Emco Mill bent spindle mystery

Edited By ady on 08/07/2011 09:28:44

Hello Ian,

Can you tell me the outside diameter of the Mentor Mill Quill please?

The reason I am asking is that I have just produced a design for the Emco FB2 Quill that incorporates a taper roller bearing at the front and an angular contact at the rear. If the Mentor Mill quill is 52mm outside diameter then there is every chance the modification will suit this mill as well.

Gray,

Graham

Put simply, its not going to fit!

The quill on the Mentor mill (4 speed head) is 48mm diameter. I have done a CAD drawing of the whole spindle assembly and it its any use to you I can send the file.

Regards

Ian

Hello Ian,

To get this new taper roller race to fit on the FB2 has involved extending the quill by 8mm, which means making a new quill out of EN8 and a new spindle from EN24T, but I think for the improvement in the spindle bearings I think it is worth it. I was fortunate enough to obtain the drawings of the spindle assembly and detail parts drawings from the factory to carry out this modification.

The Mentor mill could be extended in a similar fashion with the new bearing external to the existing quill, outside the head, the quill would be similar to a "top hat" in shape with the new bearing in the brim, but in this case it would need extending by 20mm, to gain enough room for bearing seal and a suitable section for strength, as this would get the spindle bearings further apart this would add to the spindle rigidity.

One saving grace on the Mentor Mill is that you do not have a 6 sided spline to machine which is what I am about to go and machine.

Just for interest the taper roller bearing is 30mm bore, 48mm outside diameter and 12mm overall width and cost £13.00, the bearings do come in a wider section but not thinner unfortunately.

I would appreciate the drawings, if you could send me your email address via a PM or I will send you mine, which ever you prefer.

Gray,

Edited By Graham Meek on 17/05/2012 09:13:20

I’m not sure if my experience with my EMCO mill is helpful, but add my thoughts. I purchased an EMCO FB-2E mill fifteen years ago. I had the choice between the one made in Austria FB-2 and the equivalent made “in the East” designated FB-2E. I purchased the FB-2E as it was considerably cheaper than the Austrian version, and I was assured that EMCO were vigilant in quality control of the Eastern model. As usual, you get what you pay for and for some time I wished that I had found the extra cash and bought the Austrian model. Eventually I managed to get the machine into a satisfactory state. The table was jerky in its x and y movement and I had to completely strip it down and replace all the solidified grease. The grease formed solid lumps in the bearings of the hand wheels. After a couple of years play developed in the roller bearing of the spindle. The area of the quill around the roller bearing also became hot on the highest speed. With some trepidation and difficulty, I dismantled the quill and found gritty residue in the region of the rollers. Quite obvious really as it is the lowest point in the system and debris in the oil will descend into the roller bearing. I imagine that the debris results from inadequate cleaning in the factory at assembly. I saw that the bearing surface was scuffed but left it alone, not knowing what to do. I purchased a new roller assembly from EMCO and as the unit was disassembled decided to fit a new thrust bearing also. I put it all back together with the new bearings. I also replaced the oil as the original stuff looked terrible. You can imagine my disappointment when I found that the play in the spindle was reduced but not gone. I was going through options with a friend well versed in machine tool matters and he suggested that the roller bearing design would make it difficult to eradicate side play. He suggested that I replace the existing bearing with a bronze bush. I scoffed at the idea at first as being beyond my capabilities. I then came to the conclusion to have a go, as the machine was useless for accurate work. The quill was again stripped into components. I put the spindle in the lathe and polished the bearing surface with fine silicon carbide paper followed with metal polish. Mine was not as badly marked as the one shown in the photo. I then found a suitable piece of bronze in my store and turned up a bush that was a firm fit in the quill and a very tight fit on the spindle. I also drilled an oil way to the centre of the bearing. The spindle was put in the lathe with the bush in place together with some metal polish. I use Autosol for these jobs. The lathe was started at a slow speed and I held the bush against rotation. It was hard to hold the bush at first but became easier. I changed the metal polish a few times as I had heard that the cutting action of Autosol reduces as the particles in the polish break down and become less effective. Eventually I had a smooth running bearing with no play. All was put back in place and happily the spindle rotated freely with no side play. It has now been used regularly for several years and no play has developed. The sole problem is a very minor oil leak around the spindle. It is not sufficient to be a nuisance and proves that oil is getting into the bearing so I leave it alone. Perhaps I should have replaced the oil seal when the bronze bush was fitted. I cannot comment on the bent spindle except to express surprise as it seems a very sturdy construction. After all this I am now content with my machine. It is sturdy for its size and produces good results. I might add that the gearbox was noisy in the early days but following the addition of some molybdenum sulphide additive sold for motor car engines it runs quieter and smoothly. I hope that this is a useful contribution.

Hello Raymond,

From the assembly drawing for the Quill supplied by Emco there are three different spindle diameters in the form of ground masters that are used to gauge the needle roller bearing installed in the Quill housing, for each ground master there is a size to grind the spindle to, (selective assembly). With this in mind just replacing the roller bearing is bound to cause problems, given the variation in the bearings themselves which should be P6 grade. The variation over the three ground master gauges is only 0.01mm and the limits on the diameters that the spindles are to be ground to is +0.003mm and -0.006mm, which is pretty close in my book.

Heat in the roller bearing at high RPM is normal, the oil in the bottom of the Quill is having a tough time with the rollers churning it up.

The Bronze bearing is something I had considered a possibility so thanks for trying it out, I had a feeling it should work and rest assured the quill will fill completely with oil during use.

The oil leak is common and I have completely cured mine on both FB2's that I have owned by simply providing a spring loaded ball valve to vent off the pressure that builds up in the head during use or due to fluctuations in the workshop temperature. I made a new screw in oil filler plug with the ball valve in, knurled on the outside diameter and an O-ring to act as a seal beneath the head,( the thread is metric, M14x1.5P).

Gray,

Hello Gray,

Very many thanks for the data on the rollers. It reminds me of my AJS motorcycle in the 1950’s. The big end became noisy so I had it rectified. The mechanic told me that he had fitted oversized rollers to take up the slack. My Pitman’s “Book of the AJS” notes that oversize rollers 0.001in. were available but the journal and liner needed to be lapped by a skilled mechanic.

I am extremely grateful for your comments on the oil leak and how to cure it. The spring loaded ball valve will be high on my list of jobs. Until then I may slacken the plastic oil filler cap to allow air pressure to equilibrate. I had a problem with my FB2 in the early days in that the compressible nut on the Z direction screw rapidly became fully collapsed, so it became difficult to take up play. I replaced the nut which enabled me to take up play, but do wonder how long this will continue. Do you have experience of this?

Ray

Hello Ray,

My apologies for the delay in responding I have been pressing on trying to get the new Quill assembly for my FB2 finished.

AJS were a bit before my day, BSA C15 was the only bike I had, but I do recall now that you mention it the fact that you used to be able to get oversize needle rollers.

My current FB2 was purchased in 1996 and I have only adjusted the tubular nut once, current backlash is in the order of 0.05mm. The alloy is a very good bearing material provided there is an adequate supply of EP grease, a replacement nut from Emco should last for quite some time.

Gray,

Hello Ian, Ray,

I thought you might like to see the finished conversion for my FB2 Mill, I have just tonight assembled the Quill into the milling head and the new bearings have surpassed my expectations.

Run-out is within the manufacturers tolerance of 0.01mm TIR and the improved finish when using the side of an endmill was well worth the effort. Total outlay was well under £100.00 .

Gray,

Hello Gray,

Sorry for the tardy reply, but we took a few (sunny) days in Cardiff on family business, without the laptop. I must complement you on the excellence of your pictures. The super machining and the high quality photos are a joy to the eye. I attach a photo of the old roller assembly take from my FB2.

Ray

Hello Ray,

We too have just returned from a few days holiday in Mid Wales, we both certainly had some good weather. The clear atmosphere gave us some spectacular views and we had a wonderful time staying at a small hill farm at Howey, the food there is to die for.

I have dismantled my existing spindle and after 16 years very hard work the needle roller race is not in bad shape. I intend obtaining a new one and rebuilding the spindle. Sod's law dictates that if I do not rebuild this spindle I shall need it, but if I rebuild it I shan't need it.

Gray,