Cast iron laps - correct depth/spacing of grooves? - Page 3
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  1. #41
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    Quote Originally Posted by Peter from Holland View Post
    I am talkinng late 80ies early90ies Not the current situation

    Peter
    Some questions are best left unasked.
    Actually 70s and some agreements on pricing to stabilize things and maybe reduce the loss of life as much money and power involved here. All this to say a bit under the table.
    It was a very different time when even the largest corporations in the USA would not cross the line. It also was to the good to keep prices inflated so win/win..
    Prices did fall like a rock in the late 80s.
    Bob

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    Quote Originally Posted by rimcanyon View Post
    Yes, but where can I purchase it? The only distributor listed in California is Jorgensen Steel, and they do not list it on their website. Also, the durabar website lists availability as 72" lengths for the size I need, and I only need 14".
    Get a hold of one of the Durabar Metal Distributors, probably Ft Wort, TX, and tell them you want to buy a rectangle and you only need 14" worth. They will sell you just what you need if you ask for it. For some reason, Durabar decided not to stock rectangular bars at any of their distributors nation wide, only in their Woodstock, Ill location. I give my salesman bloody hell over it almost every time I talk to him. Another option is to buy slices of say 16" OD bar and square them up after you get them. You may come out ahead doing it that way. Ken

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  4. #43
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    When I buy Dura-Bar I order it from Woodstock. I send them a drawing or a size and they saw it from a plate. I had some shipped to Portland OR no problem. They can machine and grind it too if you need it. They get super deals on freight charges too.

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  6. #44
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    Those interested in Prism SE's can buy a square from them and they can saw it diagonally - a lot cheaper then a casting.

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    Quote Originally Posted by rimcanyon View Post
    Where did you get the rectangular cast iron slices? I have been looking and all I find is round...
    From “metal supermarket” in Ohio. On RT 747 I believe.
    They have a 12x12 drop of it, it’s been there since they bought the place, I had them cut me a 4inch ISH slice And I went and cut it myself again, they only charged me 20-30$ for the 12x12x4 slice. I don’t know if that’s high but I can live with it

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  9. #46
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    Quote Originally Posted by Homebrewblob View Post
    They only charged me 20-30$ for the 12x12x4 slice. I don’t know if that’s high but I can live with it
    Be happy: you got 69kg = 152lbs of cast iron. A bargain price would have been $200-300, you paid 10% of that, the scrap value is probably more than you paid. (London Metal Exchange price for iron/steel scrap is about $400 per metric ton, so $28 for your slab.)
    Last edited by ballen; 01-05-2021 at 08:18 AM.

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    It's more than scrap, but still a VERY cheap price. I'd grab the rest of it if I was close by.

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    Quote Originally Posted by Milland View Post
    It's more than scrap, but still a VERY cheap price. I'd grab the rest of it if I was close by.
    IIRC they had a roughly 3ft or more 12x12 bar of it. It was so cheap because they couldn’t be sure it’s cast iron as it predates the current owners.

    One end of the bar has a broken face from an incomplete cut and it had (from what I know) the tell tail cast iron grain structure.

    And when I was cutting it on the lathe it definitely felt like carving wet sand but cut really nice.

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    Quote Originally Posted by Homebrewblob View Post
    When I was cutting it on the lathe it definitely felt like carving wet sand but cut really nice.
    I love machining cast iron, but I hate the mess and clean-up afterwards.

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    Quote Originally Posted by ballen View Post
    I love machining cast iron, but I hate the mess and clean-up afterwards.
    So do I. Even after cleanup it remains. It adheres to any bit of oil. I feel like I need to disassemble the machine to get it clean.

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    Quote Originally Posted by rimcanyon View Post
    So do I. Even after cleanup it remains. It adheres to any bit of oil. I feel like I need to disassemble the machine to get it clean.
    Machine dry, with a HEPA vac to control the dust.

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    I used to wear a mask when I machined and ground it, if I didn't my nostrils would get black....

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    Quote Originally Posted by dgfoster View Post
    Too bad you aren’t closer—-I could cast the plates for you They could be nicely designed with 3 feet, ribs, etc.

    Denis
    damn .... wish you was closer to me too XD
    i have a hard time to find one .... here in Canada the resurfacing service is practically non-existent .... and the material to DIY it is as hard as it is to find someone doing the job right -_-

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    Quote Originally Posted by lucky7 View Post
    I’ve purchased from a Canadian distributor in Edmonton. Not much help to you, but if I can get it here, I’m sure an email to their Illinois office would get a reply or forward to a seller local to you. And they do custom saw to your length.

    L7
    what was the name of that company in Canada?
    I'm curious to see if they sell again and the price for a flat cast iron plate

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    This was on the back burner for a while, but I am finally getting back to it.

    I started lapping the plates today, A/B A/C B/C B/A C/A C/B and so on. It's going slower than I was expecting. I'm using petroleum (kerosine) as a lubricant and Timesaver green lapping powder (fine). I have the impression that most of the lapping compound ends up in the grooves and doesn't do much. It is definitely removing material, but is slower than I expected..



    Is this the nature of the game? Or is there a way to speed it up?

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    Quote Originally Posted by ballen View Post
    This was on the back burner for a while, but I am finally getting back to it.

    I started lapping the plates today, A/B A/C B/C B/A C/A C/B and so on. It's going slower than I was expecting. I'm using petroleum (kerosine) as a lubricant and Timesaver green lapping powder. I have the impression that most of the lapping compound ends up in the grooves and doesn't do much. It is definitely removing material, but is slower than I expected..



    Is this the nature of the game? Or is there a way to speed it up?
    Ask poster Orbital77 to explain how it is properly done. He made a lot of those and still does.

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    The Timesaver lapping compound wears out very fast. Have you got any SiC lapping compound?

    I lapped my 600mm x 900mm surface table down to 2.7µm and then used it as a 'master' to scrape a 450mm x 600mm cast iron surface plate to use as a lap for the 900mm x 1200mm surface table. After 7 cycles of lapping and measuring it is now at a total flatness of 4.3µm I'm aiming for 1.5µm if I can reach it, before using it as a master to re-scrape the surface grinder.

    It still takes far longer to do the measurements than it does to do the lapping!

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    Quote Originally Posted by ballen View Post
    This was on the back burner for a while, but I am finally getting back to it.

    I started lapping the plates today, A/B A/C B/C B/A C/A C/B and so on. It's going slower than I was expecting. I'm using petroleum (kerosine) as a lubricant and Timesaver green lapping powder (fine). I have the impression that most of the lapping compound ends up in the grooves and doesn't do much. It is definitely removing material, but is slower than I expected..



    Is this the nature of the game? Or is there a way to speed it up?
    Not much I can say as I don't know what the project is about. Kerosene is good but the lapping compound must be some carborundum powder, as coarse as you can bear for your expected result. I use a lot of 80 grit from a large bag I bought ages ago. By switching grits intelligently you'll be able to comfortably see where things are moving towards. There was on YT a series of videos of a chap making some large optical flats together with all the explanations etc. That was years ago. I use a spherometer to see where things are and I compare with a large optical flat which is better than lambda/20 . You need a way to measure because you CAN and up in a situation where whichever way you swap the disks/laps you get no improvement and then you'll have to use small laps aprox 1/4 dia or even less if you go for under 0.5um overall. Success !

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    Also, it is not necessary to lap/grind three or more disks together. That's a waste of time, muscle and cast iron. You only need a lap and some system to measure quickly and effectively. You need three disks when you can not measure.

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    Quote Originally Posted by Mark Rand View Post
    The Timesaver lapping compound wears out very fast. Have you got any SiC lapping compound?
    Yes, I do, a friend sent me a number of small bags of SiC in grits from very coarse (sand!) up to very fine (2000). What grits would you suggest? Will this embed in the cast iron or just wash off?

    I lapped my 600mm x 900mm surface table down to 2.7µm and then used it as a 'master' to scrape a 450mm x 600mm cast iron surface plate to use as a lap for the 900mm x 1200mm surface table. After 7 cycles of lapping and measuring it is now at a total flatness of 4.3µm I'm aiming for 1.5µm if I can reach it, before using it as a master to re-scrape the surface grinder. It still takes far longer to do the measurements than it does to do the lapping!
    That's exactly why I am making these laps, I want to correct my 800 x 1200 surface plate, which is concave and 11 microns deep in the middle. I've gotten good enough with my Talyvel now that I can do a reliable 8x12 grid measurement of the entire plate in about an hour.


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