My (former) Sherline CNC Lathe

	I purchased a Sherline 4400 CNC-ready (stepper motor mountings but no motors provided) lathe and added a couple of surplus Vexta PH268-21 stepper motors. The yellow cables are Belden "Infinity" super-flexible machinery cable. I mounted the lathe on a piece of half-inch aluminum tooling plate, with a .09" aluminum backsplash and an overhead light bar with four fluorescent lamps.
	The driver box had Jeff Pollard's Xylotex 2.5-amp, 30-volt driver board, 24V switching power supply, high-efficiency switching converter for the 5V logic supply, filtered power entry module, fuses on both AC and DC, optoisolated input lines, ferrite EMI filter beads on all output lines, and a metal EMI fan filter. For the stepper cable attachments I used Radio Shack CB microphone connectors which have threaded locking rings. The box was a duplicate of the box I built for my Sherline mill.
	The control software was TurboCNC G-code interpreter software running on a Dell PC with DOS 7 (the underlying DOS from Windows98SE.) I installed Peter Homann's DigiSpeed spindle speed controller interface inside the spindle controller box, which let me use the M3, M5 and Snnnn spindle commands in TurboCNC v. 4.01. I calibrated the spindle speed using Spehro Pefhany's Tachulator digital tachometer, available from Little Machine Shop and MKC Tools. I added a filter capacitor across the spindle motor brushes to minimize electrical noise.
	I replaced the stock spindle motor mounting with my own mount, inspired by the Sherline mount but allowing me to change the belt pulleys on the 10krpm pulley set without disassembling the whole mount. Sherline was working under the requirement of staying within the stock belt guard, but since I'm the only one using the lathe I took responsibility for keeping clear of the belt!
	A very worthwhile addition was the Bison 3-jaw scroll chuck. It is much beefier than the Sherline 3-jaw, and uses a standard chuck key. Another great advantage is that the jaws are longer to very securely hold round pieces.
	On the Bison chuck, the threads are relieved pretty deeply to screw onto a Taig spindle. A friend with a larger lathe faced off the central spigot so that it is .180" below the rim of the chuck. The rim of the chuck is only about .090" from the face of the headstock. The threads are still recessed about .060" below the face of the spigot, but there are a full 3 turns of thread engagement. It is a very secure connection.
	I used a Taig 4-jaw chuck, which is likewise much beefier than the Sherline equivalent. Since it is larger in diameter than the Sherline 4-jaw, I bought the Sherline headstock and toolpost riser set for working on the occasional large-diameter workpiece (acrylic and Renshape only so far.)
	I likewise relieved the center of the Taig chuck mount .150" to allow full thread engagement on the Sherline spindle.
	The stock tailstock gib screws are hard to adjust, being installed from the bottom of the gib and threaded upwards into the tailstock base. After one of the screws stripped out, I redid them. I drilled the tailstock body through for #10 clearance, spotfaced slightly, and installed 10-32 buttonhead screws from above with nylon-insert nuts below. The gib was now easy to adjust using a hex key and open-end wrench.
	My favorite turning tool is a CWPR-0630 plunge-and-turn carbide insert from Century Tool. These inserts have relief on the front and both sides, and can cut to the right, left, and straight in. They are really nice for profiling. The size I use is .063" wide and has a maximum depth of cut of .250", and proportionally larger cutters are also available. With the first order of inserts Century threw in a holder. (I shortened the shank of the holder to make it less unwieldy--the holders are intended for Swiss production lathes.) Obviously, I can't turn a concave (groovish) shape narrower than the insert, but that hasn't been a limitation for me so far. The holder is .312" square, and I modified the Sherline toolpost to put the insert tip right on the spindle centerline.

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