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  1. #21
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    Well, my brayer finally reappeared. So I started on the saddle side of the cross slide.

    Immediate conclusion, I need to make some more scrapers which are much narrower.

    I was using the red oil base medium I bought from ENCO many years ago. I rework the surface plate with the brayer between spottings. So I have a nice uniform layer of medium. With the medium very thin, if I do a few figure 8s with the part, the high spots get shiny and spotting medium builds up around it. It makes them very easy to see.

    I'm contemplating making some pull scrapers with carbide blades of various widths. The high spots are less than 1/16" across and fairly broadly scattered, though favoring the inside edges of the surfaces. It's hard to see to hit those on a push stroke because the tool is in the way. So I thought I'd try pulling instead.

    I'm building a 3 point bed support out of heavy square tubing to allow me to precisely level the bed. Haven't decided yet on what pitches to use for the differential adjusting screws. I also plan on building some variant of a King Way with a dedicated 2"/2 mm vial.

    BTW Does anyone know a way to easily measure the thickness of the spotting medium? I want to push the accuracy of the reconditioned lathe as far as I can take it. Dave Broadhead scraped his Southbend to a tenth for the entire length of the bed in preparation for making the screws for John Strong's ruling engine in the late 40's. If anyone has suggestions of how to measure closer than a tenth and not get burned by temperature differentials, I'd really appreciate some references. Just for tenths to be meaningful requires good temperature control.

    My ultimate goal is to rebuild my Clausing 4902 to instrument maker standards. This Chinese casting set is just the warm up exercise for that effort. Over all the Clausing is in very good shape, but it's seen significant use and needs attention to be her best.

    In case this sounds daft. I have the complete set of all the Scientific American Amateur Scientist columns on CD. There are a lot of things I want to build that appeared in that column. Just one exposure at age 10-12 and I was corrupted for life. I spent months rereading the columns C.L. Stong selected for the anthology published in 1962.

  2. #22
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    I have been doing some pull scraping lately. Pull scraping is very time consuming and any pull scraper I have will remove the high point but will leave you with a flat area. It is good when you don't need any depth of cuts for oil pockets, but it's not for doing 40 points per inch. What you might consider is what's called bump scraping. Use a 40 mm radius and put the scraper edge where the high point is and bump the end of the scraper. This is also time consuming but a way to achieve 40 ppi if you don't have a power scraper.

    When I am scraping something to 40 ppi, which I rarely do, I don't spread the color on the table, I spread it on the part and rub it all off to take the shine off of the part. Then I rub the part on the clean table and then try to scrape the shiny spots only. Daryl

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  4. #23
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    Feb 2014
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    Quote Originally Posted by rhb View Post
    Well, my brayer finally reappeared. So I started on the saddle side of the cross slide.

    Immediate conclusion, I need to make some more scrapers which are much narrower.

    I was using the red oil base medium I bought from ENCO many years ago. I rework the surface plate with the brayer between spottings. So I have a nice uniform layer of medium. With the medium very thin, if I do a few figure 8s with the part, the high spots get shiny and spotting medium builds up around it. It makes them very easy to see.

    I'm contemplating making some pull scrapers with carbide blades of various widths. The high spots are less than 1/16" across and fairly broadly scattered, though favoring the inside edges of the surfaces. It's hard to see to hit those on a push stroke because the tool is in the way. So I thought I'd try pulling instead.

    I'm building a 3 point bed support out of heavy square tubing to allow me to precisely level the bed. Haven't decided yet on what pitches to use for the differential adjusting screws. I also plan on building some variant of a King Way with a dedicated 2"/2 mm vial.

    BTW Does anyone know a way to easily measure the thickness of the spotting medium? I want to push the accuracy of the reconditioned lathe as far as I can take it. Dave Broadhead scraped his Southbend to a tenth for the entire length of the bed in preparation for making the screws for John Strong's ruling engine in the late 40's. If anyone has suggestions of how to measure closer than a tenth and not get burned by temperature differentials, I'd really appreciate some references. Just for tenths to be meaningful requires good temperature control.

    My ultimate goal is to rebuild my Clausing 4902 to instrument maker standards. This Chinese casting set is just the warm up exercise for that effort. Over all the Clausing is in very good shape, but it's seen significant use and needs attention to be her best.

    In case this sounds daft. I have the complete set of all the Scientific American Amateur Scientist columns on CD. There are a lot of things I want to build that appeared in that column. Just one exposure at age 10-12 and I was corrupted for life. I spent months rereading the columns C.L. Stong selected for the anthology published in 1962.

    I used a metric m30 x 2mm thread on the jacking screws on my lathe, (all 8) it was pretty easy to level the bed to within 0.0002"/10" and finer if you can be bothered. (thats about 0.080" pitch on the screws - not too fussy turning a 12" spanner 1/16 of a turn and certainly no effort.


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