Part 3 Kingsbury Michelle Aerodynamic Bearing Collaboration 

I'm led to believe that even machine tool slides benefit from 90 deg sharp corners when they're close fitting, particularly if there's grinding grit about.

I wondered about this too, my thought was maybe the air molecules need a chamfer to be drawn in and float the part? you added doubt that thought though

i get what you're saying, but just a facing operation is easier to setup .. less clicking and making sure everything is perfect :) you can even do it conversationaly right on the machine

The grinding wheel diameter only breaks down at the leading edge of the interface between the wheel and the part. As you feed from front to back the front edge breaks down revealing new grinding media, the original diameter of the wheel follows across the newely ground surface. The wheel is occasionally dressed for a true cutting surface and to remove any embedded particulate, at that point the wheel is fed down the appropriate amount.

@@sshep7119 thanks, great answer 👍

Yes, but there is a second constraint. The axial bearing must be normal ("vertical") to the plane of the face. So just having a 3 point contact is not enough, you have to be able to either adjust the spheres to bring the axis into plumb, or machine it perfectly from the start.

I'm guessing stainless steel tool wrap heat treating foil. The stuff available where I am is 0.05mm thick, and comes in rolls 610 wide x 10000 long.

Because the part will bounce until the vise is snugged up.

@@RambozoClownOK, thanks. I'm surprised there's no danger of the part being pulled up or pushed around out of the vise if Tom is able to tap it down with what look like relatively delicate blows.

Every time it slows to a stop there is contact, and it's not in a clean room environment, so there's two reasons for hardening. Third reason is that you cannot readily achieve nanometer flatness with soft materials, if fact they do not respond that well to lapping. The bigger the hardness differential between workpiece and lap, the better.

likely stainless steel foil

ru-vid.comstore Click on the "STORE" tab.

It's not quite that easy in the real world. You would need an expensive benching DMM and even the wires and connections come into play when measuring that. It's not something you could feasibly do, especially if you aren't an EE.

@@xenonram Yes, the capacitance is probably in the range of picofarads perhaps below the range of most multimeters. This device: www.ebay.com/itm/L-C-Meter-LCR-LC200A-Handheld-Capacitance-Inductance-Multimeter-Electric-Bridge/182584739286?hash=item2a82e605d6:g:pkwAAOSwusdcJuFA claims to be good down to 0.01 pF. At $35.59 it might be worth a try. (Yes, I know that the spec's are from you know where. ;-) )

It was (Tom mentioned) a very free cutting wheel, specially for hard tool steel. With coolant, and a small stepover, it's usual to use quite "heavy" cut depth with such a wheel. This resulting wheel wear is thereby concentrated at the leading edge of the wheel, leading to longer intervals before the entire wheel loses diameter and has to be re-dressed. As a side benefit, the finish is better.

@@Gottenhimfella interesting, thankyou. So, to pick your brain, the term free cutting refers to the 'self sharpening' properties of the wheel; like having a soft matrix allowing wheel wear expose new abrasive grits, and/or friable properties in the abrasive, so is breaks down into a sharp edge after use, or have I got that wrong? And if you had to guess at the appropriate cut depth, what would you say? So he's working the wheel hard and that helps the cutting action, is that correct?

​@@ASP1NALL Yes, counterintuitively, you need a "soft" matrix and somewhat friable grains to grind hard material for the reasons you give: As soon as a particle of grit gets dull, it needs to either fracture or be released. As with cutting tools, it's essential to use a sharp edge for hard materials, otherwise you are just burnishing and the cutter will push away from the cut. You can to some extent manipulate the characteristics if you can vary the spindle speed; running slower makes the wheel behave as if it is softer. If you plunge grind (downfeed only, with a wheel as wide as the work) you have no chance of achieving a flat surface because the entire width of the wheel will be reducing in diameter, unevenly. So the best plan is to downfeed a decent amount before commencing a new pass (perhaps as much as 0.2mm, if you have the right wheel, a decent-sized spindle and a rigid machine, and of course enough motor power) with the wheel beside the work, and then use small increments of stepover so that most of the periphery of the wheel is only sparking out, and all the work happens at the leading edge (which will quickly 'dress' itself to a radius followed by a slope) Use a rapid traverse, and flood coolant, which (with a suitable wheel) will keep the workpiece cool. Never stop, or even slow down, on the work. Grinding hard material is easier than soft, if you follow guidelines like this. This is also the best way to true your magnetic chuck. It's (by definition) the largest workpiece your machine can cover, so it's important that the effective diameter of the wheel does not reduce by the time you get to the far corner.

@@Gottenhimfella I was just reading on Norton's website some general things about grinding. They said the opposite, faster wheel behaves harder. This makes sense to me as one time I tried grinding a carbide scraper with a green wheel on a slow speed grinder.. all it did was chew up the wheel

@@metepack4872 Thanks for catching that, of course you're right and I miswrote. I've corrected it.

You should always climb mill on a cnc, when machining the inside like he is at the end, run counter clock wise and when machining an outside profile run clockwise, tool compensation always on the left

@@Kyran31 though that on cast iron or hardened materials conventional milling was preferred

@@kemc77 I’m not sure on that to be honest, you may well be right, I’ve just always thought climb was the preferred method

@@Kyran31 I would always climb on a rigid machine with well-maintained ballscrews or backlash compensators, hard material included.

That's to exclude oxygen in order to prevent "scaling". Yes, there will be _some_ oxygen inside the package (unless you do the wrapping inside a purged glove box), but (practically) no additional oxygen will be able to reach the part once the oxygen inside the package has done its worst. You could also use an exclusion coating (such as boric acid), or heat treat in a vacuum or inert gas oven.

@@stanrogers5613 thanks! I'd still like to know how the oxygen contributes to this "scaling" you're talking about.. Would the expanding air cause deformation on the piece or what?

@@tohtorizorro scaling is oxidation, which (as the name suggests) relies on free oxygen

@@tohtorizorro Wrapping also prevents loss of carbon (I presume it combines with oxygen to form CO and CO2). Carbon is essential to tool steel and its loss will inhibit austentite formation when the steel reaches a bright red heat . Quenching is the method whereby the steel is trapped in the austenite structure, as there is not enough time for the face centered atoms to migrate back to the body center of the fundamental cubes of the crystal structure. This is why there is a risk of cracking, because the change in structure causes a change in volume of the workpiece.

It is a demonstration piece

That's such a load of bull...