The Sherline Miniature Machinist's Newsletter
Customer Project of the Month
Making a “Bull’s Foot” file/Jerry Kieffer
Here is a secret from master model engineer Jerry Kieffer for those who wonder how he and others get perfect finishes on small parts. Have you ever had to file down a pin that sticks up above a flat surface, only to end up making things worse by putting file marks in the whole surface? How do you file the pin without touching the rest of the surface? Horologists (watch and clock makers) have developed a tool for just this purpose called a “Bull’s Foot” file, and you can make one yourself on your Sherline mill. You may have a broken file on hand you can use, or you can sacrifice part of a new one, but it should be sharp and of good quality. Here is what Jerry Kieffer suggests:
“The bull’s foot file consists of a short section of flat file set into a round or square piece of steel stock as in the photo below. In this case it is held into the machined groove with epoxy. The side surfaces of the stock are then machined/stoned/polished to about .0005" above the face of the file section. In other words, the side surfaces of the metal stock hold the file section less than a thousandth of an inch off the part’s surface so it can flush file anything that protrudes above a flat surface without affecting the surrounding area. Note that the sharp corners on both ends of the file sections have been rounded off to avoid any marring of the part’s surface. Because the side surfaces are polished smooth, they will not mark the surface they make contact with.
A custom made "Bull's Foot" file
The example in the photo above is made from 0.800" diameter steel stock with a #4 cut, .250" wide pillar file section epoxied into the machined groove in the middle. They are generally used for smaller projects; however, they can be made in any size for whatever projects you have in mind. I have my students at the NAWCC School of Horology make them as a way to fine-tune their machining and hand finishing skills, and I do find myself using this item on a regular basis on all sorts of projects to save time and give my parts a professional looking finish.”
You can see more workshop projects on the Sherline web site at www.sherline.com/workshop.htm.
Installing a free RPM gauge on your lathe or mill/Joe Martin
Knowing the exact speed your machine is running is not all that critical. It is how the cut is progressing that will determine final adjustments to the speed and feed. Those of you who own the optional digital readout will already have electronic speed readout. For others, starting at 1/4, 1/3, 1/2 speed, etc. on the speed control knob will usually get you close enough for a good cut. However, some people find it helpful to know what speed their machine is actually running, and this simple gauge can help you determine that if you don't have a DRO with electronic speed readout.
See the link below to download and print out a better quality copy of the 2-1/2" diameter gauge from Sherline’s web site.
How the gauge works
The gauge was posted on one of the Internet newsgroups and has been passed around long enough that it is unclear as to who actually came up with it first. It is similar to gauges that were used to adjust the speed of vinyl record players to exactly 45 or 33-1/3 RPM. Under light from a fluorescent bulb that runs on 60 cycles/second current, the gauge will give you an accurate reading when you are running at one of the speeds on the gauge. The “flashing” of the fluorescent bulb at 60 cycles per second will cause one of the bands to appear to stop moving at the RPM indicated by that band. The gauge will not work as well with an incandescent light bulb because the filament glows and doesn’t dim as much during the cycling of the current. The speeds indicated on the gauge from the outer ring in are: 100, 300, 400, 480, 600, 720, 800, 900, 1200, 1800 and 2400 RPM. Simply cut out the printed circular gauge, cut out the center hole to clear the spindle shaft and use spray adhesive to apply it to the Sherline spindle pulley.
New Product Spotlight
Sherline 5C Pneumatic CNC Rotary Indexer, P/N 88000 ($3295.00)
Designed for use on a full-size
About the new 5C CNC Indexer
Years ago, while setting up to do an indexing job on some round stock in the Sherline factory, Joe Martin found that he had to remove the vise from his mill, clamp and indicate in a 5C manual indexer, do a single machining operation and then remove the indexer, lift the heavy vise back into position and indicate it back in again. This cost about 45 minutes of setup time for one simple indexing operation. It occurred to him that the jaws of his high quality Kurt® angle lock vise were capable of clamping a plate precisely in place, and the vise was already on the mill. What he needed was an indexer that could be held either vertically or horizontally in the vise. To speed up the process even more, the 5C collet should be able to be opened and closed with the push of a button and the indexing process controlled by a simple, programmable electronic keypad. He set about designing and patenting just such a product, and it is being introduced this month after many years of hard work.
The indexer clamped vertically in a vise.
The indexer clamped horizontally.
(Vise not included)
What you get
The package includes the vise mounted indexer with pneumatically closed 5C collet. The hardened steel mounting plate clamps vertically in a vise and a machined step in the sides of the plate help align it for clamping horizontally. The enclosed NEMA 23 stepper motor is connected to a simple programmable keypad by means of a heavy duty control cable with Cannon plug. The keypad and stand include a large red “Emergency Stop” button and a green “Cycle Start” button. Also included are complete instructions for use, an in-line oiler for the air line and a 5C collet wrench for installing, removing and adjusting the collet.
· Spindle rotation speed adjustable from 1°/sec to 41°/sec
· Backlash compensation is electronically programmable
· Body is hardened and ground 4140 steel
· 5C Spindle is case hardened steel
· Indexer has hobbed gear and worm teeth of different steels to prevent galling and provide long life
· Stepper motor holding torque: 98 ozf.in
· T.I.R. of spindle nose is .0004" or less
· Positioning accuracy: ±.006°
· Spindle concentricity: 0.0004"
· Perpendicularity, body to spindle: 0.0008"
· Spindle zero collar laser marked in 1° increments
· Manual adjustment knob laser marked in 1/10° increments
· Holds long stock up to 1-1/16" in diameter all the way through the spindle
· Pneumatic collet clamping system for quick operation
· Rotational position verified by an encoder
· Auto shut-down in case of positioning error
· Stand-alone controller is easy to program and operate—no g-code knowledge required
· 90 day limited warranty
More details on the indexer can be found at www.Sherline.com/88000pg.htm.
Complete instructions for setup and use of the Sherline 5C CNC Pneumatic Indexer can be found at http://www.sherlineweb\88000inst.pdf.
Did you know?
• HELP! If you need help tuning up or maintaining your Sherline tools, there is a web page to direct you to help sheets and instructions for adjustment of your machines. Just go to www.Sherline.com/hlpsheet.htm for links to many helpful instructions.
• Handy Calculators—Threads, taper offsets, helical gears, metric/inch conversions and other types of calculators are linked from www.Sherline.com/calculators.htm.
• Download a Sherline Catalog—Read the Sherline print catalog on your own computer. Get the PDF file here: www.sherline.com/catalog8.pdf. It is 48 pages of color and takes up 2.38 MB of file size, so give it a few seconds to load. Note also that due to the way the file is created for print publication, the front cover ends up being the last page in the PDF file.
Upcoming Model Engineering Shows
• Cabin Fever Expo,
• North American Model Engineering Society Expo (NAMES),
Send us your show details and we will post them here…
Joe Martin Craftsmanship Foundation News
• In Memoriam
—We are sorry to announce that 2002 Metalworking Craftsman of
the Year Young C. Park passed
away February 5th. Mr. Park’s 1/16 scale cutaway aluminum aircraft
have become famous on the internet after several viral e-mails have gone around
the world showing photos of his work. We are proud to have all three of his
models on display at the
• New Museum Displays
—Recently added to the museum is a display of 90 miniature guns and knives courtesy of members of the Miniature Arms Society. CLICK HERE to see individual photos of each piece in the collection or visit the museum in person to get a better view of the fine detail work on these incredible historic miniature arms. They will be on display for at least the coming year.
—Metal artist Christopher Bathgate has contributed an outstanding piece of his work for display. Be sure to take a look at his page to see some of his work, and now you can come by and inspect one of these finely crafted and unusual pieces in person.
• Groups Visiting the Museum
—This past month has seen a
number of groups meet up at the
-January 19th, Hidden Valley Model T Club
-January 23rd, Not really a car club, more like a group of people who like cars and go on trips together
See the Group Visits page for photos of the vehicles and members of these visiting groups.
Engineering Craftsmanship Museum in
Anyone interested in volunteering your services at the museum, please contact firstname.lastname@example.org or call 760-727-5857 and ask for Craig.