Counter Sink Drill Bits

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Old 07-18-17, 12:37 PM
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Counter Sink Drill Bits

Don't counter sink drill bits create a cone shaped hole? I have to counter sink a thru bolt with a hex head in a wooden work bench surface so that the top of the bolt is flush with the wooden surface I am dropping it into. Will a counter sink bit that creates a cone shaped hole be OK for this or is there another kind of counter sink bit that should be used for hex head bolts
 
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Old 07-18-17, 12:50 PM
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When you need to countersink hex head bolts..... use a spade bit first to drill the depth of the head. Then drill the hole for the bolt itself.

Keep the spade bit slightly on the smaller size as you'll need to tap the hex head into the wood to keep it from spinning when tightening.

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Carriage bolts also make a good fastener for table tops and workbenches.
No countersinking required.

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Old 07-18-17, 01:36 PM
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Just to add to what Pete said, you might also want to use a washer with your hex bolts. (Don't need them with carriage bolts.) And drill slowly... those spade bits will drill pretty fast and you don't want your countersunk hole to be too deep, so go slow.
 
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Old 07-18-17, 02:00 PM
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What you want is a counter bore, not counter sink. The spade drills mentioned by PJ along with the washers Xsleep mentions are the way to go. They do make counter bore bits if you want accuracy.
 
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Old 07-18-17, 05:45 PM
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difference between counter sink and counter bore

 
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Old 07-18-17, 05:56 PM
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Forstner bits make great flat bottom holes. Drill the counter bore first and the follow up with the regular drill bit.
 
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Old 07-19-17, 02:27 AM
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When you need to countersink hex head bolts..... use a spade bit
Forstner bits make great flat bottom holes
Spade bits are somewhat crude, work OK for decks and pick nick tables, but forstner bits are much more precise for furniture and trim.

Just another right tool for the right application.

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Old 07-19-17, 05:32 AM
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Yes, from the pictures, that looks correct, counterbore. The spade bit should work, no need for the accuracy of a forstner. I assume it's OK for the outer hole created by the spade bit to be a little larger than the head of the thru bolt?
 
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Old 07-19-17, 05:38 AM
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If you need to buy the bits, go for the forstner, it will be useful for later projects. But if you already have the spade drill bits then just use them.
 
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Old 07-19-17, 05:41 AM
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Use the bit that is the same size as your washer. 5/16 = 5/8 and 3/8 = 3/4 if memory serves. (Bolt / spade)
 
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Old 07-19-17, 05:51 AM
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I noticed the spade bits pictured by PJMaxhave a sharp pointed tip, as do they ones I own:

. The Dewalt ones I saw yesterday in the store have a threaded end with a sharp tip:


. What's the difference, does it matter?
 
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Old 07-19-17, 05:59 AM
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Not really!_______________________________________
 
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Old 07-19-17, 06:02 AM
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I have both, the ones pictured at the top are easier to sharpen but the bottom pic [imo] does a better/quicker job.
 
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Old 07-19-17, 06:37 AM
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The threaded tip helps pull the bit forward for faster drilling... not what you want if you only want a shallow hole. But thats why it says 10x faster.
 
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Old 07-19-17, 06:47 AM
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I assume that it would be OK to make the outer hole a little larger than the distance across the hex head of the bolt, e.g. the hex head of the thru bolt is 1/2" across, so I am guessing a 5/8" or 3/4" spade/forstner bit would be best. I'd hate to but a 1/2" bit and then find out the hex head is really 17/32" not 1/2"
 
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Old 07-19-17, 06:57 AM
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Don't forget the size of the washer, that helps prevent the bolt head from digging into the wood.
 
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Old 07-19-17, 07:02 AM
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Ahhh, good thought, I definitely will do that
 
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