The Sherline Miniature Machinist's Newsletter
Sherline Workshop Project of the Month
NASCARís Top AwardóThe ìGOODYEAR Gold Carî/Mike Dunlap
Michael Dunlap has
been making model cars for many years. He started out with soldered wire-frame
models and then developed a way to make bodies by the use of electroplating.
With much inspiration and guidance from books on making model cars by Craftsman
of the Year winner Gerald
The primer gray wooden body is seen in the middle. At the top is a urethane mold pulled from the body. At the bottom is the copper body plated inside the mold. It is shown after the windows have been cut out and the body has been polished to a mirror finish.
A special mixture of metals is applied to the inside of the urethane mold so that electrical conductivity is achieved, allowing a layer of copper to be built up inside the mold. When built up to about .025" to .030" thick, the copper body is then pried out of the mold, the window and other openings are cut out, spoilers and other details are soldered on and the body is fitted over a detailed frame with complete interior. Instead of paint, all sponsor decals, numbers and lettering are professionally engraved into the body and then the whole thing is gold plated and polished before final assembly. It is almost a year-long process to make this one model, and it is among one of the most highly prized trophies in the world.
The interior is detailed to match the layout of the winnerís car too. Many small parts have to be machined, polished and gold plated. Above, Michael works on the brass frame and interior.
Here the polished, engraved, gold-plated body and some of the other components can be seen.
Left to right: Team co-owner Jeff Gordon, Michael Dunlap, 2010 NASCAR winning driver Jimmy Johnson and team co-owner Rick Hendrick. Jimmy now owns five of these models, having won the championship a record-setting five years in a row in only his ninth season racing full time.
Michael Dunlap in his shop working with his Sherline CNC mill.
Shop Tip of the month
Lubrication tips for your Sherline machines
The mating surfaces of the arm, the column and the column cap on the Model 2000 mill are to be kept free from lubrication. Tightening the column bolt causes friction between these surfaces to resist movement of the arm during the forces and vibration of machining. If these smooth surfaces are lubricated, the arm or the column could move during machining even if the bolt is securely tightened. Clean these surfaces periodically with mild detergent or bathroom spray cleaner to keep a good "bite" between surfaces. The same goes for the surfaces between the "knuckle" and the ends of the swing arm. These surfaces are smooth enough that adjustment is easily accomplished with the nut loosened even without lubrication. They should be free of dirt and chips, but please resist your natural inclination to lubricate them, as they do their intended job better when dry.
The mill oiler is located in the front right corner of CNC mill saddles. (Click on photo to view larger image.)
Use of stepper motors and computer control can but a lot more turns on a leadscrew in a given amount of time compared to turning it by hand. Since the machines were developed before the advent of CNC, you should be aware that CNC demands lubrication more often than when used manually. Machine slides and the Z-axis column in particular should be lubricated about every two hours during CNC use. To help keep the X and Y slides on the mill lubricated, we have introduced a mill oiler as standard equipment on new CNC machines. (It is optional on manual machines.) This small reservoir holds oil that is distributed to the X and Y leadscrews. The oiler is located in the right front corner of the mill saddle. Unscrew the cap and fill the reservoir before each CNC session and refill if necessary after several hours of use. Oil may continue to leak out after use, but the reservoir does not hold an extremely large volume of oil, so cleanup should not be a problem. Even so, we suggest that CNC machines should be set in a shallow metal pan like the kind used under auto engines on a garage floor. This will help contain chips, coolant and excess lubrication, making cleanup easier. They are available from any auto parts store.
For future reference, these lubrication tips can be found on Sherlineís web site at www.sherline.com/lubricat.htm. Sherline also now offers the same Teflon-based PTFE grease we apply at the factory as an accessory. See P/N 7550 for a 3-ounce tube of the grease ($6.50) or P/N 7555 for an 11-ounce spray can ($9.50).
A Digital Readout box is shown with its power supply on the right. A DRO handwheel is installed on a mill at the left. An optical encoder is enclosed in the housing behind the handwheel. The large diameter of the handwheel puts the increments far enough apart to make visual interpolation to one or -thousandths of an inch possible.
Digital Reaouts (DRO) for the Lathe and Mill
A digital readout used to be considered a luxury, but now you would be hard pressed to find a modern manual machine in machine shop use that did not have one. Why? They make a machinistís life easier and cut down on mistakes. Sherlineís DRO reads to 0.0005" or 0.01mm and can be set to zero on any of the three axes with the push of a button. Unlike the more expensive DROís usually seen on larger machines, Sherlineís does not read the markings on an engraved scale mounted to the slide. To keep costs appropriate for a small machine, Sherlineís DRO reads rotation of the leadscrew by means of an optical encoder in each handwheel housing reading surfaces of teeth on a gear as it rotates. The electronics in the readout box translate these signals into a linear dimension based on the leadscrew pitch. The box can be used in conjunction with either the 20 TPI or 1mm pitch leadscrews that Sherline uses. When the DRO is first used, the user checks to see that it has been initialized to read the proper leadscrew for the machine it is mounted to.
Why use a DRO?
When turning a handwheel, especially over longer travels, it is easy to lose count and go one turn too far or too short. This will leave your cut exactly .050" or 1mm off. Moving each inch requires 20 turns of the handwheel on an inch machine, so a movement of 3.0" would require 60 turns. If the phone rings or you are distracted while counting turns, you could lose track and have to re-home the slide and start over. With a DRO, you just zero the reading at its starting position and turn the handwheel until the readout reads 3.0000".
BONUS FEATUREóIn addition to the advantage of having a DRO, we have included a handy extra feature. An additional encoder is supplied that reads marks on a decal applied to the spindle pulley to give a constant readout of spindle RPM. Knowing exactly what your RPM is takes all the guesswork out of setting cutter speeds.
What about Backlash?
Backlash is accounted for and eliminated electronically by the DRO. The user first measures the backlash on a particular axis. Then the power button on the DRO box is held down for a few seconds until the ìBacklash Settingsî screen appears. Each axis reads 0.0000" or 0.01mm. Each time the button for that axis is pressed the backlash setting advances 0.0005î or 0.01mm. Once the proper setting has been input for each axis, the power button is again pressed and the reading returns to the actual readout. Now, when you turn the handwheel in one direction and stop, when you reverse direction the calculator in the control box allows the handwheel to turn the pre-set amount before it starts counting in the other direction, thereby eliminating backlash. It is clever and it works to as high a degree of accuracy as you are capable of measuring your backlash.
Shown above is the installation kit for a Sherline mill. Included is the box and power supply, three handwheel/encoder units, a stand for the box and a decal for the RPM readout.
Any new Sherline machine can be ordered with a DRO factory installed simply by adding the letters ì-DROî to the part number. In addition, any existing manual lathe or mill can have a DRO added with a minimum of effort. In fact, no holes are drilled, and the kit just bolts on. The DRO is specially designed for Sherline machines, however, and will not work on machines with different pitch leadscrews.
Use with CNCóA DRO-equipped machine can be upgraded to CNC and the DRO function still retained by re-mounting the DRO handwheels and encoders on the rear shaft of the stepper motors. Although this does not comprise a ìclosed loopî system (where the encoders communicate electronically with the CNC controller), it does offer the ability to retain DRO function during manual operation and also acts as a cross-check to actual movement when comparing the reading to the CNC position readout.
Kit Part Numbers and Prices
8100/8160ó3-axis DRO upgrade kit for Sherline 5000-, 5400- or 2000-series mills: $375.00
8200/8260ó2-axis DRO upgrade kit for Sherline 4000 or 4400-series lathes: $325.00
Kits without a readout box for use where a machinist is upgrading a lathe and already has a mill with a DRO are also available as are 3-axis kits for a lathe with a vertical milling column. See the Accessories Price List in the 8100 to 8200 part number area for details.
Did you know?
ï Searching Sherlineís web siteóWe have mentioned this is the past, but we are constantly adding new subscribers, so it wonít hurt to remind you of the easiest ways to find what you are looking for on Sherlineís huge web site.
If you arenít sure of a part number, see item number 1 above on how to locate it by name using the Google search feature.
ï A steam powered Sherline lathe? See http://www.youtube.com/watch?v=3GmbeuJGqLI. The commentary is in Spanish, but the video is pretty much self-explanatory. Weíve seen Sherline tools used to build steam engines, but weíve never seen a steam engine used to run one.
ï Sherline isnít Sure-Line
spelled wrong. It was named after the original manufacturer of the tools in
Upcoming Model Engineering Shows
ï Western Engine Model Exhibition (WEME)óAugust 27-28, Alameda County Fairgrounds, Pleasanton, CA, to be held in conjunction with the Good Guys car show. Hotrods, show cars and model engineeringóa great combination! See www.wemeshow.com for details. Sherline will be there! Craftsman of the Year winner Louis Chenot will also be there to display his incredible 1/6 scale Duesenberg and demonstrate the running of its straight-8, 32-valve engine.
Gas Engine and Antique Reproduction Show
ï Estevan Model Engineering Showó
Send us your show details and we will post them hereÖ
Joe Martin Craftsmanship Foundation News
ï Jim Alexander is joining the museum staff as a volunteer. Jim will be starting on Mondays later this month. The museum is always seeking volunteers to help out with tours. These ìdocents,î as they are called in the museum world, learn about the exhibits and help make a visit to the museum an interesting and educational experience for other visitors. Jim does not consider himself a gifted craftsman, but he finds the projects very interesting and wants to learn more about them himself. This interest and enthusiasm is what we are seeking. If you also happen to be an outstanding craftsman, that is great too, but it is not a requirement. We can teach you what you need to know to educate our visitors. Call us at (760) 727-9492 if youíd like to volunteer. We are also seeking experienced machinists to volunteer to build projects in our machine shop under Tom Boyerís supervision.
The McCulloch 2-cylinder drone engine has had a special base made to hold it,
and it can now be seen on display along with some historical information on its
use in the Radioplane target drones of the 1950ís. A photo of a very young
Marilyn Monroe working at her first job in
The meeting of the