I recently acquired a 50's model Craftsman 7-inch bench grinder, which is known as a "Pre-Block" model. I've owned a dozen of the later Block models, but never one of the early versions. I set about trying to learn more about their history, but found very little accolades for them--so why no love?
I'd like to hear comments from other owners, as my first impressions are very favorable. I'll start this thread with what I have already gleaned from mine:
--The housing is cast iron as opposed to the die-cast aluminum alloy used in the later Block models. This makes the grinder much heavier and stable under use. My 7-inch Pre-Block tips the scale at a tad over 55 lbs, which I believe is nearly twice that of a comparable alloy block grinder. Plus, cast iron has more internal damping than alloy aluminum, so it runs quieter.
--The motor structure is far more substantial than the later versions. I didn't split the cases on mine, but was able to measure some key dimensions with the center sheet metal removed. My Pre-Block is rated at 1/3 HP, and employs a 2-inch thick lamination stack and a 3.5" diameter rotor. In contrast, a 1/2 HP Block has a 1.5" stack and a much smaller 2.62" diameter rotor!
--Amperage of my 1/3 HP Pre-Block is 5.5 amps, which is about what an early 1/2 HP Block draws. More significant is that it is over an amp more than my 1/2 HP Baldor and Rockwell grinders of comparable build & weight. This is a powerful grinder!
--Construction is heavy duty throughout. For example the rests are bigger/thicker, and absolutely more rigid. The eye shield frames are heavier gauge: I measured .063" thick (16 gauge) when I couldn't bend the tabs to remove the glass! Even the arbor shaft is heavier, and much thicker inside the rotor.
--Operation is much like the later Blocks, with the extra oomph of the capacitor start, and the long running at turn off. The Pre-Blocks used centrifugal switching of the start winding (as opposed to the current-sensing relay), yet it is also of very high quality and engineered for long life, but it does reduce the spool down somewhat.
There doesn't seem to be any downside to these older models, so why does all the attention go to the later versions? Surely, I'm not alone here.
I'd like to hear comments from other owners, as my first impressions are very favorable. I'll start this thread with what I have already gleaned from mine:
--The housing is cast iron as opposed to the die-cast aluminum alloy used in the later Block models. This makes the grinder much heavier and stable under use. My 7-inch Pre-Block tips the scale at a tad over 55 lbs, which I believe is nearly twice that of a comparable alloy block grinder. Plus, cast iron has more internal damping than alloy aluminum, so it runs quieter.
--The motor structure is far more substantial than the later versions. I didn't split the cases on mine, but was able to measure some key dimensions with the center sheet metal removed. My Pre-Block is rated at 1/3 HP, and employs a 2-inch thick lamination stack and a 3.5" diameter rotor. In contrast, a 1/2 HP Block has a 1.5" stack and a much smaller 2.62" diameter rotor!
--Amperage of my 1/3 HP Pre-Block is 5.5 amps, which is about what an early 1/2 HP Block draws. More significant is that it is over an amp more than my 1/2 HP Baldor and Rockwell grinders of comparable build & weight. This is a powerful grinder!
--Construction is heavy duty throughout. For example the rests are bigger/thicker, and absolutely more rigid. The eye shield frames are heavier gauge: I measured .063" thick (16 gauge) when I couldn't bend the tabs to remove the glass! Even the arbor shaft is heavier, and much thicker inside the rotor.
--Operation is much like the later Blocks, with the extra oomph of the capacitor start, and the long running at turn off. The Pre-Blocks used centrifugal switching of the start winding (as opposed to the current-sensing relay), yet it is also of very high quality and engineered for long life, but it does reduce the spool down somewhat.
There doesn't seem to be any downside to these older models, so why does all the attention go to the later versions? Surely, I'm not alone here.
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