Yet another Quorn

[Chipswitheverything]

This change to the design is a good one, and the roller tensioner is very neatly executed.  Lengthening the motor plate to help it shield the back end of the spindle is an effective way to help to keep the grit away from the bearings at that end.  Dave

[Charles Lamont]

Thank you for your comments.

A smaller departure from the drawings is the micrometer on the left of the bed, used feed the work onto the wheel.

The original design calls for a 3/8 BSF thread (20 tpi). I have made mine 1/2" x 40 to give a finer feed. I have made the nut a replaceable bronze bush inside the body, and have put a hardened ball in the end of the screw for a thrust pad.  The screw is cut without a root radius and with truncated crests to ensure the thread rides purely on the flanks. The fit is a shade looser than I would have considered just right, but I think with some grease it will have the desired feel. The screw is finished, but the body isn't, and I have not started on the micrometer thimble.

[Charles Lamont]

While doing a bunch of steel turning, I decided to get the ball handles out of the way. I have seen other builders do them early too. These were all done by the George Thomas method with split chucking cups to hold the balls in the later stages. I made a Radford type 'up and over' spherical turning tool many years ago.
1) bags of balls made for the small ends, with a couple of spares each size
2) small handles back to back, faced, grooved and spherical turned,
3) same with the large ones, then part the small ones, face them all to length, turn the seats for the small end balls, and centre drill,
4) with ball in chucking cup and tailstock support, rough out the shanks,
5) same again, but with taper turning attachment deployed to finish the shanks, then face the seating, drill and tap, and finally stick the small balls on with Loctite.
I don't work fast. It took me 41 hours for the lot from the bar stock, including modifying a holder, and sharpening a couple of lathe tools.

 

[Kim]

That's a beautiful fleet of ball handles you made!  That last picture represents a LOT of work! 

Kim

[Chipswitheverything]

The set of ball levers look superb!  Certainly they prove how effectively the method devised in detail by GH Thomas, and using the Radford tool and the various home made holders for the different sizes, works to produce a most pleasing result. For all that, a set such as these is inevitably a hell of a lot of work, and needs care to produce those crisp junctions between the tapered shaft and the large ball. I bought some known bars of leaded, free cutting steel for making mine, which was quite a help in getting a nice result.  Judging from the excellent finish of your levers, I wonder if that is what you also used?   Dave

[Charles Lamont]

Yes, I used leaded EN1A. This has consequences. I dropped one of the finished small handles and it bounced off the compressor air vessel. I spent half an hour in the evening failing to find it. The following afternoon a thorough search was instituted. One quarter of the workshop floor is now fit to eat off. It was eventually found (in the last place I looked). Under a table, in an open plastic tub full of old cotton fabric that is waiting its turn as workshop rag, it had buried itself. The shop is pretty dry, but even so the ball handle was beginning to rust. While the rust came off easily, it was not easy to get back the right grain of finish to match the off-the-tool finish of all the others. Leaded EN1A notoriously rusts at the drop of a hat ball handle.

You are right about the ball/shank corner. The tapers were turned with power feed, and the taper turning set-up on the Myford means you lose the cross-slide feed. You have to swing the topslide round and use that to put on a cut. That in turn means you can't use the topslide to finish a cut into a corner. I used my headband magnifier to help me snap the half-nuts open at the right instant. This was taking a risk, but it worked out well. I was a trace premature on just a couple of them and had to disengage the power feed and use the leadscrew handwheel to finish, but with the high ratio for a 0.0022" feed, it was difficult to turn the handwheel in a controlled way.

[Charles Lamont]

After completing the ball handles I set the Quorn aside for a while to tackle some other jobs. I picked it up again in late October, and started by making a 1" internal lap of the Boyar-Schultze type, to deal with the slightly uneven bore of the workhead base, as mentioned in post #6. I have the lap recorded as taking 9-1/2 hours shop time to make. The bore was rectified with 600 grit silicon carbide paste in about 30 seconds.

The lathe tray contained a lot of cutting oil soaked steel swarf. I like to do cast iron work with a dry machine, so I decided on one more steel job that would produce enough swarf to make a clean down really worthwhile. Here we have the motor pulley. Actually it took two goes. The finished cross-section of the pulley is quite light to keep the weight and inertia down. I managed to machine the deeper recess on the wrong side of the first one, and had to order another slice of leaded free-cutting bar. The pulley is made for a three-ribbed H-section poly-V belt.

[PaulR]

What tool did you use for those grooves Charles?

[Charles Lamont]

Paul, you can just see the tip of the tool at the bottom edge of the middle photo. It is an HSS tool bit I ground to the correct 40° included angle and roughly the right tip radius for the groove roots. Now of course, if I had a Quorn, I could have ground the radius more accurately. I put the radii on the tops with a fine file.

Back to the Workhead Base, which could now be clamped to a piece of 1" bright bar as a mandrel for turning the seating OD for the Rocking Lever, and for facing the other end for a dust cover.

To machine the facing and hole for the Tilting Bracket pivot, the milling machine set-up used the same piece of bar resting in V-blocks. The clamp hole has already been positioned to provide a datum for rotation about the bar. A vertical peg fitting in the clamp hole (with a scallop cut to miss the big through bar) is pressed into a small block, seen behind the tap.

Using the tapped hole to mount the casting on a threaded stub mandrel, I first faced the back of the boss (not shown) and then turned the job round to clean up the protractor arc enough for some measurements. 

[Charles Lamont]

For the dust caps used on the front bed bar, I made a d-bit countersink, using it to cut holes in which the heads of M2.5 socket csk screws will just sit flush. I made the holes before boring out the internal recess that will hold felt wipers.

[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