Metalworking
plug gauges
Plug gauges are high-precision cylinders, sold in sets to allow the inside diameters of holes to be easily measured. A typical set will contain 250 pins, covering the range from 0.2508" to 0.4998" in 0.001" steps. The 0.0002" reduction from the nominal 0.251" - 0.500" range allows the pins to be inserted & removed without undue difficulty. Some plug gauges have handles, but those that are supplied as simple cylinders can in principle be used two or three at a time. I wrote a program (updated 8/15/11) that, using Descartes' Theorem, allows one to find a set of three gauges that together will just fit in a hole of given diameter.
letter-stamp dies
My only metalworking innovation to date has been a trivial device to facilitate the use of letter-stamp dies.
heat-treating furnace
I built a heat-treating furnace, making use of ideas from http://www.viddler.com/explore/rashid11/videos/3/, http://www.practicalmachinist.com/vb/general/heat-treat-oven-homemade-one-off-199644/, and http://www.youtube.com/watch?v=qtMlV6V-zQI. My furnace is smaller than any of those, with a working volume of just 9" deep × 4" wide × 4½" high. I expect this size to be more than adequate for the cutters and similar small items that I may wish to harden.
The walls of the oven are made of K23 firebricks, held together with furnace cement (Harvey's #45005). Three bricks (A–C) were laid flat to form the floor, one on edge (D) forms the back wall, two on edge (E & F) form the side walls, and two laid flat toward the rear (G & H) form the roof. In use, the opening is closed by resting two more bricks (I & J) in position to close the front wall and the front third of the roof.
I cut a serpentine of grooves in the inner walls of Bricks D–F by feeding the bricks through my mill, working in a sort of router mode with the head tilted by 30° and a ¼" ball-nosed end mill in the quill. The heating element that fits in those grooves is of Kanthal wire (product #7101 from Budget Casting Supply). Two home-made connector rods run from the ends of the heating element, through holes in Brick D, to lengths of high-temperature hook-up wire (BCS item #7105). The connector rods are just pieces of ¼" stainless steel 416, cross-drilled near each end to pass the wires, and drilled and tapped in each end for M3 socket-head cap screws that clamp the wires in place.
To provide some mechanical protection for the friable firebricks, the furnace has a skin of 18G galvanized steel, held in place by beams from the MicroRAX system. I lined the steel sheets with some asbestos paper that I acquired years ago.
The control system uses electrical scraps to complement a PID controller (item #SYL-2362), a solid-state relay (#RS1A40D25) and heat sink (#HS25), and a K-type thermocouple (#WRNK-191), all from Auber Instruments. The thermocouple enters the furnace through another hole in Brick D. Notwithstanding the informality of the furnace's door, the Auber PID is able to bring the furnace to the highest temperature I've tested (1600 °F) in about 12½ minutes, overshooting by no more than 5°, and thereafter easing off to hold the set temperature within a degree or two indefinitely.
Sieg C4 lathe
My lathe (S/N 00303) has an attached table (Part #94 in the manual) of suggested gear combinations for the production of various threads. The suggested combination for a 14-tpi thread is
30-100-127-35
but this is wrong. This gear combination is not physically possible within the available space, and if it were, it would provide a feed of about 11.7 tpi. A gear combination for 14 tpi is
30-120-127-35
Unwanted rotation of the C4 tool post is reduced by the Positioning Pin, Sieg part #238. This small part is spring-mounted in a well in the compound slide, from which it pushes a tooth up against the base of the tool post. I discovered that the Positioning Pin of my lathe had been lost, probably fired away by its spring during manipulation or replacement of the tool post. I believed (correctly) that it would be easy to fabricate another, but I was uneasy in the absence of any sort of drawing or description (the pin is shown on Sieg's assembly drawing of the lathe, but as little more than a smudge). I appealed to various Web-accessible sources of information, and I am happy to acknowledge the help of Luc Morin, who went to the trouble of dissecting his own C4 lathe and producing this elegant drawing. I made the replacement pin of mild steel. Along the way, I was struck by the uncanny similarity of shape between the Positioning Pin and this old xray anode that I happened to have around the house.
Stops of various kinds are invaluable with the lathe, and designs for carriage stops are easily found on the Web. One carriage stop should be made to carry a dial indicator. With a simple stop toward the headstock and an indicator-bearing one toward the tailstock, boring to a fixed depth is just a matter of
-
picking up the surface with the boring bar;
-
locking the right-hand stop close enough to the carriage so that the indicator engages the carriage;
-
zeroing the indicator;
-
moving the cross slide so that the boring bar clears the work;
-
advancing the carriage toward the headstock until the indicator shows the desired depth;
-
bringing the left-hand stop next to the carriage and locking it; and
-
repositioning the cross slide and boring, advancing the carriage toward the headstock until it runs into the stop.
Stops for the cross slide and compound are not quite as useful, but the effective rigidity of the lathe turns out to be strikingly improved when simple locks for the cross slide and compound can be engaged when these components should not move. I improvised locks for the cross slide and compound that rely on the existing threaded holes for the follow rest and for the compound rotation mechanism, respectively. I've made no drawings; I'll post photographs if there's any expressed interest.
The mechanism that advances the lathe's tailstock quill is graduated in thousandths of an inch, and I have no reason to doubt its accuracy, but its backlash makes the scale almost valueless when a pecking technique is used for drilling. To drill to controlled depth, I use a collar that fastens to the quill and projects downward to where it can run into the carriage; a drawing for the collar is here. With the collar in place, drilling to fixed depth involves
-
picking up the surface with the drill bit;
-
locking the tailstock;
-
moving the carriage to run up against the bottom of the collar;
-
locking the right-hand stop close enough to the carriage so that the indicator engages the carriage;
-
zeroing the indicator;
-
advancing the carriage toward the headstock until the indicator shows the desired depth;
-
locking the carriage; and
-
drilling, advancing the quill until the collar runs into the locked carriage.
To allow a Proxxon rotary tool to be used as a toolpost grinder, I bought a mounting block from Little Machine Shop. I knew I could have made the mounting block myself, but the LMS version was inexpensive, and I thought I could put it to immediate use. As it turns out, the LMS mounting block is not immediately compatible with the CR lathe. The bolt and sleeve of my QTCP were not appropriate for attachment of the mounting block to the compound, and I needed a 0.1" shim under the mounting block to get the axis of the Proxxon tool up to the level of the lathe axis.
My most useful commercially-obtained add-on to the lathe has been an ER32 collet holder and a set of ER32 collets. The collets are available everywhere, but the only evident source for the collet holder seems to be Axminster.
Sieg SX3 mill
Early in my use of my mill, I managed to shear the End Shaft (Part #86 in the manual), and I had to install a replacement part. The End Shaft is part of the mechanism that controls head tilting on the mill; this mechanism is not documented in the manual or, as far as I can tell, anywhere else. I got some hints from the CreviceReamer site, but for the most part I was on my own. I found that the head-tilt-control mechanism of the SX3 mill works this way:
- Head tilt (that is, rotation of the Spindle Box (Part #33)) is prevented by the deadbolt-like Orientation Small Gear Shaft (#78), which protrudes from a hole in the Vertical Slide (#75) into an off-center hole in the Spindle Box.
- The Orientation Small Gear Shaft is pushed forward into the Spindle Box by a compression spring (#80) that is restrained in a well at the rear end of the Orientation Small Gear Shaft.
- To permit head tilt, the Orientation Small Gear Shaft is retracted by a rack-and-pinion mechanism whose rack is formed by grooves on the Orientation Small Gear Shaft.
- The pinion of this mechanism is the fluted left end of the Inlay Shaft (#85).
- The Inlay Shaft is held captive within the Vertical Slide by a setscrew (#84) that enters the Vertical Slide from the rear and engages a journal in the Inlay Shaft.
- A well in the right end of the Inlay Shaft accepts the socket-headed End Shaft (#86).
- The Inlay Shaft and End Shaft are cross-drilled, and the Taper Pin (#88) couples them.
- Clockwise rotation of the End Shaft is thus transmitted through the Taper Pin and the Inlay Shaft to retract the Orientation Small Gear Shaft and allow rotation of the Spindle Box with respect to the Vertical Slide.
The most useful modifications I've made to the mill have been
- addition of a spindle lock, using Paula Stephens' design;
- addition of a 3-axis digital readout from DRO Pros. My installation of the DRO followed the method used by Dan Kautz for the X and Y axes; I initially installed a 150-mm Y scale, but subsequent failure of the mill's Check Ring 12 (part #167) led to destruction of that scale's read head, and I replaced the scale with a 200-mm unit. For the Z axis, I had to improvise, and I describe my arrangement here; and
- replacement of the shoddy factory-supplied Check Ring 12 with an E-clip made of genuine metal.
There are 2 unused threaded M4 holes on the front of the Saddle
(#178), and there is a T-slot on the front of the Work Table (#184), with
clearance sufficient to admit 13 × 14 × 6-mm
nuts. Using these, it is trivial to implement X-axis carriage stops.
These are useful when one is tediously removing a mass of material by taking
many, many shallow cuts.
Home
Page revised: 12/12/2011 12:11