DIY surface grinder

[tonyfoale]

Some updates on this.
When used as a "tool post" grinder (more like a cross-slide grinder, because it is solidly bolted to the cross slide) the finish was not quite as good as I thought possible. I swapped out the grinding spindle for one made from a heavy cast iron housing. This made a big difference. Here is a photo with it on the lathe and another showing the strong steel wheel guard.

click images for full size.

This is a view of some grinding tests, greatly magnified with a digital microscope, I forget the actual magnification. On the right of the first photo is the finish obtained with the previous spindle and on the left with the current version. For comparison the photo on the right is of the finish on a quality 5C collet.



I also found an electro-magnetic flat chuck on the usual auction site at a cheap price. The seller said that he tested it and it did not work too well. His test power was AC and DC is necessary so I took a chance that the chuck was OK but the test method was not. I was right, it works fine. It was also rusted all over but it cleaned up easily.




As for surface grinding on the mill that will be made obsolete by a new project, which unfortunately had to be put on the back burner for a few months due to other more pressing tasks. The new project is a dedicated high precision CNC surface grinder. The table will move on linear ball slides and be driven by closed loop steppers controlled by my dedicated software. To test certain features prior to cutting metal I cut wood instead and mocked up the table and drive system to test whether the stepper size that I calculated would be capable of throwing the table and mag-chuck about at the usual surface grinding feeds. I used a 20 mm pitch ball screw to get the speed. I'll make the base of this grinder in epoxy/Granite and I have a piece of solid granite of suitable size to make the table from. I'll make a full post on this when it is finished, I will be getting back to it later this coming week. In the meantime here are some pix of the wooden version which passed all the tests.