Edgar lathe by holbrook

The "Edgar" Lathe by Holbrook

If any reader has an Edgar lathe or information about the company, the author would be pleased to hear from them.
Manufactured by the machine-tool company Holbrook - but using the founder's Christian name "Edgar" - this most unusual and interesting lathe was announced at the January 1923 Model Engineer Exhibition held at the Royal Horticultural Hall in London and was marked as incorporating a British patent No. 194047 granted in 1922. Quite why Holbrook chose not to market the machine using the full company name is not clear - though perhaps the aim was to create a new, high-quality brand aimed at the experimental and top-end amateur sectors. In this sense the lathe did succeed, for the writer has encountered several that have passed through interesting hands including one belonging to R. H. Clarke AMI. MechE, author of several books (including one on Brough Superior Motorcycles and Chronicles of a Country Works, a history of Burrells of Thetford) and another was owned from new by an eminent engineer involved in the development of guided missiles, parts of which were scattered around his unbelievably untidy but productive attic workroom (he was still experimenting well into his late eighties).
Unfortunately, by the early 1930s, the machine - always a very expensive proposition - had disappeared from the maker's lists. Interestingly, at the same 1923 exhibition, Holbrook announced a 2.5-inch precision miniature lathe, though an example has yet to come to be found.
While the basic specification of the "Edgar"- gap bed, backgeared, screwcutting with a set of eleven changewheels and treadle drive - was entirely conventional, the bed was of the "double" type, with the headstock and tailstock mounted on a separate rear section - with one flat and one V - while the carriage ran along flat (gibbed) front ways and was able to pass completely by the tailstock. This very unusual arrangement was obviously not enough for the ambitious Edgar designer, for the front bed was also arranged to pivot at the headstock end and could be set over, under the influence of two screws, to allow the carriage to run out of parallel with the headstock spindle axis by an amount equal to 1/2" per foot in either direction. To permit the leadscrew to drive the carriage when the bed was set at an angle, its clasp nuts were mounted in a pivoting bracket arranged to slide freely in and out of its mounting slot on the apron.
A most useful adjustable cut-out could be set to disengage the carriage drive (through a dog clutch) in either direction whilst the compound slide-rest feed screws (and the graduated handle on the leadscrew end) all had micrometer-dial divisions engraved on the flat surface that formed the outer rim of their large-diameter handwheels - a design that produced, for the time, unusual well-separated and clear markings. To give the top and cross slides as much travel as possible their feed screws ran through brackets on the end of extension bosses; where similar designs used extension pieces that covered the screws in this case they (the screws) were left exposed to the wearing properties of dirt and swarf. The toolpost could be dropped into one of two holes bored in the top slide and retained by a cotter pin.
With a centre height of 5.5", the capacity between centres 21" and the deep gap in the bed allowed a disc of metal 3 inches thick and 18 inches in diameter to be turned on a faceplate. Unfortunately, the generous capacity of the gap brought a problem - experienced owners reporting that, when used on really heavy jobs (though not during ordinary work) flex could be detected. However, as it was a well made lathe (as were all Holbrook machines) bolting the lathe down onto strong foundations brought about a partial solution.
With a 9/16" bore and a No. 2 Morse taper, the headstock spindle ran either in bronze bearings (according to the sales literature) or, from evidence of machines encountered, direct in the cast-iron of the headstock A 3-step flat-belt "cone" pulley was used, with diameters 5.25", 4" and 2.75" diameter and driven by 13/8" wide flat belt from a variety of different "fast-and-loose" countershafts designed for wall or ceiling mounting. There was also a rare built-on countershaft system that used lengths of brazed tube, a system not unlike that supplied for American Hendey lathes of the time. The countershafts were intended to be run at 350 rpm that gave recommended spindle speeds from around 25 rpm in backgear to a maximum of 700 rpm in "open-belt" drive. A self-contained treadle stand was also available with a ball-bearing supported flywheel - as illustrated below - in which case the maximum rpm was in direct relation to the health, or otherwise, of the operator's cardiovascular system.
A lathe of similar appearance to an Edgar, but smaller (and treadle-operated) is reported to be on HMS Alliance, the WWII submarine in the Gosport museum.
A 7-inch centre height Edgar - again with a very unusual two-part bed - was also manufactured.

Source; http://lathes.co.uk/