Yet another Quorn

[Charles Lamont]

My Mk2 Quorn Tool & Cutter Grinder kit was bought in 2004. It has finally emerged from under the bench and work has started. It will be mainly a Mk2, with pad/split-cotter clamps rather than split castings, some ideas from the Mk3, and numerous, mainly minor, tweaks of my own.

This job will proceed at my usual snail's pace, and I am not doing a full build log, but intend to post occasionally with more interesting set-ups, problems, wrinkles, ideas, questions.

The first alteration has been to move the column forward by 1/16" to suit the casting. The cored hole was really too big, and gave almost no latitude at all on the hole position, especially as there was a divot right at the top. I was lucky and the boring tool just managed to scrape all the primer off. Note on the far right of the first pic, a piece of blue plastic shim under the back of the angle plate to get it dead square to the spindle. Borrowing from the woodworking department, I was able to do a little preliminary blending of the chamfer into the cast surface.

[Admiral_dk]

Last Picture shows a new one for me - logical when you think about it - but I don't think I would have come up with this one by myself 

Per     

[Chipswitheverything]

Will be interested to see your posts about the Quorn build, and the ways in which you have gone about some of the set-ups for the more "interesting " operations that builders of this machine have the sometimes challenge of concocting. I must admit that, partly for the reasons I outlined when I wrote up my finally finished Quorn back in early 2023, my example has not done much since completion, but it was satisfying to have done the job. My various non-model engineer visitors to the house, seeing it proudly displayed on a table in the living room, have not sought to engage me in conversation about what it might be!  Dave

[Charles Lamont]

Boring the holes in the base castings for the bars.

The RH bed was fixed just by one bolt through its leg, so I clamped the back end to an angle plate for security. Straps are not practicable for this job as they are bound to distort the light Myford boring table which has to be free to move backwards and forewards between the two holes.

I went to the considerable expense of getting the longer, chrome-plated Mk3 bed bars from Hemingway. These turn out to be hydraulic cylinder rod, and they are within tolerance, barely, being evidently centreless ground and markedly lobed.

The front holes are bored very close to 1.000" - a good running fit on the bar, while the rear ones are 1.002" to allow 3 thou on diameter for Loctite.

As the assembly photo shows, I have nearly finished already.   

[Dave Otto]

Nice work!
If it is anything like the Universal Pillar Tool, once you get the basic machine done you are only about 1/2 finished

Dave

[Bruno Mueller]

I also used these hydraulic lift rods for my Bonelle. My rods were surface hardened and hard chrome-plated.

[Charles Lamont]

Six months after the last post I managed to get back to the Quorn.

During that interlude I have made the little instrument vice I posted a while ago, dug out and cleaned up the cam grinder and made some cams for demonstrating the thing at MMEX last October, and have completed the Power Hacksaw Refurbishment, also being reported here.

Now I can get back to the Quorn as No 1 job. I am trying to make an impression on the castings, having an extended session on the iron. I am doing a bit of work on each part, establishing initial datum surfaces and then putting it aside for coggitation before the next step.

Now, I decided long ago to use pad clamps rather than split the castings. For the best results, and following GHT's methods, the main hole is bored with the clamp pad in place. This means that the hole for the pad has to be made first. I am allowing just 1/64" clearance between the main hole and the clamp bolt, to give the clamp pads as much contact patch area as possible. I am finding it hard to organise proper datums on the castings so that I can be sure of getting the pad and main holes at the correct centre distance. There will be more on this shortly.

The next castiing to attack was the Workhead Base, two photos showing boring for reaming the 1/2" hole for the split pad clamp, and two of boring the main 1" bed bar hole. The angle plate and 123 blocks provide squared up surfaces to clamp against. These two set ups were infuriating because the casting is lopsided just where it sits on the packers, and every time I put clamping pressure on top, the blasted thing tipped over.

At the right hand end (left in the photos as it is mounted back-to front) I increased the bore very slightly as it can be compressed by clamping the Rocking Lever on to the rather thin walled seating spigot that is turned at this end. The main part of the bore finds the roundness faults in the front bar and is too tight in places. In boring I could hear some variation in the texure of the metal at different parts of the circumference. It will need a little lapping.

The final photo shows the Wheelhead Bracket being roughed parallel and square to unmachined surfaces. This has now been machined both sides to final width. I will probably follow the bible and make the spindle housing to finished OD to use as a gauge for boring the big hole.
   

[Krypto]

While I have no plans of making a Quorn grinder, I really enjoy seeing the interesting setups used to machine the parts.

[Chipswitheverything]

The Quorn casting machining is coming on very nicely, the shapes of the castings are certainly a test of patience and some ingenuity in holding them for the various operations.  I should think that every clamp, tee-nut and packer that I could find in the workshop was hauled into use at some stage when I was tackling them.  Your set up photos bring back to mind some of the rather laborious contrivances that I was "enjoying" playing about with ...  Dave

[Del_61]

I have built my Quorn using the mk 2 castings but to the drawings of Hemingway which has several modifications and is now called the mk 3.

I also built mine using the split cotter method and slightly longer bed bars of p.g.m.s. I have to say that "Time Saver" lapping compound was used on getting the final lapped finish on some key components.

There are lots of improvements and modifications to the Quorn design over the years, there is also a dedicated forum to the Quorn as well.

The most difficult part (so far!) Is the spindle. I decided that treppanning was way to stressful and built up these components carefully individually and loctited them together then finished them off on a specially made mandrel.

I still have to make up some bits yet, is a Quorn really ever finished?, but it was a challenge and has taken up about 5 years on and off.

I found a parvalux 3 phase motor from Ebay that I drive using a small inverter, but I am having significant issues joining the round plastic belt !!! All those difficult to hold, tricky castings and I cannot get my round belt to stay joined without the join failing. I might just buy a ready made one !

Good luck with the build, I made all the ball handles as it looks so much better, but I haven't decided if I am going to make the spiralling attachment though.

Regards

Derek

[Charles Lamont]

Well, you certainly did not want that Wheelhead Collar going walkies! Mine was the next to get some attention.

The first photo shows getting an initial datum surface, square to the body in two planes. Second photo, roughing the other end parallel to the first. After measuring up, both ends were finished to size, along with the little pads for the tilt adjusting screws. Next, it is set up square two ways for marking the hole positions for the clamp pad and the mounting pivots for the Wheelhead Bracket.

The fourth photo shows the casting packed up to centre height and set square with reference to the angle plate. (Setting square to the spindle means doing just that - with a turn round test. Traversing the cross slide past a stationary DTI tells you if the angle plate is parallel to the cross slide, but not necessarily that it is square to the spindle. Cross slides are mostly set on a new machine to turn a face slightly concave.) That hole looks as though it is too close to the bore. That is because the casting is intended to be slit through for clamping, but with pad clamps the hole needs to be closer in. The casting will be cosmetically dressed to suit. The hole may also look too close in because it is. Subsequent measurement shows it is 0.048" too close. Expletives.

I don't know how that happened, but it is going to have to be remedied. I don't propose to scrap it. Firstly, setting it up again is easy. Sat on the same packers, it can be lined up accurately with a 1/2" bar in the chuck passed through the hole, and can then be offset to get the hole in the right place using the cross slide dial. Boring bigger in the right place and fitting a sleeve would leave the casting too thin. What I mean to do is make an iron plug to go in the hole (to be fitted after setting up).

It will be no good pressing it in, because re-making the hole will leave the plug as just a thin crescent on the inner side. It would probably fall out. So, it will have to be glued in. But what with? Because the clamping pressure pushes outwards, fortunately the plug will not actually be subject to any load. Options I am considering are Loctite, JB Weld, and Araldite. Of these, I think Loctite in this situation may be a bit brittle and liable to chip in re-boring, and I think JB Weld may be too viscous to coat a thin joint that has to be assembled by sliding. I am thinking Araldite may be the best bet, as it will make a fairly thin joint and machines OK, but I would welcome thoughts.     

[Chipswitheverything]

Well, I must say that when I looked again at the forest of clamps that I'd used to hold down the Wh. Head casting, it did strike me as a bit frenzied : but I think that the idea had been to get a sure grip for the boring operation while not using too much clamping force at any individual point , so that the bore remained round rather than being slightly ovalized when the job was released. Probably! 
  Bit of a bind about the quite small discrepancy in the plug position, but I wonder, could you bore with the brass plug inserted in the present position, and make good with some minor dressing back of the plugs where they contact, and a similar small necking in diameter of the locking bolt to clear the column ?  Dave

[Del_61]

I use pieces of card or thick paper interposed between clamps, castings and the machine table. This provides better grip without having to result in overtightening the clamp or studs.

Regards
Derek

[Charles Lamont]

Dave and Derek, thanks for your comments. I agree on being careful about clamping pressure. I have a pack of redundant business cards that I use a lot for clamping, often as protection as well as for improved holding, though not when working to a dimension above the boring table.

I have been on Quorn Owners on Groups.io and its previous incarnations going way back, but there does not seem to be much traffic there of interest these days.

I don't know about making the belt joint. Are you using a guide such as a V-block for bringing the hot ends together? I am planning to use a little Poly-V belt on mine, H-section, 3-rib.

I have had a think about using the Wheelhead Collar casting as is, with a necked-down clamping bolt. I think it would work, but I am not sure I would feel happy with my workmanship. Plugging and reboring will be a more 'interesting' exercise anyway.

 

[Charles Lamont]

To solve the problem with the wrongly positioned hole in the Wheelhead Collar, the first job was to make a plug to fill the hole, with a two thou radial clearance for adhesive. I could perhaps have used steel, but chose iron for the bodge to be as near as possible.

Next, I reset the job on the boring table using the preserved packer stacks and recreating the position with a silver steel bar through the hole. Once clamped, the cross-slide could be moved the necessary 0.048" and locked at the corrected hole position. With that done, I could Araldite the plug in place. As the shop was pretty cold I let it cure for several days before re-boring the hole.

With the same set-up and the offset measured on the cross-slide dial, I counterbored and centre drilled the pivot hole. As originally planned, I then turned the job round, reset with the 1/2" bar, wound the cross-slide the other way and put the matching pivot hole in the other side.

The last, not very good photo, shows the glue line round the remaining crescent of the plug, appearing wider through the hole as it and the 0.002 thick cylinder of glue are tangential.     

[Charles Lamont]

I have also started work on several other castings. The toolholder and spiralling arms both have machined front and back faces, square and parallel, but not to finished sizes.

Clamping the toolholder arm in the vice for initial clean-up cuts did not yield faces that were parallel or square to the cast body, so I had to redo one face with the arm clamped to an angle plate (poor focus) and use that as datum for the other side. (The marker pen symbol on the vice is to remind me it has not been squared up.)

The tooth rest collar is a minor landmark as the first casting to be finish machined.

[Charles Lamont]

Enough of the cast iron for now.

After making a start on some of the turned steel parts, I decided to have a brass session. Among the various jobs I tackled was the Tilting Bracket, which I will go through in some detail as it is a tricky little job.

After careful measurement and planning the sequence of operation, I filed the few lumps off the back of the pointer finger. This is a clean flat surface that has accurately cast geometry in relation to other surfaces and will not be machined, so I used it as the first datum surface, setting the top of the casting level as a first guess, and took a cut over the top sufficient to clean up.

Next, using the top as a temporary datum, I set the casting in the machine vice, top against the fixed jaw. The 'tower' and the arc piece ('battlements'?), which forms the stop faces for the Rotating Base, both have very little spare metal and needed to be adjusted on packers and shims to correctly level the two. Milling the front face of the finger, enough to clean up most of the surface, establishes a vertical plane. I also temporarily faced the clamping lug for marking the hole position, and drilled and reamed a temporary clamping hole as close to the pivot point as I could get it at this stage.

With the front face clamped to the milling table I could take a cut to clean up the boss at the back.

After a little filing to clean up the sloping sides of the pointer finger I set it up on an angle plate with equal angles measured each side of the pointer to get it vertical. I want the finger tip as broad as possible as I am hoping to be able to engrave it with a vernier scale. In this position I could now take another cut sufficient to correct the top surface plane.

At this point the casting had two geometric datum planes fixed, and the next job was to finalise some dimensions. I took the casting and angle plate to the surface plate and made four sheets of sketches, taking more than 20 measurements, mainly with the height gauge. I drew it all   in 2D CAD. Armed with this, I could decide where best to find the part inside the casting. It turned out to be generally pretty accurate, the biggest problem being the clamping lug which is rather lopsided. As I am using pad clamps that need a 1/2" hole, rather that the 5/16" hole used for the original split casting, this is going to result in less wall thickness around the hole than I would have liked, considering the considerable bursting forces that the clamp pads can exert on their housing. The last photo in this group shows how it was marked out for the pivot and pad holes, using a plug in the hole already made. I think I must have staged this shot, as the holes are already centre popped.

[Charles Lamont]

Next, the job is set up on the faceplate for boring the pivot hole. The revised design for this now has a taper seating both sides so that the assembly is more firmly clamped, with a smaller parallel bore between the two tapers. Having finally persuaded the the centre pop to run very nearly true, using a wobbler and DTI, I pulled the single clamping dog up hard and then carefully balanced the job with my faceplate balancer. The bolt just showing behind the casting is there just for balance. In vindication of the use the balancer, I was able to run this set-up at 1000 rpm without vibration.

I faced the back of the boss to size and, as there was already an off-centre hole, I started to open the bore up using slot drills rather than twist drills, then bored it true before finishing with a tapping size drill.

I then bored the taper, realising early enough to reset the topside to 15° instead of the 20° I had started with. The original design (as revised) calls for a 40° included taper. I cannot think why, apart from that the Prof seems to have standardised on that angle. A shallower taper will clamp better and will still be self-releasing. I have revised the revision and settled on 30° included, and increased the diameter a tad to boot. There is still plenty of meat round the hole. I had already made the clamping bolt with its tapered seating to use as a gauge, and tweaked the topside angle until the hole blued up properly.   

A useful idea from the Mark 3 is to tap the central hole so that the part can be mounted on a stub mandrel for boring the second taper seating.

[Chipswitheverything]

Your full write up of the work on this component will be helpful to prospective "Quorners" , if such there are these days. Perhaps the Hemingway revision of the package will have generated a new interest in the Quorn, though there must be many around in workshops already.  And a lot of half finished ones!, as mine was for so many years ...
 I did the pad clamp modification, and the taper seating when I machined this bracket, and it all works securely.  Perhaps one can fairly say, that if one can sort out this awkward casting, then most other castings will not present much worse in the way of holding conundrums ...  Dave

[Charles Lamont]

Making the clamp hole was simple enough to do with the casting bolted to the milling machine table. A 3/8" drill with its cutting edges ground for zero rake went through nicely. On opening out with a 15/32 drill which had not been 'dubbed', it grabbed ferociously, twisting the casting round on its mounting bolt. It also pulled the chuck off its taper arbor, which may have saved things from worse damage. Hmm. Plan B required.

After mulling it over for a couple of days and doing a bit more work on some garden gates, I set the casting up on the boring table, using the clamping bolt in the chuck to position the casting and then offsetting the table as before with the Wheelhead Collar. I gingerly bored the hole to a working fit on 1/2" silver steel. The photo shows the patch of marker ink that was left after boring.

With the job set up the other way round, I bored it enough to clean up: 0.534" diameter for 3/8 depth. I made a sleeve to fit, using a piece of phosphor bronze that was not at all keen on being machined, Loctited it in, and put a 1/2" reamer through by hand to finish.

With that sorted, it was back to the surface plate to mark out for the vertical hole. An L-shaped piece of aluminium plate allowed me a secure mounting on the angle plate. (There are nuts securing the ally plate to the angle plate while allowing to casting to be adjusted before tightening the strap.)

 

[Charles Lamont]

With the job set up and almost ready to go, I thought I had better check for square. (The first photo actually shows a final check, but illustrates the method.) It was a bit out. A shim under the angle plate put it right. (This photo was actually taken at the end of the job.)

The third photo shows the centre pop being set to run true using a spring-loaded wobbler against the tailstock centre.

Next, with the job running true, the faceplate has been transferred back to the faceplate balancer and the balance weights added and adjusted.

Meanwhile, I remembered that, unable to think of any other way to measure the 1-1/2" inside radius of the stop arc, I needed to make a gauge for it. It is 3" diameter, and has an accurate 1/2" hole in the middle.

Lastly, all the machining at this step is done, with the hole bored 1/2", the top faces finished to the correct heights, the 90° taper turned, and the inside of the stop arc machined to clear the Rotating Base. A bit of the mounting plate got machined away, and the brass blank for the clamp pad has been removed for inspection.

[Chipswitheverything]

Almost there on this awkward component. There are times during the bolting up and packing when to have several extra arms and hands, like some Gods, would be rather helpful ...  I had already made the rotating base when I tackled the radius on this casting, so had the guide to the size.  Dave

[Charles Lamont]

Next, I milled the bottom face to size. Then I turned the temporary holding flange off the clamp pad blank, and split it. I used the pads to clamp the casting to a piece of bar in the lathe chuck. This allowed me to cut the relief in the back of the finger and very lightly face a bearing surface for the retaining washer that holds the Rotating Base in place. I also machined the outside radius of the stop arc, and, for aesthetic purposes, a slightly coned underside and a series of chamfers on the corner, which will be blended to a radius by hand.

With the stub mandrel made, the casting was fitted onto it and the finger front faced to size. At the tip, the radius and a bevel will need to be done later. Finally, I bored out the front tapered seating. That is as far as I have got with this bracket, but there is more work to do, mainly the crenellation of the battlements to form the radial rotation stop faces on the merlons and the central embrasure for the index line. By the time I get there, I may have come up with more metaphors from the terminology of mediaeval fortification architecture.   

[Chipswitheverything]

Well, at least all the "murder holes" have been created now .... Dave

[rklopp]

"...but there is more work to do, mainly the crenellation of the battlements to form the radial rotation stop faces on the merlons and the central embrasure for the index line."

I'm a big fan of big words, but need help on this one...:-) Please translate.

[crueby]

"...but there is more work to do, mainly the crenellation of the battlements to form the radial rotation stop faces on the merlons and the central embrasure for the index line."

I'm a big fan of big words, but need help on this one...:-) Please translate.

Translation: needs fancy stuff like at the top of a castle tower!      Time to go re-watch Monty Python And The Holy Grail!   

[Charles Lamont]

This may help:

[crueby]

Thats a very complex part!

[Charles Lamont]

Perhaps the most drastic modification I am making to my Quorn concerns the belt drive.

Firstly, I liked the idea of being able to run the spindle at a higher than normal speed. The Prof shows a large laminated wooden motor pulley capable of driving the spindle at 15,000 RPM. I thought I might be able to work in something less cumbersome.

Secondly, although the round belt is no-doubt perfectly adequate, I just felt it was a bit crude. Now, an early example of the Quorn was made by Neil Hemingway (of Hemingway Kits), and he used a poly-V belt (J-section, I think). A photo of it being used as a toolpost grinder appears towards the end of the Quorn book. Turners even used it a one of the montage of photos on the cover of their Poly-V brochure.

I found that by using the less common H-section poly-V, I could get a 2-speed drive inside the belt guard. However, an aspect of the design which caused me a great deal of head scratching, was how to implement a reasonably easy way of tensioning the belt. The original arrangement of sliding the slotted motor mounting plate on its three mounting bolts was a non-starter. All these bolts also serve some other function. Besides which, I wanted to extend the motor plate to encompass the spindle housing, the better to keep grinding dust out of the drive. I fiddled about with an eccentric mounting for the motor, but eventually gave in to the idea of trying a jockey pulley.

The design manual tells you not to use a spring tensioned jockey pulley on the tension side of the belt, but as the Quorn needs to run in both directions that is is out of the question; it has to be positive in action. After much doodling in AutoSketch, I eventually managed to squeeze in a mechanism that would do the job, and then realised that it was the same cam-operated arrangement as used on my lathe. To get stable quiet running, the jockey pulley is mounted on two ball races, with a wave washer to provide a light axial preload.

The jockey pulley is close to the minimum recommended size for running on the back of the belt, but the smallest driven pulley is comfortably larger than the minimum. The pulley ratios give nominal speeds of 4500 and 8000 rpm. The pulley sizes were calculated by using an Excel spreadsheet to calculate the trigonometry and using the goal-seeking function to adjust the pulley diameters to arrive at the correct belt length for each ratio. The resulting drive parameters are comfortably within the manual's design envelope. (And the envelope of the drive within the belt guard.) It remains to be seen if in practice the belt really does tension equally in both positions (but if not, pulley diameters can be tweaked). I have the belt in stock, and as a result of forgetfulness, three spares.

Wanting to see what it would look like, and while having a brass-shop session with the Tilting Bracket and some other bits and bobs, I started work on the fabricated brass belt tensioner arm. All the other tensioner parts seemed to get made before the arm was finished, mainly as silver soldering is not my favourite job, and I needed to devise a jig to hold the four pieces for soldering.

[rklopp]

Charles,

That is top tier craftsmanship. My hat is off.

RKlopp

[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.