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Making a CI surface plate

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  • rmcphearson
    replied
    Here are the latest videos on gauges in general and my plate
    https://www.youtube.com/watch?v=bvnZdTCzkoA&t=2s
    https://www.youtube.com/watch?v=eQXVoVEMhYs&t=2s

    I scraped the prototype you see in the video by hand and took it to the trade show in San Diego a few days ago. I was happy with the reaction from those who saw it but I have continued making changes to the design. I now realize that it does not need to be long enough to act as a lapping plate for non-flat gauges, actually it only really needs to be long enough to span the contact points (where the two .010 shims are placed) under the gauges, so 18" is more than long enough. And I realize it only needs to be only slightly wider than 2". That's going to change the game. I may just buy solid bars of gray iron (durabar) 2-1/4 wide, and approximately 2-1/2 tall and have the bottom cavity hogged out and milled. Then I will have a large selection of shops to do the surface grinding since it's only 18" long.

    It's been pointed out the me that Snap-On trucks have a calibration tool on the truck for techs to use for their torque wrenches. This product will be very similar. There are a similar amount of mobile techs (trucks) in this industry as there are Snap-On trucks. The retail price of this tool will be insignificant to the dealers to have in each truck. If I can get the retail price down to around $600 I'll get one into a good percentage of each golf course shop too. There are 15k courses in North America and 35k worldwide. I have a few preorders ("send me one, I don't care about the cost"), one of those preorders is from Europe.

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  • rmcphearson
    replied
    I got my flimsy flat bar back from the local shop with rabbits milled in each side and 12-24 holes drilled and tapped. My aluminum never arrived so I made the support base out of walnut. I attached the base with countersunk 12-24 screws. This is enough support for demonstrations and experimentations. And I can remove the base for re-machining the counterbore and other future changes.

    https://www.youtube.com/watch?v=Q-goFMrMlwM

    One thing I've failed to explain is that my plate will calibrate a gauge that's not perfectly flat (most of the gauges are not perfectly flat). Using a multistep process with a granite plate and a gauge block under the catch will calibrate a gauge only if it is perfectly flat.
    Last edited by rmcphearson; 02-05-2022, 02:30 AM.

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  • rmcphearson
    replied
    I did support the prototype plate under each end, pushed down in the middle with maybe 40 lbs of pressure and measured .003 deflection.

    In the past few days I have read so much and watched so many videos about preparing CI straight edge castings by plaining, milling, and grinding my eyes are crossing. I've learned that plaining may be the ideal preparation for scraping a part this size. Whatever I do, I still see stretching a length of belt sanding paper on a plate and "lapping" or "grinding" from let's say .002 to .001 a legitimate option. There's no clamping distortion when doing that.

    I also decided to add stiffness/support (before final surfacing) to my prototype by attaching legs. The end result will be a channel shape with the legs appx 3/8 thick and 3" tall running the length on each side. The legs can be removed for easier machining of the many changes to come (the shape and dimensions of the counterbore will be changed). Since CI stock of this size for legs is not available I planned to use cast aluminum. My suspicion that this may also be a legitimate idea has been confirmed by this:
    https://www.penntoolco.com/a6100/
    A precision parallel/straightedge that uses a cast aluminum "leg" to provide support for a thin CI surface with straightness of .0003 over 36". The fact they are mating these two different materials and expect the complete assembly to remain stable to .0003 ($2500 worth of .0003) is informative. Oh, and they are "ground or scraped".

    The CI plate is at a nearby shop to be machined to accept the legs. Aluminum material for the legs is on the way. I'm working on the walnut mock up legs now which will do until the aluminum ones are done. I ordered my Biax hand scraper starter kit today. And the CI straightedge castings (for practice scraping) are being rough milled at another shop. He claims he can get them to .001 by milling. And I dropped a steel plate yesterday, crushing the small bone and fracturing the middle bone of my big toe. Hence, the marathon of research I've done today on the couch.
    Last edited by rmcphearson; 01-18-2022, 07:38 PM.

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  • Paul Alciatore
    replied
    I gotta tell you, it has been quite a while since I have been on a golf course, but I am going to visit one as soon as I can. I really have to see this layer of grass that is 1/8" or less thick. I want pictures.

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  • reggie_obe
    replied
    Originally posted by rmcphearson View Post
    Y’all are trying to poke holes in my plate! That’s not nice! But it is necessary. Y’all are correct, there is a multi step alternative. It don’t happen.

    This reminds me of the time I was on watch duty on a frigate off the mouth of the Amazon and a passing ship desperate for drinkable water kept ignoring my advice to “cast your buckets down where you are.” They thought I was three sheets to the wind.
    Because the Amazon river has such a large flow, the salt water is displaced by fresh from the mouth of the Amazon.

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  • rmcphearson
    replied
    Y’all are trying to poke holes in my plate! That’s not nice! But it is necessary. Y’all are correct, there is a multi step alternative. It don’t happen. There’s a lengthy explanation which i will not attempt.

    This reminds me of the time I was on watch duty on a frigate off the mouth of the Amazon and a passing ship desperate for drinkable water kept ignoring my advice to “cast your buckets down where you are.” They thought I was three sheets to the wind.
    Last edited by rmcphearson; 01-11-2022, 11:39 AM.

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  • SVS
    replied
    After watching videos I’d think a few gage blocks to calibrate the indicator and checking flatness of the flat iron gage on the edge of a surface plate, one side at a time, would accomplish same thing.

    Heck, a carpenter square would show if the flat iron was warped. Body heat during use will probably move it further than you are trying to measure.

    More power to you if you can sell’em though.

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  • mikey553
    replied
    Roland, I have watched your videos, but failed to understand the purpose of the counterbore. Maybe you are trying to measure the thickness of the remaining lip? But you can use standard gage blocks to set the gage to size. By the way Grizzly sells the 18 x 24 x 3" surface plate for $80.
    Good luck with your project, but I am done with it.

    Leave a comment:


  • rmcphearson
    replied
    Here are the short videos that explain my plate. Yes, they are awful and yes I misspelled gauge. I don’t want customers to see this. I’m posting them here purely for feedback about manufacturing them.
    https://youtube.com/shorts/GrujdS1s97g?feature=share
    https://youtube.com/shorts/nBaMCzqDe98?feature=share
    https://youtube.com/shorts/eEfpZIHSlRQ?feature=share
    https://youtube.com/shorts/biBma2_qkCU?feature=share

    I have ordered two grey iron 24” straightedge rough castings from two vendors here on the west coast. If I can get one of them to widen the molds to 4” for me I think I’ll be in business.

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  • Bented
    replied
    Originally posted by A.K. Boomer View Post
    Wow that's still a chunk of stone... thanks for letting us know, by all the staining it looks like it gets it's fair share of use...

    It almost looks regulation billiard table size --- you thinking what im thinking? little bit of felt and some rails and you have the worlds most precision pool table....
    If it was made from black granite there would be no fingerprints or discoloration visible, a black plate always looks pristine

    I use a black granite plate for small parts at the machine, this does not require a forklift to move.
    8 X 12 X 3" Starrett


    Cost less then $300.00

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  • rmcphearson
    replied
    Originally posted by mikey553 View Post



    What I don't understand is why do you need a special plate. What's wrong with a standard 18 x 24" granite plate? It is more than accurate enough for your needs and it does not cost that much. It does not have a counterbore, but do you really need one? Just put 2 gage blocks on a surface plate and set you DOC gauge on top of them and zero the indicator.
    That would calibrate the distance from the indicator tip (crown of the mushroom) of the blade catch to the business surface of the gauge. That’s not how the gauge works. The distance being measured is from the underside of the catch to the business surface of the gauge. You’ll see when I upload the video to my YouTube channel.

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  • rmcphearson
    replied
    Originally posted by genea View Post

    I haven't seen this mentioned elsewhere in this thread.

    As a rule of thumb, calibration standards are usually specified at an accuracy several times greater than the characteristic being measured, factors between 4x and 10x are common. If you need to calibrate a tool to 0.001" accuracy, your standard, following this rule of thumb, needs to be between 0.00025 and 0.0001".


    Excellent info. Thank you.

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  • mikey553
    replied
    Originally posted by rmcphearson View Post
    https://youtu.be/0PqFFPVxjXI
    This shows just two of many brands of gauges. There is a market for a tool to calibrate them accurately.

    I’d like to discuss home shop machinist stuff relating to my plate…

    Thank you to those of you helping.
    Roland, after reading your first post again and watching your videos I understand your project a little better. So you want to make a special plate to calibrate and set the depth of cut gauges. In such case I would agree that .001" flatness is required. For that you would need a plate with substantial rigidity, 3/4" thick material is out of the question. The suggestions in my previous posts are still applicable.

    What I don't understand is why do you need a special plate. What's wrong with a standard 18 x 24" granite plate? It is more than accurate enough for your needs and it does not cost that much. It does not have a counterbore, but do you really need one? Just put 2 gage blocks on a surface plate and set you DOC gauge on top of them and zero the indicator. Of course, that would mean the death of your project...

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  • genea
    replied
    Originally posted by rmcphearson View Post
    Yes, if I can have them made of granite that will work. I don’t know where to go for that and I suspect CI will be adequate and cost less. My customers want their gauges to measure to an accuracy of 001”. So my plate that they are using to calibrate their gauges needs to be of similar accuracy. The prototype was milled, there was a .003” bow in the middle. That was not acceptable. Y’all have me wondering if 3/4 is not thick enough.

    Thanks for the suggestions. Even if I farm this out to a grinding shop, I need and want to learn to scrape to make more prototypes and maybe even sell some prototypes. I’m ordering the scraping tools and supplies now.

    I’ll post a video of the tool soon.
    I haven't seen this mentioned elsewhere in this thread.

    As a rule of thumb, calibration standards are usually specified at an accuracy several times greater than the characteristic being measured, factors between 4x and 10x are common. If you need to calibrate a tool to 0.001" accuracy, your standard, following this rule of thumb, needs to be between 0.00025 and 0.0001".



    Leave a comment:


  • A.K. Boomer
    replied
    Originally posted by Mcgyver View Post

    if he makes a ton of money from it, he'll be doing the the Mcphearson strut
    Alright --- go to your room and sit in the corner for 1/2 hour... and don't come back out till you know you can behave yourself lol

    Leave a comment:

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