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Ways to measure holes center to center?

Discussion in 'METROLOGY - MEASURE, SETUP & FIT' started by Uglydog, Jun 14, 2017.

  1. BGHansen

    BGHansen United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Here's the 13" Sorenson I picked up off eBay for $50 plus shipping. Pretty happy with the mike, hit the same 11.000" every time on the standard. Daryl, thanks again for the tip!

    Bruce

    20170623_140900.jpg
     
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  2. Dresden

    Dresden United States Iron Registered Member

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    Daryl, I suggest you just ask Dennis, your scraping instructor
     
  3. Dr. B

    Dr. B United States Swarf Registered Member

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    If the holes are the same diameter, may I suggest merely measuring left-edge to left-edge or right-edge to right-edge?
     
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  4. gr8legs

    gr8legs Active User H-M Supporter-Premium

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    After reading about the Sorenson Center Mike I knew I had to have one (It regularly made me crazy to try to accurately find the distance between two holes). All I can say is that the Center Mike is slicker than boiled owl snot. Wow. What it does is measures the near distance and the far distance, mechanically adds them together and divides by two, which is the indication on the Vernier. Takes 10 seconds and indicates to 0.001

    They sell on eBay very reasonably and if you ever need to measure hole center-to-center distances this will become your go-to tool.

    Stu
     
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  5. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    gr8legs,
    Which length Sorenson did you purchase?
    I've wondered if there is any advantage with the little one. They appear to function the same.

    Daryl
    MN
     
  6. BGHansen

    BGHansen United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Pretty sure the function is the same regardless of size. The vernier scale is double-sized; 1.000" measured is 2.000" on the Sorenson scale. Pretty simple (but ingenious) device. Start with the LH side at 0.000", measure the distance between the holes on the inside (or outside would work too, just have to do the opposite on the second measurement). Then slide the LH stop from zero to the RH which now starts your next measurement at "where you left off". Do the 2nd measurement and because the scale on the Sorenson is 2X, you are reading the total of the inside and outside dimensions divided by two. Pure genius!

    Bruce
     
  7. gr8legs

    gr8legs Active User H-M Supporter-Premium

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    I purchased the 8" version and liked it so much (and besides that, I'm a tool junkie) I just eBay'd a 13" one plus the measurement extension bars.

    It's a horrible addiction with no 12-step program. Luckily, this site serves as a support group - the only difference being it's a cheering section :)

    Stu
     
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  8. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    If you get a chance, I'm looking forward to hearing about how the extension bars work for you.
    My projects tend to be on a larger scale.

    Thank you,
    Daryl
    MN
     
  9. gr8legs

    gr8legs Active User H-M Supporter-Premium

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    For Daryl and anyone else interested:

    The "Booster Bars"arrived yesterday along with a 13" Center-Mike from another eBay seller and I tried them out.

    First and most important, these extensions only work with the 13" version of the Center-Mike. They extend the 13" range up to 22 inches center-to-center. Sorensen was clever in providing a full-range of measurements but you had to have both the 8" and 13" basic versions to get the 0.25" to 22" range.

    <edit> No, that's not right . . . The 8" will measure 0.25" - 8" and the 13" will measure 0.25" to 13" . . .duh! But the extensions do only work with the 13" </edit>

    I'm happy with my purchase - another tool! Woo hoo!

    Stu
     
    Last edited: Jul 27, 2017
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  10. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    That's great information. Huge thanks!

    Daryl
    MN


    Sent from my iPhone using Tapatalk
     
  11. C-Bag

    C-Bag United States Active Member Active Member

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    I was going to wait to pile on my thanks Daryl until my 8" Sorensen got here tomorrow, but I couldn't wait. Having terminal TAS( tool aqusision syndrome) I can't tell you how timely this thread is. Hole layout has always been a tough process for me and I'd never heard of the Sorensen. Makes sense there would be a tool for it but not being a machinist by trade I'd never bumped into it.

    But through the other suggestions offered here I used my calipers and my numbered drills as a Gage to accurately figure centers of the 4 hole pattern I've tried over and over to do accurately. The revelation was I'd assumed the pattern would be 1" centers. It was actually .990! So since I just upgraded my mill with a cheap 3axis igaging DRO it was quick and easy to just place the first hole and layout .990" apart 4 holes. And for the first time it came out perfect. For me measuring is just half the battle. I wish I would have gotten a clue and gotten the lo buck DRO before as it has made all the difference. Best $130 I've spent so far
     
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  12. Bob Korves

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

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    [QUOTE="C-Bag, post: 504000, member: 45394
    But through the other suggestions offered here I used my calipers and my numbered drills as a Gage to accurately figure centers of the 4 hole pattern I've tried over and over to do accurately. The revelation was I'd assumed the pattern would be 1" centers. It was actually .990! So since I just upgraded my mill with a cheap 3axis igaging DRO it was quick and easy to just place the first hole and layout .990" apart 4 holes. And for the first time it came out perfect. For me measuring is just half the battle. I wish I would have gotten a clue and gotten the lo buck DRO before as it has made all the difference. Best $130 I've spent so far[/QUOTE]
    What kind of mill do you have? .990" is very close to 25 mm. If it is an Asian or European mill I would not be guessing 1 inch, very unlikely...
     
  13. C-Bag

    C-Bag United States Active Member Active Member

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    I guess the points are getting scrambled. My focus was accurately measuring hole centers, not repairing my mill/drill so I didn't catch Daryl's project just the measuring.

    For the record I've got an old RF 30 mill/drill I picked up cheap because it needed a lot of TLC. But it fit my noob capabilities and as time has gone on and my skills and need for greater accuracy have gone up I've upgraded and repaired the old war horse as needed. The project I've been working on is making a machine with 80/20 extrusions. The series of 80/20 I'm using is the 10 series which is supposedly based on 1" and multiples there of. There is also a metric series but your observation Bob makes it seem that while the overall dimension of this material may be 1"s the slot and bolt pattern spacing is metric. Tricky of them.
     
  14. Superburban

    Superburban United States Active Member Active Member

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    I have always just measured the far side to far side, and inside to inside. Then take the farside to far side, and subtract the near side measurement. Divide that figure by two (That gives you the two center to center distances for just the holes), then add the near side to nearside measurement back in.

    A Little simpler written for the math guys:

    (far side- nearside)/2 + nearside
     
  15. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    or just (far side + near side)/2
     
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  16. Doodle

    Doodle United States Active Member Active Member

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    The way I do it is select a drill bit shank that tightly fits the hole, draw an x line in CAD, intersect the x with a Y line, create a circle Tangent to X, Y lines and type in the circle diameter (drill shank size). Stick a tight fitting drill bit in the second hole, use digital calipers to measure outside dimensions of the two drill shanks, create a line parallel from the y axis line the distance just measured. Create circle tangent, tangent, and circle diameter (second drill shank size). Now you have a CAD drawing started, CAD has measured distance for you between centers.
     
  17. C-Bag

    C-Bag United States Active Member Active Member

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    I received my 8" Sorensen and with some cleanup(it was corroded and stuck) along with training with the provided gage I'm very pleased. It also showed my previous process was off by .010. The bolt holes were exactly 1" apart, not .990 like my caliper/Gage plug method came up with. The Sorensen is far quicker and more accurate and was totally worth the $50+ shipping to me. I guess the good fit this time was due more to the accuracy of the new DRO along with cleaning and adjusting X Y lead screws than super accurate measuring. Wish I would have known of the Sorensen along time ago.
     
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  18. Uglydog

    Uglydog United States Active User H-M Supporter-Premium

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    Someday perhaps I'll understand CAD. Thus far I only used a beat up little drafting board and some Trig Tables. I'm pleased to know that CAD is so flexible!!

    Daryl
    MN
     
  19. Doodle

    Doodle United States Active Member Active Member

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    I could not get a picture posted to support this post, try this:

    upload_2017-8-9_7-16-29.png

    Also, YouTube has lessons posted for using CAD programs and they are very helpful.
     
  20. Splat

    Splat Active User H-M Supporter-Premium

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    I'm with RJ on this one. If the holes are known to be the same diameter then I measure one with the calipers, zero the caliper, then measure the distance between the outside edges of the holes. Good enough for govt work. :)
     

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