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  1. #21
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    Quote Originally Posted by Spyderedge View Post
    Those bearing points appear to be too large and irregular. Try to even things out and the bearing area will last much longer and wear "straight down"

    Sent from my XT1053 using Tapatalk
    Spyder, do you have some photos of hardened surfaces you've spot ground to show what you mean and maybe to show Demon just what's possible for points per inch?

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    Not Spyder, but this is what i worked to on the HLV. First pic shows why I went to spot grinding:- the grinder still needs a rebuild and the bed plate is longer than the travel on the grinder. Lapping plates for increasing spot size in background:-



    Second pic shows a closeup:-


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    Quote Originally Posted by TGTool View Post
    Spyder, do you have some photos of hardened surfaces you've spot ground to show what you mean and maybe to show Demon just what's possible for points per inch?
    Nope. Anything hardened I surface grind.

    What's possible for PPI? As higu as you want/can go with the tools you have and your patience. Same with regular scraping.

    Bearing points on cast iron and hardened steel work just the same, and as with softer metals leaving large bearing points at random isn't good practice and will prematurely wear.

    All Demon has to do is a few more passes and split the large points, which might be more easily done with a Dremel point that's come shaped and dressed true with a dressing stick (those aluminum collets aren't very repeatable).


    Sent from my XT1053 using Tapatalk

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    There is always too the possibility of making a holder for a fine ceramic stone. We lapped the ball ways of a surface grinder using a square section ceramic 10,000 grit stone using my Biax and a specially made holder to hold the stone.
    The possibilities of very high spot counts is there, working under 10 or twenty power lighted visor. The heat generated must be lower as well, though far too slow for roughing.

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    Quote Originally Posted by partsproduction View Post
    There is always too the possibility of making a holder for a fine ceramic stone. We lapped the ball ways of a surface grinder using a square section ceramic 10,000 grit stone using my Biax and a specially made holder to hold the stone.
    The possibilities of very high spot counts is there, working under 10 or twenty power lighted visor. The heat generated must be lower as well, though far too slow for roughing.
    You mounted a stone in the Biax? Wow, I've never heard of that. Do you have any photos?

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    Quote Originally Posted by Spyderedge View Post
    Those bearing points appear to be too large and irregular. Try to even things out and the bearing area will last much longer and wear "straight down"

    Sent from my XT1053 using Tapatalk
    Not to worry Spyder, all my objectives on this exercise were satisfied and some. No1 objective was to hit a consistent 20ppi in an orderly speedy fashion, took around 20mins to come in including taking the 0.001 hump out centre.

    On the job the plan is sort the three main surfaces on this old Schou grinder, theyre bellied out something in the order of 0.006 over 7' ish.



    The plan is to build a climate controlled tent around the machine and maintain 20°c + - 0.1°c, then let the machine and all equipment to be used soak for 3 days. I'll be using the pro scraper plus suit available from OZscrapingsupplies.ufkm for the entire job (essential piece o kit imho). Using ultra low temp head mounted Led lamps ill be aiming for 20ppi for the roughing stage, might take a day or 2. The other 3 weeks will be dedicated to refining the surfaces to 55ppi (as detailed in 'Graping the Fibonacci way') with a TIR no greater than 0.00035, takes longer cos you have cool with a fan every 13 grinder dabs.
    Is a shame we have to go the hand grinder (graping) route as I know it goes against all that is great and good in this world. But after a the customer had a quick measure up, he told me the machine was to big to go on his surface grinder.

    Cheers
    D

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    Quote Originally Posted by Demon73 View Post
    Not to worry Spyder, all my objectives on this exercise were satisfied and some. No1 objective was to hit a consistent 20ppi in an orderly speedy fashion, took around 20mins to come in including taking the 0.001 hump out centre.

    On the job the plan is sort the three main surfaces on this old Schou grinder, theyre bellied out something in the order of 0.006 over 7' ish.



    The plan is to build a climate controlled tent around the machine and maintain 20°c + - 0.1°c, then let the machine and all equipment to be used soak for 3 days. I'll be using the pro scraper plus suit available from OZscrapingsupplies.ufkm for the entire job (essential piece o kit imho). Using ultra low temp head mounted Led lamps ill be aiming for 20ppi for the roughing stage, might take a day or 2. The other 3 weeks will be dedicated to refining the surfaces to 55ppi (as detailed in 'Graping the Fibonacci way') with a TIR no greater than 0.00035, takes longer cos you have cool with a fan every 13 grinder dabs.
    Is a shame we have to go the hand grinder (graping) route as I know it goes against all that is great and good in this world. But after a the customer had a quick measure up, he told me the machine was to big to go on his surface grinder.

    Cheers
    D
    Since you are concerned with heat, did you consider using an air angle grinder? You can put a larger air tank in the tent to equalize the air temp for the grinder. Also an air grinder is much lighter so gives you a bit more control. Agree with others that you have highs far apart and not enough bearing surfaces. Mark's marks look better

    just an idea.

    dee
    ;-D

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    Do you have any photos?
    I still have the aluminum holder somewhere around here. What we were doing wasn't really related to scraping in that all we were able to do was go straight down, the steel balls had worn a visible track in the hardened steel V ways and we took pains to make sure we kept constant time lapping (Stoning) the same amount of time on all areas until those tracks were gone. It took days.

    To use a stone against markings from a plate would require a very small area stone and very short stroke, this I've not done. I'm still thinking about an XY bridge holder with laser pointer so that it marks the exact spot of the blue marking center.
    An earlier poster mentioned tapping the top of a small grinder held just over the surface, I hadn't gotten to that thought because I wanted a mechanical movement, but that lends an even higher degree of control than a linkage.

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    Quote Originally Posted by Mark Rand View Post
    Not Spyder, but this is what i worked to on the HLV. First pic shows why I went to spot grinding:- the grinder still needs a rebuild and the bed plate is longer than the travel on the grinder. Lapping plates for increasing spot size in background:-



    Second pic shows a closeup:-

    I have an HLV which is quite worn near the headstock. I'm going to get it ground (Schaffer grinding in So Cal) I noticed (at least on mine) a lot of wear on the nearside dovetail, the backside was unworn. Did you have to do any scraping on the dovetails on your machine?

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    Quote Originally Posted by triumph406 View Post
    I have an HLV which is quite worn near the headstock. I'm going to get it ground (Schaffer grinding in So Cal) I noticed (at least on mine) a lot of wear on the nearside dovetail, the backside was unworn. Did you have to do any scraping on the dovetails on your machine?
    Yes, I had to grind about 10 thou off the dovetails, which was similar to the worst wear on the top of the bed plate. I spot ground the dovetails as well as the top surface, but don't have any pictures of that process...

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    Quote Originally Posted by dcsipo View Post
    Since you are concerned with heat, did you consider using an air angle grinder?
    dee
    ;-D
    At the risk of thread drift, and recognising that it might deserve a thread in its own right, I had a salutory experience with remperature effects at the end of last month.

    I took voluntary redundancy/early retirement at the end of last year and had got a dose of cheapness into my mindset. In the past, I've run the A/C-heatpump on my shed to keep the temperature pretty constant all the year round. I decided that wearing a woolly jumper was cheaper than running the heat pump and had let the temperature drop. By the time the inside temperature had dropped to 9°C/48°F, I decided that it was no longer a shirt sleeve environment and turned the heat pump back on. Trouble is, that I was in the process of scraping the cover plates of some box ways. The scraping was coming along very nicely and I'd finished the flattening process at the end of one day. Since it was getting too cold in the shed I turned on the heat pump so it'd be nice and cozy for me the next morning. When I came in the next morning I rubbed the plate on the surface plate and was shocked to see that it seemed to have gone banana shaped.

    Investigation showed that there was at least a 1.5 thou bow in the 14" long plate, but the bow seemed to be different depending on whether I measured it at the centre of the 12"x18" granite plate or along the mid line of the plate. This got me to thinking:- The small granite plate I was using was sat on top of my 36"x48" surface table, that I know has some flatness issues. When I turned on the heat pump, the air in the shed became warmer than the lumps of granite. Of course the surface plate would warm up from its top side, since the bottom side was sat on a much larger heat sink. This lead to a bow (hogging actually) in the surface plate. The steel plate I was working on stabilized much more rapidly and wasn't affected.

    I got around the problem by chocking up the little surface plate on a couple of bits of 1.5" square cast iron bar and directing the air from a box fan across the plate for a few hours to equalise its temperature.

    The moral is that temperature gradients can really ruin your day.

    This is the plate shortly after I discovered the problem. The day before, I'd had bluing all along the length and was ready to refine the spots to use it as a master on the mating way. :-



    and this is the plate after the surface plate had had the fan blowing on its top and bottom faces for a few hours:-



    I think it didn't come out 'perfectly flat' because the temperature had been steadily dropping while I scraped it the day before, so the surface plate was probably concave at that time...

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    Quote Originally Posted by Mark Rand View Post
    The moral is that temperature gradients can really ruin your day.
    YES! Absolutely they can. I made that point recently, however my point didn't go down too well. I personally feel everyone should always have temperature (specifically temperature gradients) in the back of their mind when scraping. Even if it's not be important in the work you're currently working on, if you're nevertheless ticking that off in your mind each time, it's much less likely to catch you out. Dismiss it as never being important and it will surely bite you on the butt big time and can lead to a lot of tail-chasing and wasted time.

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    What's to stop one from using this technique on non-hardened parts?

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    DAPRA used to sell some 2" x 2" aluminum blocks with black blade holder . Then you clamped in a white stone in it. I used to have a couple and tested them on hardened ways and I never had any luck with them at all. DAPRA told me they made them for die makers to stone dies. They never sold enough to warrant stocking them and discontinued them had t have been 20 years at least. When get home I'll look around and see if I still have them in the junk bin.
    Last edited by Richard King; 02-17-2017 at 06:22 AM.

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    Quote Originally Posted by ewlsey View Post
    What's to stop one from using this technique on non-hardened parts?
    I've been thinking the same. I'm probably going to try it at some point, as such tools are cheap and available compared to a proper Biax. I can think of at least a couple of concerns though:

    1. On soft material the removal rate may be too high, giving a high chance of digging holes.

    2. Grit getting embedded in the parts, accelerating wear.

    I'd guess both can be countered by experimenting with shape, speed, type of grit etc. and switching to hand scraping for finishing. I wouldn't try it on anything that matters, unless I have practiced and experimented on some scrap first.

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    Quote Originally Posted by Mark Rand View Post
    At the risk of thread drift, and recognising that it might deserve a thread in its own right, I had a salutory experience with remperature effects at the end of last month.

    I took voluntary redundancy/early retirement at the end of last year and had got a dose of cheapness into my mindset. In the past, I've run the A/C-heatpump on my shed to keep the temperature pretty constant all the year round. I decided that wearing a woolly jumper was cheaper than running the heat pump and had let the temperature drop. By the time the inside temperature had dropped to 9°C/48°F, I decided that it was no longer a shirt sleeve environment and turned the heat pump back on. Trouble is, that I was in the process of scraping the cover plates of some box ways. The scraping was coming along very nicely and I'd finished the flattening process at the end of one day. Since it was getting too cold in the shed I turned on the heat pump so it'd be nice and cozy for me the next morning. When I came in the next morning I rubbed the plate on the surface plate and was shocked to see that it seemed to have gone banana shaped.
    I'm not looking to argue the validity of temperature impact on moving metal in regard to scraping. Seems there are plenty here that agree that temperature IS a factor that needs to be watched so this has nothing to do with temperature.
    My question is about you project. These are covers right? In other words these don't need to be precision scraped to a reference and then mated with another moving, or non moving part correct? I guess perhaps they still need to be precisely fit to whatever they are covering but not in the sense that they need to be to the same level of precision AND have other characteristics such as bearing points etc??? If this is the case, and judging by the size of the parts in the photo, it doesn't seem as if they are thick and/or heavy enough to be stable. These look as if they would easily "bend" while handling them during scraping. Seems to me, and this is ONLY from what I've been reading, that the simple act of hinging these on a surface plate could make them change shape???
    These are just questions BTW. I'm not casting aspersions or telling anyone they are doing anything improper.
    Thanks

    Galaxy S4, Slimkat
    If I wasn't married I'd quit fishing

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    Quote Originally Posted by dcsipo View Post
    Since you are concerned with heat, did you consider using an air angle grinder? You can put a larger air tank in the tent to equalize the air temp for the grinder. Also an air grinder is much lighter so gives you a bit more control. Agree with others that you have highs far apart and not enough bearing surfaces.

    just an idea.

    dee
    ;-D
    Theres an idea

    Unfortunately ive already started work prepping the mini grinder. No pics of the framework that holds the ducting to the grinder im afraid but will upload pics when its done, complete with handle - guard and vac pipe attachment. Looks so dinky next to the 9" grinder ill be using to rough out with.
    The fan in background doesnt look like much but its fully calibrated, ive a piece of paper that proves it.

    img_0454.jpg

    Mark's marks look better


  24. #38
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    Quote Originally Posted by ewlsey View Post
    What's to stop one from using this technique on non-hardened parts?
    Nothing, except deep seated beliefs. Am sure I remember the mention of sanders / grinders for roughing out, in connellys iirc, so nothing new.
    Havent tried any finishing work on the soft stuff as yet tho, would be interesting to give it a go.

    Edit:- yep, chapter 4

    sanders.jpg

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    Quote Originally Posted by Mark Rand View Post
    At the risk of thread drift, and recognising that it might deserve a thread in its own right.
    Done

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    Quote Originally Posted by Demon73 View Post
    Nothing, except deep seated beliefs. Am sure I remember the mention of sanders / grinders for roughing out, in connellys iirc, so nothing new.
    Havent tried any finishing work on the soft stuff as yet tho, would be interesting to give it a go.

    Edit:- yep, chapter 4
    It is not just deep beliefs, but also deep gauges . If you ever used a grinder on cast iron, you know how easily it can gauge the surfaces and go all over the place. I just cut up a casting using and angle grinder and it is like sinking a hot knife into butter .

    dee
    ;-D

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