36 - Miter Trimmer, страница 14

SELECTING TOOLS

Performance

Test Procedures. A sabre saw has an incredibly tough job — making a controlled, accurate cut in all different kinds of materials. To test the performance

of these saws, we plowed through 2"-thick oak (left), made intricate scroll cuts in plywood (center), and sawed heavy-gauge metal (right).

[?l| When it comes to the overall ■performance of a sabre saiv, what exactly are you looking for?

Bryan: It's really a combination of things. A sabre saw has to run smooth. Yet it needs to have enough power that I don't have to coax it along.

At the same time, I want a sabre saw that makes it easy for me to make a controlled, accurate cut — regardless of the type of material I'm working with.

That's why having variable speed control is so important to me. For making rough cuts in lumber or plywood, I adjust the saw for a fast cutting speed and don't worry too much about the quality of cut.

Guide Blocks. ►

Two guide blocks on the Porter Cable keep the blade from deflecting to the side as you make a cut. And a roller supports the back of the blade.

Guide Roller. ►

A roller with a centered groove supports the blade on all the other saws. The sides of the groove fit closely around the blade which limits the side-to-side movement.

But if I'm working with metal or plastic laminate (or if the accuracy and quality of cut are more critical), I'll adjust the saw for a slower speed setting.

Kurt: The nice thing about each of these saws is I can dial in the exact speed I want. But the DeWalt has one additional feature that gives me just a bit more control over how fast I'm cutting.

With this saw, the trigger acts like the accelerator on a car. I can change how fast the blade is cutting by the amount of pressure I use to squeeze the trigger.

That comes in handy if I'm cutting around a tight curve. By easing off the trigger, I can slow down the cutting speed and make an accurate cut around the turn.

Editor's Note: The trigger on the top handle model of the Bosch has this same built-in speed control, see chart on page 13.

But isn't there more to getting accurate results than being able to control the cutting speed?

Kurt: You bet. All the saws have some sort of guide system that keeps the blade from deflecting as you make a cut. But they go about it in different ways. ₍

To limit the side-to-side movement of the blade on the Porter Cable, there's a pair of steel guide blocks attached to the base. (See photos at left.) And a roller provides support for the back of the blade.

The rest of the sabre saws

plunge rod housing

bearing engages cup _v

cup raises and lowers plunge rod

rocker plate presses pin into roller arm

blade cuts on upstroke

roller arm

grooved roller pivots blade forward

▲ Orbital Action. To produce a more aggressive cut, the roller \ pushes the blade forward into the workpiece during the upstroke. On the downstroke the blade returns to its normal position.

14

ShopNotes

No. 36