Dear Search Engineer: I am looking for a non-conductive lead screw that is 2,500 mm long and capable of handling a load force of 50 lbs. —G.R., Milwaukee, WI
Dear G.R.: Lead Screws International (http://rbi.ims.ca/3849-514) should head you in the right direction. If they can't help, try contacting a local machinist who should be able to produce what you require from glass-reinforced nylon bar stock. Failing that, you might consider using a conductive lead screw, electrically isolated from the drive or follower mechanism.
Dear Search Engineer: I'm looking for some references for single-crystal silicon machining and grinding calculations. Specifically, machine speeds and feeds, material removal rates, cutting forces, and power requirements. —J.G., Vancouver, WA
Dear J.G.: Try Crystal Systems in Salem, MA (http://rbi.ims.ca/3849-515). They manufacture silicon billet slicing machinery.
Dear Search Engineer: I'm looking for a product/technique to blank threaded holes before and during hot-dip galvanizing, which can be easily removed post-dip. Does anything exist that can take the high temperatures of 450F+? Many thanks, and cheerio. —J.W., U.K.
Dear J.W.: There are silicone rubber plugs made for this type of application. They can withstand 500F or more . Try McMaster-Carr (http://rbi.ims.ca/3849-516). Or consider high-speed steel, which has the ability to maintain high hardness at temperatures up to 600C. Typical grades to consider are M42 (conventional metallurgy) or even ASP2030 (powder metallurgy).
Dear Search Engineer: On occasion, I get files of drawings in PDF format. How can I convert these files to DXF format? —J.F. in CA
Dear J.F.: Try this procedure:
Convert the .pdf to .eps with Adobe Acrobat
Convert the .eps to .dxf with ghostscript/gsview with the pstoedit plugin (www.pstoedit.net/pstoedit).
In some cases, for example, when outputting a SolidWorks drawing in PDF format, Acrobat can preserve the original drawing's vector format. But even then, most of the original dimensional data can be lost in the conversion to PDF.
Dear Search Engineer: Where can I find formulas for rigid syntactic foam—the kind used in deep water flotation devices? 3M sells the micro-glass beads used in the foam, but not the epoxy polymer used to make the actual rigid block of foam. —L.C., Hawaii
L.C.: Try Emerson & Cuming Composite Materials (http://rbi.ims.ca/3849-517).
Dear Search Engineer: I need a way to measure a range of 6-10 inches ±0.03 inch with a display with no mechanical devices. —F.C., Danville, IL
Dear F.C.: Try a laser or ultrasound measuring device.