The Sherline Miniature Machinist's Newsletter

Number 6, June 16, 2008

Customer Projects: A Small Supercharger by Robert Rosenfield

    The supercharger turbine blade in production and finished. The body and other parts are also shown.

According to Robert Rosenfield, this is the brand new Model SC125 supercharger designed for 50 cc thru 125 cc four-stroke motors used in pit bikes, super pocket bikes, go-karts, Honda 50's, etc. Overall dimensions are 4-1/2" O.D. x 5-1/2" tall x 4-3/4" wide. Turbine: 63 mm (2-1/2") 30º blade with left-hand thread. Design features include 2-1 pressure ratio variable boost, maximum 100,000 RPM shaft speed and 24-34 mm carburetor sizing. Pressurized oil feeds to plain bronze bearings with VitonT seals for high temperatures.

The photos show that Robert has also been able to obtain really nice finishes with his manual and CNC Sherline machines. The main body is made from one large billet of aluminum. It can take several days of machining time to get it down to size. Although this could be done quicker on a larger, more powerful machine, it is interesting to note that the hobbyist with time and talent but limited funds and space can still achieve superb results with tabletop machine tools.

More on this and other projects done on Sherline CNC machine tools can be found on the CNC Projects page at

New Products

  Holder and carbide inserts

P/N 2267—3/8" Insert Holder for Threading and Grooving Inserts—Offered in the past as a tool made by Valenite, Sherline now manufactures its own holders for carbide threading and grooving inserts. The 3/8" shank fits the optional P/N 7600 tool post. The 7.32" hex key for tightening the 6-32 clamp screw is included with the holder. Double-ended carbide inserts are available for threading (60°, P/N 2268, $23.00) and in two sizes for grooving: P/N 2269 is .031" wide and P/N 2270 is .062" wide. They are also $23.00 each. For those who like working with carbide inserts, this tool gives you some additional choices.

Shop Tip of the Month—Direct Reading Crosslide Handwheel by Fred Smittle

 The metric handwheel has 100 marks rather than 50. The adjustable zero version is shown here.

On the Sherline lathe, the crosslide feed on inch machines utilizes the same 20 tpi leadscrew pitch as the other axes. Because you are removing metal from the radius of the spinning part, a given movement of the crosslide feed takes twice that amount off the diameter. For example, if you advance the handwheel .010", the part diameter is reduced by .020". Many modern lathes take that into account and provide a handwheel that reads half the actual travel, so that if you want to remove .020" from the diameter, you turn the handwheel to read that same amount. Because the Sherline lathe has the option of being used as a milling machine with the addition of a vertical milling column, it was decided that it would be too confusing to have different units of travel in the X and Y axes.

Owners of inch lathes who wish to have a direct-reading handwheel on the crosslide can solve that problem by simply ordering a metric handwheel. These handwheels have 100 marks on them instead of 50. That means the number of marks you advance the handwheel will represent the actual reduction in the diameter of the part in thousandths of an inch. The numbers on the metric handwheel actually say .1, .2, through .9 and back to zero with 10 marks between each number. Just remember the decimal place moves over one place so that .1 actually means .010" and each individual mark represents .001" off the diameter.

Standard metric 1-5/8" crosslide handwheels are P/N 4105 ($10.80) and 2" adjustable zero handwheels (metric) like the one shown are P/N 3430 ($35.00)

Web site facts

• Google Search Feature—The navigation bar at the top of the opening page of Sherline’s site has a “Search This Site” button. Clicking on that (or scrolling down a little on the opening page) takes you to the Google Search Bar. Type in any part number, name or phrase and hit “search,” and Google’s super-fast search engine will search just the Sherline site and show you all instances of your search word or phrase. It’s easy to find parts and accessories that way when you can’t remember the part number. Also, say you saw an interesting project or photo on the site but now can’t find it. If you can remember the builder’s name, what the object was or anything unique about it, this can help you find the page again. On a site as large as Sherline’s this is a handy thing to know. The product line and the site itself has gotten so big even the folks at Sherline use it now and then to find things we know are there but can’t remember the navigation path to get there.

Coming Events

• For those in Southern California, the Vista Antique Gas and Steam Engine Museum ( will be hosting their semi-annual show the weekends of June 21-22 and June 28-29. We will be there with a small exhibit from the Joe Martin Foundation and a lathe to demo on the first weekend, June 21-22.

• The next major model engineering show we will attend will be the Western Engine and Model Engineering  (WEME) show in Vallejo, CA July 19 and 20, 2008. See their web site at for details.

Joe Martin Foundation News

 Tom Boyer and Craig Libuse give a presentation to the Ocean Hills Senior Community woodworking club in Vista, CA in June. We’re always trying to find ways to let the local community know about the museum and web site.

Special Saturday Museum Hours, June 28. To allow people who work during our normal weekday hours to see the new additions to the museum we will be having an “open house” from 10 AM until 3 PM on Saturday, June 28th. This is the second weekend of the Vista Antique Gas and Steam Engine Museum show in case you are in town for the show and would like to venture to another spot in Vista on that Saturday. As always, admission to the museum is free.

Visit the on-line museum at