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  1. #181
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    Quote Originally Posted by radiocontrolhead View Post
    My intention is to scrape in the dovetails on my "thing"
    Dove tails? Kinda limits your ability to find compatible partners, don't it?
    I mean - even Bridgeport started out with a "round ram".



    I'm no scraper, but I'd put that 5-point list you posted very nearly in reverse-order as to where the challenges are most likely to be coming from.

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  3. #182
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    Quote Originally Posted by thermite View Post
    Dove tails? Kinda limits your ability to find compatible partners, don't it?
    I mean - even Bridgeport started out with a "round ram".



    I'm no scraper, but I'd put that 5-point list you posted very nearly in reverse-order as to where the challenges are most likely to be coming from.
    gave it quite a few hits with the dead blow hammer. hopefully that set it straight...

  4. #183
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    We have a 2nd California class next month - May 15-19 in Petaluma, about 1 hour north of San Fran. Sign up for the 5 day class and you will be scraping like a pro. Give me a private message and lets see if we can figure out a way you can come. Rich

    PS: Then you don't have to guess or get advice from NON Scrapers

  5. #184
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    Quote Originally Posted by Richard King View Post
    We have a 2nd California class next month - May 15-19 in Petaluma, about 1 hour north of San Fran. Sign up for the 5 day class and you will be scraping like a pro. Give me a private message and lets see if we can figure out a way you can come. Rich

    PS: Then you don't have to guess or get advice from NON Scrapers
    "PPS" Didja tell him the "uniform of the day" for "rookies"?

    "Humble Pie" beanie cap, (no propellor on top - that's for the intermediate course..) safety glasses, plastic beach sandals with steel toe-caps, and not a damned thing in between but freshly-deburred bare skin with a light coat of Canode yellow, is it?



    "THIS IS A DRILL".. either you've recovered your sense of humour. Or not.

    Pictures... if anyone has the guts..

  6. #185
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    Quote Originally Posted by Richard King View Post
    We have a 2nd California class next month - May 15-19 in Petaluma, about 1 hour north of San Fran. Sign up for the 5 day class and you will be scraping like a pro. Give me a private message and lets see if we can figure out a way you can come. Rich

    PS: Then you don't have to guess or get advice from NON Scrapers

    Thanks Rich. Will do. My challenge will be requesting time off during the week to attend. If i cannot attend i'll end up picking up your video content and continue on with my self-taught path...

  7. #186
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    Bill did you get chased out of the Monarch thread and came back here to pester us again? I figure you get swatted from forum to forum. Showing up here and then going away, then go to another forum, get swatted and your off to another forum. Time to fly back to another forum and bug someone else.

  8. #187
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    Quote Originally Posted by Richard King View Post
    Bill did you get chased out of the Monarch thread and came back here to pester us again? I figure you get swatted from forum to forum. Showing up here and then going away, then go to another forum, get swatted and your off to another forum. Time to fly back to another forum and bug someone else.
    So long as you take care of yer health, live long and keep sharing your lore?

    "Swats" are worth it!

    You managed to GET well. Again.

    Now please take it easy and STAY well! Longer.

    Hundreds of us out here, similar dice-roll. We can't Iron-Man Bulldoze our way through it. SHORTER than you are for one thing. Possibly smaller dicks, too, if we actually knew. Or even cared.

    Some health challenges, one just has to work around the edges of with a certain dedicated and steady finesse as to meals, beverages, schedules, sleep, "pacing" ourselves as to work & travel stress, and living off annoyingly bland diet and life-styes. Does beat the alternative. Mostly.

    As-in, ten-hour - or even six-hour road trips, legs not helping circulate blood and lymphatic fluids, can be a real hardship. Same again long airplane rides when unable to stroll about.

    Learning scraping lore clear back to the Old World Masters was one thing. THIS part of Europe's expertise? Good for the circulation, buuut best leave the balance challenges to others, now:

    Extreme Mountain Unicycling - YouTube

    "Hundreds of us?". Could be thousands, actually.

    With a few possible exceptions, most of the rest of us can't scrape worth a damn, either, let alone TEACH it.

    Like it or not - guess that makes you special enough to try to save!

    Knew it would all come good eventually, didn' yah?

    Last edited by thermite; 04-16-2018 at 04:15 PM.

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  10. #188
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    Some more info for you to absorb. Done by my friend, student and famous You Tuber Tom Lipton

    Monday Night Meatloaf 117 - YouTube

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    Quote Originally Posted by Richard King View Post
    Some more info for you to absorb. Done by my friend, student and famous You Tuber Tom Lipton

    Monday Night Meatloaf 117 - YouTube
    Uhhmm.. well. y'know that bit about minding our schedules and eating habits?

    Thanks, Br'er Richard. For the "meatloaf" part most of all.

    Past midnight, and I've once again forgotten to fix meself a supper..

    Or did I, really?

    Hmm.. AHA! Check dishwasher for the forensic evidence!

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    Quote Originally Posted by thermite View Post
    Uhhmm.. well. y'know that bit about minding our schedules and eating habits?

    Thanks, Br'er Richard. For the "meatloaf" part most of all.

    Past midnight, and I've once again forgotten to fix meself a supper..

    Or did I, really?

    Hmm.. AHA! Check dishwasher for the forensic evidence!
    Looking for my fly swatter or bug spray.

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    Quote Originally Posted by Richard King View Post
    Looking for my fly swatter or bug spray.
    Wondered where all those empty aerosol cans out in the yard came from.

    That last air-strike was you, then?


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    Quote Originally Posted by lucky7 View Post
    Nice work! Are you hinging from side to side as well as end to end? I use a 1-2-3 block without holes for side to side checks.

    Lucky7

    Lucky,

    Thank you for the advice here. I went back and rechecked my work and low and behold, i believe i was high transversely when checking w/ a 123 solid block along the length of the SE.

    I believe my error was focusing too much on the flatness along the length where i have taken many cuts down the middle just to avoid any errors in printing only to re circle back to square 1.

    What i found was at the ends where i didn't pay much attention at all(due to the focus of keeping it concave longitudinally) was where it was convex transversely leading to the inconsistent printings I've been experiencing. I hope my analysis is correct at this point but it's worth a shot to proceed with these findings.

    I've come up with a preliminary plan that I'd like to bounce off everyone as to my correction strategy.

    I want to take circular "step" corrections down the middle until i get all four corners in contact. This will assure that I've got 4 extreme bearing points of the SE. Once that is achieved, i'll work my way back in by knocking down all the highs (working outside in) until everything comes in. My resolution (or PPI) if you will will stay around 20 as my cuts will stay tight and small so i'm hoping that when it comes in it'll be at a perfect place to spot for higher bearing.

    What is everyone thoughts on this? I have attached a plan of attack for reference.
    Attached Files Attached Files

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    Hey Rich,

    I must have watched them several times. Stefan shows the 123 block method for checking convexity transversely which i skipped doing. The tid bits is what i'm figuring out here. Another "Ah Ha" moment that's all.

    The videos were absolutely perfect for getting me to where i'm at now. but now I've realized i have a convexity problem i need to correct.

    I'm not convinced because i cannot get reliably consistent prints. I'm at a PPI i'm happy with but it's a rocking chair i believe.

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    If you cannot get a consistent pattern, it's possible the surface is out of flat across, on the short dimension.

    You could try scraping a few passes in a strip down the middle 2/3 of the width or so, or just concentrate on scraping more deep in the middle.

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    One red flag that your part is convex across its width, when you go to hinge it on the plate usually it walks sideways across the plate as you sway the one end back and forth, not always, but if it does you may want to stop and check that.

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    Quote Originally Posted by lucky7 View Post
    Nice work! Are you hinging from side to side as well as end to end? I use a 1-2-3 block without holes for side to side checks.

    Lucky7
    Lucky, How often should I check this? I might not be identifying which points are high highs and it appears i'm taking down the edges more than the center and after a couple passes find myself convex transversely again. I'll correct it and get it to hinge pretty far out transversely and tell myself i'm good to pinspot only to circle back to inconsistent printings. Paolo had a really good mention of keeping it high along the edges until the very end which i'm trying to figure out how to do. need help!



    Quote Originally Posted by Paolo_MD View Post
    I think you’re on the right path.
    Remember Richard’s five rules and learn how to read the blue. In your picture it is very easy to spot a few very high spots, where the ink has been displaced from the highest point and has accumulated just below the summit (circled in red in the picture) and less high spots where the summit has barely touched the ink film on the master. The mere size of the spot doesn’t matter much (although, in general, larger spots, like larger mountains, are also higher). I’ve circled in green a spot that, at least for what I can interpret from your picture, despite the size is rather low.


    Attachment 224845

    At this point you should switch to individual rows of individual short (~1/4”-3/8* long) scraping marks in the areas where you have most spots. Before starting, map the surface and mark with a sharpie the areas that are at least half thousand low. Of course, do not lay any scraping mark in such areas.

    After a couple of passes without bluing (just spread uniformly either blue or yellow to easily see where you’ve already scraped), you can stone the burs and re-evaluate the situation.
    One common mistake is to interpret as flat the spotting of a piece that is instead convex either along the whole length, or across, since it is rather easy to rock it while spotting it.
    It is therefore important to hinge the piece to make sure the hinging points are ~30% in, and mot at the very ends or in the middle. In general, it is a good idea to keep the straightedge tendentially high close to the long edges (i.e. transversely concave) and bring it to flatness at the end.

    Just my two cents.

    Paolo

    I' think I've gotten down everything mentioned above up until the convexing transversely part. Where i'm stuck is the next steps after i'm convinced that the part hinges well in both directions. Based on what you are saying, i should focus on pinspotting (the high highs) only within the central region of the part so as to get the edges to bear properly, then work the ends to bring it to a full proper bearing condition.



    On a side note, i decided to get the table and table edge within relatively flat tolerances.. I plan to use the table edge as a reference for the dovetail scraping. Can't get there without first getting my straight edge in check first though!

    img_5296.jpg

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  23. #198
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    On my opinion, the first step will be to quantify the convexity you have. This would be my approach, others might disagree.
    Blue your straightedge and place it on three packs of shims so that the top is more or less parallel to the surface plate.
    Now, with your tenth indicator mounted on a height gage, survey all the highest blue spots of your straightedge.
    If you were unable to make the surface of the straightedge parallel with the top of the plate, you need to subtract the slope from your measurements.
    While doing this exercise, you will gather information about the depth of your scraping marks: with this data in hand, it should be relatively easy to figure out where to scrape and how many passes.
    If everything is already within the thickness of one of your scraping marks, I'd suggest to make a pass or two of Zs everywhere except for 1/4" all along the perimeter.

    Paolo

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    Better check the edge ifnyour going to use it as a platform to indicate off of to do the dove tails. Lay the table on the top of the plate and hit it with a rubber hammer. If its solid all over and hinges at 30%, good enough. Your not scraping a rongfu Jig bore and you can scrape 40 PPI but you will still have a Rung Fo. If it hinges good and solid, check the front side of table for flatness and if it hinges at 30% and you can't slide a .0005" out from under it. That means lift table and slide in some plastic shim, set the table down and try to pull it out all the way on both sides. That will show you it's with-in .0005". And for a rung fo good enough.

    Then set it back on top and indicate the bottom so its coplanar in length and width and it should be .0005" to .001". Then do the same thing to the saddle to prepare it before using the table as a master to scrape the saddle to a match fit.

    Here is something I posted on another thread,a rung fo type table that was eventually scraped in a class, the hammer trick on a Myford grinder table but you get the idea I hope and my drawings. The charts are my Copyrighted material I have in my scraping manual. Another item of interest a rung-fo like other conventional basic machine tools are scraped to 15 to 20 PPI and 40 to 60% contact. Only Super precision machines (that were designed to be super precision from the get go) are scraped to 38 to 42 PPI and 40 to 60% contact.

    Your scraping looks good. To good for a Rung-fo...lol
    Attached Thumbnails Attached Thumbnails dsc01975.jpg   2014-02-26_13-50-05_372.jpg   ppi-booklet-chart.jpg   ppi-booklet-chart.-2.jpg  

  25. #200
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    Quote Originally Posted by Richard King View Post
    Better check the edge ifnyour going to use it as a platform to indicate off of to do the dove tails. Lay the table on the top of the plate and hit it with a rubber hammer. If its solid all over and hinges at 30%, good enough. Your not scraping a rongfu Jig bore and you can scrape 40 PPI but you will still have a Rung Fo. If it hinges good and solid, check the front side of table for flatness and if it hinges at 30% and you can't slide a .0005" out from under it. That means lift table and slide in some plastic shim, set the table down and try to pull it out all the way on both sides. That will show you it's with-in .0005". And for a rung fo good enough.

    Then set it back on top and indicate the bottom so its coplanar in length and width and it should be .0005" to .001". Then do the same thing to the saddle to prepare it before using the table as a master to scrape the saddle to a match fit.

    Here is something I posted on another thread,a rung fo type table that was eventually scraped in a class, the hammer trick on a Myford grinder table but you get the idea I hope and my drawings. The charts are my Copyrighted material I have in my scraping manual. Another item of interest a rung-fo like other conventional basic machine tools are scraped to 15 to 20 PPI and 40 to 60% contact. Only Super precision machines (that were designed to be super precision from the get go) are scraped to 38 to 42 PPI and 40 to 60% contact.

    Your scraping looks good. To good for a Rung-fo...lol

    Thank you Rich,

    I had another "ah-ha" moment last night. I did some more reading and digging, rereading threads I've read several times but found a post of yours mentioning that if the scrapes are too shallow the blue will come and go. What I neglected to do was follow your rule number 3 of measuring the scrape depth... i knew about it but never thought to apply it.... Frustrating...now I know.

    I've since re scraped the surface with a real "scrape" depth per RK rule number 3 and not the "chicken scratches" i was putting on the surface. I stopped last night about 4-8 PPI and pivot points just outside the middle thirds...and i'm pretty happy about it so far.

    Another "tid-bit" I found of yours Rich was that you have your students practice their scrape marks for several hours before even thinking about bluing. This was an exercise I never put into practice.. I'll be acquiring a scrap piece of CI to practice on for consistency and accuracy.

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