Mounting and Grinding a Surface Grinder Magnetic Chuck 

AMEN!

Funnily enough, Keith’s voice is the last one I hear before going to sleep at night. Very soothing. 😂😂

I think the previous owner of my grinder did the same thing. It goes up three thou on the left side and up six on the right side

thought the same!

no the way he did it was correct. When the chuck is ground it negates everything such as oil. When he runs the indicator along that trumps everything else.

@@jaysilverheals4445 That method proves parrallel but does not prove flat. I have seen many grinders that would indicate the chuck flat but made parts that were ground thin in the middle because the grinder ways are worn in the middle.

...Yeah, a friend of mine had a very old Jig-Bore machine....used vacuum tube supply for the DC spindle motor.....

the silly autofocus combined with the small monitor screen, he uses a very nice camera, but still autofocus issues happen, i kinda of like the gopro way, as its fixed focus, one less thing to worry about, such as abom uses

Keith does such a good job normally that the rare times he messes up it's really obvious, hopefully he won't take a little teasing as anything but the fun it's intended to be. And the strong grain on the wall DOES show up super clearly, likely why the camera grabbed it for focus instead of the 'soft' machine.

although selenium plate rectifiers go back over 50 years, even they have their fragility, before then it was things like rectifier valves or mercury arc. basically modern rectifiers are superior in every way compared to the old ones, and a no brainer to replace

That or you built a motor-generator to mechanically convert your AC to DC and while that did away with needing mercury or selenium, now you had more moving parts, another shaft to keep lubricated, and in the case of this machine, likely a third motor to power. So yes, modern solid-state rectifier still a far better option.

would the chuck itself get hot from the electricity resistance too? one of them cool mist might be an easy way to go?

The screws were in the wooden pattern used for casting the table. There are no screws in the center of the table, only the imprints of them in the casting sand, and then in the cast iron.

Ah that makes sense! Thank you for that information!

I noticed that too. On the plus side, the cut reduces when it settles but does mean careful final measurements will be needed due to the uncertainty.

Jusb1066 Agreed - may be the gibs need a bit more adjustment as it looks like the table is lifting at alternate ends each time the direction of travel changes. Check it out at around 17:30

yes steve, it does indeed seem to show both the leading edge floating up and it dissipating over a second or so, just like his dial gauge did

My grinder is functionally the same as Keith's. No gibs. The table is only held on by gravity, lifts right off the slide ways. Yes, there is a sort of a "bow wave" thing going on, and I see the same action on my surface grinder. It is no doubt caused by the oil on the ways. It also seems to change some with time elapsed since oiling on my manually oiled machine. Tells me when to oil it again... As a surface grinding newbie, I am still trying to learn and make my peace with the machine. Working to the higher level of accuracy that some work requires is a whole new learning experience. Getting a good surface finish on different work is often a lesson in humility.

Another possible issue with the sparks pattern on Keith's grinder might be the electromagnetic chuck warming up and warping. I am using a permanent magnet chuck, but I also get the same issues Keith was having in the video. I think it is mostly the oil on the ways causing the issue.

Keith,, I'm rebuilding a B&S #5 surface grinder 8×24 Serial #963 30s 40s ( know anything about this one)

Yes heat buildup is a problem. When you dust the chuck you are doing the hardest operation you can on your machine. You are grinding to its max capacity. Ie highest heat buildup. There are many ways to do it. The way I do it, on my mitsui ball way grinder is. New 7" 46 grit j wheel. Usually a sg (Norton ceramic or gell wheel as it's what we have. But they are not conducive to light cuts. They like heavy so that they can shatter and expose new grains vs a conventional wheel) Dress open structure with a cluster diamond (not a multi point but a cluster. Think of a diamond file but on a cylinder. With more thickness) I run my speed reducer (ac frequency inverter) at half speed, so about 1800 rpm on my grinder. Light oil film of wd 40. Quick to fast table Traverse with .025 step over. Max downfeed of .0002 Max cut between wheel dusting of .0004 but once the whole chuck makes contact. A couple of passes at .0002 and then a finish at .0001 with a dress between each. Doing this, minding my carbide dust (it's about all I grind) I can keep my chuck flat to .00015 for 3 to 4 months. At 6 to 8 months I have to take a whole .001 off to clean it up. Sorry if that's too much info, that's how I dust my chuck. Some day I'll try different wheels, but I don't want to so that with my work grinder. I'll get myself a grinder one day....

Advice

considering the size of the box, it must have a transformer, a rectifier is about the size of a postage stamp

RMS is not the same as average, the average of 110V AC would be zero (because its symetric AC). RMS is the DC equivalent voltage that produces the same power on a resistive load as a similar DC voltage. Just a rectifier would be fine, but if you add smoothing capacitors you would indeed increase the voltage and the magnet is likely to burn out.

EscapeMCP Technically you are correct but the power rating of a resistive load is the is the same for AC or DC (generally). There will actually be less watts into the coil using rectified DC because of the rectifiers loss. Even with a perfectly rectified AC sine wave the output DC voltage will never be very close to RMS... And that's basically why mathematically you use RMS in most circuit design not peak AC voltage like you could read on a scope. The reason for rectifying the voltage at all is like Keith said to control the magnetism in parts and even use it to your advantage. Just because you rectify a 120v AC circuit does not give you 150v DC there will still be peaks and valleys (especially under load). Granted there may have been more loss with the older circuit but it's negligible if it's rated for 120v... Great question tho really, I'm new to his channel and have some electrical background. Keep up the good work Kieth!

Guys, the problem is the coil would be hit by the filtered voltage for just an instant. But would this cause an effect over time? Greg

it is a coil. and coil resist sudden change in current so it acts as filter as well. I bet coil for such machine is made much over specs and it can handle much higher voltages and currents then 110v.

it does, but you cut light over the entire job so hopefully wont affect your finish, might have to redo the wheel truing from time to time