The Sherline Miniature Machinist's Newsletter
ìBaby Beamî steam engineóa CNC project/Alan Marconette
††Alanís project is seen before the socket head screws were replaced with more period-appropriate fasteners.
ìThe "Baby Beam" Steam Engine was inspired by the M.E. Beam engine published in '59, which was scaled from the 1914 M.E. article by George Gentry. George did an accurate prototype model of the engine. I've heard that it is of the form of engines designed by William Fairburn around 1840-1850.
The engine is approximately 6" tall, 11" wide and 6" deep. Shown is a 5" flywheel made using CNC, and the plans include an optional 6" flywheel of an alternate design. This engine was built using many CNC part files and was entirely machined on the Sherline mill and lathe. This version was built with a brass cylinder, steam chest and beam, although aluminum could be used as well. The base is aluminum, and, although 10" long, was machined on the Sherline mill as well!
The bore is 3/4" and the
stroke is 1 1/2". The design incorporates a slide valve driven
through considerable linkage. The piston drives the 6-1/2" beam through
Alan Marconett KM6VV
Shop Tip of the month
A fixture to keep from breaking small taps/Bob Shores
"I have read many tips on tapping holes-some good, some not. Five years ago I dreamed up a tapping method for small holes. I tap a lot of holes with 0-80 and 2-56 threads, and since I have been using this method, I have not broken a tap in five years.î
This simple fixture is easy to make and can help keep you from breaking expensive small taps.
The tap is held in perfect alignment by the chuck. When the chuck is loosened slightly, the tap can be rotated using the disk and your fingers , providing an excellent "feel" for the process. The tap goes in straight making it less nlikely to break.
ìAfter drilling the hole in your part to the proper size for tapping, the drill bit is removed from the chuck without disturbing the work. A 2" aluminum disk, knurled on the outside and drilled and tapped for a 4-40 hex bolt grips the tap just above the flutes. The end of the tap is gripped in the drill chuck and lowered until it just touches the work. The chuck is then loosened to allow the tap to turn freely. The disk holding the tap is turned with your thumb and forefinger. The drill chuck acts as a guide to keep the tap running true, and your fingers are very sensitive to the amount of torque being applied. To break a tap you would have to apply a lot of force.î
This and more than 50 other helpful tips for Sherline machinists can be found at www.sherline.com/pages/tips.htm.
Chucks and Collets
†4-jaw, 3-jaw, 4-jaw self-centering and drill chucks
†The 1160/1178 set comes with 5 WW collets, a drawbar, knockout bar and collet adapter.
The easiest and most versatile way to hold work in the headstock of a lathe is through the use of a 3-jaw or 4-jaw chuck. There are several types and each has its advantages and disadvantages:
1. 3-jaw self-centering chucksóAvailable in 2.5î or 3.1î diameters, these chucks have three scrolling jaws, making it possible to grip round or hexagonal parts. The disadvantage of scrolling jaws is that centering accuracy cannot be controlled. Advantages include the ability to grip work that is not perfectly round and ease of use.
2. 4-jaw independent chucksóAgain available in 2.5î or 3.1î diameters, these chucks have 4 jaws that are closed independently. The advantage is, this lets you grip just about any shape part either off-center or perfectly on center. The disadvantage is that it takes a while to accurately locate a part. A 4-jaw can also make an excellent ìviceî for use on the mill.
3. 4-jaw self-centering chucksóAvailable in 2.5î or 3.1î diameters, these chucks offer the quick closing advantage of a 3-jaw with the ability to hold round, square or octagonal stock. The disadvantage is that, unlike a chuck with 3-jaws that will always be able to find three points of contact, work must be accurately square or round to be gripped in this chuck or all four jaws may not grip the part. Another advantage is the ability to spread out the grip to an extra jaw, which can be helpful when gripping thinwall tubing without crushing it. Runout on all 3- and 4-jaw chucks is specified to be less than 0.003î.
4. Drill ChucksóAvailable in 5/32î, ºî and 3/8î sizes, these chucks made for holding drills or reamers. Interchangeable arbors on the ºî and 3/8î chucks mean they can be used in the headstock of a lather or mill or tailstock of a lathe. Runout is specified to be less than 0.003î
When a runout of 0.001î or more is not tolerable, maximum centering accuracy can be obtained using collets. A collet is essentially a small chuck that holds a particular size part. Since they donít have much closing range, the part must be within .002î or so of the colletís size, but collets are available size by 1/64î or 0.1 mm increments, so the size you need is always available. The collets shown are WW collets, which have a ºî through hole and external threads and are sized up to 5/16î or 8.0 mm. They are placed in a collet adapter that goes into the #1 Morse taper of the headstock and pulled closed using a hollow drawbar from the back side. These are particularly popular with watch and clock makers, but can be used in any machining application where you must accurately hold a small round part.
Mill collets are also available that have a #1 Morse taper and are pulled directly into the headstock spindle with a drawbolt from the rear. These are used to hold end mills that come in common shank sizes from 1/8î up to 3/8î.
Sherline manufactures all its own 3-jaw and 4-jaw chucks, mill collets and WW collets in order to control accuracy and keep price at an affordable level.
Did you know?
ï Illustrated instructions for the use of all Sherline accessories are posted on our web site. Go to www.sherline.com/accessor.htm for links to both HTML and PDF versions of each. This is a tremendous source of free information on machining. A copy of the 48-page instruction manual can also be found at www.sherline.com/InstVol6.pdf. Also, if youíve got a friend who might like a Sherline catalog, send them a link to www.sherline.com/catalog8.pdf.
ï This month Sherlineís radius cutting attachment is on sale at 20% off, meaning you can save $24.00. To learn more, see www.sherline.com/special.htm or go to www.sherlinedirect.com and click on the ìMonthly Specialî link to order on-line any time of day or night.
ï Two handy free calculators developed by Joe Martin are available on our web site at http://www.sherline.com/calculators.htm. One helps with gear tooth calculations and the other helps when cutting threads. They are in the form of Excel spreadsheets.
WEME (Western Engine Model Exhibition),
GEARS (Gas Engine Antique Reproduction Show), September 19-20,
Joe Martin Craftsmanship Foundation News
ï Two new craftsmen were added to the On-line Craftsmanship Museum in the past month. Both exhibit somewhat unusual skills. GarE Maxton makes very artistic and challenging metal puzzles, while Randy Boni turns tree stumps into naturalistic works of art using a tool not usually associated with precision workóa chainsaw.
ï Also added to the on-line museum is another all-wood steam engine by Australian woodworker Harold Manwaring. This time it is a stationary engine called ìMaryî rather that a locomotive, but equally impressive.
ï Thanks to Jerry Kieffer for his donation of 139 back issues of the NAWCC Bulletin magazine for our museum library, bringing our collection of that magazine up to a point where only a few of the more recent issues are missing. Others wishing to donate back issues can contact Craig at firstname.lastname@example.org for a list of the issues still needed.
The Foundationís Chairman of the Board, Paul Knapp will be displaying part of
his extensive engine collection at the WEME