Sharpness measurements . . . Tread straps . . . Non-metallic fasteners . . .
Dear Search Engineer: Is there some simple, inexpensive way to measure the sharpness of a cutting edge, such as on a drill bit, lathe bit, end mill, hockey skate blade, etc., and get some type of numeric readout that would indicate how sharp the edge is, and thus help predict when sharpening is needed? —D.R., St. Paul, MN
Dear D.R.: Use the tool in question as an indentor into a soft copper or aluminum surface. The depth of penetration should be an indicator of sharpness.
Dear Search Engineer: To create a tread strap, I remove the sidewalls from a tire and cut the resulting tread crosswise once. I will overlap the end of one strap with the end of another by 1.5 ft and connect them. Treads used will vary from 6-8 inches wide and from 0.5-0.75 inch thick. The strength of the strap is in the steel belt, not the rubber. The connection should have the tensile strength greater than a tread—about 12,000 lbs—and should last for 25 years. It should be created with hand tools. Naturally, I want it to be as quick and cheap as possible, and aesthetics are not an issue. Any suggestions?—A.T., Louisville, KY
Dear A.T.: A few suggestions from our readers: Instead of overlap, cut the ends in matching male/female patterns, then staple and/or vulcanize in situ the bonding element; try riveting a joiner strip or directly riveting the treads; or contact a tire manufacturer's engineering department for their advice.
Dear Search Engineer: I'm looking for some sort of stranded weave metal mesh with 0.5-mm thick wire. It should be arranged in four-wire groups (no space between the wires) and the opening between the groups should be about 0.5 mm in both ways (horizontally and vertically). Any finishing will do. Any suggestions?—M.M., DN reader
Dear M.M.: Is this a basket weave mesh or are the four wires twisted around each other and then woven? If it is the former, one reader suggests that a flat sheet of metal with photochemically etched holes might serve a similar purpose. Flexibility could be a different issue. According to the McNichols website, they offer alternative weaves and shows illustrations of plain and twill (http://rbi.ims.ca/4389-556). Or depending on quantity, you could try Textum Weaving (http://rbi.ims.ca/4389-557).
Dear Search Engineer: I'm looking for a tiny fastener to join small housing parts together (cellphone components) that isn't metallic. Any ideas? —B.G., DN reader
Dear B.G.: Try one of these: snap latches, molded/integral with product; Velcro; ultrasound welding for non-dismantables; or elastomer interference joining. For a specific example, you could try a silicone/acrylic double-coated tape that is used to mount components inside cellular phones. The silicone side is typically laminated to silicone foam and die cut into dots, and works with low surface energy substrates. The acrylic adhesive is resistant to plasticizer migration. (http://rbi.ims.ca/4389-558).