Tool and Cutter Grinder
Castings and materials
The kit for this was purchased way back in July 2005 and I remember feeling sorry for the Postman who had to deliver it! The parcels weighed a ton and it took me all my time to carry them upstairs to the workshop. At the time I just unpacked the bits, had a look at the drawings, and then carried on loco building! Details of the grinder can be seen here
The Kennet is a fairly basic tool grinder from Model Engineering Services (run by Ivan Law). MES also do a kit for the more complex Quorn but I felt at the time that the Kennet would be easier to build and would be capable of all the tool grinding that I would need to do. The kit consists of all the castings in iron and aluminium and all the raw materials, bearings, knobs, and screws, bolts etc. At the same time I also purchased a set of 6 grinding wheels for use with the finished machine. I already had a suitable small induction motor to drive the spindle so was spared that extra expense. The 'raw' materials include four lengths of 1½" dia. mild steel bar that have to be cut up at some point and this prompted me to obtain an electric bench hacksaw as I did not fancy sawing that lot by hand. Fortunately I managed to get one locally off Ebay very cheaply which should be man enough for the job.(see equipment)
Anyway, I've decided it's time to start work on it as I really need to be able to sharpen tools to a better standard than I can do them by hand on my old cheap bench grinder. I'll probably work on it over the winter along with other things.
The base is a single iron casting and comes with the mounting faces for the grinding spindle and the tool platform, already surface ground. The only major operation to do on it is to mill a long slot at the front so that the main tool platform can be moved backwards and forwards. This is apparently the only operation on the kit that cannot be done in the ML7 and really requires the use of a milling machine. I may be able to do it in my small mill if I chain drill it first and just clean up the slot with the mill or I could take it to Whitwick and use the club's facilities. They have a very well equiped workshop on site including a large vertical milling machine. If all else fails, I can go to a friends round the corner who has a Dore-Westbury that he built from another MES kit (Sadly the Dore Westbury kit is no longer available as Ivan says it is just too expensive to get the castings made nowadays).
I've decided to have a go at milling the slot in the base in the small mill. To make this easier I've chain drilled the slot first so the milling tool will have less metal to remove. The table of the mill has just enough travel to machine the slot in one go but the base overhangs the table a lot and it was not easy to clamp the base casting securely. However the cast iron is very good quality with no hard spots and it drilled very easily. Tomorrow I'll have a go at milling it to finished size with a slot drill.
Chain drilling the slot prior to milling it to size
I've managed to endmill the slot in the base quite easily much to my surprise! By holding the endmill in a collet rather than the chuck and locking the quill etc. up solid I managed to clean up the 1/2" deep slot without too much chatter or vibration. I firstly removed the metal between the previously drilled holes. I had to do this in two cuts as it didn't like cutting full depth all in one go but once this was done I opened the slot out to full width using a single cut per side. During the milling operation I noticed that the main source of 'flex' in the miller seems to be the head casting that holds the quill and motor drive so it might be worth trying to beef this up at some time in the future. Either that or the square column that the milling head moves on is twisting slightly.
The next casting tackled was the column head which holds the quill for the grinding spindle. There are probably several ways to approach machining this. I chose to true the base up with a file so that it could be clamped onto the cross-slide of the lathe and then fly-cut one end of the casting to get it flat. I then upended the casting and bolted it to the cross-slide again with a large bolt through the bore of the casting. This enabled the base of the casting to be skimmed dead flat.
Fly-cutting the end of the casting
Fly-cutting the base
The now machined base of the casting was then clamped onto the cross-slide again for boring out the casting to take the spindle quill. This job could also be done by mounting the casting on an angle plate on the face plate but I think mounting it on the cross-slide is probably easier. It is interesting to note that the centre of the casting bore should be 2-1/16" from the base which just happens to be the height of the lathe spindle above the top of the cross-slide. I am sure this is intentional as all the MES kits are designed to be machined on the ML7.
The ideal tool for this job is a between centres boring bar but I didn't have one that would fit into the rough bore. Instead I used my old trick of holding a square shank boring tool in the 4 jaw chuck and adjusting the cut by moving the jaws. I initially used a HSS boring tool but the rough casting took the edge off that straight away so I changed to a carbide tipped tool that came with a cheap set of lathe tools. I should have used this in the first place but I thought the tip would probably fall off if I tried using it! It actually cut quite well but I had to take several finishing cuts at the same setting to get the bore parallel due to spring in the tool.
Boring the head casting to size
Incidently, I don't think there was ever a set of building instructions for the Kennet (at least I can't find any!) so any builder is pretty much on their own. The Quorn has the advantage of a complete ME series dedicated to it's construction and use although it is a lot more complicated. Hopefully my account of building the Kennet may be of some use to other builders.
After boring the head casting it was turned around on the cross-slide and a skim taken off the unmachined end just to tidy it up. The casting needs to have a slit cut into the top of the bore at some point and drilled and tapped for 2 cross screws. This is so that the quill containing the grinding spindle can be clamped into the head. Presumably the quill can be moved backwards and forwards to suit different thickness grinding wheels?
I decided to drill and tap the two holes for the clamping screws first. The holes were drilled right through with the tapping size drill for the 1/4" BSF screws and then opened out halfway through with the clearance drill. The holes also need to be spotfaced slightly to give a clean, flat surface for the heads of the screws to bear on when tightened up as the castings have quite a steep taper on all the surfaces. As I don't have any spot drills I used an endmill instead.
Spotfacing the clamping screw holes using an endmill
I then marked out and drilled the 4 holes for the screws holding the head to the column base.
Drilling the 4 mounting holes in the base of the head
The tops of these 4 holes also require to be spotfaced so again I did this with an endmill.
Spotfacing the mounting holes
Next I decided to machine the column that the head bolts to. This is a simple rectangular casting that just requires the top and bottom surfaces machining flat. I did this by filing the base reasonably flat, clamping the base onto the lathe face plate and skimming the top flat. The base was then turned end for end with the top clamped to the face plate and the base of the casting skimmed. There's no dimension given for the height of the column so I just took enough off to clean up the faces. I didn't take a photo of this at the time but if I get chance I might 'pose' one just to show the setup.
All that needed to be done now was to drill the holes to bolt the column to the base and drill and tap the holes to take the screws holding the head to the column. The holes in the base of the casting were just marked out and drilled. The holes in the top were spotted through from the head after clamping it in position and then drilled and tapped 1/4" BSF.
Spotting through the holes from the head and then drilling them tapping size
Again the holes in the base need spotfacing for the mounting screws but the top of the casting prevents using an endmill as before. This time I mounted the casting on its side and just machined the top of the 'foot' flat.
Machining the top of the foot flat
Returning now to the head, I still needed to cut the slit in the top of the casting and rather than saw this by hand I managed to do this by mounting the casting in the mill and using a slitting saw.
Cutting the slot in the head with a slitting saw
At least when the grinder is finished I'll be able to sharpen all my blunt slitting saws!
Finally the head was temporarily bolted to the column and clamped in position onto the base so that the holes in the base could be marked out, drilled and tapped. Before marking the holes, a length of bar was placed through the head and the column/head assembly adjusted until the bar was parallel to the long slot in the base.
Head assembly mounted on main base
I must admit that my opinion of the Micro Mill has got more favourable over the last few days as I've pushed it to it's limits. The flexure in the column and/or head casting is a problem but so long as the milling cutters etc. are held in a collet rather than the chuck it can do passable work.
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