Making a CI surface plate

[Bented]

I say get some steel that is about 1.5" thick. Anneal it. Mill it flat on both sides and flip it over on each successive 0.005" pass until it is about 1.455" thick. Then do two 0.002" passes, again on opposite sides, to 1.451" thick and a final pass of 0.001 to 1.450" thick. Then check it on a surface plate. It should be around +/-0.005" and that should be good enough for those mowers. Use toe clamps on your mill to avoid excessive warping when it is clamped.

You take everything posted seriously.
The best way to assure that the grass is accurately trimmed above the variable substrate is to measure each plant individually, this is time consuming and therefor expensive.

However if the Country Club has enough money then virtually anything is possible.

There is no simple engineering problem that can not be overcome, throw money at it until it works.

[rmcphearson]

A layer of grass that is only 0.125" thick could not even be relied upon to actually cover the ground at all places. There would be holes in it where it's thickness would be essentially zero.


On top of all that, just how does the mower sense that ground level? I mean, REALLY, HOW? Are they equipped with some kind of sensor to measure where the surface of the ground actually is?

If you park your car in the lot of a decent public course and walk on the practice green which you are welcome to do without paying a dime, you will see better than any picture will show, that you’ll be standing on turf .125 thick. At a ritzy private course it may be .080 and flawless, like carpet or artificial turf.

The “sensors” are the full length front and rear rollers (not casters or wheels), typically 2” diameter with a TIR of .003 on average. I know guys who discard the OEM rollers and have some made to a spec of .001 TIR because.003 is not acceptable to them. They want precision despite the fact the ground is not perfectly flat. .005 variation wouldn’t bother some. Some would be horrified. I’m just giving them what they want.

[Bented]

If you park your car in the lot of a decent public course and walk on the practice green which you are welcome to do without paying a dime, you will see better than any picture will show, that you’ll be standing on turf .125 thick. At a ritzy private course it may be .080 and flawless, like carpet or artificial turf.

The “sensors” are the full length front and rear rollers (not casters or wheels), typically 2” diameter with a TIR of .003 on average. I know guys who discard the OEM rollers and have some made to a spec of .001 TIR because.003 is not acceptable to them. That want precision despite the fact the ground is not perfectly flat. .005 variation wouldn’t bother some. Some would be horrified. I’m just giving them what they want.

This is fascinating, how is the grass length measured?
From the base to the height of the tallest blade?
A height gauge, I can picture someone pushing such a tool around on the soil.
https://www.amazon.com/s?k=mitutoyo+...l_8rwpz60725_e

[Jim Stewart]

This is fascinating, how is the grass length measured?
From the base to the height of the tallest blade?
A height gauge, I can picture someone pushing such a tool around on the soil.
https://www.amazon.com/s?k=mitutoyo+...l_8rwpz60725_e

Your predictable snark notwithstanding, perhaps you should pay some attention to Roland's past posts.

It's clear that he has a broad and deep understanding of his specialty - which none of the rest of us, it looks like, do.

He's an expert in his field, looks like to me. Perhaps you could learn something?

-js

[rmcphearson]

RMcphearson- what ever happened to your situation at work where they were harassing you, or whatever it was?
Did you get that straightened out or did you move on?

Sid

Hey Sid. I left that situation months ago in disgust. I have plenty of time to take legal action. The new job is going very well. We’ve made some investments to the new shop and my budget for next year’s improvements has been approved. (Purchasing a shop truck, parts washer etc)

[JoeLee]

Are you actually talking about cutting grass to an accuracy of +-.001"?

Only on the greens.

JL.................

[Jim Stewart]

Hey Sid. I left that situation months ago in disgust. I have plenty of time to take legal action. The new job is going very well. We’ve made some investments to the new shop and my budget for next year’s improvements has been approved. (Purchasing a shop truck, parts washer etc)

Where are you now?

-js

[rmcphearson]

Where are you now?

-js

Hey Jim. I still have my house near you, there on weekends. I’m living and working in south San Jose during the week. I’m actually self isolating right now in San Jose since I have family at the house in Concord at high risk to covid. So far I’ve found one grinding shop, it’s in Oakland. I plan to see what they say about this project, maybe next week.

[Bented]

Your predictable snark notwithstanding, perhaps you should pay some attention to Roland's past posts.

It's clear that he has a broad and deep understanding of his specialty - which none of the rest of us, it looks like, do.

He's an expert in his field, looks like to me. Perhaps you could learn something?

-js

I have learned a good deal about horticulture from this thread, never realized that plants and the earth that they grow in were this uniform, I stand corrected.
Next time a large part needs to be inspected I will simply toss it on a golf course green rather then a granite surface plate.

[Paul Alciatore]

I do understand that you are giving them what they want. I just say that they have no way to check it. None what-so-ever. If they did, they would already be using that.

This reminds me of the audio guys who insist that their speakers be connected with gold plated wire that is constructed in some particular way and with solid gold connectors, etc. Yet they themselves can not hear any difference what-so-ever when they don't know in advance which is which when compared to ordinary lamp cord. Yet they swear by their preferred wire and connection technique.

And it's rollers, not wheels. So what? I see no essential difference except two rollers would only effectively provide three point contact while four wheels, with some kind of suspension, would provide four. Four points at known locations would be a better sample than three points with unknown locations. OK, if the rollers also have some kind of suspension, then they do provide four points, but they are still at unknown locations.

And if all of this is considered so important, why do the manufacturers of the mowers not advertise how accurate their machines achieve it? Perhaps, just perhaps they realize that there is no way they can publish an accurate spec on it?

I still can't see why you can't give them what they are asking for with a piece of steel that is carefully annealed and milled. A tolerance of +/- 0.001" over 24" should not be all that difficult with those techniques and a good milling machine.

If you park your car in the lot of a decent public course and walk on the practice green which you are welcome to do without paying a dime, you will see better than any picture will show, that you’ll be standing on turf .125 thick. At a ritzy private course it may be .080 and flawless, like carpet or artificial turf.

The “sensors” are the full length front and rear rollers (not casters or wheels), typically 2” diameter with a TIR of .003 on average. I know guys who discard the OEM rollers and have some made to a spec of .001 TIR because.003 is not acceptable to them. They want precision despite the fact the ground is not perfectly flat. .005 variation wouldn’t bother some. Some would be horrified. I’m just giving them what they want.

[rmcphearson]

Thank you Mikey553, your insight is helpful. I didn’t think about flex. I don’t see a thick custom casting in the cards. I’m going to try to measure the amount of flex I get with the 3/4 prototype. Maybe the flex can be minimized with a “smart” 3 point support rig. Spent all day researching scraping, airy and bessel points etc. Came Across this video below. I didn’t realize scraping was used for liquid tight seals. Doesn’t apply to me but it’s interesting.

https://youtu.be/k4lUmE945js

[J Tiers]

As for production, you want them ground. You'd never get done with 100 of them hand scraping. I do it, and I know. It would take longer than your sandpaper treatment. That's a big area, and it's just not practical.

Getting the "lip" to be 0.100" +- 0.001" is entirely do-able. You should be able to get that.

two ways.... grind first, and machine to that depth, or, probably better, machine to over 0.100" by enough that the big surface will "clean up" with the thickness just over the 0.100". Then have the grinding establish the thickness of the lip. I'm not sure that is the surface that gets ground, though.

Material is your choice. Steel would be OK, it grinds well, but does not scrape well. it dents, and bends, and may warp while being ground, causing more expense in processing it if not annealed. But annealing makes it soft so that it bends and dents more easily.

CI can warp also, and can crack. But it often is a bit harder than annealed steel. It can be scraped or ground, depending on hardness. CI is probably more expensive than most steel.

It depends on whether you are going for not very expensive, or for expensive and top notch. I'd bet (without knowing) on your customers wanting the top notch more than the low price, based on what you have written here..

If you park your car in the lot of a decent public course and walk on the practice green which you are welcome to do without paying a dime, you will see better than any picture will show, that you’ll be standing on turf .125 thick. At a ritzy private course it may be .080 and flawless, like carpet or artificial turf.

The “sensors” are the full length front and rear rollers (not casters or wheels), typically 2” diameter with a TIR of .003 on average. I know guys who discard the OEM rollers and have some made to a spec of .001 TIR because.003 is not acceptable to them. They want precision despite the fact the ground is not perfectly flat. .005 variation wouldn’t bother some. Some would be horrified. I’m just giving them what they want.

I have to say, I am surprised.... I'm a gardener, and am somewhat familiar with plants and grass. A lot of grass has more than 0.080" of outer sheath that is brown, above the "crown". Must be a special grass that will grow the way that is wanted. Not being a golfer, I have never looked at the turf on a course.

Probably the groundskeepers that want the super low runout could not measure it if they wanted to, but that's no reason not to give them what they want. All you need is to have someone show you up as "out of spec", and then you have trouble.

[Mcgyver]

They want precision despite the fact the ground is not perfectly flat. .005 variation wouldn’t bother some. Some would be horrified. I’m just giving them what they want.

this fact escapes many; its a marketing driven requirement. Nothing wrong with that. Its like $25,000 hand bags or fly reels. You are proposing a specialty product that will perform to a high level and it needs cache. If you can achieve all that, and package it properly (say hard leather case or wood case) you can get some amazing margins.

The way the light comes off a freshly scraped surface I think fits the bill. Everyone has seen a ground surface but will marvel at a scraped surface. I'd get them ground for flatness then do a bidirection diagonal pass with a biax. You're wouldn't be scraping for flatness, just putting on the finish. Guarantee it to .001", should be easily done by grinding. Do a drawing, spec the tolerances and get quotes (and have a plate and surface gauge so you can check) Scraping can be to .0001" but you don't need that to bedazzle, a thou, 1/3 the thickness of a human hair, would (imo) be enough. This lets you claim the cache and take an hour for each one not a day.

[Richard P Wilson]

A long shot, but a planer fitted with a skew bit would easily cope with length, in fact you'd be able to mount multi[ple plates at the same time, and the skew bit would give a finish not far off a ground finish.
Only problem is probably finding a shop with a planer still in use.

[nickel-city-fab]

Its fairly easy to dial in tenths on a CNC mill, using the cutter comp and tool wear parameters. I think the best bet is to find a decent CNC shop, be sure of your engineering re warpage, and have the parts face milled. Followed by Blanchard grinding.

For example:
https://arrowgrinding.com/

I know that Arrow Grinding can do both the CNC and the Blanchard grinding.
A lot of local (and not-local) shops outsource to them.