'll find that all three combi-

nations produce 90° corners. If the joint

made with one board cut on each side is

good, but the joints made with both

boards cut on either the left or the right

side are off, chances are the fence was

not set quite right. In that case you

should readjust the fence for square. If

the saw can't produce good miter joints

in all combinations of left and right cuts,

remove the turntable and examine the

alignment notches. With luck, you'll find

sawdust packed in one or more of the

notches, and the problem will be solved

with a simple cleaning. Another option Is

to align the fence to create a good joint

on one side of the blade, with a loss of

accuracy to other turntable positions.

Built-in adjustability. The two

screws on either end of this fence

pass through holes that are slotted,

which allow you to square the fence

to the blade.

Most owner's manuals say to use a

square to align the blade to the fence,

but I think that approach is a waste of

time. You're better off measuring the

squareness of an actual cutoff and ad-

justing the setting as needed. Joint and

mark one edge of a board that's 4 in.

wide or more. For all of the test cuts,

place this edge against the fence and

use It to check the cuts with a square.

Correct for out of square by shifting

the fence. But before loosening the bolts

that clamp the fence to the table, scribe

a pencil line at each end of the fence to

mark its location. These marks will make

It easier to judge how much you move

the fence as you square it up. Once the

saw has been properly aligned, set the

pointer on the miter-angle scale to line

up precisely with the 0° mark.

CHECK THE 45°-MITER SETTING

To check whether the saw will cut accu-

rate 45° miters, you'll need two scraps at

least 3 in. to 4 in. wide and a couple of

feet long. As in the tests for square cuts,

one edge on each board should be joint-

ed straight and marked as the test edge.

With most saw designs you can only

check whether the 45° stops were ma-

chined properly at the factory. The saw's

turntable is positioned by a pin that en-

ADJUST THE FENCE FOR A SQUARE CUT

Ignore the owner's manual.

Joint the edge of a piece of

scrap, place it against the

fence and make a cut. Check

the cut edge with a square to

determine the blade-to-fence

setting.

Give yourself a reference line. Use

a pen or pencil to mark the location

of the fence on the tabletop before

making adjustments, which can easi-

ly be made by pivoting the fence.

TEST FOR ACCURATE VERTICAL ANGLES

bevel-angle scale to line up precisely

with the 0° mark.

With the vertical and horizontal

square stops set, you can adjust the stop

for cutting 45° bevels. You'll need two

boards about 3 in. wide and a couple of

feet long. Square up the boards and

mark the best edge on each board. Lock

the saw head to the 45° vertical stop.

Miter-cut one end of both boards, with

the boards held vertically against the

fence, keeping the designated edges

against the tabletop. Cutting the boards

vertically gives you a bigger miter to

check for accuracy than what you'd get

by cutting a bevel in the thickness of the

boards. Assemble the joint on a flat

benchtop. If the two boards don't form a

square corner, it'll probably take several

adjustments to get the joint square, but

the effort is worth the trouble.

Vertical adjustments are

easy. Two bolts with locknuts

act as 45° and 90° stops.

To check the vertical alignment, follow

the same procedure used for the horizon-

tal setting, employing a test scrap 2 in.

to 3 in. wide and a couple of feet long.

Joint one edge until it's dead-on straight,

then mark it. This edge will sit flat on the

tabletop for all of the test cuts.

Set the saw at both the vertical and

horizontal 90° settings and lock them in

place. Make a test cut on one end of the

scrap and check it with a square. If the

cut end isn't square, adjust the stop,

which is a simple job on most saws-

typically it is a bolt and locknut easily

accessed at the back of the saw. Some

saws come with a special wrench to

loosen the locknut because clearances

can be tight.

To make an adjustment, tilt the saw

head to take pressure off the stop bolt,

then loosen the locknut. Turn the

bolt to correct the alignment, lock

it down again and make another test

cut. It may take a couple of tries to get a

perfectly square cut on the test piece.

Once you're there, set the pointer on the

You need two pieces to test miters.

Scraps at least 3 in. wide are better than nar-

row pieces to get a good reading on a miter.

Two wrenches required. To adjust the 45°

and 90° stops, you may have to tilt the saw

head to access the bolts and locknuts.

Troubleshooting at a glance

SYMPTOM

SOLUTION

Replace the mediocre blade that came with the

machine with a new 80-tooth crosscut blade

Rough sawcuts

Loss of power,

sparks in the motor

Replace the brushes (see the photos at right)

This brush is still in good shape. Worn-out brushes can

lead to sparks coming from the motor, and they can indicate

a loss of power. Replace brushes when they get too worn,

which would be about half the size of the one shown here.

Out of square or

off-angle cuts

Tune up settings and stops as indicated

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