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Surfac Gage Rec (for Dti)

Discussion in 'METROLOGY - MEASURE, SETUP & FIT' started by petertha, Dec 6, 2016.

  1. petertha

    petertha Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    I've been checking out granite surface plates & factoring cost, weight, size etc. for my newby requirements.. I'm gravitating towards a 12x12" because most of my foreseeable parts should be accommodated on this footprint.

    But another shopping consideration will be the surface gage apparatus to hold my DTI. Most of the ones I see are either set up for scribers, or are those big long dial/digital assemblies, or the ones with a dial on a fixed pillar where you slid the parts underneath. I figure I want to use my granite real estate wisely & position my gage around the part from different orientations based on shape etc. so it needs to be smallish footprint. Something like attached pic? If so, any brand names / model recs?

    Am I barking up the wrong tree? I guess using my mini mag base DTI holder in arm-locked position is considered dodgy & not as reliable as a post/clamp arm style? Is there something special about the base like ground flat or maybe relief cut so it slides & positions better?
     

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  2. T Bredehoft

    T Bredehoft Active User H-M Supporter-Premium

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    That thing you illustrate, (I've not learned a real name for it in 40 years) is ideal. By setting your upright, and DTI in various positions you can use very little real estate and still get very exact measurements (to compare with stacked Jo Blocks.)

    Edit: I guess Surface Gage is right.
     
  3. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    I recommend if you have room for it to get at least a 12x18 surface plate, 18x24 better yet. It needs to be in current calibration. Real estate runs out quickly on a surface plate. A surface gage is great for testing parallel and comparative heights on the surface plate using a tenths DTI. For that task, the heavier the surface gage the better, and make sure it is really flat on the bottom. You can also scribe parts with it. A height gage is also good for marking parts, and of course for measuring heights accurately. It needs to be flat on the bottom and perpendicular to the surface plate. It can also test parallel or comparative heights using a DTI, though not as well. A cylinder square and/or a granite angle block tests for a true 90 degree angle. Those and a good sine bar, and sine plate also if possible, will test most things as accurately as you need to in a hobby machinist shop. You will also need gage blocks for putting known dimensions to things.
     
  4. petertha

    petertha Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    Yes, I certainly hear you. The 12x12x3" is 48 pounds (85$). The 12x18 would be nicer size, is only 5$ more but 72 pounds. The 18x24 is <ugh> pounds. Shop space utility wise, I figure I'll have to pull this from a shelf when I want to use it which is not great. If I could park it somewhere safe with a cover that would be ideal, but I'm not sure...

    Does this (KBC) look like a catalog pic typo? It seems to be 'ledge' style would have, well.. a ledge!
     

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  5. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Well, the ledges are marked in red... I made a nice lightweight cover for my 18x24 surface plate. It is padded below with 1/2" closed cell foam (backpacking sleep mat), has .200" underlayment covered by rubber sheeting for a top surface, and ~.75" square pine around the edges. with dadoes for the underlayment. It only weights a couple pounds, but protects the surface plate and allows it to be used as a work surface when it is not in use as a surface plate.
     
  6. petertha

    petertha Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    Sorry I should have said, I sketched the red lines. Their photo is a solid rectangular block...just like their 'no ledge' model. Just like I bought a front mount chuck with a pic of front mount bolts... until the real one showed up that had a different fastening arrangement. I mean is it really that hard to get the right pic in there? :)
    Good idea on the cover, more noodle thinking required.
     

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