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Continued:
On early lathes the top of the headstock was machined flat and the bronze bearings bolted to it. On the very first examples, the bearings were in two parts, with the upper and lower sections separated by adjustment shims; next came a simplified type with the bearings formed in one piece with the clearance set by a slot and pinch bolt. The large bolt at the front was screwed into the headstock casting while at the back two small screws were used to held the rear section down. Another minor difference on the latter headstock was the method of locating the bearing caps, some being found with small studs screwed into the headstock casting and others with locating dowels - though it is not known which came first.
From correspondence in contemporary Model Engineer magazines, it has been discovered that all early examples were fitted with a white-metal liner for the tailstock spindle. Unfortunately, though a good idea, this wore rapidly and Drummond invited owners to return their complete lathe for modification with a hole reamed directly in the cast iron - alignment problems obviously compromising any attempt to fix the tailstock on its own. On the latter point, the centre height on the Round Bed can vary by up to 1/8" from nominal, it almost certainly being the case that selective assembly of parts was necessary to get everything lined up.
In 1919/20 - when the Serial number prefix changed from "MCHA" to "O" - the design underwent some revision and improvements: the left-hand headstock bearing "arm" was increased in size; the bolt-on bronze headstock bearings abandoned and the spindle made to run direct in the cast iron of the headstock with the clearance set by nipping up a clamping screw at the rear. Other changes introduced at the same time (although, as with the flat-bed lathes, there would inevitably have been some overlap) were a reduction in the number of T slots in the cross slide from 4 to 3; a modification to the tailstock where the barrel was increased in diameter (and the previous use of a white metal liner abandoned); the adoption of push-in spring retainers on the changewheel studs instead of the previous slow-to-operate, screw-on rings (that tended to come undone when the changewheels were run "in reverse"); the replacement of the detachable changewheel reversing arm by a forward-facing forked bracket cast as part of the headstock - and the very overdue use of a gib strip with adjustment screws on the tool slide. Very early examples appear to have had a slightly different spindle with a thread 1.040" in diameter by 14 TPI (with no plain section to act as a register before the abutment face) and bored out to 0.325" rather than 0.375". The spindle was then modified to carry a 7/8"-diameter, 10 t.p.i. thread on the nose and given a ground (rather than turned) finish on the bearing surfaces; as standard it was not hollow, but the 0.375" diameter hole could be ordered for a small extra cost. Later spindles (fitted to lathes where it ran direct in the headstock casting) had a 3/4"-diameter by 10 t.p.i thread with a small plain register about 0.25" long before the abutment face. If you find a Round Bed that differs from these specifications do not be surprised; over the years many have been fitted with replacement spindles and the factory did not seem averse to the occasional experimentation with altered dimensions. The three-step cone pulley on all models was in cast iron, rather heavily made with diameters of 6", 4.5" and 3.5" and driven by a 1" wide belt.
From the start of production until 1925 a set of eight changewheels was provided as standard: 20t, 24t, 28t, 32t, 36t, 40t 44t and 64t with an extra set to generate metric pitches (at additional cost) of 25t, 35t, 45t 50t and 63T. Thereafter a set of 9 gears was supplied - which included those necessary for metric threading: 20t, 25t, 26t, 30t, 35t, 40t, 45t, 50t and 66t giving a threading range of: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 18, 20, 24, 26, 28, 32, 36 and 40 t.p.i. Because early headstock castings lacked the cast-in slot provided on later examples (that accepted a stud on which to run an extra changewheel to produce left-hand threads) the makers offered (at extra cost) a slotted bracket that bolted to the left-hand face of the headstock. This positioned the extra "reversing" changewheel in a rather distinctive fashion above the others. As on all small Drummond lathes the changewheels were 14 DP with a 14.5 degrees pressure angle; today, unfortunately, the standard pressure angle is 20 degrees so "off-the-shelf" gears will not match and if new gears are required they have to be specially made. To connect the gears in pairs for a compound train each gear carried a pin and a pin hole (a useful tip is to know that the pins are pressed into tapered holes and, if driven out the wrong way, will fracture the gear). By combining extra changewheels a large number of odd pitches and metric threads could also be cut - however, one serious drawback with the lathe was its lack of slow speeds to help with screwcutting and large facing jobs; no backgear was fitted and the bottom speed with the maker's countershaft was approximately 120 r.p.m. To some extent this could be overcome by re-jigging the belt drive to give lower ratios or, more effectively, by resorting to various third-party accessory suppliers who offered two solutions: the ingenious WALRAM unit or some form of backgear. The (now very rare) Walram bolted in place on the end of the headstock casting using the reversing stud bracket as one of its mounting points. Its ingenious design provided several features: a means of driving the headstock spindle, through gears, either faster or slower than normal; allowed an ultra-fine carriage feed to be set up and permitted the generation of left-hand threads. The backgears offered were either of a conventional design - that bolted on in some way - or rather splendid epicyclic mechanisms built into a slightly larger-than-standard headstock pulley. At least two types of the latter were offered: the first, by George Gentry, being published in the "Model Engineer" magazine during 1912 and the second, by A. E. Bowyer-Lowe complete with illustrations and detailed drawings, in the same magazine for April 1st, 1915.
A limited range of accessories was offered There was no fixed or travelling steady) including an angle plate and a vertical slide that, when mounted on a swivelling adapter with a graduated base, could also be used to mount a neat and effective Indexing and Gear-Cutting Attachment. The swivelling adapter part must have been either very popular as an accessory, or later supplied as standard, for many used machines come with one in their stock of kit.
Over the years various drive arrangements were available including the usual type of fixed and fast-and-loose countershafts for wall and ceiling mounting - but the most popular and common arrangement was a pair of legs and a chip tray (all in cast iron) fitted with a 100 lb flywheel running on a plain bearing and with operation by treadle.
Though of simple design and construction the Round-bed Drummond was, in sympathetic hands, capable of accurate work and many examples are still in use today. In standard short-bed form its overall length was 2 feet 11 inches (889 mm) and the basic machine weighed approximately 105 lbs. (48 kg).
Colour: the writer is often asked what the original colour was. Evidence from removing the maker's badge from an early (detachable headstock bearings) models shows this to have been a very dark shade of blue - almost a black. On exposed surfaces over many years this original paint would have oxidized to a an even darker shade, so giving the impression that the lathes were, indeed, painted black.
Machines with an "A" prefix are pre 1920 - afterwards "0" was used. However, on some machines this is missing - while others have no Serial number.
Yearly figures from the introduction in 1908 to 1912 are not known - but thereafter factory records show that:
From 05/07/13 to the end of 1914 Serials 5300 to 6175
1914 to 1915 Serials 6176 to 6379
1915 to 1917 Serials 6380 to 6515
1917 to 1919 Serials 6516 to 6719
The above figures show that just 543 examples of the Round Bed were made during WW1.
The next set of records started with a new numbering system - a prefix "0" being used. However, although Company ledgers record the "0", research shows that it was not physically stamped on every machine.
1919 Serial numbers to 0680 (the start number is not known, but might have been 0101)
1920 to 1923 Serials 0681 to 02144
1923 to 1924 Serials 03398 to 03991
1924 to 1926 Serials 03992 to 04585
1926 to 1928 Serials 04586 to 04981
1928 to 1930 Serials 04982 to 05377
1930 to 1932 Serials 05378 to 05641
1932 to 1935 Serials 05642 to 05905
1935 to 1938 Serials 05906 to 06103
1938 to 1943 Serials 06104 to 06193
The very last Round Bed was sent to Myford on May 18th, 1943.
Production from 1908 to 1913 around 1500 - and the grand total, to 1943, about 9253
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