Popular Woodworking 2000-10 № 117, страница 29
center. If your bearings are too cheap and have so much play in them that the work chatters when you're turning, you can compensate a bit by adjusting your cutting style to put more of a "push" from rubbing the bevel. Bronze bearings may have less play than cheap ball bearings. You can even turn the bearings slightly out of square with the shaft to tighten them up. Still, machines tend to give you problems at places where motion changes direction, like when car engines "throw a rod," the conversion of the reciprocal motion of your foot on the treadle into the rotary motion of the flywheel is a potential trouble spot. Just as a car needs accurate timing, so too does the foot operating the lathe need timing, as a sudden stop in the foot will meet with considerable resistance from the flywheel, snapping the connection at the end of the tie rod. You will develop considerable expertise with this lathe, but it is so inviting for others to try that you will have a lot of inexperienced feet on it, they will snap the bolt, and excuse themselves by making a com- Jigsaw Table The turnbuckle is right off the shelf, with the addition of a lock nut to one of its eyebolts (obviously not the one with the left hand threads).Without the lock nut, the turnbuckle will work loose in seconds. I also inset a bronze bearing (sawn into a /z" length) into each of the arms at their pivot points.This is not so much to reduce friction in operation as it is to keep the wood from wearing and again loosening the tension on the blade. The bent crankshaft is attached to the jigsaw through a hanging armature link.The mount is attached to the jigsaw with a piece of steel strapping screwed into a saw kerf in the mount, and attached loosely to the lower jigsaw arm. An L-shaped tool rest is shown here attached by bolt and wing nut to the lathe frame.The tail-stock is best attached with a wedge.This is the fastest and the firmest way to move and mount the tailstock.The wedge gives just the right "pinch"to the wood being turned if you slightly cock the bottom of the tailstock towards the center before tapping the wedge home. ment about "walking and chewing gum at the same time," so keep a few spare bolts on hand. Jigsaw As if this treadle lathe were not cool enough, now you can make the jigsaw attachment that sits atop it. Curiously, the jigsaw is basically a way to convert the rotary motion of the flywheel and pulley back into reciprocating motion of the blade. This conversion requires that you loosen the set screws in the stop collars of the driven pulley, remove the drive center and replace it with a crankshaft. Unless you are Superman, you cannot bend these sharp angles in cold V2" steel shafting — you'll have to heat it with a torch and bend it in a vise. The frame of the jigsaw is quite straightforward. I used big dovetails for the front and back posts as the best combination of strength and quick disassembly. The arms of the jigsaw are the only pieces that aren't scrap pine; they are scrap oak for strength. They have to be strong because the turn-buckle at the rear must tension the coping saw blade at the front. I have seen many homemade jigsaws from the past century, and every one used the blade holders from an old coping saw. Often the maker would just hacksaw off the arms of the coping saw and bolt them onto the ends of the jigsaw arms. This has the advantage of allowing you to turn the blade at right angles to the arms when necessary for clearance. It's quite a spectacle when this whole thing is going. The flywheel looks like something off of Fred Flintstone's car, the bearings are rattling, the drive rope twanging, and the jigsaw jumping as your knee goes up and down. But there at the business end, the saw cuts along beautifully, the lathe turns like a top. Won't the kids be proud! PW |
