68 - Our All-New Router Jig, страница 25
Aluminum T-frackT-track is a great piece of hardware for building jigs that are accurate and adjustable. T-track is available in varying lengths and fastens in place with a few screws that pass through the bottom of the T-track. (Note: T-track varies in thickness, so be sure to design your jig to accommodate it.) For shorter lengths, you can easily cut the T-track with a carbide-tipped saw blade or a hacksaw. Regardless of the manufacturer, all T-track operates on the same basic principle. A slot in the track accepts a flange (or toilet) bolt (upper photo) or the head of a hex bolt (lower photo). By slipping an accessory (like a stop block) over the bolt, you can position it anywhere simply by sliding it along the track. Locking it in place is just a matter of tightening the knob. Ratchet Knob your knuckles against an exposed bolt. A captured knob has an insert embedded inside that fits over the end of the bolt and covers it up (see lower left drawing on opposite page). This type of hardware works fine for a stop block where the total movement is limited. But the drawback to a captured head is that the bolt may bottom out before the knob is tightened down completely Studded Knobs - To solve this problem, you can turn to a knob with a stud (threaded shaft), like you see at the bottom of the opposite page. The studs are embedded in the knob when it's manufactured. Studded knobs come in a number of different lengths. Although you can cut the stud to whatever length you need, it's a good idea to keep a few different lengths on hand. Through Knobs - But there's a small problem. Studded knobs are typically only 1" to IV2'1 long. So when the thickness of what you're clamping varies quite a bit, it's better to switch to a through knob and a carriage bolt, as in the lower drawing on the opposite page. Like a captured knob, a through knob has an insert embedded inside to accept the threads of the carriage bolt (or other fastener). But a hole in the top of the knob means you can use any length of fastener. Ratchet Knob - In most cases, any of the knobs mentioned will work. This way, you can even use a large knob to get a good grip and make full turns, like you see in photo P above. But in tight situations, I turn to a ratchet knob, see photo Q. It's an adjustable knob with a large handle that can be tightened (or loosened) in close corners. By lifting up on the spring-loaded handle, you can ratchet the handle back and forth until it's tight. T-TRACK Knobs and fasteners don't always have to stay in one spot. An easy way to make a jig adjustable is to use knobs, fasteners, and a piece of hardware called T-track. (See the box below for more information). You won't find T-track at the local hardware store. But there are a number of woodworking catalogs and stores that carry it (see page 35).
USE RATCHET KNOB IN UGHT , LOCATION Note: Ratchet handles come in studded or captured versions (to use with a threaded fastener). FENCE A LARGE KNOB WILL WORK IN OPEN SPACE TO PROVIDE FULL TURNS USE RATCHET KNOB IN UGHT , LOCATION No. 68 ShopNotes 25 |
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