Surface grinding experiment with Shopsmith

[Philip Davies]

I have a plate 9” square, 3/4” thick, rough, concave and perhaps to be cut into 3 parts, and then use it to make smoothing planes. I don’t know whether it is cast iron or steel. But I don’t fancy filing it flat. I saw on HMT a rig for an angle grinder. A very good idea! I could not produce an accurate rig like that and don’t have the materials, but thought of mounting a bench grinder on to my Shopsmith.

This is in our workshop, which is really for repairing furniture for residents in need, so, being a commercial property, the grinder has to be fully guarded, per regulations. So an old salvaged steel toolbox, happily the right size for the grinder, had a slot cut, then mounted on a stand,as shown, which slides along the Shopsmith’s bars, and the headstock can be used to advance it, and lock it. I brought my compound table from home and mounted it on the Shopsmith’s table, and made a pair of bars to secure the plate.

This shows the first traverse.
After all that, it became rather tedious to continue for long. It’s not a priority. Also, only about 4” of the surface can be ground at a setting. It is apparent that the surface is not wholly free from blemishes. Probably the workholding needs set screws to lock onto the plate. Needing the bench for other jobs, I dismantled the Shopsmith and put the components away, as before. It can be put together again. Also, you may observe that the Shopsmith’s lower structure is missing. It’s mounted on a softwood base, which is very unsatisfactory, and has now been discarded in favour of high density fibreboard, which hopefully is fully flat.

[ductape]

With some care and the use of a fairly good grinding wheel, there's no reason why this wouldn't work for the intended use of the plate.
The process itself provides a spark test to determine the metal. Cast iron will make short, dark red sparks. Mild steel will make longer, yellow/white sparks. Another way to tell is to rub a sheet of white paper over the freshly ground area. Cast iron will leave graphite smudges on the paper. Steel will generally not.

[DIYer]

Thanks Philip Davies! We've added your Experimental Surface Grinder to our Metalworking category,
as well as to your builder page: Philip Davies's Homemade Tools. Your receipt:

Experimental Surface Grinder by Philip Davies

tags: grinder, surface

[Philip Davies]

With some care and the use of a fairly good grinding wheel, there's no reason why this wouldn't work for the intended use of the plate.
The process itself provides a spark test to determine the metal. Cast iron will make short, dark red sparks. Mild steel will make longer, yellow/white sparks. Another way to tell is to rub a sheet of white paper over the freshly ground area. Cast iron will leave graphite smudges on the paper. Steel will generally not.

Thanks. I couldn’t see the sparks very easily, but I thought it was probably steel. I did not know about the paper test.