Popular Woodworking 2001-08 № 123, страница 26
General 75-050 Ml General International's new benchtop mortiser suffers from one major flaw: the hold-down. Though it looks like the champion hold-down on the Multico,the General's is different.The General's is in two pieces that ride on the dovetailed ways on the post of the mortiser.The hold-down is tricky to adjust flat on the work, and it is prone to slipping under heavy use. Unlike other mortisers, there's a clamp on the front of this machine that holds the work against the fence. This assists the hold-down, but it slows your work down considerably.This slow-speed motor was beefier than most and would stall only occasionally under heavy use. It also had the best handle of any of the machines tested. If General could tweak the hold-down to grip the post tighter, this machine would be an excellent slow-speed model. Contact General at 819-472-1161. Grizzly G3I83 Grizzly's fast-speed mortiser is identical to the Woodtek and Bridgewood machines, except in the paint.And in that one difference, Grizzly did a good job. Of the three clones we tested, Grizzly's fit and finish was the best, edging out the Bridgewood by a nose. Like the Woodtek and Bridgewood, this machine was gutsy and plowed through ash, maple and white oak without a care.Once you figure in shipping costs, the Grizzly is basically tied with the Bridgewood as the least expensive machine tested (the Bridgewood actually is more expensive when shipped to some states). If you can't afford the Multico (or perhaps you want two machines for about $500), we recommend the Grizzly. Contact Grizzly at 800523-4777. JET JBM-5 Of all the slow-speed mortisers,Jet's had the most power. In fact, it stalled only once, and that was in hard maple. Jet put a lot of thought into this machine, and it shows.The chuck key is longer than normal, which makes it easy to maneuver to the chuck.The fingers on the hold-down are 3" long, while most mortisers have shorter fingers, usually 2" to 2 'A". And the fit and finish are excellent.The table on ours needed to be squared to the chisel with two pieces of tape.And the gap between the fence and table is , which helps clear chips out of your way, but not much.Also, the hold-down worked a little loose after several mortises. But overall, when you consider that you get three chisels with the JBM-5, it's a hard deal to say "no"to.This is our favorite slow-speed machine. Contact Jet at 800-274-6848. to buy a fast-speed machine or a slow one. When benchtop mortisers first hit the market, they were all powered by induction motors that turned at 3,450 rpm, the same speed as the motor on your table saw. Recently, manufacturers have introduced slow-speed mortisers that turn at 1,720 rpm. What's the difference? Plenty. Take a look. • Smoking: The slower speed is supposed to reduce the smoking you see in fast machines. All mortisers can produce smoke when plunging the chisel and bit into the wood. In tough woods especially the tremendous friction caused by the combination of the cutting and the chips passing up the flutes of the auger bit inside the hollow chisel causes the chips to scorch. We found that slow-speed machines reduce, but do not eliminate, smoking. • Stalling: Without a doubt, fast-speed mortisers were much less likely to stall during a difficult cut than slow-speed machines. In fact, we couldn't stall a fast machine, even when we pushed it. With the slow-speed machines, some performed better than others. We stalled the Jet only once during our test. But the Craftsman machine stalled more than a dozen times in each 11/4"-deep 10"-long mortise we cut during testing. Why are slow-speed machines more likely to stall? It's simple math. One of the formulas for determining horsepower lays it out simply. To determine horsepower, you multiply the torque of the motor by the rpms and divide that number by 5,250. So it's logical that if you reduce the rpms by half, you're going to reduce the overall power of the motor. It's important to note here that not all slow-speed motors are weak. The burly 1 hp motor on the Powermatic floor-model mortiser 719A (which is not in this test) turns at a slow speed. But because the motor is so much bigger, it has no problems with stalling. It was some of the V2 hp slow-speed machines that gave us trouble. Reducing the clearance between the chisel and bit reduced, but did not eliminate, the stalling in slow-speed machines. It also noticeably slowed the cutting rate of the machine. • Temperature: Slow-speed machines are supposed to reduce the amount of heat in the chisels compared to fast-speed machines, so your tooling will stay sharp longer. In our tests, fast-speed mortisers heated up the chisel to an average of 237° after one 10"-long mortise. The slow-speed machines' chisels averaged 209° after the same amount of work. Heat is the enemy of a sharp edge, so you probably will be caring 32 Popular Woodworking August 2001 |
