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  • Reamer question.

    I have to ream two holes ,10mm and 12mm.
    What size prehole should I be drilling. This is in what I suspect is phosper bronze. I only have 9.5mm and 11,5mm as nearest size drills. I tried the 10mm reamer but could feel the bronze got hot real quick and i suspect enough to want to jam the reamer.I was reaming much slower than a drill and used air to cool it down.
    Also if I were to make a d bit ,how accurate does it drill and what amount of material can it take out.
    Its a case of not having enough odd sized drills.

  • #2
    0.2 or 0.3mm smaller than the reamer.
    Bronzes of unknown grade can be really tough stuff to machine. Your reamer better be really sharp. Did you use cutting (oil)fluid?

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    • #3
      http://www.hannibalcarbide.com/docum...size-chart.pdf

      Admittedly, that charts in imperial units, but conversion to metric isnt that difficult. Guideline is leave 2% of the hole size for the reamer to cut, so youd need a 9.8mm drill. In a pinch id prefer to go slight higher in drill size, in this case to 25/64ths if you cant find a metric bit. Not ideal, the reamer isnt taking very much off at all, but better than the next closest size smaller bit, 3/8, which would leave a little bit much for the reamer to remove.

      As far as speed goes, the way ive heard it recommended is "half the speed, twice the feed", so cut the rpm in half and double the speed you feed the reamer through the hole, compared to a drill. Dunno how accurate that advise is, but its always worked for me

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      • #4
        On the 10mm I predrilled it 9.5mmand used engine oil.I actually dont know what the material is. It has gone green in patina but when milled it is golden. But oddly enough the swarf is slightly metallic.
        I have never made a d bit. I am curious to know how true it drills. I am thinking of making a 11.8mm d bit and then ream it.Will a d bit handle a pre drill of 11.5mm if I make it 11.8 or 12mm?

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        • #5
          Sharpen your reamer(bottom only). Do not lubricate. Slow speed. 9.5 drill is OK.
          Last edited by Juergenwt; 08-25-2017, 04:34 PM.

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          • #6
            I made a d bit of 11.78 mm (I was aiming for 11.8mm) I am pleasantly suprized how well it worked . The reamer then went through with no problems.

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            • #7
              Originally posted by plunger View Post
              I made a d bit of 11.78 mm (I was aiming for 11.8mm) I am pleasantly suprized how well it worked . The reamer then went through with no problems.
              Pics or it didnt happen, i love seeing shop made tools! D-bits in particular have always fascinated me for some reason, it almost boggles me how something so simple works so well

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              • #8
                Originally posted by epicfail48 View Post
                Pics or it didnt happen. i love seeing shop made tools! D-bits in particular have always fascinated me for some reason, it almost boggles me how something so simple works so well
                Why? Why do you need a picture of his D-bit. If they fascinate you then surely you already know what they look like.

                His D-bit probably looks about like everybody else's.

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                • #9
                  Originally posted by lynnl View Post
                  Why? Why do you need a picture of his D-bit. If they fascinate you then surely you already know what they look like.

                  His D-bit probably looks about like everybody else's.
                  It could have been longer .But its for a one off job. Actually I would be curious to see other peoples bits because I am not sure of the correct geometry.I am not sure if its as simple as milling it down to exactly half diameter. Do you not bother at all with relief and how should the tip look. ?

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