Woodworker's Journal 1992-16-6, страница 71

powers the lower arm b\ means of a counterbalanced eccentric cam on the motor shaft, which is connected to the lower arm by a short tie rod; in other words, they are direct-drive saws (see Photo I). The two exceptions are the I:\calilvr and Shopsmilh. which are belt-driven saws.

Currently, there .ire three different constant tension arm designs.

features I feel are desirable for production work, such as cranking out dozens of items ai a shot for crafts fairs. These saws range in price from about $700 to $900. and are roughly comparable in performance and quality of manufacture. The four companies also sell larger and smaller models (with throat depths ranging from 16 in. up to 26 in.) with or without variable speed.

Hie models tested for my "apples-to-apples" comparison include the Delta 40-601 ( I8 in.), Excaliber EX 11(19 in.). Hegner Multimax 18V (IX in.), RBI Hawk 220VS (20 in.) and RBI Hawk 2I6VS (16 ill.). I also included the Shopsmilh 20 in. scroll saw in this group. Even (hough il didn't perform quite as well as the others in several respects, it does fall into the same approximate price range. Also, it's one of several "accessory machines" that Shopsmilh enthusiasts can attach to their Mark V. I tesled ihe freestanding model (with motor and stand): the Mark V v ersion comes with a conversion ku and costs ahoul SI80 less.

For those who need a large-capacity saw but don't w ant to pay $650-plus foi one. I've also reviewed three machines in the $300 lo $400 price range. One is ihe Sears Contractor's Series 20 in scroll saw. While not as mechanicalK refined as the Delta, Excaliber, Hegner,

Noveiiiber/IX-ceinber JSiSC

and RBI models, this new addition to the Sears line performed surprisingly well, making it a good value at $390.

Likew ise. I look a look at a couple of Taiwanese-made "monster" scroll saws: the 23-in. AM I (model 46711 and 26-in. Reliant (model DD26). Because these behemoths offer n lot ol cutting capacity for ihe price ($320 and $330, respectively). I was curious to see how well ihey performed My rationale was that they might be a reasonable alternative for ihose of you who need a saw 23 in. or larger, but can i iustify spending a thousand dollars or more tor one. Because I didn't think n would be fair to compare these and Ihe Sears saw directly to their "high end counterparts, I've discussed ilk in separate!) on pages 74 and 76.

Analotm of a Scroll Saw Be lore gcilmv mto Ihe specific features ■ if (Ik ..i - - ii r >l I feel it necessary lo provide an hu'imcw ot how modern -.. loll saw woik. main!) because the ha i, .inn <l<--.iyiis ot the various saws do milium e ilieti cutting action. You vet-< t.iii i.til avwers can skip ihe anat-oni) lesson, il you want.

I ir i ill modern scroll saws are of a ci hi slant tension design; that is. Ihe M.i.li i lu kl in, iinstant tension between ........... tli.it move in unison throughout the culling stroke. On the older "rigid arm" saws, the top of the blade is attached to a spring, which in turn is mounted lo a rigid top arm. On rigid arm saws the thin blade tends to flex, resulting in frequent breakage and bowing in the cut. Constant tension saws minimize blade flexing, thus enabling the blade lo make tight radius cuts without breaking or bowing. On most of the saws tested, the molor

Photo 1

Photo 2: To adjust blade tension on most parallel arm sans, you loosen or tighten a knob-operated tensioning rod at the back of the saw.

Parallel Arm: Exemplified by ihe Hegner, RBI, Shopsmilh, and most Taiwanese imports, parallel arm saws have two arms that pivot independently, connected by a threaded tensioning rod at the back of the saw, as shown in Photo 2. The arms drive the blade nearly vertically, with a slight forward culling motion on the downsiroke.

C-Arm: The Delia and Sears saws have a C-arm design, in which both the upper and lower arms are a single solid casting, operating oft one pivot point at ihe rear of ihe saw. The result is an aggressive vertical arcing motion: you tension the blade b\ turning a knob thai lifts a short extension on the front of the upper anil.

Double Parallel Link: The Excaliber saws have a unique double parallel link design. Both arms move horizontally instead of vertically: pivot points at the front of the arms transfer the horizontal motion into vertical motion.

One thing I noticed immediately was thai ihe C-arm saws lake a bigger bite on the downsiroke than the parallel arm saws do. The blade on the double

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