Chris

Spindle diameter is probably insufficient for MT2 adaption. Minimum diameter for MT2 seems to be around 1 1/8" inches, 1 1/4" sounds safer. Yours is probably about 1".

Picking up on the mention of Corona models by DiogenesII it looks like these, later machines, were fundamentally an update of your drill with muti groove vee belt drive, silly skinny looking thing, and a few, mostly cosmetic changes. The Corona 100A/1 I owned before I getting the 15AY was fitted with an MT1 taper in the spindle.

Generally the Corona versions appear to have been for woodworking use with appropriately higher speeds.

Pollards made a huge variety of machines and there is lots of commonality through the ranges. I suspect the sliding carrier for the quill & spindle assembly is the same as that used for the metal working machines with MT2 and, possibly, MT3 spindles. Easily checked by measuring quill diameter. If so it would be mechanically practical to chop the end of your spindle off and weld on an MT2 carrier.

Something I considered for mine when frustrated by the inability to use larger drills. Plan A being to operate on an MT2 jump up sleeve.

Never summoned up the courage to try! Sleeve is still kicking around here if you fancy a go!

I'd previously asked Pollards, who were still supplying limited spares at the time, if an MT2 spindle could be obtained and fitted. As I recall it they said that although an MT2 spindle could theoretically be fitted the job was impractical because the splines wouldn't match my pulleys.

Clive

DiogenesII

I think the 12AX was current up until the mid 1960's or so when it was replaced by the Corona 100/A that I had. Which basically gained more boxy styling, a larger spindle and multi-vee belt drive. Lost the screw feed belt adjuster tho' for a simple permanent spring loading system. Push the motor against the spring to shift the belt.

Pretty much the whole Pollard range got re-vamped to more modern styling in the 1960s -1970s but little change in the innards.

I suspect that Chris will find a Corona 100/A manual adequate for general what goes where and how does it go together information subject to a bit of engineering experience to sort out detail differences.

Clive

Hi Chris,

I adapted a Corona 12FX for milling and the article I produced to describe the saga appeared in MEW issues 216 & 217, if I recall correctly.

My original adaptation of the spindle for milling involved machining a bespoke ER32 chuck incorporating a female J2 taper. The spindle end drilled readily to accept an axial screw to keep the thing attached. The closing nut was bought in. This arrangement worked fine but anything other than fine cuts (< 0.1mm) led to sideways deflection. I half expected this because the 72mm chuck length produced far too much overhang from the bottom bearing. I should quickly add that I replaced the ball race with a tapered roller bearing ground down to size to fit the existing bearing housing. Eventually the lack of rigidity became too much to live with and I tried a different approach; one that may suit you better than welding. I cut the end off the spindle, and fitted a sleeved and bored ER32 collet chuck extension, glued using anaerobic adhesive and pinned through with a roll pin. This runs in a much larger tapered roller bearing in a housing with a spigot that fits into the original bearing housing. Retention is via the existing three screws (not equi-spaced, incidentally; I spotted through the original retaining plate. I allowed sufficient 'hollow' length of the spindle extension to accommodate a MT1 to parallel adapter in one of the larger collets to make use of some imperial taper shank drills I have. Larger drills are held directly by collets and smaller ones in a Jacobs chuck on a 19mm diameter straight shank arbor.

The original three-speed flat belt drive has been replaced with a two stage poly-vee system, giving eight speed from approximately 160 to 2,500 rpm from a 2,400rpm single phase motor (the original was 3 phase.

Although it could never compete with a proper mill, performance is not bad at all and edges produced by side-milling are square, so no deflection as before. The slim (around 5/8&quot spindle has survived so far and I have done quite a bit of milling of steel and aluminium. Incidentally, my machine did not come from a wood working shop and I don't believe it was ever designed for such use. The 12FX is a high-speed drill and was sometimes supplied as a 'ganged' machine with up to four spindles.

Alan

Chris

Further to what AlanW has said it doesn't seem unreasonably difficult to come up with a functional equivalent to the spindle on my 15AY which has a similar style of large diameter bearing carrier to Alans modifications.

Mine has an MT 3 taper. The exposed spindle is 1 1/2" diameter and the quill carrying it only 1 5/8" diameter so the main body of the spindle must be rather smaller to allow adequate quill wall thickness. I imagine a inch or so. The bearing carrier is around 3 1/2" in diameter.

If you obtain an MT 2 to parallel sleeve it could be joined to the spindle by a simple tube having the appropriate diameters to accept the sleeve at one end and the spindle at the other. I imagine a couple of inches or so overlap on both would be plenty for high strength loctite bonding. Even without the pin used by Alan. The joining tube will need slots cutting in opposite sides to take the ejector drift.

Obviously you will have to accept some loss of quill travel and clerance between table and spindle to accommodate the bearing mount and MT taper extension. Fitting the bearing on the joining sleeve would be the most rigid arrangement and minimise the reduction in spindle to table clearance. I suspect Pollards used an angular contact ball bearing to take the loads.

In your position I would use it as is and decide what to do later to make it exactly what you want. Start wih a 3 phase motor and VFD.

Clive

Edited By Clive Foster on 16/01/2022 21:22:51