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  • Frusterations

    So I decided I needed to make a dovetail master for my Shaper project. Just by serendipity, I had a piece of 2" by 4" by 4" (roughly) cast iron in the stash I bought over the weekend.

    I decided I would fly cut it square (err "rectangular" ), saw the approximate 55* angle and then fly cut the angle. Only, I'm at my little garage shop now. It's nice because it's warm and all of my tools, hardware and scrap are here but it sucks because the only machine is my Smithy

    Well the head is out of tram by 0.01" over 4". Fantastic. I haven't even seen a good way to tram these as the head has not nod/tilt and it doesn't have a rigid column where you can shim the base. The whole damn head is basically mounted to a largish (3-4") diameter ball screw so you can move the head up and down.

    Anyhow, the flycutter is 2" so out of tram in the direction of travel I can live with. It's the out of tram in the other direction that is going to make the 55* angle tough. I haven't yet figured out how I'm going to get it all lined up properly.

    Sure wish I had that 2D here, now...

    I guess I'm just complaining to sympathetic (unsympathetic?) ears

  • #2
    Tram that thing right out of the shop...

    No problem for my old Bridgeport, or Cinci, or Antique Cinci

    I had a round column mill for a long time but it did tram.. And had a seperate flange if it needed adjusment

    Had good tools in school, never felt the urge to go Anvil bottom quality...

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    • #3
      Guess you need one o' them round column mills
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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      • #4
        All else fails, bend the dam thing

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        • #5
          just get the files out

          Ideally, you want the reference to be as long as the dovetail, right? is 4" enough?
          .

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          • #6
            Sounds like you need a bigger tramming hammer.

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            • #7
              If you're holding the work in a vise perhaps you can shim the vise so it's aligned?

              Not ideal, but I did this with my shaper and it made life much easier.

              John

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              • #8
                Sorry. Double post.
                Last edited by Forrest Addy; 12-22-2009, 12:48 PM.

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                • #9
                  Originally posted by Fasttrack
                  I'm at my little garage shop now. It's nice because it's warm and all of my tools, hardware and scrap are here but it sucks because the only machine is my Smithy

                  Well the head is out of tram by 0.01" over 4". Fantastic.
                  Tom, unless you have a big surface grinder, you're going to need to hand-scrape the dovetail master anyway, so rough-cutting the angle doesn't have to be that accurate.

                  By the way, make sure to leave yourself enough allowance on the prism shape that you can tilt the dovetail master up to spot the top of the dovetail.
                  "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                  • #10
                    Maybe a bit off-topic becuase what I have to say doesn't deal with an out of tram head but a summary of the steps in re-scraping dovetail slides may be in order at this point. This is a summary not a detailed treatment; I may have glossed over a point or two.

                    Scraping dovetails accurately requires several reference techniques used in selective rotation.

                    The male dovetail flat is perfected by scraping the slide's female dovetail flat into a plane on a surface plate neglecting for now the angles.

                    The slide is then used in conjunction with the dovetail straight edge to scrape the flats of the male dovetail into a plane while simultaneously tracking as you go with a precision level on 1-2-3 blocks to keep the twist hollow and hump under control. The angled surface of the dovetail straight edge may or may not be scraped. The angle is best scraped/machined at a more acute angle than dovetail you're working on. The thin edge of the reference's angled surface only function is to slip under the overhang and detect high metal all the way to the intersection relief.

                    The angle block is the "reference angle." or "scraped prism". It's only one scraping reference tool. That little block is at first scraped in to the best part of the existing angle and then all reference surfaces scraped flat while keeping the angle matched to that of the existing dovetail. It's used to perfect the angle as scraping progresses but is not in itself trustworthy as a straight edge. If it's made too long it become tempting to regard it as a substitute for a straight edge and that may lead you into error. I've seen them 4 ft long and crooked as a dog's leg from the heat input of one use.

                    The dovetail straight edge is used to perfect the flatness/straightness of the two surfaces that intersect to from the dovetail angle.

                    THEN you also have to use pins to keep the dovetail angle parallel.

                    Once the male dovetail flat is accurately scraped and the intersecting angles scraped flat, straight, and at the original angle as represented by the angle block, you can move onto the female dovetail. It has two angled surfaces: one is the way bearing and the other abuts the gub. If the gib is tapered, the gib abutment has to be straight and flat but not developed to the quality of a bearing surface.

                    Did I mention that you have to keep aware of axis alignments to other part of the machine while scraping is in progress? It's very possible to do a beautiful job of scraping only to find the column ways are out of square with the spindle axis for example and thus unsatisfactory. All the axes have to be mutually perpendicular as well as straight, flat, and fitted.

                    Scraping machine tools is not an easy job but if was done on a production basis by immigrant farmers and teamsters in sweat shops 80 years ago it can be done again by people like you are now.

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                    • #11
                      lol Thanks guys. Shimming the vice was the only easy(ish) solution I could come up with over night.

                      Mcgyver - the biggest piece of aluminum, cast iron or brass/bronze that I had was this 4" chunk of CI, so 4" it is!

                      Robert - I was planning on scraping it, but I was affraid it would take my unexperienced hands several years to scrape 0.01 off I was hoping to deal with 0.005 at most. I suppose that was a naive wish, given my equipment...

                      Forrest - Thanks for the summary! I'm still working through how to do this and thinking about it. I just like to be doing things with my hands while I'm thinking, so I thought I'd start making the blank and doing some other "set-up" type jobs. The only thing that I don't have is a precision level. I was planning on making a bracket for a DI as is shown in Machine Tool Reconditioning. I'm not sure if this is really ideal, but I recall Connelly mentioning that it could be used in place of the level, if need be.

                      Also, I'm not too worried about the other axes of alignment. Since it's for a shaper and this part rotates, it seems like the only thing I really need to worry about is keeping the ways perpindicular to the round "snout" that fits inside of the shaper ram. That way, when I move the tool up and down, I don't get undue cosine error in my height adjustment. If the ways tend to "drift sideways", this can be corrected by rotating the head until they are once again perpindicular to the table.

                      They are in pretty decent condition, the only major thing wrong was the broken gib. Hopefully they don't need more than a "touching-up"...

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