Baldor Tungsten grinder project
Posted: Sun Aug 02, 2015 4:11 pm
Tungsten grinding on cheap China bench grinders grrrrr I'm done with that its on now!
Here are the first bits, the blue diamond wheel is 180 grit, the yellow diamond wheel is 320. Those are lathe chuck guards I'm hoping to use them instead of the dinky grinder eye shields. I have had bits of metal in my eye twice, I'm not looking for a third trip to the ER for that.
I'm not messing around with a stand either, this is the larger Baldor cast iron stand, 120 lbs, get some!
The 1/2hp 7 inch Baldor grinder arrived, model 762. Here it is vs the 6 inch China bench grinder. Its quite a bit larger.
The arbor is .625 inch for the 7 inch wheels, that's a burly 15/16 inch nut.
These are the supplied aluminum washers .625 arbor, they appear to be cast and don't exactly spin true but the fit has enough slop that they are fine.
Houston we have a problem. So I turned on grinder and it took off across the bench with some speed, whoa there Baldor. Severe vibration. Here's the problem, the motor shaft is actually .750 they turn down the outer few inches to .625 for the grinding wheels and washers. But that big steel inner spacer doesn't fully cover the .750 section of shaft, there's a .060 x .060 shoulder sticking out. The large aluminum washers were resting on that cockeyed instead of up against the tall steel spacer, hence the vibration.
I turned a couple of 1.25 inch tall brass shims on my lathe with a recess for that shoulder, problem solved. I also turned a couple of brass .625 x 1.25 arbor adaptors for the diamond wheels.
Here's an action shot, vibration is now quite minimal, it just sits there purring. Run out measured on the outer edge of the 6 inch diamond wheels is .0035 left, .0040 right that's pretty good.
This stand is for the larger Baldor grinders, I'll have to fabricate an adapter to bolt it down but the feet fit fine on the cast iron flats. Note the holes in the base they are a whopping .900 a bit overkill.
I may fabricate different tool rests for grinding the tungsten, something at the proper angle, maybe a groove for 2-3 of the common Tungsten sizes, and in aluminum to draw the heat out of the tungsten during grinding they get hot.
This was the other manufacturing defect. The bottom/third hole for the outer wheel covers was not tapped and no screws were included. They also appear to have used self tapping screws on the other two, the threads were crap. I tapped the third holes 10/32 and chased the threads on the others. I replaced the screws with stainless allen head machine screws since I want to be able to swap out grinding wheels and use this for other grinding purposes.
Here's the bottom of the Baldor stand just for reference. Its 17x20 by the way.
Next...this motor can be run in reverse Baldor notes the wires to reverse in the manual. I may buy a 4 pole DT on/off/on switch. It would be easier to grind the tungsten with the wheels rotating up and away from me. I see guys on youtube grinding on the top of the wheel against the rotation. I ground a few that way but stuck the Tungsten in the China grinding wheel 2-3 times, once shattering the Tungsten. The danger is bits of Tungsten flying up from below perhaps getting under my safety glasses, I'm hoping the lathe shields will take care of that.
That's all for now, stay tuned.
Here are the first bits, the blue diamond wheel is 180 grit, the yellow diamond wheel is 320. Those are lathe chuck guards I'm hoping to use them instead of the dinky grinder eye shields. I have had bits of metal in my eye twice, I'm not looking for a third trip to the ER for that.
I'm not messing around with a stand either, this is the larger Baldor cast iron stand, 120 lbs, get some!
The 1/2hp 7 inch Baldor grinder arrived, model 762. Here it is vs the 6 inch China bench grinder. Its quite a bit larger.
The arbor is .625 inch for the 7 inch wheels, that's a burly 15/16 inch nut.
These are the supplied aluminum washers .625 arbor, they appear to be cast and don't exactly spin true but the fit has enough slop that they are fine.
Houston we have a problem. So I turned on grinder and it took off across the bench with some speed, whoa there Baldor. Severe vibration. Here's the problem, the motor shaft is actually .750 they turn down the outer few inches to .625 for the grinding wheels and washers. But that big steel inner spacer doesn't fully cover the .750 section of shaft, there's a .060 x .060 shoulder sticking out. The large aluminum washers were resting on that cockeyed instead of up against the tall steel spacer, hence the vibration.
I turned a couple of 1.25 inch tall brass shims on my lathe with a recess for that shoulder, problem solved. I also turned a couple of brass .625 x 1.25 arbor adaptors for the diamond wheels.
Here's an action shot, vibration is now quite minimal, it just sits there purring. Run out measured on the outer edge of the 6 inch diamond wheels is .0035 left, .0040 right that's pretty good.
This stand is for the larger Baldor grinders, I'll have to fabricate an adapter to bolt it down but the feet fit fine on the cast iron flats. Note the holes in the base they are a whopping .900 a bit overkill.
I may fabricate different tool rests for grinding the tungsten, something at the proper angle, maybe a groove for 2-3 of the common Tungsten sizes, and in aluminum to draw the heat out of the tungsten during grinding they get hot.
This was the other manufacturing defect. The bottom/third hole for the outer wheel covers was not tapped and no screws were included. They also appear to have used self tapping screws on the other two, the threads were crap. I tapped the third holes 10/32 and chased the threads on the others. I replaced the screws with stainless allen head machine screws since I want to be able to swap out grinding wheels and use this for other grinding purposes.
Here's the bottom of the Baldor stand just for reference. Its 17x20 by the way.
Next...this motor can be run in reverse Baldor notes the wires to reverse in the manual. I may buy a 4 pole DT on/off/on switch. It would be easier to grind the tungsten with the wheels rotating up and away from me. I see guys on youtube grinding on the top of the wheel against the rotation. I ground a few that way but stuck the Tungsten in the China grinding wheel 2-3 times, once shattering the Tungsten. The danger is bits of Tungsten flying up from below perhaps getting under my safety glasses, I'm hoping the lathe shields will take care of that.
That's all for now, stay tuned.
