The Sherline Miniature Machinist's Newsletter

Number 65, October 16, 2013

http://www.sherline.com

 


Product Spotlight

ï Crosslide Anti-Backlash Adjustment Added to Manual and CNC Lathes

MANUAL LATHEóBoth the CNC and manual lathes benefit from the addition of backlash control on the crosslide axis. This photo shows the manual lathe. New lathes featuring this upgrade will see a price increase of $25.00. All 4400-series lathes now incorporate this feature. Only a few 4000-series lathes remain in stock with the standard saddle and at the lower price.

What is Backlash?óBacklash is the distance a handwheel turns before the slide starts to move when changing directions. Threads cannot be so tight that they rub on both sides at the same time, or they will be too hard to turn and will wear at a rapid rate. Backlash is a fact of life on machine tools and is not a fault in the machineóit simply must be accommodated by proper machining technique. Ball leadscrews with a spiral track filled with tiny ball bearings can reduce backlash to near zero but are expensive, and ones that can handle the torque of our stepper motors are too large for a machine of this size. They are generally only found on larger CNC machines.

On a manual lathe, backlash on the crosslide axis is less of a factor, because the backlash is already eliminated as the cutting tool advances toward the part. However, in a CNC operation where the crosslide might be moving in and out during the cut, minimizing backlash is more important. Sherlineís milling machines were originally designed with backlash adjustment on the X and Y axis leadscrews. This same design has been adapted to the lathe crosslide and will now be standard equipment on all Sherline lathes made after November 1st, 2013.

How it worksóLike the mill X and Y screws, a brass ìnutî on the leadscrew is tightened against the side of the saddle, putting tension between its threads and those of the slide screw insert inside the saddle. Pulling the two threads against each other reduces backlash. The anti-backlash nut has a knurled gear tooth pattern on its outer edge. A brass ìlockî gear with the same tooth pattern engages teeth in the backlash nut, and when the button head screw in its center is tightened down, it locks the anti-backlash nut in place.

CNC LATHEóThe CNC version of the Sherline lathe includes the 4417Z backlash adjustment on the long axis as well as the new crosslide adjustment feature.


Sherline Shop Project of the Month

Brass 1/12 scale 1932 MG J2/Geoff Rhodes

Back in 2009, Geoff Rhodes of England submitted photos of a beautifully polished brass music box that we featured in Newsletter #18. He also sent along these photos of his 1/12 scale brass MG he was working on. Currently Geoff is working mostly on clock projects using his Sherline equipment purchased through Millhill Supplies in the UK, so this project remains as a running chassis without bodywork for now, but it does make it easier to appreciate the engine and chassis details.

Details of the chassis and engine will mostly go unseen when the bodywork is eventually added.

Right side engine details show the twin SU carburetors and right-hand drive steering box.

Left side engine detail includes an exhaust manifold and starter.

The differential, rear axel and batteries can be seen in this view.

Other projects done on Sherline machine tools can be found on the Workshop Projects page at www.sherline.com/workshop.htm.


Shop Tip of the Month

Using SuperGlue to hold small parts for machining/William R. Smith et al.

There are several methods for holding small parts for machining once they have been parted off or have already had most of their surfaces machined. When they canít be clamped in place or held in a chuck, they can often be glued down using a Cyanoacrylate glue of the type commonly sold under the names ìSuperGlueÆî or ìCrazy GlueÆ.î Cyanoacrylate (often abreviated CA) is the generic name for a family of strong fast-acting adhesives with industrial, medical and household uses. This type of glue works best in applications where the surfaces are smooth and make good contact, allowing for only a thin layer of glue. It does not fill gaps and has less shear strength the thicker it dries.

Watch and clock makers use custom made lathe arbors to hold gear blanks. The flat surface has a series of concentric grooves cut into it to contain excess glue and to reduce the contact area to make the part easier to release later. William R. Smith describes the use of several such arbors to hold gear blanks in his books and videos on clock making.* Parts glued to an arbor or a flat tooling plate are easily removed after machining operations are completed. Heat from a torch will break down the glueís strength, allowing the part to be twisted off of the holding surface. Acetone can be used to soften and clean up excess glue on the part. (Be careful not to overheat the part.)

* Master watch and clock maker William R. Smith offers a detailed series of books and videos on clock making techniques. E-mail wrsmith2@aol.com for details.

Image courtesy of W.R. Smith

Bill Smith notes that the key to a good bond on his gear blank arbor are the plunge cuts in the surface. They allow excess Superglue to be squeezed into the channels so only a thin layer of glue remains between the part and the arbor surface. This allows it to dry quickly and with high strength. Do not flood the grooves with glue. Just place a little on the surfaces that contact the object to be held and let the excess collect in the channels.

CAUTIONóIt should be noted that some people are allergic to the fumes of CA glues, particularly when it is heated, so be sure to use in a well ventilated area. Also, CA glues have a shelf life of about a year unopened and one month once opened, so if your part is not sticking well, your glue may be too old.

Alternative holding methodsóAlternatives to using glue include double-sided carpet tape for flat parts and, for larger parts with no flat surfaces to clamp to, automotive body putty such as BondoÆ can be used. Bondo is a 2-part putty that hardens rapidly. Place a blob of it on a piece of tooling plate and push the part down into it, leveling it before the putty hardens. Once the Bondo has hardened and the machining is done, the part is broken loose from the brittle hardened putty and cleaned up.

See the Sherline TIPS page for more useful machine shop tips. If you have a useful tip from your Sherline shop that you would like published, please send photos and a written description to craig@sherline.com.


Did you know?

ï The lathe is an ancient tool, dating at least to ancient Egypt and known and used in Assyria and ancient Greece. The origin of turning dates to around 1300 BC when the Ancient Egyptians first developed a two-person lathe. One person would turn the wood work piece with a rope while the other used a sharp tool to cut shapes in the wood. (www.Wikipedia.org/wiki/Lathe)

ï Sherlineís web page offers a number of free calculators at http://www.sherline.com/calculators.htm. These include calculators for threads, tapers and gear teeth plus links to many other types of handy conversion calculators.

ï Sherline will be closed November 28th and 29th for the Thanksgiving holiday.


Upcoming Model Engineering Shows

2013/2014Ö

ï Estevan Model Engineering Show, Estevan, Saskatchewan, Canada, October (Next show: October 19-20, 2013 the weekend following Canadian Thanksgiving). For updates and info see http://estevanmodelengineeringshow.com/

ï Mid-East Ohio Model Engineering Expo, October 19, 2013,Muskingum County Fairgrounds, Zanesville, Ohio. Sponsored by Debolt Machine, www.deboltmachine.com.

ï April 11-13, 2014ó18th Annual Cabin Fever Expo Model Engineering Show & Auctions in the Utz Arena (Formerly Toyota Arena), York Fairgrounds & Expo Center, York, PA 17404

ï April 26-27, 2014óNorth American Model Engineering Society (NAMES) Expo, Wyandotte, MI. Sherline will have a booth there and the Joe Martin Foundation will present its annual award to Metalworking Craftsman of the Year during the show. See www.namesexposition.com for details.

(Send us your show information and we will post it here.)


Joe Martin Craftsmanship Foundation News

ï Groups Visiting the Craftsmanship Museum in the past monthó

††††††††††† September 16th: CanAm Curmudgeons car club

††††††††††† September 24th: Solana Beach Seniors

††††††††††† September 25th: Hotrods and Pickups San Diego SuperTour

See the Club Visits page for a photo of the groups. You are welcome to visit our museum with your club or group. Call to arrange a group visit. The museum is open Monday, Tuesday, Friday and Saturday from 9-4. Admission is free.

New Exhibitsó

ï Several pieces of Harley-Davidson related silver jewelry by Bryan Freund of McHenry, IL were added courtesy of Craig Libuse. Displayed are a wrench pin, several Harley engine cases and a tiny Panhead engine pin plus two tiny knives. Bryan says more items are on the way.

ï Paul Knapp returned the Alphonse Vassallo Stirling engines to the museum display after showing them at the WEME show in Pleasanton, CA in late August. Along with these he also added eight new engines to the museum display. See the museum web page on his collection for details. In addition, the Novi V8 powered º scale sprint car by Jim Riggle, a supercharged Conley V8 and three other pieces that had been on loan to the San Diego Auto Museum for a special show on auto-related toys have been returned to our museum and are now back on display.

ï A new and very unusual full-size running prototype engine was just received by the museum. It was built in 1964 and patented in 1965 by Peter C. Grunstra. Featured on the cover of the February, 1967 issue of Science and Mechanics magazine, the 4-cylinder ìRodless Rotary Engineî is only about 18î in diameter yet is said to put out 280 horsepower or more using only 12 moving parts. The engine is an air-cooled, supercharged, two-cycle design with no camshaft or moving valves. It is not a Wankle type rotary but rather has four pistons turning on the crankshaft using a scotch yoke principle. It also requires no distributor, oil pump or water pump. The engine is now on display so the public can see this unusual engine for the first time. We thank his sons Robert and Peter Grunstra for the donation. It is seen above its protective ventilated safety cover removed and standing behind the engine.

Museum VolunteersóOur newest Volunteer to join the museum staff is Ed Stewart of Encinitas, CA. Anyone interested in becoming a volunteer and sharing your time at the museum to help us show visitors around or to help out in the machine shop, please contact craig@craftsmanshipmuseum.com or call 760-727-5857 and ask for Craig.