 With my Sherline 4000 lathe I got a steady rest as part of the package. This steady rest provides 3 brass bars acting as end-support when cutting thin stock. However as these brass bars rub against the stock it is unavoidable to get marks/scratches when cutting soft metals as brass or aluminum. Therefore I wanted to modify my steady rest to include end ball bearings to counterfeit this problem.
The following items are needed - 3,2mm (1/8") milling bit, e.g. Dremel
- 3,0 mm milling bit, e.g. Dremel
- Three ball bearings 3mm/8mm/3mm (axle diameter/outer diameter/width)
- 3mm brass rod for the axles (steel rod if press fitting the axles to the brass bars)
- Soldering equipment
- Steady rest
There are different ways of attaching the ball bearings and axles to the brass rods. Originally I was thinking of drilling holes for the axles, and press them into place. But as brass is a very soft material and I was afraid to jam the ball bearings if accidentally applying to high pressing force. therefore I decided on milling grooves for the axles, and solder them into place instead. If you do prefer press fitting the axles, just remember to make the hole on one side a little bit larger so the Axle easily passes trough, and the hole on the other side a little bit tight so the axle is held firmly when pressed into place. If both holes are made tight the brass will bend due to the insertion force, and the ball bearing will be jammed. The following drawing shows all the dimensions for the cuts to be milled. Milling using the lathe Milling using the lathe is a bit different than milling using a mill, especially when it comes to holding the material to be milled. You have to find alternative ways of mounting the part to be milled relative to the chuck. The brass bars of the steady rest are 1/4" wide. The same width as the Sherline lathe cutting tools. Hence the Sherline tool holder can be used to hold the brass bars for machining. However as the tool holder is made to hold the cutting edge at the lathe chuck center, the brass bars must be offset by half of 1/4". This could be done by putting a 1/8" shim underneath the brass bar. Or, as in my case, if you have a quick change tool post the tool holder can be offset directly in the tool holder. To hold the Dremel milling bit in the lathe you should ideally replace your lathe chuck with a mill collet or other milling holder. But as brass is a very easily cut material, the clamping force of the chuck will be sufficient for holding the milling bit as long as small cuts are made. The following short movie clip shows milling of the ball bearing grooves in the brass bars of the steady rest.
If you look closely at position 0:29 you will see the milling bit jamming in the brass, and the milling bit stops rotating, slipping in the chuck. This is due to the low clamping force of the lathe chuck, and the drawback of holding the mill bit in the chuck instead of using a milling collet. This can be avoided by lowering the feed rate of the slide. Start by milling the groove for the ball bearing using the 3,2mm milling bit, as shown in the movie above. Then rotate the brass rod 90 degrees and mill the axle "cradle" using the 3mm milling bit. This cut should be a maximum of 3mm deep. After the cuts are finished, polish off the edge burr. Assembling the steadyrest To get the axles trough the ball bearing centers it might be necessary to grind a small taper on the axle rods using a fine grit sanding paper as shown in the images below. Cut the axle rod at the right length using a parting tool. Solder the axle to the brass rod and grind down the excess solder to ensure a nice finish. Repeat the process on all three steady rest brass rods, mount them in the steady rest frame, and you are done.
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