Can't drill a straight hole?

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wrote:

Same reason all handsaws are either set or taper ground.
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On 3/4/11 3:12 PM, Father Haskell wrote:

I'm guessing there may be one type of specialty bit that is as you describe. I'm certainly no expert, but every drill bit I've ever used, save tapered wood bits, are the same exact diameter for the entire length of cutting surface.
I suspect your "bits are generally tapered a few thou" statement is grossly inaccurate.
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Same reason all handsaws are either set or taper ground.
FH:
Again, my understanding departs. If you are using a worn drill bit for measurement, because most abrasion will occur at the tip, it would reason that the wear pattern would progressively erode the diameter from the tip towards the terminus of the cutting surface preceeding the shank. A new, quality, regular twist drill used in machining operations should have a uniform width along its cutting length short of the shank.
How could you simply drill a straight, shallow hole if the drill bit tip were tapered? How could you drill a blind hole for an even interference fit along its length if the drill bit had the described taper? There are second operations to deal with these problems, but why would be a drill bit be designed to necessitate them?
Handsaws are very different animals in many respects. Some have a taper grind for blade clearance plus minimized binding and a reduced tooth set which makes for a cleaner cut along with less binding. Importantly and differently from power drilling apparatus, they have a comparitively feeble human unsteadily driving them, not a reliable motor delivering continuous performance in a fixed line to a cooled tool.
I'd be happy to hear your position on drill taper was endorsed on rcm by machinists with specialty knowledge superior to mine. It is always good to learn something new to lighten the load of my ignorance.
Regards,
Edward Hennessey
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Edward, I agree with you about drill bits not normally being tapered, however, I believe the poster who asserted that meant that the taper was such that the diameter was smaller at the shank end, not the cutting end.
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Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar.org
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LW:
Well, Larry, maybe I misread it. I know that there are, in fact, taper-shank drill bits. But my impression that we were talking about the working length of the tool got a spur from the reference to the working portion of handsaws.
Regards,
Edward Hennessey
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Well, a good quality hand saw IS thicker at the cutting edge compared to the spine.
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Larry Wasserman - Baltimore Maryland - lwasserm(a)sdf. lonestar.org
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LW:
I agree with you as the quote from a post above went:
Handsaws are very different animals in many respects. Some have a taper grind for blade clearance plus minimized binding and a reduced tooth set which makes for a cleaner cut along with less binding.
Yet there are hand saws which are an exception to this rule, which was remarked.
Bought a Bosch flush-cut saw the other day. That's an interesting item, though fairly limited in application.
Regards,
Edward Hennessey

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Same reason all handsaws are either set or taper ground.
If the bit tapered back from the tip chip evacuation would jam and burn the insides of the hole.
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Would an Enco vernier count as a cite? Mine shows the butt end of a 1/2" bit to read 0.005" narrower than the working end.
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wrote:

Would an Enco vernier count as a cite? Mine shows the butt end of a 1/2" bit to read 0.005" narrower than the working end.
On a "brand new" never used drill bit? Bits do wear.
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On 3/5/11 9:55 AM, Leon wrote:

No. You checked one bit. You didn't state a policy by bit manufacturers or manufacturing standard for making bits tapered.

So it's smaller at the end that gets put in the chuck and bigger at the cutting tip? That would make sense. Now you have me thinking.
So where's the good Father Haskell to clarify?
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Verify if you like. Drill a test hole in a piece of aluminum plate. Use the bit for a gauge, see which end has the most play in the test hole. 0.005" should be easily detectable by feel.
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On 3/8/11 7:16 PM, Father Haskell wrote:

What, you couldn't just tell us which end you were talking about?
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I probably have all of one hour's use put into that 1/2" twist bit over the past 10 years. The yellow titanium coating is still intact. My 1/2" brad points see the most use, followed by 1/2" Forstners where I need a clean, flat bottomed pocket hole.
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wrote: snip
Drill a pilot hole before using a cheap bit. Chuck in a steel rod instead of a drill bit to test for square -- bits are usually tapered a few thou to prevent binding, and a longer rod gives you a better reading than a short bit. Test the rod for straightness by rolling it.
Can't say I agree here, roll a standard drill bit on a flat surface, does it roll in a circle or arc? Mine don't. If your hole ends up being wider than the shank of the bit the cutting tip the bit is improperly sharpened or bent.
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Leon:
Here's a readable page:
http://en.wikipedia.org/wiki/Drill_bit_shank
Time to work and regards,
Edward Hennessey
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On 3/2/11 5:49 PM, Father Haskell wrote:

Can you clarify this. Are you talking about the bit being smaller at the check end than the cutting tip? This would make some sense to me and I'll retract the BS if that's the case. :-)
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You have enough info here to get you started. One more note on holding the work. See: http://patwarner.com/holding_the_work.html *************************************************************

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gives errors not enough storage to complete operation
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Best regards
Han
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wrote:

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