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Re: [mill_drill] Undersized (5/8") drill bits...

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  • Vern
    I have, and will. But I should also mention here that the shaft I was attempting to fit the cast hub to, wasn t terribly precise either. Just some commonly
    Message 1 of 76 , Jun 22, 2013
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      I have, and will.  But I should also mention here that the shaft I was attempting to fit the cast hub to, wasn't terribly precise either.  Just some commonly available 5/8" cold rolled bar stock.  I do realize ( and did at the time) that the hole would need to be larger in order to fit the two.  I was simply surprised to find that the CR bar measured to advertised spec, but the expensive drill bit did not...  

      My thanks again to everyone here for sharing your knowledge, wisdom and experience on such a basic and fundamental aspect of metal work. It is clear now, that I was taking too much for granted!

      Best regards,
      -Vern

      Sent from my iPhone

      On Jun 22, 2013, at 8:56 AM, Dallas Richardson <classicpoints@...> wrote:

      Vern;
      I would take to heart what RICK was telling you about the Drill bits.
       
      I don't believe that you can buy a bit in a store that is "accurate".  In
      that I mean to say within .003...  If you stop and think about it?  All
      of the drill bits and nuts and bolts that you buy now days in stores like
      Home Depot, Lowe's, Harbor Freight, are mass produced by the Gazillions
      and like the 5/8 bits are close..  That is the KEY Fraze here.. They are
      CLOSE.  But, as Mr. Sparber said. To get right on, you need to go to
      a boring bar or a reamer..
       
       
       
       
      Dallas
       

      From: Rick Sparber <rgsparber@...>
      To: "mill_drill@yahoogroups.com" <mill_drill@yahoogroups.com>
      Sent: Saturday, June 22, 2013 9:27 AM
      Subject: Re: [mill_drill] Undersized (5/8") drill bits...
       
      Vern,

      Drills are for "knocking through holes". If you need precision, follow up with a boring bar. If you want smooth walls and precision, I follow the boring bar with a reamer.

      Rick

      On Jun 21, 2013, at 8:23 AM, Vern <mailto:n7gtb%40yahoo.com> wrote:

      > The other day, I had drilled a hole in an aluminum hub I had recently cast. When I attempted to fit it onto a 5/8" shaft, I discovered that the hole was undersized, so I measured the bit...I was surprised to find that it was 0.004" undersized. I later purchased a 'quality' HSS 5/8" bit from a local 'tool' supplier, thinking this would be better than the previous one from the big box hardware store. It too was undersized at 0.6225"...
      >
      > The second bit cost, was as much as the entire set that had the first, but doesn't appear to be any closer tolerance than the first. Is this a consequence of overseas production, or am I simply making false assumptions here?
      >
      > Thanks,
      > -Vern
      >
      > Sent from my iPhone
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
      >
      >
    • leasingham_connelly
      BS328 part 1 (Specification for twist drills), which is equivalent to a number of ISO standards, gives the cutting diameter of a drill as measured across the
      Message 76 of 76 , Jun 28, 2013
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        BS328 part 1 (Specification for twist drills), which is equivalent to a number of ISO standards, gives the cutting diameter of a drill as measured across the lands at the outer corners as h8. Back taper is between 0.0002mm and 0.0008mm per millimetre linear distance from the outer corner towards the shank. The total back taper not to exceed 0.25mm. Below 6.0mm back taper is not a requirement.

        I imagine that all other drill standards will be the same as, or very similar, with regards to these dimensions. Just divide by 25.4 for inch equivalents and you should be close to USA standards.

        Martin

        --- In mill_drill@yahoogroups.com, Goran Hosinsky <hosinsky@...> wrote:
        >
        > Searching Ebay (the German one) for a missing drill size (metric) I find
        > that they offer two types of HSS drills: Rolled or ground, the second
        > one being the more expensive. Might there be a difference in precision
        > between the two types - and could that be the explanation of the start
        > of this thread?
        >
        > Goran
        >
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