Thread: Toolpost Grinder - Safe for the lathe?

I'll look into some method of adjustable(?) pre-load for the bearings to eliminate the possibility of end play.
I suspect that any manual adjustments will need to take into account the operating temperature of the spindle...otherwise, maybe a small diameter thin wave washer or spring between the shaft step and the inner race at the pulley end to preload both bearings' outer races against the housing end plates?

Andrew

Rob,

Just as I sent the last post, it dawned on me that I had all the bits that were needed to do
the spindle correctly but I had machined and assembled them wrong.

I machined the wheel-end bearing bore 3mm deeper so that the wave washer just contacted the
bearing when the housing was assembled.
I then turned the bearing locating step on the shaft at the pulley end so that when the
spindle was fully assembled there was 1.5mm compression of the wave washer at the other end
(out of 4mm compression available).
This gave the bearing assembly a preload of about 5kg (~50N) measured on weighing scales.

Effectively, the wheel-end bearing can now float against the wave washer, and the pulley end
bearing is fixed, located against the spindle end housing. The shaft is compressed between
the two bearings and so there is zero end play (at <50N loads!). Therefore, the grinding
wheel is fully supported during a front facing operation, and can support a load of up to
50N when back facing. This shouldn't be an issue as the TPG will only be used for very
light finishing operations.

The TPG seems to run somewhat quieter and smoother now, probably because any wear or play in
the bearings is removed. We'll see now how long the bearings survive.

Some pictures attached of the spindle parts and assembly.

Andrew
DSCN8668.jpgDSCN8667.jpgDSCN8666.jpgDSCN8665.jpgDSCN8664.jpg

Hi Andrew,

You've done a nice job of machining that and it looks good.

There is no adjustment, or need for adjustment to compensate for temperature rise as all the components expand uniformly.

The bearings will probably last a very long time if they are reasonable quality.

Ideally the inner shields of the bearings should be removed, and the spindle used as a reservoir for oil up to the level of the ball race.

That is how Waldown and most TPGs stay cool and are lubricated. The bearings can run in grease, but will run hugely cooler in an oil bath due to low drag and thermal heat transfer by the oil.

Here's a write up on my TPG that you may find informative.

Waldown tool post grinder

It looks like you could easily convert your spindle to oil bath if you wished.

Cheers

Rob

I found this amongst some old emails - High Speed Spindle Design and Construction : Modern Machine Shop

I can't get the graphics links to work but even without them there is some interesting information. My Dumore utilises oil mist for lubrication. When I was trying to find the correct oil for the thing I contacted Mobil. The recommendation was fork oil. I'll will dig out some photos of the Dumore in a dissected state. They will illustrate how the misting was acheived.

BT