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Thread: Making a Spade Bit

  1. #1
    Join Date
    Nov 2007
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    Making a Spade Bit

    I want to make a spade bit (aka a paddle bit), for a special project, and I'm wondering what kind of steel I should start with. Carbon steel, like 1045? Or 4140/4142? Or what? I have access to a heat-treating company, so I can have that process done after I've 'machined it' to the needed size/shape. I figure I'd start with a 1/4" or 5/16" thick flat bar about 6 - 8" long, cut part of it away to form the shaft and then grind three flat spots on it to register in my drill press. Then maybe grind the shape of the paddle end, making the pointed part and the two wings. Then grind the cutting edge on the two wings and the point, then have the whole thing heat treated. Am I on the right track with this process? Has anyone out there ever made a specialized spade bit? And what degree of heat treated do I need to go to?

    Thanks in advance for any help...........

    Walter
    Don't let it bring you down,
    It's only castles burning,
    Just find someone who's turning,
    And you will come around

    Neil Young (with a little bit of emphasis added by me)

    Board member, Gulf Coast Woodturners Association

  2. #2
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    Quote Originally Posted by Walter Mooney View Post
    ... Am I on the right track with this process? Has anyone out there ever made a specialized spade bit?
    I don't know if it will work in your case, but when I want a special size or shaped spade bit I start with an existing spade bit and grind it as needed. This gives me the shaft and hex connection. I don't know about the hardness - most of the spade bits are pretty cheap and don't seem well hardened or made from the best still. For a better bit maybe you could braze a piece of good steel to an existing shaft, shape, then harden the working end.

    JKJ

  3. #3
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    John, thanks. The largest spade bit I can find is 1-1/2", and I need some tapered holes (15* taper) that top-out at 1-3/4", so I can't grind down a store-bought paddle bit. The brazing idea is certainly worth looking into!
    Don't let it bring you down,
    It's only castles burning,
    Just find someone who's turning,
    And you will come around

    Neil Young (with a little bit of emphasis added by me)

    Board member, Gulf Coast Woodturners Association

  4. #4
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    Feb 2008
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    E TN, near Knoxville
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    Quote Originally Posted by Walter Mooney View Post
    John, thanks. The largest spade bit I can find is 1-1/2", and I need some tapered holes (15* taper) that top-out at 1-3/4", so I can't grind down a store-bought paddle bit. The brazing idea is certainly worth looking into!
    Another idea then is to start with a 1.5" spade bit then add metal to the edge by either welding a piece on either side or just by building up a 1/8" weld bead on either side, then grinding it sharp, depending on the material being drilled and how many holes you need to make, of course.

    JKJ

  5. #5
    Join Date
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    How about a large countersink? The angle isn't what you want, however. They are also expensive.
    https://www.mcmaster.com/#countersinks/=17asrfe

    Maybe this one? The angle isn't listed so you'd have to inquire. Still spendy. Scroll to the "Variable Diameter Drill Bit"
    https://www.mcmaster.com/#standard-drill-bits/=17asxo8

    None of the above, however, are meant for wood but could work reasonably well...perhaps....

    Maybe start with some drill rod and machine what you want? This one lists 4 different drill rod metals...might help guide you.
    https://www.mcmaster.com/#drill-rods/=17asuej

    Here is an adjustable spade bit...but it'll cut straight sides. Might be worth it for a start?
    https://www.mcmaster.com/#spade-drill-bits/=17asvmb
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  6. #6
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    i think you may be barking up the wrong tree... the sides of a spade bit do not cut the wood, only the spurs and the bottom edge do. I do not believe you will get your desired results with a spade bit with tapered sides. The sides will scrape and create a mass amount of friction and terrible hole quality if you have enough to power them scraping through the hole. how deep are the holes you need to drill?

    what you really want is a tapered reamer.
    Last edited by Adam Herman; 04-21-2017 at 8:18 PM.

  7. #7
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    http://www.leevalley.com/us/wood/pag...80,42240,53317
    Lee Valley has a cheapER adjustable spade bit.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  8. #8
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    Quote Originally Posted by Adam Herman View Post
    i think you may be barking up the wrong tree... the sides of a spade bit do not cut the wood, only the spurs and the bottom edge do. I do not believe you will get your desired results with a spade bit with tapered sides. The sides will scrape and create a mass amount of friction and terrible hole quality if you have enough to power them scraping through the hole. how deep are the holes you need to drill?
    Well, ASSUMING a spade bit in the 1 3/4" existed, one would have to grind a cutting angle into the sides, of course.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  9. #9
    Join Date
    Jun 2005
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    Shorewood, WI
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    While it's not what you asked, a way to make a tapered hole is to drill a straight hole the size of the small end, and then ream it out to a taper with a separate tool. You could use the 1 1/2" spade bit, followed by a reamer you could make as described here: http://www.greenwoodworking.com/SawS...redReamerPlans

    This reamer gets around the problems with cutting on the edges of a spade bit --the hole tends out of round.

  10. #10
    Join Date
    Nov 2006
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    TX, NM or on the road
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    Drill your hole at the smallest diameter of the taper then with your homemade "Windsor chair reamer" taper it to size.

    How to make a Windsor Chair Reamer. http://chairnotes.blogspot.com/2009/...suit-your.html

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