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Yet another Quorn

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Charles Lamont:
To finish the main bed castings, they need machined faces with tapped holes for mounting the micrometer body on the left, the spring retainer/cover on the right, and dust caps on the inside faces. Unfortunately, the castings are not provided with raised bosses to be machined for these faces. Machining spot faces below the general surface creates an awkwardness to deal with when painting. But the clincher for my next wheeze/modification/bodge is that the radial wall thickness of the castings is deficient in places. In the first photo the nearest point to the camera is only 3/16" thick, when it should be (at least) 1/4".

The mounting pins on the mill table are adjusted to line up the bores in the X direction. Then the right hand bore is clocked on centre and  the X and Y dials zeroed. The faces are fly-cut and holes drilled on a 1-1/4" PCD by coordinates, the marker dots indicating the orientation, which varies. Another 1" peg is fitted on the table of the tapping machine to ensure the holes are tapped square.

The cunning plan is that in fact I am using these 6BA holes to hold in place turned steel false face rings, which have been roughed up on 240 grit on the underside. Everything is cleaned with acetone. The casting is popped over the pin in the tapping machine to centre the false face as it is fixed on with JB weld and screws. The minimal glue smear in the bore is cleaned out immediately after tightening down.

The glued-up photo shows how much the dust cap would have overhung the original edge, and how much filler will be needed for a decent cosmetic appearance.

Charles Lamont:
With the glue cured, the pieces go back in the same setup on the mill, and the false faces are fly-cut to finished thickness. The countersink depth in the false faces allows some of the conical head of the screws to remain, while milling below the bottom of the slots to produce an almost invisible join. This one needs the final cut. Chamfers are cut on the outer faces and holes drilled and tapped in the correct final positions, between the first set - 4BA on the outsides and M2.5 inside.

These parts are now finish machined, but there will be quite a lot of work to do to give them a good paint finish.   

Chipswitheverything:
Your build log of set-ups and things to take account of will be most useful to others still to embark upon their own Quorn build.  As a means of exercising one's ingenuity in machining practice , mainly using the sort of standard workshop equipment that most of us are familiar with, tackling the castings and other components of a Quorn is an interesting and sometimes challenging project!

 You like to bring your toolmaking builds to a very high standard of finish and presentation, which does involve a little more refinement of the cast lumps, and the result is superb. Encouraged by Prof. Chaddock's advice on filling, priming and fairing the castings, I did end up spending a lot of time at the sink with the wet and dry, but I probably stopped off at the "that'll have to do" point by comparison!   But an effort in that direction does certainly give the Quorn grinder something of the look of a proper piece of machine tool equipment in the workshop. Dave

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