A few words of caution about these old grinders:
-these grinders typically had no guards around the wheels, and no "tongue strips". Tongue strips are pieces of steel with slotted holes that are set above the wheel near or the 12:00 position. The tongue strips are adjusted to 1/8" gap or a little less. The reason for the tongue strips is to contain pieces of a grinding wheel if the bond fails. Otherwise, the chunks of the wheel would be propelled at the person using the grinder. I did a case years ago as an expert witness involving a bond failure on a larger grinding wheel used on an unguarded older grinder. The chunks of that wheel destroyed the shoulder of the shop owner using that grinder, and also blasted holes through corrugate metal siding on the shop wall.
-When you install a wheel on that grinder, verify the rpm the grinder is going to run at based on motor shaft rpm and pulley ratio(s). Make sure the wheels used on that grinder are rated for a higher rpm than the grinder's mandrel will be turning at. Since there is no "namplated rpm" on that grinder, it is up to whomever installs and uses it to check this.
-When wheels are to be mounted on the mandrel of the grinder, use washers cut from blotting paper (an obsolete thing, but it is a thick rag bond type paper) between the steel washers on the mandrel and the sides of the wheel.
-Inspect the wheels for soundness, no visible cracks or chunks taken out of them. Years ago, the wisdom was to hang a grinding wheel on a piece of twine thru the center hole and tap it with a wrench. If the wheel "rang" and you did not hear a dull clunk, the wheel was considered as having a sound bond. This was taught to me over 50 years ago, so may be obsolete and no longer valid.
-when the grinder is powered up with the wheels mounted, step off to one side and out of direct line with the wheels. If anything is going to break loose and get hurled from the wheel(s), it will happen during acceleration to running speed.
-Keep the wheels dressed and the tool rests properly adjusted so not more than 1/8" gap between the wheels and the rests.
-Bear in mind that just because a wheel was sound when first installed and run, it may not be sound as it wears down. As crazy and unlikely as this sounds, this was the crux of that grinding wheel failure. The wheels were made with a vitrified bond. When the wheel was manufactured, the granules of abrasive (aluminum oxide) were mixed with clay and sawdust and other substances and packed into a mold. This was then fired in an oven. The oven temperature got high enough to melt some of the materials in the mix and fuse them together, hence the term: "vitrified bond". What happened in the manufacture of this wheel was the batch was not thoroughly mixed and there were areas where there was insufficient bonding. The outer circumference of the wheel was soundly bonded. As the wheel wore away with use, the areas with no or weak bonding came to the outer circumference and centrifugal force did the rest. I likened that grinding wheel to a wagon wheel when I made the case during a deposition. A wagon tire is made of wooden parts consisting of a hub, spokes, and rim sections called "felloes". A steel tire is shrunk onto the outer circumference of the assembled wooden wheel. This tire holds the wheel together. With use and sometimes in very dry weather, a wagon wheel will get wobbly and have the tire come loose. When that happens, the wheel can collapse under load. In the case of the grinding wheel failure, it was as if the steel tire on a wooden wagon wheel had parted company with the wheel when the wheel was used and worn deeply enough to wear through the soundly bonded section. Once that happened, the result was akin to setting off a fragmentation grenade in that shop. This was a BIG grinding wheel, on at least a 5 HP pedestal grinder.
Call this a word to the wise. These old grinders never had guards, and often used natural sandstone grindstones. Probably never run too fast. With a "modern" aluminum oxide grinding wheel, centrifugal force and hurling pieces of a failed wheel are a reality. This is why guards with tongue strips are fitted on most grinders.
I am an engineer, not a book maker, so can't fix the odds of having a grinding wheel fly apart due to unsound bonding. I will say that the wheel which failed in the case I wrote about was sold under a well-respected US manufacturer's label, but, like so much nowadays, was manufactured offshore. While the materials used in the manufacture of the wheel were consistent with what had been used when the same wheels were made in the USA, the quality control during manufacture offshore was another matter. That case settled out of court, in favor of the injured plaintiff. It opened my eyes to the kind of damage a grinding wheel failure can cause, let alone the personal injury.
The old grinder is fine, but just be forewarned that it is up to you (or your son) to take the extra steps in starting that grinder by standing out of line with the wheels, and to be sure the rpm of the grinder mandrel is less than what the wheels are rated for. No nameplate on those old grinders to give rpm since there is no motor coupled to the mandrel, nor to give an rpm the mandrel was to be run at. One person might well have put a soft natural sandstone wheel on that grinder and ran it rather slowly with a can of water dripping on the wheel to sharpen scythes and similar. The next person in a truck garage or weld repair shop might have belt it to run at a faster rpm to use aluminum oxide wheels needing a higher "surface speed" and bonded to hold together at a bit more than that speed. Old machinery and the times it was made relied on the users to know what they were doing and take responsibility for their own actions. No cautionary stickers and guards, no manuals, just a simple grinder sold as it was, with the user having to decide how to drive it, what wheels to use, what lubricant to use in the bearings, knowing how to adjust the tool rests, mount the wheels, etc. Different times when people worked with machinery and tools routinely and no one thought in terms of liability or making things "idiot proof". The attitude often was: if you got hurt around machinery, or on a job, it was your fault not the fault of the machinery or the job conditions. Be forewarned: this old time grinder is made for that old time mindset and old time skill-set.
