Another Cutter Grinder

[Hawkeye]

I did think of using Locktite, but there may be a slight chance of it setting up with the spindle a thou or two off centre. I suppose I could turn it with the spindle vertical while it cures. The viscosity of the liquid might work to centre the shaft.

 

[Hawkeye]

I spent some time today making the bearing carrier for the spindle. I really need to get some more tapered-shank drill bits. They are the best way to drill large holes on the lathe.


The usual boring work to make the through-hole and the two pockets for the bearings. I managed to sneak up on the pocket diameters for a press fit on both bearings.


The fit was tight enough that the arbor press wouldn't quite do it, but the hydraulic press had no trouble at all.


I figured I'd better check the runout, so I set it up as shown. Unfortunately, there is about 0.006" TIR. I'll see what I can do to improve that. It's possible that the economy bearings have some runout.

 

[Bill Gruby]

Mike;

If you used the economy bearing the TIR could be coming from the tight press fit. Tight fitting bearings in that category will distort some.

"Billy G"

 

[DMS]

Do you have any provision for pre-loading the bearings Hawkeye? If not, that could be part of the issue, as those look like deep groove ball bearings. Without a preload they will precess within the outer ring.

If you already have the bearings preloaded, then another tip I picked up is to cut the final spindle taper with the spindle assembled. When I did it on the small grinding spindle I made a while back I mounted the spindle body in my steady rest, and grab the drive end of the spindle in my chuck. This is quite effective, but it relies on the bearings not moving, so if you ever disassemble, you will need to re-cut the taper again.

 

[Hawkeye]

DMS, I do have a preload nut at the pulley end of the spindle. It's an interference fit, so it will stay put when it's adjusted.

When I was looking at it this morning, I was visualizing exactly what you suggest. Good to have confirmation. The steady is quite robust, but the through-hole is only 2 1/2". Good thing the spindle body is 2 3/8".

 

[Bill Gruby]

Check the run out in the same manner only use a Granite Plate if you have one. I'll bet it's less than you see. I used tapered roller bearings and everything was fine.

"Billy G"

 

[Hawkeye]

Bummer! I mounted the pulley end of the spindle in the MT3 collet on the lathe, then tried to slide the steady onto the bearing carrier.


The through-hole is not centred on the lathe spindle.

Plan B. I clamped the carrier to the compound, with appropriate shims. That held it solidly while I touched up the MT2 socket with the tapered reamer.


Still reading 0.005" TIR in the test setup, but a ground centre in the socket measures 0.003". It's important to note that this spindle is for the grinding wheel, not for the toolholder. If it's off a couple of thou, it will still work, more like a flycutter. The cup wheel can be trued up, but would have to be repeated each time the wheel is remounted.

 

[DMS]

True, once you dress the stone that runout should be invisible. I doubt you will be swapping wheels frequently, so it shouldn't be much of an issue.

 

[Bill Gruby]

I agree that after dressing the run out will be all but gone but what about any vibration left? Won't that hurt the finish? The wheel will be true but the shaft will still be out. Just thinking out of the box. Just how fast will that spindle be turning? Mine will max out at 5100 RPM with the low end at 3400 RPM. Any vibration at those speeds won't be fun.

"Billy G"

 

[Hawkeye]

I am planning on building a balancing system into the mount. It worked wonders with my 8" pedestal grinder.