HHIP 4401-1597 6インチ X 8インチ X 2インチ 御影石表面プレート グレードB 0 レッジ

Initially I was very skeptical of this surface plate, the low price coupled with mixed reviews on other sizes from the same manufacturer placed it solidly in the "too good to be true" zone but I figured I'd give it a shot and if it didn't meet the advertised tolerances I'd just return it. I'm glad I took the gamble because it ended up not only meeting but surpassing my expectations despite a major hiccup in delivery. I knew it was heavy so when I saw it was out for delivery and my dog started barking at the door I opened it to take it directly from the UPS guy so he didn't have to awkwardly set it down. As I opened the door he stumbled a bit coming up my front steps and dropped it from chest height onto my concrete front porch and it landed right on the corner. When I was unpacking it to inspect it for damage I initially wasn't very impressed. It came packaged in a cardboard box that contained a wooden box with the surface plate inside of it wrapped in a thin foam sheet, maybe 1/8" thick at most. I'd seen some reviews say it came in a wooden box and for some reason I had it in my mind that it would have a nice storage/protection box like gauge blocks do, this is not the case. The wooden box is made from the worst quality OSB you could imagine and sloppily put together, it is only there to protect the surface plate in transit and nothing more. I sliced my hand pretty good on some of the staples that had been holding the wooden box together before the drop as they were sticking out into the cardboard but I don't think that's entirely from the drop as they were sticking out similarly in other places so be careful when opening it. As unimpressed with the packaging as I was it did do its job, the OSB in the corner it landed on had basically disintegrated so there were a ton of splinters and chunks of OSB as well as a fair bit of granite chips, gravel, and grit which had me worried. After very careful examination though the surface plate came out undamaged, no chips, cracks, or any indication it had ever been dropped aside from the mess of a box it had came in so I have no clue why there was granite debris in the package with it. After inspecting it for damage and sending the UPS guy on his way I inspected the surface plate with both a Mitutoyo 543-793 digital indicator (0.0001"/1um resolution, +/- 0.0001" accuracy) and a Mitutoyo 513-409 dial test indicator (0.0002"/2um resolution, +/- 3um accuracy) mounted to a Starrett surface gauge and boy was I impressed. The listing for the "Grade A" plate I purchased claimed +/-0.0005" and the maximum deviation I was able to measure across the plate was ~4um or ~0.00016" with the majority of the plate being dead on flat not even a wiggle on the needle. On the plate I received two of the corners and one spot near the edge are high by 1-2um and a third corner is low by 2um. All of the high or low sections are very small, a single to a few square centimeters at most. For the price tag of $120 I went in with basically zero expectations and honestly would have been happy if it was within 0.001" and maybe I'm just a lucky winner of the cheap Chinese surface plate lottery but I'm extremely impressed. That said though, this is not a Grade A plate per ASME standards, even calling it Grade B in its current state is generous and the example I received is much better than advertised, I'm sure that won't be the case for everyone. I'm certain that if I put a little bit of work into cleaning up the high spots I could have it calibrated and certified as Grade B, anything beyond that would require equipment that I don't have. Overall, for the price, I'd say this plate is definitely worth it if you're just getting into machining as a hobby or looking for a small plate for inspection of smaller parts that don't require crazy tight tolerances. I think the biggest value, at least in the example I got, is how little work is needed to clean it up into a higher grade plate than it is out of the box.

Perfectly flat and smooth

Have yet to test the accuracy, but from first impressions the quality is very good. The product arrived very fast and ahead of schedule. It came with a calibration certificate similar to the sample. Very impressed, for a hobbyist I don't think you can beat the price for the quality.

Heavy but absolutely flat and ideal for my model engineering applications.

The smooth side is flat to 0.001" of an inch in 5 vertical and 5 horizontal cross sections and 2 diagonal cross sections from corner to corner and edge to edge with calibrated gauge. rough side is flat to about 0.0015" - 0.002" of an inch with an unfortunate falloff on one corner that is around 0.0035" of an inch on the corner. The taper is two inches from the corner in both direction making an even triangle low gradient from 0.0015 at a diagonal line to the lowest point at the corner 0.0035". This is still exceptional for my use as I only need one side to be perfectly flat. It will not be sitting flat side up during use. They package this block in a quarter inch wooden box with little wiggle room for safe shipping. My block came in perfect condition and as stated by the spec I ordered. The material is genuine black granite, and at least one side is within a super flat spec. Overall I strongly suggest getting this! Specially if you're going to be doing what I am, and decking an engine head at home like a mad man instead of just getting it machined.