Welcome! Forums General Woodworking Discussions Tools and Tool Maintenance/Restoration Vintage Irwin auger bits Boring Oversized Holes

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  • #133058
    AnthonyH
    Participant

    I recently acquired a beautiful 13-piece set of vintage Irwin auger bits in their original box. I’ve bored a few holes and most of the bits approx. 1/64 – 1/32″ oversized. Is this normal?

    Irwin Auger -DM Carpenters Set

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    #133065
    Scott Chensoda
    Participant

    I can’t see how the bits could have widened through sharpening over the years, maybe the original bits have become ‘exchanged’ over time? Perhaps it might be an idea to forget possibilites as to how or why and just drill a set of holes with each bit and re-catalogue the actual as is dimensions even if you have to venture into metric for accuracy. You can then re-mark the holders with the new sizes and use them as they are.

    #133072
    Matt McGrane
    Participant

    I haven’t measured all of my auger bits, but I do recall that the dimension from tip to tip of the cutting edges was a bit oversized on one of mine. I think the dimension of the flutes (behind the cutting edges) were a bit less than nominal. That part makes sense so that the rest of the bit won’t bind in the hole, but I’m not sure why the front end of the bits would be oversized.

    Matt, Northern California - Started a blog in 2016: http://tinyshopww.blogspot.com/

    #133077
    AnthonyH
    Participant

    Thank you for the reply Scott. I must say I am disappointed with these sizes as I paid a pretty penny for them. I have sent an email to the seller inquiring about their performance. I assumed they’d be manufactured spot on their stamped sizes. This why I have asked here because I don’t know what the norm is for Irwin auger bits. I will relegate their use for other than precise drilling.

    Thank you Matt for your response as well. Using a Fowler dial caliper on the #6 (3/8″) bit measures 51/128″ (0.398″) across its diameter, from spur to spur. Additionally, the bit will not fit through a 25/64″ bore in a General Tools Drill Hole Gauge but will fit though the 13/32″ hole.

    I’m new to vintage boring tools, so were auger bits not designed for precise hole drilling? I do enjoy using the bits, just not for precise drilling such as the bores on draw-bore tenons.

    #133084
    FrankM
    Participant

    Could it be possible that the bits are metric and not imperial?

    #133088
    AnthonyH
    Participant

    I’m afraid not Frank. Each one has the appropriate 16th-inch number stamped on its tang.

    #133089
    Greg Merritt
    Participant

    This is common with vintage auger bits. It is also why there used to be auger bits referred to as doweling bits. Those were shorter and exact in diameter to match dowels. There are several theories as to why the standard auger bits were slightly over-size. My personal theory is as follows.
    These bits came in 1/16″ increments. If, for instance, you wanted to insert a 3/4″ bolt thru a piece of wood you had two choices. A 3/4″ or a 7/8″ bit. The 7/8″ would be too sloppy and, if the 3/4″ bit was exact to size, the 3/4″ bit would result in a hole too tight to drive the bolt thru. So the bits were manufactured slightly over-size to accommodate the limited range of 1/16″ increments. That’s my theory anyway.
    So unless you are planning do a lot of dowel work, you should be just fine.

    http://hillbillydaiku.com

    #133091
    AnthonyH
    Participant

    Greg, Thank you very much for the enlightenment. I feel much better knowing that this is normal. Your hypothesis is a rational one. Have a Merry Christmas & Happy New Year.

    #335414
    Jeremy
    Participant

    I know this is a old thread but I finally got a vintage set of Irwin Auger bits and mine are exactly the same. Oversized! I really wanted to try some draw boring with them, but it’s defeats the purpose when a dowel is loose in the hole. Kind of a real bummer. I measured my 1” auger with a caliper and it was 1.015”. Not sure why they did that. I guess I can still use them for drilling out mortise holes but really wanted to fit dowels into the holes they would bore. If anyone’s knows why Irwin did this, I’d like to know.

    #337359
    Larry Geib
    Participant

    It’s not your imagination that the bits are oversized. From the 1954 catalogue:

    “All auger bits, except those made especially for doweling work, are ground approximately 1/64” oversize. This is done so that holes bored for bolts, pipe, cable, etc. can be bored with the same size bit (8/16” hole for a ½” bolt) and a snug fit will result. Dowel bits are made close to actual size so dowels will fit snug.”

    So you don’t have the doweling bits, but the standard oversized ones.

    I’m not sure the doweling bits are made anymore, so when I go to flea markets and I see bits in good condition, I measure them with a pocket calipers. I’ve been trying to get a full set of doweling bits for a while.

    #337376
    Jeremy
    Participant

    Thanks so much Larry. I appreciate the info. That has been bugging me so much. I did some digging around and heard that was normal but could not find out why. Now it all makes sense. I would like to get some doweling bits! It’s a shame they are not made anymore. I can totally use regular bits, I just like using the vintage style now that I have a Brace. Thanks again.

    #337387
    Larry Geib
    Participant

    I just went to the shop and measured my Jennings pattern bits, and the whole set is randomly a couple thou over or under the stamped sizes. My 1”, for instance, measures .996” while my number 12 measures .754” with my cheap digital calipers, which are probably only good to the nearest couple thou.
    functionally, I’d call those both spot on for woodwork.

    ( 1/64”~~ .0156”)

    • This reply was modified 3 years ago by Larry Geib.
    #337505
    Jeremy
    Participant

    True. I could also get better at just making my own dowels anyways to accomadate the differences when I have store bought dowels that don’t fit. Thanks for checking your bits.

    #337506
    Larry Geib
    Participant

    Once you get bigger that about 5/8”, there is another alternative, which is adjustable bits made by several companies over the years and still made by Irwin.

    381A8A62-184C-4920-AA32-1090F013A5C4

    The picture shows an original Clark patent bit followed by two Miller Falls 152 bits with a worm screw adjustment followed by a Miller Falls number 48 on the right.

    They generally came with two cutter that allowed complete adjustment from 5/8 or 11/16 all the way to 3”. Great for door hardware. you could get by with 3-4 smaller fixed size bits and the adjustable one. I always had one in the day chest.

    The snails are usually fine, so they cut well and tolerably well even in hardwoods. The trade off for infinite adjustability is they cut a little slower with only one cutter.
    Irwin makes one with two different size cutters for about $30.
    One with three cutter intended for a drill press ( no brace end diamond) is about $60, but I found all of these for under a tener each. Many times it will only have the cutter in the bit, but sometimes you get lucky.

    If you are going to cut a lot of large holes, get a brace with a 14” throw.

    • This reply was modified 3 years ago by Larry Geib.
    • This reply was modified 3 years ago by Larry Geib.
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