从国外一个论坛上看到的，用菜板做的，简单实用，呵呵
第一次发帖，不知道图能不能看到
By Terry Downs
Make Your Own Inexpensive Fret BenderGeneralWhen installing frets, it is standard procedure to apply a radius bend to the fretwire, a radius that is smaller than the fretboard radius. It is typical to hammer the frets in the fret slots on each end of the fretboard first. Hammering the "arced-up" center part of the fret pushes the fret barbs sideways into the fret slot. This results in more holding friction. By hammering or pressing the fret straight down, the fret barb leaves an open path for the fret to pop out. This sideways motion of fret installation makes the frets less likely to pop out (or so I've been told). There are several companies that make a fret bender device, similar in operation to the one described here. The nominal cost of such device is $90-100 US$. The parts I used in this project cost about $20 and can all be purchased at Home Depot, in addition to a plastic cutting board from a grocery store. The ball-bearing rollers are simply patio door bearings. They have an outer U-shaped groove, which is particularly applicable for the rounded fret tops. Most other fret benders have flat bearings. The crank is a standard replacement crank for a window casement operator. The plastic used in cutting boards is really easy to work with. I chose to cut the roller from the same board with a circle cutting jig on a router. If you don't have that equipment, you will need to find an alternate way to get a 2" disk. Perhaps one could find some 2" diameter dowel rod and cut a piece off the end.
 This layout allows for adjustment of the roller bearings via slotted holes in the substrate. It is adjustable from infinite to 3" radius. The model below shows the bearings in their extreme positions, going from no bending to a 3" radius. If a smaller radius is desired, an increase on the slot length for the bearing mounting will be required.
Parts ListItem | Qty | Description | 1 | 1 | Bearing, Patio Door (Prime-Line Mfg PN D-1765) 2 per pkg | 2 | 1 | Casement Window Handle (Prime-Line Mfg PN H-3531) | 3 | AR | 3M Safety Walk Outdoor Tread tape (3M 7635NA) | 4 | 1 | 8' x 11" Plastic Cutting Board | 5 | 1 | Machine Bolt, Hex Head, 3/8 -24, 2" with shank | 6 | 2 | Nut, Plain, 3/8 - 24 | 7 | 2 | Washer, Flat, 3/8 | 8 | 2 | Machine Bolt, 1/4 - 20, 1.5" | 9 | 4 | Washer, Flat, 1/4" | 10 | 2 | Washer, Split Lock, 1/4" |
I got these parts from Home Depot.
Making the RollerI made the roller from a portion the cutting board near the handle slot. The rest of the board will be the substrate of the fret bender, plus some scrap.
I set the circle cutting jig on the router to yield a 2" circle. The center roll pin on the jig is 0.130" unsprung. It's designed to go into a 1/8" guide hole. I subtracted half the guide pin diameter from the desired radius and adjusted the distance from the edge of the pin to the flute of the bit to be (1.00 - (0.130/2)) = 0.935". I drilled a 1/8" hole in the plastic cutting board for the guide pin. Here is router in place to cut out the circular piece. I screwed the cutting board to a scrap piece of wood,so that when the bit break through the bottom of the board, it has a surface to cut through (instead of my workbench). I enlarged the 1/8" guide pin hole to 3/8" diameter in the circular piece. I inserted a the hex head 3/8" bolt, and traced around the hex with a pencil. I used a Dremel tool to remove some material around the hex area so the bolt head can have a place to seat. This results in an anti-turn device. That's a bit sloppy, but it works. Cutting the groove in the diskA groove must be cut in the disk to allow the fretwire tang a place to ride in during the bending process. I put the 3/8" bolt in the roller piece using enough washers stacked up to cover up the shank and allow a nut to tighten on the bolt. I then chucked up the assembly into the drill press. I colored the outside of the disk with a felt tip pen. I opened the jaws of a dial caliper to half the distance of the roller bearing thickness (centerline) and used the jaws to scrape between the top of the disk and the side of the disk. This results in the white line within the blue ink. The bearing bushing thickness is 0.372" in this case. Since the plastic roller and the bearings are going to be on washers, the delta is simply half the roller bearing bushing width or 0.186". The caliper jaws make a clear line through the ink. I apologize for the focus issue. It was work in progress pictures.
 I then held a hacksaw against the inscribed line made by the calipers to cut the groove while it turned in the drill press. The groove must be big enough to accept the widest barb of fret tangs, but no so big that the width of the fret falls into the slot. LayoutI cut out the 7" x 4.4" rectangle on the table saw.
The holes in the substrate can be easily laid out by printing the Fret Bender Layout PDF file. I taped the template to the top of the substrate as shown below.
I used a scribe to accurately poke a hole in the center of the cross marks to make a indentation into the chassis top. I recommend using an automatic center punch to make the scribed indentations larger to eliminate walking of the drill bit. I removed the template and drilled the holes next. I used a Dremel tool to make the (2) 1/4" hole pairs into a slot. Note, the ball bearing mounting holes are slotted to allow adjustment for various bend radii.
AssemblyMake sure there are flat washers on each side of the substrate when mounting the bearings and the bender roller. You can see I used lockwashers on the bearing bolts outside the flat washers. I applied some petroleum jelly on the roller disc bolt shank and the 3/8" washers. I installed the 3/8" - 24 nut first. I tightened it gently so the roller will turn freely, but not so loose that it wobbles. I then installed the second nut (jamb nut) and tightened it against the other nut while holding it with a wrench. The hole in the handle was slightly too small. I drilled it out with a 3/8" bit, but be careful. The spline features that mate with the window casing operator will catch on the drill bit. Clamp the crank down on a vise and hope for the best. I was able to hand-thread it onto the bolt, and then tightened the set screw. Your mileage may vary. The bare roller wheel turned out to be too slick to pull the fret wire through. I had to help push it. At that point, I decided to install some 3M Safety Walk Outdoor Tread tape (the stuff used on stair steps to avoid slip and fall) around the roller. Friction is needed. I applied the tape, then cut out the opening for the groove. I then used a scraper to open the slot up a bit. I also applied some Superglue to join the tape ends (see the picture below). I'm hoping that will help keep it from peeling up. The adhesion of the tape to the plastic is not the best of bonds. OperationI've used it with the bearings all the way up (min radius) and not tried any other setting. I use my fingers to bend the end of a fretwire for the initial start into the roller and bearings. Make sure the fret tangs are seated in the roller. The rest is a simple crank action. | 
发表于 2010-9-20 18:40:31
