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Jobber length drills

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  • Jobber length drills

    I'm wondering about consistency in jobber length drills. I ordered a few through Amazon to fill out an order and get free shipping, precision twist sizes 43-48, and the 46 drill is quite a bit longer than the 45 (and about 1/8" longer than what was specified on Amazon). I wouldn't really care, except that it is about 1/16" too long to fit in my drill index. I can't really shorten it, as I don't yet have a grinder, and my dremel tool ate it last weekend, so it will have to be stored separately (I made a plastic sleeve for it and put it in the bottom of the index). I did verify that it is larger than the 47 and smaller than the 45, so it does seem to be the right size drill, and it is 135 degree split point, as specified.

    I'm just curious, how much consistency in length can I expect when ordering single jobber drills? I would have expected it to be somewhat standardized.

    I just like to make stuff.

  • #2
    "...I can't really shorten it, as I don't yet have a grinder..."

    You need to get yourself addicted to tools, and fast.
    No known cure, but man am I happy!
    I have way more than 10 grinders that I can think of
    right now, and I am always willing to let another one
    follow me home. And I think I have 5 complete sets
    of drill bits, not counting the boxes of sizes that I don't
    know what all is in there.

    Last edited by Doozer; 02-08-2010, 12:48 AM.


    • #3
      A jobber length drill should have flutes that are as long as 10x the diameter. That is in addition to the shank. I can't find a spec for the OAL.


      • #4
        No need for any pesky looking it up in the Machinist Handbook. All you need to do to figger proper length is:
        1) measure the length of the spot where the drill fits into the index. Shorten about 1/16 to 1/8 and you're good to go.
        2) measure the two drills which fit into the index on either side of the problem drill, split the difference and you're good to go.

        Actually though, a good quality drill is probably pretty damn consistent these days. Lower quality likely varies a lot, so I'm guessing that is what you bought maybe?
        I know in a CNC machine I can change out quality taps from the same maker without adjusting a length offset. Not sure if drills are made to such tolerances, but that's pretty dang good.


        • #5
          Cut a little off the shank end, then you will still have a new point.
          Kansas City area


          • #6
            Precision Twist Drill normally makes good stuff, so I assume as far as quality goes it's okay. I don't know about any standards for overall length though. Over the years I've found quite a bit of variation in drill length, so I suspect the acceptable length tolerance is pretty wide.
            Try to make a living, not a killing. -- Utah Phillips
            Don't believe everything you know. -- Bumper sticker
            Everybody is ignorant, only on different subjects. -- Will Rogers
            There are lots of people who mistake their imagination for their memory. - Josh Billings
            Law of Logical Argument - Anything is possible if you don't know what you are talking about.
            Don't own anything you have to feed or paint. - Hood River Blackie


            • #7
              There is some standardization, but with multiple standards. For example, a 1/4" jobber is available in 3.25", 3.5", and 4.0". Some manufacturers make their cobalt jobbers in different lengths than their HSS jobbers.

              The only way to be sure is to check the specs, but of course that doesn't work when the specs are wrong (as with your Amazon order).


              • #8
                OK, thanks for the info. Probably got one with another spec mixed in there. At least the business end is correct

                I just like to make stuff.


                • #9
                  Precision Twist makes some quality drills. So the first thing I'd check is to be sure the seller actually sent you PTD drills.

                  My one beef with Amazon is that their shopping system does not always default to Amazon: sometimes it will default to one of their "Marketplace Sellers", even if Amazon currently sells and stocks the item in question. Most of the Marketplace Sellers are reputable, but I've read some negative reviews on products after a buyer has bought from a party other than Amazon. (And the most common complaint against third-party sellers seems to be product "bait and switch"; shipping an inferior product in lieu of the brand-name product listed and purchased.) I myself have placed quick orders in the past, only to find I accidentally purchased from a vendor other than from Amazon itself. Mind you, I'm not saying it's bad for Amazon to offer alternative sources, I just don't like that it will automatically give you other sellers without warning.


                  • #10
                    I'm not sure how I can tell if it is actually a Precision Twist Drill make. The smaller ones don't seem to have a label on the shafts. The finish and grind of the cutting edge seems to be equivalent, to my untrained eye, to the larger drills I have that are label PTD.

                    I guess I'll just have to go with how well it cuts. We'll see.

                    I just like to make stuff.