Ryobi TR31-1 User Manual download pdf (Page 10)

Page 10

chips, and a rougher finish. Bigger chips also require more

power, which could result in the trimmer motor becoming

overloaded.

Under extreme force-feeding conditions the relative speed

of the cutter can become so slow — and the bites it has to

take so large — that chips will be partially knocked off (rather

than fully cut off), with resulting splintering and gouging of

the workpiece.

See Figure 6.

Your trimmer is an extremely high-speed tool (23,000 RPM

no-load speed), and will make clean, smooth cuts if allowed

to run freely without the overload of a forced (too fast) feed.

Three things that cause “force feeding” are cutter size,

depth-of-cut, and workpiece characteristics. The larger the

cutter or the deeper the cut, the more slowly the trimmer

should be moved forward. If the wood is very hard, knotty,

gummy or damp, the operation must be slowed still more.

You can always detect “force feeding” by the sound of the

motor. Its high-pitched whine will sound lower and stronger

as it loses speed. Also, the strain of holding the tool will be

noticeably increased.

TOO SLOW FEEDING

It is also possible to spoil a cut by moving the trimmer for-

ward too slowly. When it is advanced into the work too slowly,

a revolving cutter does not dig into new wood fast enough

to take a bite; instead, it simply scrapes away sawdust-like

particles. Scraping produces heat, which can glaze, burn,

or mar the cut — in extreme cases, it can even overheat the

cutter so as to destroy its hardness. Dull cutters can also

contribute to scraping and burning.

In addition, it is more difficult to control a trimmer when the

cutter is scraping instead of cutting. With practically no load

on the motor the cutter will be revolving at close to top RPM,

and will have a much greater than normal tendency to

bounce off the sides of the cut (especially, if the wood has a

pronounced grain with hard and soft areas). As a result, the

cut produced may have sides that are rippled instead of

straight.

“Too-slow feeding” can also cause your trimmer to take off

in a wrong direction from the intended line of cut. You can

detect “too-slow feeding” by the high-pitched sound of the

motor. Always grasp and hold your trimmer firmly when

trimming.

DEPTH OF CUT

See Figure 7.

As previously mentioned, the depth of cut is important

because it affects the rate of feed which, in turn, affects the

quality of a cut (and, also, the possibility of damage to your

trimmer motor and cutter). A deep cut requires a slower feed

than a shallow one, and a too deep cut will cause you to slow

the feed so much that the cutter is no longer cutting, it is

scraping, instead.

Making a deep cut is never advisable. The smaller cutters—

especially those only 1/16 in. (1.6 mm) in diameter — are

easily broken off when subjected to too much side thrust. A

OPERATION

Fig. 6

TOO FAST

TOO SLOW

Fig. 7

large enough cutter may not be broken off, but if the cut is too

deep a rough cut will result — and it may be very difficult to

guide and control the cutter as desired. For these reasons,

we recommend that you do not exceed 1/8 in. (3.2 mm) depth

of cut in a single pass, regardless of the cutter size or the

softness or condition of the workpiece. This will result in a

higher quality cut.

To make deeper cuts it is therefore necessary to make as

many successive passes as required, lowering the cutter

1/8 in. (3.2 mm) for each new pass. In order to save time,

do all the cutting necessary at one depth setting, before

lowering the cutter for the next pass. This will also assure

a uniform depth when the final pass is completed.

WARNING:

If desired depth of cut is greater than can be safely cut in

one pass, make cuts in two or more passes.

WIDTH

OF CUT

DEPTH

OF CUT

2ND.

PASS

1ST.

PASS

1ST. PASS

2ND. PASS

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Ryobi TR31-1 User Manual Page 10

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