TOPIC II: ADJUSTING THE GAP WIDTH VIA SCREWS (PROPOSED)
(a) Preliminary Discussion. In the standard Pro-Filer procedure, the clearance between the blade and the guide slot of the Pro-Filer is adjusted by applying tape over the surfaces of the blade. In this procedure, the tape also protects highly-polished surfaces of the blade (such as chrome plate) from scratches. The tape is removed after completion of sharpening, and fresh tape needs to be re-applied for the next sharpening. In practice, taping the blades is time consuming, and often unreliable and frustrating; see previous discussion here:
http://skatingforums.com/index.php?topic=6837.0, Replies #12 – 26.
An alternative approach would be a method or a mechanism to adjust the gap width of the guide slot on the Pro-Filer chassis. One such approach is applying tape to the inside surfaces of the slot, as discussed in Reply #1 of this present thread. A principal goal of an alternative approach is to achieve a quasi-static solution: a sharpener that does not require extensive preparation for every operation, yet can be adjusted [infrequently] to accommodate different blade thicknesses as needed. The assumption here is that the typical Pro-Filer user sharpens the same set of blades over an extended period, but wants to be able to reuse the same Pro-Filer when he gets a new set of blades; i.e., the typical Pro-Filer does not need to dynamically change the gap width to accommodate multiple sets of blades over the same period.
(b) Important Note. Even if the slot is lined with a soft material, such as plastic tape, the surfaces of the blades can still be scratched if tape is not applied over the blade surfaces; e.g., if abrasive grit, such as from swarf, comes in contact with the blade surfaces, it likely will cause scratches when the Pro-Filer chassis is slid over the blade. I myself am not particularly concerned with scratches because I’m now using Paramount blades with stainless steel runners: these are not chrome plated or mirror polished. I have previously used Wilson Coronation Ace (chrome-plated carbon steel) and Eclipse Aurora (mirror-polished stainless steel); these blades invariably accumulated scratches from slipping blade guards on and off the blades and from clamping the blades in skate holders for power sharpening. Light scratches on such blades, however, are purely cosmetic. [Some runners for hockey skates are fabricated from mirror-polished stainless steel and coated with diamond-like-carbon (DLC) or other materials all the way to the edges; manufacturers caution that scratches can affect skating performance; however, I’ve not seen these coatings applied to figure skate blades yet.]
(c) Proposed Modification for Adjusting the Gap Width with Screws.
(1) Pix4 shows a rough sketch (not to scale) of the proposed modification superimposed on a photo (end view) of the Pro-Filer chassis (stone removed). The chassis is fabricated from a single block of aluminum alloy. It has a cylindrical chamber for holding the stone and a guide slot with a fixed gap width for sliding over the blade. Viewed from the end, the chassis has an approximately rectangular shape with rounded shoulders and a pair of extended rails. The inner walls of the slot extend along the rails and shoulders.
(2) In the proposed modification, the gap width is adjusted by two rows of opposing screws; the longitudinal axes of the screws are orthogonal to the planes of the inner walls of the slot. One row is installed along the rails; the other row is installed along the shoulders. Since the shoulders are relatively deep, the screws there are installed in wide counterbored clearance recess holes.
(3) In the proposed modification, 0-80 screws are used. The 80 refers to 80 threads per inch (TPI); therefore, one full rotation advances the screw by 0.0125” (under ideal conditions). This should provide sufficient control of the gap width. These screws are readily available and inexpensive. They are available in a variety of materials, including brass, stainless steel, and (surprising to me) nylon up to a 1/2” long. There are even special combos with a metal body and a nylon tip. Also of importance, 0-80 taps are readily available; see further discussion below.
(4) For initial setup, the blade surfaces would be covered with tape, approximately .002 – .003” thick to provide adequate clearance (after the tape is removed). The screws are adjusted such that the tips just contact the tapes. Centering of the blade is done by inserting feeler gauges between the inner walls of the slot and the taped sides of the blades. [This assumes that the slot in the chassis is properly centered to begin with; if not, the screws can be adjusted to provide a proper offset, again using feeler gauges between the inner walls of the slot and the taped sides of the blades.]
(5) To hold the screws in place, gasket adhesive or other suitable thread-locking compound can be applied to the threads before the screws are inserted. After adjustment, a small dab of suitable adhesive can be applied at the interfaces between the screws and the chassis.
(6) Pix5 shows a rough sketch (not to scale) of the proposed modifications to the chassis superimposed on photos of the chassis. Pix 5(a) shows an end view; Pix 5(b) shows a side view; and Pix 5(c) shows a top view. As shown in Pix5(c), the thumb notch partitions the chassis into four similar quadrants. In each quadrant, a row of 0-80 holes are drilled and tapped along the rail. In each quadrant, a row of recessed clearance holes are counterbored along the shoulder, and a row of 0-80 holes are drilled and tapped. For illustration, each row has four screw holes; but depending on the particular screws used (different diameters of screw heads), more screw holes can be added; in particular, the screw holes in the rail can be more closely spaced than the screw holes in the shoulders, since no counterbores are needed in the rails. The configuration of screw holes along the rails can be different from the configuration of screw holes along the shoulders.
(7) The above operations are difficult to do with a hand drill and a hand-held tap wrench (especially the drilling operations on the shoulders). They are more readily done with a good drill press (small run out). For tapping, a spring-loaded tap-wrench guide is held in the drill chuck and used to maintain alignment of the tap wrench. I personally haven’t tried this modification because I don’t have a drill press (good or bad). When I was a grad student many moons ago, I had access to a good machine shop; and I personally drilled and tapped 0-80 threads.
(8) Note that each Pro-Filer kit for figure skates comes with two chassis: one outfitted with a cylindrical diamond-coated mandrel for sharpening, and another outfitted with a cylindrical ceramic stone for polishing. As supplied, the cylinders are captured with roll pins, not intended to be routinely removed. If you remove one or both roll pins, you only need one chassis, because you can readily interchange cylinders. [See Bill’s elegant solution in Reply #6 of this current thread, or my simpler solution in Reply #1 of this previous thread:
http://skatingforums.com/index.php?topic=7896.0.] In this case, you’ve got two chassis that you can customize.
(9) The proposed modification will work only for parallel blades, not tapered or parabolic. I think it will also work for slimline/thinline dance blades, as long as they are parallel. Similarly, for side-honed blades, as long as they are parallel, though the screws may need to be adjusted after repeated sharpenings (most side-honed blades I’m familiar with are tapered or parabolic, but I believe a few are parallel).
Topic: Modifications to the Pro-Filer Hand Sharpener (Actual and Proposed) (Read 7262 times)