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NEWS FROM THE WORKSHOP: New Rotary Table arrives in the Gunsmith’s Workshop

I’ve been on the lookout for a medium sized, well-made,  rotary table with indexing for a while now and eventually the right one came along at a fair price.

A West German “Walter” horizontal / vertical, 10″ table with 120:1 gearing, good brakes and an indexing plate recently found its way to the workshop. This fine rotary table will join the family of high-quality engineering tools we’ve accumulated over the last couple of decades or so.

As is often the case with second-hand tools, the table had suffered some abuse and neglect in the past but, due mainly to its fantastic build-quality and extremely sturdy construction (it weighs just under 60Kg / 1cwt), it was able to be refurbished to like-new condition with just 20 hours of work and a couple of new small parts.

The table had received an “apprentice paint job” and been over-painted with a Hammerite type paint many years ago. Fortunately it hadn’t been properly cleaned beforehand and the lack of preparation meant that the new paint was not fully adhered; so a couple of hours with wire brushes and scrapers revealed the original Walter signature RAL green colour in pretty good nick, especially considering the table is at least 25 years old. Internally, the mechanism was found to be in mint condition – the massive precision-scraped main thrust bearing inside the base of the casting is untouched and the worm and wheel show absolutely no signs of use at all. The only real fault was that the worm engagement control had been over-ridden at some time and its sacrificial shear-pin screw was snapped – the broken screw was drilled out and replaced during reassembly. All the lubricated areas were found to be glazed with old oil and a little surface corrosion was present on the unprotected areas but a good dose of elbow grease, solvent and light oil quickly sorted both of these issues. There is a neoprene seal under the table rim,  designed to keep swarf and debris out of the oil sump and even this was found to be in good nick.

Once all the parts were cleaned, inspected and oiled, reassembly was a relatively straightforward job. The main 3″ diameter radial bearing and its journal (seen at the top, centre of the photo below) are as snug as you could possibly want and again exhibited no signs of use – they went together with that satisfying resistance so characteristic of large, close-tolerance plain bearings.

The Rotary Table’s components fully disassembled for cleaning and inspection

After the reassembly was complete and the sump was filled with a couple of pints of good oil, it was time to verify the Walter’s accuracy. I lugged the unit over to our 24″ square by 6″ thick granite surface table to do some precision measurements (60Kg is no problem for this heavy duty surface table). An Interapid .0001″ indicator mounted on a Mitutoyo dual column height gauge was employed to verify table flatness, radial and axial run-out, concentricity of the Morse Taper #3 center socket, movement under braking and backlash etc. No errors greater than two ten-thousandths of an inch (0.005mm) were detectable anywhere so after an hour’s inspection the table was declared ready for use. A pair of locating dogs were made to allow the table to lock into the tee-slots of the milling machine – these are good and snug, so no further set-up is needed except for super critical jobs.

As a first trial, a long awaited little workshop job eventually got done – my 10″ 4-jaw Pratt Burnerd chuck for the Cazeneuve lathe had never had a good fitting 3/8″ hex chuck key; but I had a nice 1/2″ one that was too hard to mill with High Speed Steel and grinding it had always seemed more trouble than it was worth. I mounted a 5C collet holder centrally on the Rotary Table, removed the T-bar from the chuck key and clamped the shaft in a 3/4″ 5C collet. After clocking one flat of the key to align it correctly to the zero degree mark on the table, a 12mm 3-flute carbide end mill made short work of turning the 1/2″ hex into a 3/8″ hex – the sharp corners were then milled off by rotating the table against the cutter  – no chatter, no vibration no drama.  The key was tried in the chuck and fitted first time – another little job off the list!

Just the right size for our Omniveral Mill
Hard-milling the hex-key