Every time we see that stand in the future, we'll all think about how cruddy it is under that stone.

@@stargazer7644 YES... We *ALL* will know... so in part 2 let's see if Adam bows to the pressure of KZfaq commenters to clean it up... reluctantly... LOL 😁

Do they make surface plates that are just equilateral triangles instead of rectangles or squares? Would make them awkward in term of usable space, but seems like it would be very stable.

I posted the reply below a day after your comment but didn't see it until now. Perhaps it best resides under your comment. I would hope the OEM knew where those points should be. The folks at "Quality Digest" did a great piece on Surface Plates some 15 or 20 years ago. It would be a great add on your link. "I won't (or shouldn't) say what lab it was in, but I was told by technician from Starrett Strategic that not only should a granite plate be on a 3 point mount system but they should be on the same 3 points used when the manufacturer created the plate. Ours were huge and probably 18" thick, so I never saw the bottom. Are the bottoms of these plates clearly marked as to those 3 original points?"

@@ramosel The paper in the link, which dates from 1997, says that at that time there was no standardized layout for plate supports. Rather, the recommended locations varied between manufacturers. As you note, provided that the support locations are are not changed from when it is lapped flat, within reason, it doesn't matter what locations are used, just so long as they stay the same. However, the locations that produce minimum distortion would also generally minimize stress due to the self-weight of the plate and therefore assist with longer term stability. But as I said, its a nerdy point, but I thought it might interest Lance as he seems to delight in gnat's whisker precision for its own sake. I did a rough calculation of the instantaneous elastic deflection of a 4'' slab of granite cantilevering 12" from a central support. The sag from the support to the edge should be of the order of 25 millionths, That is about one quarter of the overall variation that Lance quoted for an AA plate of that size. So replacing a plate wrong-way-around on its three supports would definitely mess with its accuracy. I don't know if the support locations are marked by the manufacturers, but if a plate is re-lapped such as Adam's plate, the support positions should be marked so that the plate can always be replaced in the same orientation. An equally satisfactory kinematic alternative to three supports would be a symmetrical layout of four supports with two adjacent pads located on the ends of a centrally pivoted bar. Cheers

Serious. Spray adhesive on UHMW and the implication that they need a press fit to stay in place.

@@Orxenhorf There is no kill like overkill. Ha!

I think that once the granite slab is sitting on those tiny pads. It is going to move.

Yeah, that's a Monarch and a pretty one at that

I doubt it worked, bonding UHMW is non trivial, you're not going to do it with just an off the shelf spray adhesive.

Spray glue is about the only thing that halfway works on polyethylene. But, he only needs it to stay in place long enough to set the stone, gravity will hold it in pkace

I would have roughed em up on a coarse belt so that adhesive had something mechanical to grab onto.

With UHMW it has to be hit with an abrasive and usually flame etched. Then there is only one glue I ever found that sort of works. I think it was called (Bond It ) or something like that. It is an epoxy that uses the tertiary hydrogen to help form a bond.

I'm guessing he'll probably do all of that cleanup back at his shop. He's got to transport it back to his place after the granite is lapped.

That really bugged me too. Especially when he was hammering in those pucks and the dust/filings were going everywhere.

I know right?

No kidding. I was amazed after he said that surface grinder spindle was within 50 millionths, he's obsessed with precision.

@@NP-rh3dt that's standard runout on a surface grinder spindle. the nicer ones are within ten millionths.

@@SuperAWaC Wow really, I didn't know that. That's pretty insane.

@@NP-rh3dt Wow that's a little better accuracy then my tape measure :))🤣

three point contact takes away the risk of rocking you could get with a four point contct

Three points keeps it from rocking if there are high and low spots on back, or if the stand isn't perfect.

SAME REASON MILK STOOLS HAVE THREE LEGS, IT WILL NOT ROCK ON UNEVEN FLOOR, OR STONE. MASTER STONE WILL NOT ROCK IF BASE IS NOT 100% EVEN ON ALL FOUR SIDES.

KZfaq deleting my comments, but google GGG-P-463c, AIRY POINTS, and BESSEL POINTS

@@spwhateverable The replies have helped and your recommendation for what to search nailed just what I was looking for and has returned some really detailed sites. Thank you to all all the replies! 👍

From the Starrett website " A surface plate should be supported at 3 points, ideally located 20% of the length in from the ends of the plate. Two supports should be located 20% of the width in from the long sides, and the remaining support should be centered. Only 3 points can rest solidly on anything but a precision surface."

It can't wobble when supported from 3 points. Each point will have an equal load. 3 legged stools never rock.

wearing toboggans ....... huh? wtf is a toboggan?

@@danduane1413 A Toboggan Is a Hat to Southerners Here's what I found out on my end. From the research I've done, it appears that the southern region of the United States (the areas that use Southern American English) use the term toboggan to refer to a knit winter hat. This area includes the states of Virginia, North Carolina, South Carolina, Georgia, Alabama, Mississippi, Tennessee, Arkansas, Louisiana, Kentucky, and Texas. It may also include specific regions of Oklahoma, Missouri, Maryland, West Virginia, Florida, southern Indiana, and New Mexico.

Been wearing my double knit touque outside since Oct 2020. Freaking cold and windy. Edmonton Alberta. -7C(19F) today

@@philipmackin1025 FELLOW EDMONTONIAN! \o/ I'm sick of this weather too. February was absolutely frikken brutal, but it always is. -40 for 3 weeks... D:

@@SnoDawg The funny thing is, in places that get REAL winter, a toboggan is a child's sled. What you're describing, a knit winter hat, is called a toque. en.wikipedia.org/wiki/Toboggan

a few days ago it was fucking cold 50 degrees with 100% humidity sucks

@@Mr.Potato420 From the high mountain desert, Anything with 100% Humidity sucks, but now I know why I was getting funny looks from floridians as I was walking around in my shorts and teeshirt.

@@WraithlingRavenchild if it's constantly cold I can get used to it and walk around in flip flops but when it's this time a year and one day the high is 50 and the next day it's 90 it fucks with you.

I have seen it snow in Crestview Fl ,about 35 miles north of where they at!

Approx 1/3 of the length from both ends, you want the weight of the plate to balance across the points to avoid center sag.

just take it on your lap in the driver's seat and hold on tight ;)

I'm pretty sure that's a Luminox Leatherback SEA Turtle Giant - 0321.L. It's actually a dive watch.

From the Starrett website " A surface plate should be supported at 3 points, ideally located 20% of the length in from the ends of the plate. Two supports should be located 20% of the width in from the long sides, and the remaining support should be centered. Only 3 points can rest solidly on anything but a precision surface."

Mathematically, three points are required to define a plane surface.

Because 4 points can rock. 3 points can't. You don't want the stone twisting.

@@madmodifier Was expecting a mention of 'Airy points' and how he worked out the positions of the holes in the tube and the location of the tubes on the frame.

Two old dudes in touques ...

Because three points guarantees a flat plane.

Also, you don't push down on a surface plate with any pressure enough to rock the plate.

A chair with four legs will always rock, a chair with three will always be stable. They know that at Monarch Lathes, which is the reason that a 10EE sits on three mounts.

Three points is always stable, four you can have one point introducing a warp to the plate, or it could rock even minutely. Think of a three legged stool, steady as a rock, add a fourth leg and you are rocking and wobbling all over the place or if the stool body is weak enough the whole thing will flex under your weight.

three points determine a plane.

You can use four points, vehicle weighing gauges, for example. But that is a completely different application. Supporting a plate, you would need to ensure that the weight carried by each point was the same, after levelling the whole thing. With a triangle, all you need to do is ensure the Centre of Gravity of the triangle is directly under the CoG of the plate. That evens up the weight carried. CoG of a triangle is where the three lines joining each side bisector with their opposite vertices meet. (OK I did just look that up to check!) As for the optimum shape and position of the triangle... I'm not sure why this is being done with two supports on one half of the plate, and only one on the other. But I can't work out why it upsets me. I just want it to be rotated, providing three supports in both the long and short axes. I would have thought that would be good to suppress bowing. As this is, there are only two points resisting bowing along the long axis, which is no support at all. On the other hand there are three along the short axis which is already the least susceptible to bowing. Perhaps when they get down to microns, what I'm talking about will matter!

This video is a bit misleading. Adam is establishing 3 pads of contact, but not points. If he thinks he is, he is mistaken. Each of those pads is its own plane. That said, what will happen is that the weight of the block will deform the plastic and create co-planar surfaces of each pad. A point of contact is a theoretical exercise in this case, and in almost all cases as materials deform under load and what was a point becomes a surface as the support material is deformed under load.

less work

The reason for the three points of contact between the frame and the plate is to cancel the affects of any warping that the uneven floor could put into the plate. It's about flatness not stability.

He only ever shows that at the end of the SNS videos.

@@kindabluejazz Oh Ok, that makes sense.

2 are not enough and 4 are too much

It's an old Greek principle. 4 points are impossible to level and maintain equal contact. 3 points allows for this.

This is done this way because a plane can't touch 4 points at the same time. This is dictated by a fundamental geometric rule. For something to sit on 4 leg (table, chair) the plane has to have some flexibility. If you think about it, have you ever seen a tripod that rocks ? It is fundamentally stable. Have you ever seen a camera stand with four legs ? It won't sell very well.

But the stand have 4 legs. . . and no finish. . . That bothered me. . .

@@mashcury the frame can flex. The surface plate can't/shouldn't.