Posts Tagged ‘preston’
It’s been several months since the last router-related blog post, we were busy finalizing the prototypes and preparing for two Lie-Nielsen events we just wrapped up in Philly and Cinci. So a quick status on the tools: pre-orders are now available on our site as most of you know already and we’re just waiting on our final pattern changes to come in so we can place our production order at the foundry. We will soon be finishing our cutter prototype and ramping up production on everything else. Tools are set to begin shipping in June.
Now for the overview of blade positioning in the 2500 router. This is by far the most distinguishing feature of the 2500 when compared to the #71 that Stanley made so popular. With the 71, the blade mounts in the center and can, in certain versions of the tool, be mounted on the back of the center post to give an open throat or bullnose style setup. Preston’s 2500P could mount the blade in four locations: standard closed throat, reverse open throat (or bullnose), inboard of the right-hand post, and outboard of the left-hand post. When mounted on the left or right-hand post, the cutter could only face to the left, perpendicular to the standard direction of cutting. This allowed the tool to be pushed sideways, presumably for working on narrower edges or in situations where a short-wide sole interfered with something on the work piece but and long-narrow sole did not.
The WMT 2500 router maintains the same four blade positions, but we’ve added the ability to rotate the cutter in 90 deg increments when positioned on the left or right-hand posts. This allows the user to hang to tool over an edge and make sweeping cuts, such as when working with tenons. Many woodworkers have done this with the 71, but you can only go out about 1.5″ before the tool becomes unstable. Then the standard practice is to support the other end of the tool with a block of wood that matches the height of your work piece so the tool doesn’t tip… of course problems arise if the support block isn’t exactly the same thickness of your work piece. You also have to take the time to get a piece of scrap and size it accordingly. With the 2500, you can simply move the blade to the side position, rotate the cutter 90 deg, and hanging the tool out 5″ or more is no problem.
Before wrapping this up there are a few details I’d like to point out. First is simply that the cutter shown in these pictures is not our production design. We are still finishing the prototype and will cover that in more detail once it’s ready. Second is that the minimum depth of cut is limited when the blade is in the outer post positions AND rotated 90 deg. The tip of the cutter needs to stick down almost 3/16″ so that the top of the cutter clears the sole of the tool. At first glance you might think, “Why not machine a pocket into the body of the tool that the cutter recess into?” And that’s a fair question. Here’s why we left it alone. Machining into the sole that deep and that wide breaks through the inner corner of the casting and looks awful. Adding more material in that area to prevent this also looks confusing and poorly designed. Next is cost. Milling a pocket in the side of the tool would require another setup and more time which means more money. But the final and most important reason for not bringing the cutter higher into the body is because it really didn’t seem necessary. Small shoulders (less than 3/16″ deep) are typically found on smaller scale work where the tenons don’t stick out very far, simply use the tool in its normal configuration. Long tenons, where you’d want to move the blade out and overhang the work piece quite a distance, are typically found on larger scale work which means the shoulder will generally be 1/4″ deep or more and the minimum depth of cut won’t pose any problems.
Until next time, -WMT
Securing the blade at any given position in a router plane is a simple but critical task the tool must perform. It should be easy, fast, and require no tools as it will be adjusted often. It also needs to hold the blade securely so it doesn’t shift during use. To accomplish these goals a few basic elements of the tool need to be understood. As far as I know, all metal-bodied router planes secure their blades using one of two methods: either using a thumb screw to tighten down a blade-locking collar (typically on larger planes) or by driving a screw directly against the blade shank itself to clamp it against the body of the tool (common on smaller scale planes). Note that wooden-bodied routers often use a wedge to lock the blade.
Next is the geometry of the blade shank itself: round, diamond, and square.
A round shank allows the blade to be positioned at any angle (which is rarely, if ever, necessary), but it can rotate unexpectedly during use which is completely undesirable. It’s the cheapest method of manufacturing, however, as it requires only a simple hole in the body with a screw running into the side of the shank to lock it down. And while this isn’t typically seen on larger tools which see much higher cutting forces in use, it does appear on many small scale router planes where the reduced force is usually not a problem and the blade won’t spin in the body… much. If you are having trouble with a round shank that spins, scuff up the sides of the shank along its length with course sandpaper, that will typically do the trick.
The Diamond shank (where the shank face is rotated 45 deg to the cutting edge) is the most common configuration for large router planes for two reasons. First, the non-roundness of the body means it won’t rotate during use. Second, the diamond, which gets drawn into a V-notch in the body, is self centering and self aligning. It can’t rotate, tilt, or shift side to side.
The only downside is that when the collar is loosened so the depth of cut can be adjusted, the collar tends to fall down the body, sometimes binding on the blade making the adjustment a bit of a headache. Modern manufacturers have resolved this in two ways. Veritas uses a spring-loaded collar so that while the clamping pressure is removed during depth adjustments, there is enough pressure to hold the collar where it belongs and it functions very well. Lie-Nielsen did away with the collar entirely, opting to apply pressure to the shank directly with a brass screw which again, works perfectly. Preston fixed their collar problem by trapping the collar in position with a locating pin which is incorporated into the collar locking screw itself.
The Square configuration (where the shank face is parallel to the cutting edge) is rare. Lie-Nielsen uses it, but they drive a screw against the edge of the shank, not its face. This pushes the blade into the back corner of the body, essentially clamping it against a V-notch just like the diamond shank blades. Preston, however, typically used a square shank with a collar that simply pulls the shank tight against its back face.
The problem with the Preston method is there must be clearance between the side faces of the shank and the notch in the body. As a result, nothing constrains the shank except the friction between the shank and body which is produced by the collar. During heavy cuts, the blade can shift laterally or tilt slightly, neither of which is acceptable. For our design, we’re using the preferred Diamond configuration, but we are going to utilize Preston’s clever pin locator on the collar screw to keep the collar in position when loosened.
Next time, blade positioning. It’s exciting stuff…
Producing handles or knobs for any tool is a tricky thing. Everyone’s hand is a little different as are their preferences as to what “feels” right. It’s not surprising then that with the six router planes we studied the shape, diameter, and height of the knobs were all different. Stanley, for instance, had the shortest and fattest knob while Millers Falls had the tallest and second narrowest. Lie-Nielsen’s knob fell right in the middle of height and diameter and I would say theirs is the most balanced of them all. Veritas, on the other hand, was the most unique with handles that tilt roughly 30 deg off vertical and were some of the tallest in the group.
The Preston 2500P knobs were unusual due to the fact that they are designed to be quickly unscrewed and moved to different positions on the tool (more on that in a later post). The knob itself is not very tall, but its height ends up right in the middle of the other planes because of how the body is designed. The diameter, however, is by far the smallest of the six measuring only slightly larger than 1.5″ where as the others average about 1.7″. That may not sound like a lot, but you can feel the difference as soon as you put the tool to work. This left us with a decision to make; remain as faithful to the original as possible or deliver what we think is the best all-around knob we can. Ultimately we decided to leave it up to our customers. We’re going to offer knobs that are replicas of the original as well as knobs based off the Stanley which are a little over 1.75″ in diameter and have a mushroom style profile. The Stanley was our personal favorite among the all the profiles we tested so we wanted to make them available, but offering the Preston style has historical significance and will undoubtedly be preferred by some portion of the woodworkers out there. We will also be happy to sell either style knob to those of you who may own an original Preston plane with knobs that need to be replaced.
So that’s the story behind the knobs. We haven’t finalized our material yet (feel free to comment on cherry vs. walnut), but we will be offering two styles which hopefully counts for something. Next time we’ll discuss a few changes we’ve made to the original design and how that benefits the user.