Well the Old 'Arn Bit again

Sometime I hate I am interested/addicted in old iron.

This Saturday I hit the salvage yard to get some plate to convert my sheet metal work bench into a welding workbench. I came around the corner to the incoming sorting pile and guess what was standing out in the middle calling to me in it's 750# silver painted glory...

A 12"x1.5" JG Blount pedestal grinder, serial no. 1553A. It has 2 stones, one wet and one dry and the pedestal is the water tank. Motor is missing along with the pulley for the water pump which seems jammed. I figure she was built 1910's -1930's, since the drive pulley and slack adjuster have a flat belt profile, and not V Belt, and the motor mount plate was cast in and not bolted on.

I am sure you all have gone through what I did for about 1/2 hour at the yard, arguing with yourself.

Do I need it, It's too good to be scrapped, do I have enough `tool' money, might I use it, it needs..., do I have room for it, I only came for X, can I get it safely off the truck, etc... You can guess the result.

Now for the real questions, does anyone else have one? What size motor would she have had (hp & RPM), I am thinking 3hp, 1200rpm, but the ghost of the motor footprint seems larger. Was the drive sheave the same size, larger or smaller than the driven one on the wheel shaft. What diameter pulley would have been on the motor and the pump for driving the water pump. How do I change out the wet wheel?

Enjoy the photos,
Thanks,
Rich C.

Very little info on JG Blount grinders over at OWWM: OWWM - J. G. Blount Co. - History
VintageMachinery.org - J. G. Blount Co. - 1922 & 23 Ads-J. G. Blount Co., Bench Grinder

You might want to add the informations about your grinder and some images to the site when the machine is cleaned up.

When I go to the scrap yard and hang around, all I ever see is ferrous yard trash and demolished metal buildings going across the scales. Maybe I don't go often enough, but all I ever see on the pile is lathes broken in half and mills beaten into balls. I do admire you guys who can find such good stuff and cart it home. Have Fun. Regards, Clark

When I was a student at Brooklyn Technical High School (1964-1968), we had those same Blount grinders in some of the original machine shop classrooms. They were driven by lineshafting, and you pulled a rope to shift the belt from loose to tight pulley. We used the grinders for offhand grinding of high speed steel toolbits and offhand sharpening of twist drills- both of which we were required to be able to do.

A required course in those years for all freshman was wood patternmaking. In the wood patternmaking shop classrooms, there were Blount wood turning lathes. As a student in the mechanical course, I had to take an advanced wood patternmaking course in my junior year. In that course, we turned some wood pattern parts on the Blount lathes. As I recall, we had two types of Blount wood turning lathes. One type had a hollow spindle motor for the headstock with a speed selector switch. The other had a flat belt drive to a motor mounted down in the leg under the headstock.

Brooklyn Technical High School moved into what they called "the new building", ca 1924. My belief is the Blount grinders & wood turning lathes were original from when the school was built. The grinders and wood turning lathes were the only Blount machine tools that I can recall seeing. Like the grinders, the wood turning lathes built by Blount were massive by today's standards. Heavy iron castings and well designed machines.

Joe Michaels

You did the right thing crij . Who wouldn't want to have that good looking grinder sitting in their shop. Shaperhaven

Good save

Good save crij.
If you let that one go you probably would have had nightmares for the next month and been visited by the ghosts of lost old iron, past... And in my opinion one can never have too many grinders.
toolles

Thanks for the confirmation of my illness...

Back to the questions, does anyone know the horsepower and motor speed of the old motor that was installed on one of these??? As a reminder it has 12 x 1.5 wheels.

Thanks,

Rich C.

Crij,
I can't speak to the size the the original motor horse power wise.. but as a starting point why not look at a 'modern' 12 inch grinder for specs ?
Bench Grinders & Grinder-Buffers and other Bench Grinders & Accessories at MSCDirect.com.
Hope this helps
Stay safe
Calvin

Would the old flat belt pedestals have run the same speed as current grinders, or slower?

It comes down to the type of wheel you are running, what abrasive and how it is bonded. Typically, a "surface speed" in feet/minute would be specified for a particular type of wheel. The limiting factor is usually the bond, as this is what holds the wheel together when it is turning. Machinery's Handbook has some general information, but ultimately defers to the wheel manufacturer for maximum safe speed. Norton used to put out a detailed handbook for their wheels, and this might help.

Machinery's Handbook does have a value of 5,000-6000 fpm for wheels used for "Snagging and offhand grinding". This would be in line with what a grinder like the old Blount would be used for.

machinery's Handbook has a footnote to this table of values, to the effect that the higher end of the speed range is only to be used on machines where the bearings and overall machine rigidity is up for it. On something like the Blount, with plain bearings, IMO, go for the lowest value if you are going to compute RPM.

Take the wheel diameter, convert it to feet and multiply by Pi (3.14159). This is the wheel circumference. Divide the surface speed you choose to go with by the circumference and you have the rpm the grinder arbor should be turning at.

The important thing is to determine what bond is used on the wheel. Chances are good it is a vitrified bond wheel made of aluminum oxide abrasive, as this is pretty common for that application. Find a safe value in fpm for vitrified bond wheels and run the numbers.

If you can take the arbor nuts and washers off, possibly there is enough of the wheel maker's label left to give some data including maximum safe speed. This safe speed was figured for the wheel at it's original diameter. With use and resulting wear, the wheel is likely smaller. Running at manufacturer's recommended rpm will result in a lower surface speed since the wheel will be smaller in diameter, so a bit safer.

The other thing to do is to inspect and test the wheels. Dismounting the wheels and hanging them on a piece of twine and striking them with a wood handle used to be the way. If the wheel rang a good clear note like a bell, the belief was the bond was sound. If the wheel went "thunk" or sounded "dead", the belief was the bond was broken or there were cracks in the wheel.

I did a little forensic engineering on a grinding wheel failure a good 20 years ago. It was a 14" Norton wheel, used for offhand grinding. The wheel had been bought new, and the shop owner had hung it on twine and "sounded it". It rang good, so he mounted it on the arbor of the grinder using blotting paper washers. The shop owner dressed the wheel and let it run for an hour (his own idea to see if anything was going to let go, not likely with the wheel at steady speed and no grinding going on). The shop owner used the wheel repeatedly without incident over the next few months, dressing it as required. One day, while in use, this wheel exploded. The grinder was some ancient thing without a "tongue guard" and missing most of the wheel guard. Rated rpm of the old grinder was within the safe rpm recommended for the wheel.

The shop owner said he needed the grinding wheel exposed to dress plowshares and other large work and his grandfather before him had been using that same grinder that same way without incident. The wheel disintegrated at speed, and chunks of it blasted off tangentially. Some chunks caught the shop owner in the shoulder and upper arm. The energy threw him back against the opposite wall. The chunks of the grinding wheel destroyed his shoulder joint and did a lot of other damage. Other chunks of the wheel blasted through corrugated steel siding and metal roofing in the shop.

The wheel had been made by Norton in a plant outside the USA. It was a gray aluminum oxide wheel, vitreous bonded. My own theory was the wheel had some lack of consistency in the mix of abrasive, clay and sawdust that was molded to make the wheel. The result was the outer layer of the wheel circumference had a sound bond, which "hooped" the rest of the wheel like a locomotive or wagon tire. This soundly bonded area served to hold together the inner areas of the wheel were there might not have been total homogenity or a uniform bonding. As the wheel wore, the "tire" wore away, and eventually was unable to resist the "hoop stress". The unsound inner portion of the wheel, no longer having the outer sound portion to "hoop" it, and having a compromised bond, could not resist the centrifugal force and flew apart.

This theory held enough water for Norton to settle the case.

I saw the remains of the wheel, the damage to that shop building, and talked to the owner (who had undergone several surgeries to repair the damage from the wheel blasting him). It made more of a believer out of me about taking care around grinding wheels.

There is a lot of energy in a grinding wheel, so taking steps to insure the wheel is soubnd, properly mounted, and arbor and bearings in good condition are worth doing. On an older machine like the Blount, there may be no "tongue guard" to keep pieces of the wheel from being thrown off the top of the wheel and out. If you run a little slower, the wheels may wear more rapidly. But, we come back to how good the arbor journals and bearings are. A loose set of bearings and worn journals may prove to be the limiting factor.

Joe Michaels