Help with augur bits

  • Creator
    Topic
  • #553573
    Dinabandhu MitraDinabandhu Mitra
    Participant

    Hi,

    I have bought a set of used augur bits (Gilpin) and a hand brace (Stanley) off ebay. I am facing a problem with some of the bits. Some of the bits start drilling fine but after hole advances 1/4-1/2 inch the bit stops cutting and just scrapes dust. When this happens the torque needed to turn the brace becomes almost nil. I tried sharpening after watching Paul’s video but no luck. I am a newbie and bit hesitant to file too much just in case I damage the bits. This is not happening with all bits of the set but just a few, mostly larger ones.

    If any one can give some pointers on what is wrong, it would be a great help.

Viewing 10 replies - 1 through 10 (of 10 total)
  • Author
    Replies
  • #553576
    Keith WaltonKeith Walton
    Participant

    @keithmw

    are the snails in good shape?

    #553582
    Selva NairSelva Nair
    Participant

    @selva

    Apologies for the noise — that was not meant for this thread. Deleting..

    • This reply was modified 4 months, 3 weeks ago by Selva NairSelva Nair. Reason: mistakenly posted to a wrong thread
    #553583
    Dinabandhu MitraDinabandhu Mitra
    Participant

    @dinbandhu

    Hi Keith, the snail looks ok to me. At the starting the snail is pulling the bit very nicely into the wood and the bits cuts also fine. The problem starts only after the bit goes into the hole some distnce. I also thought that snail might be an issue (though they look ok) but in that case shouldn’t I have the problem right from the beginning? Thanks a lot for taking interest in this.

    #553591
    Larry GeibLarry Geib
    Participant

    @lorenzojose

    Gilpin made a couple types of auger bits, and they cut differently.

    They made bits that are indistinguishable from a Jennings pattern bit, but they also made “looped” spur bits that cut more like a gouge. These were very rare in the USA.

    In both cases, it’s usually a dull or too-short spur that is the issue.

    Post a picture of the cutting ends of a couple of your bits that don’t cut well and maybe I can give a hint as to what might be preventing your style from working well.

    Also:
    If you have calipers, make sure the bit diameter is consistent. Sometimes the bits are mistakenly sharpened from the outside, which reduces the diameter at the tip and causes the bit to bind as it enters the hole.

    The only fix then is to reduce the diameter of the rest of the helix – not easy.

    #553592
    Larry GeibLarry Geib
    Participant

    @lorenzojose

    Gilpin made a couple types of auger bits, and they cut differently.

    They made bits that are indistinguishable from a Jennings pattern bit, but they also made “looped” spur bits that cut more like a gouge. These were very rare in the USA.

    In both cases, it’s usually a dull or too-short spur that is the issue.

    Post a picture of the cutting ends of a couple of your bits that don’t cut well and maybe I can give a hint as to what might be preventing your style from working well.

    Also:
    If you have calipers, make sure the bit diameter is consistent. Sometimes the bits are mistakenly sharpened from the outside, which reduces the diameter at the tip and causes the bit to bind as it enters the hole.

    The only fix then is to reduce the diameter of the rest of the helix – not easy and probably not worth the trouble.

    #553610
    Dinabandhu MitraDinabandhu Mitra
    Participant

    @dinbandhu

    Hi Larry, Thank a lot for detail response. I have attached some photos of the two bits that are giving problem. The bit on the right side seems to have a slight filing mark on the outside just at the tip. Please check the first photo. I am a very poor photographer so the photos are not very good. I did have a digital caliper but that unfortunately stopped working sometime back. I am yet to buy another one. Any help or tips you can give would be great.

    Attachments:
    #553621
    markhmarkh
    Participant

    @markh

    All the digital calipers rely on a round button variety battery – it is usually easily replaced. It could tell you more about the bits than we can from a distance. I can’t see why the one in the left of photo 115525 shouldn’t work, especially if the leading edge of the spurs was given a little bit of a filing to sharpen it. The one on the right of this photo looks like a spur-less bit which was meant for rough work. But even so, it should work if the cutting edges are sharp. It just wont leave a clean exit hole.
    Cheers
    Mark

    #553671
    Dinabandhu MitraDinabandhu Mitra
    Participant

    @dinbandhu

    Hi Mark, Thanks for your response. The battery is not the issue for the calliper, I had it changed already. It has some other problem. The displayed measurement keeps rapidly and wildly changing. I will buy another one but this time I want to buy a good quality one and as those are somewhat expensive, can’t buy right now (hobby budget 🙁 ).

    That said, I can go to a local lathe shop and request them to get some measurements using their callipers. Could you please tell me what should I measure or check? Is it only consistency of diameter? Is there anything else?

    The bit on the right also has a spur but the spar is somewhat shorter than the other bits and the angle of the photograph makes it difficult to see. Now that you pointed this out, I think that it is probably not a Gilpin bit at all. Markings at the shank of that bit are not readable (pitting/rust mark). My guess is that some bits were originally missing from the set and the ebay seller just put in some other bits and claimed the whole set to be Gilpin.

    Thanks again for your help.

    #553682
    markhmarkh
    Participant

    @markh

    Yes, it is consistency of diameter, if you believe that someone has ground the outer circumference of the spiral. I don’t happen to think that is the problem in your case. It will be something to do with the two cutting edges and possibly the spurs. Are the two cutting edges co-planar across the cutting face? Are the cutting edges actually sharp? Compare the poorly cutting bits to the good bits – is there a difference of angle at the cutting edge? (as in bevel angle) To understand the geometry of the cutting edges on brace auger bits I can only recommend a book like Aldren Watson’s “Hand Tools: Their Ways and Workings”. His sketched diagrams are so good at explaining how the cutting edges of the tools actually work – so much better than photographs. His section on Brace auger drills is excellent and page 56 and 60 would set you right on the cutting action of the brace auger I believe. I can’t supply these pages sadly as my scanner is out of action right now. But Watson does say that with the larger diameter auger bits you must supply a much larger downwards force to the bit through the bow. He also indicates that the condition of the spurs (he calls then flukes) and lead screw does play a significant part in successful drilling in the larger diameters. Try applying a lot of force to the drill as you are making a few more test holes – if that doesn’t work and there isn’t something obviously wrong with the cutting edges of the bit, then maybe you need to consider it a worn out bit and replace it.

    When buying auger bit sets remember that only relatively few augers get used regularly out of sets and they get blunt/broken/replaced more often. When I think of my own twist drill set and how many of the bits have been replaced over the years (especially the smaller ones). It may be that the original owner replaced the auger bit in the set long ago- before the eBay seller even came upon the scene. Having said that, some ebay sellers are not exactly honest (or even knowledgeable) about what it is they are selling. You might be better off looking for a specific size auger bit and replacing just that one. Especially if most of the other bits in the set are acceptable.

    Cheers
    Mark

    #553685
    Dinabandhu MitraDinabandhu Mitra
    Participant

    @dinbandhu

    Hi Mark,

    Thanks a lot.

    Sharpening may be an issue indeed as I am fairly new to this and not very skilled. Quite possible that my hand on the file is not steady and I am changing the geometry of the cutting edge in a bad way. I will try again. Also I was not really putting too much downward pressure assuming that the snail would pull the bit in. So I will try increasing the push. I will also get the book and read it. Hopefully that would help as well.

    If nothing works, then I would buy the individual bits.

    I appreciate your help very much.

Viewing 10 replies - 1 through 10 (of 10 total)

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