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msherman95632(at)yahoo.co
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 Posted: Sat Aug 12, 2006 6:57 pm Post subject: Pilot Holes |
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Tom H.
Drilling a pilot hole for accuracy of position is only
half the reason for a pilot hole. A two flute drill
will drill a triangle shaped hole until the drill's
lands are into the hole. This is difficult in sheet
metal because it is so thin, you usually end up with a
less than round hole and oversize. That is part of
the reason Zenith uses the cs rivets, it fills the
oversized hole with rivet material and then forms the
head. Drilling a pilot hole first lets the next size
drill produce a much rounder and more accurate size
hole. All this makes for a better fit and stronger
joint for the rivet.
Do you have to do this? Nope, it's your airplane. You
can fill those oversized out of shape holes with
rivets all day long. And then the next time you hit
some turbulence wonder how many rivets are wallowing
around in those oversized holes.
Mark S.
701/912S
Painting in CA
I always found drilling a pilot hole was like
digging a post hole a little too small, then going
back to dig it the right size. If you're careful with
a drill, you won't be off more than .010". If you
notice that, you're FAR too much a perfectionist to be
building this plane. LOL
Do Not Archive
Jaybannist(at)cs.com wrote:Bill, You mentioned that you
have never used silver clecoes. I have found (upon
advice from ZAC) that a #40 drill bit is a lot easier
to control accurately than is a #30 or, especially a
#20. All the predrilled holes in the kit are #40. I
nearly always drill #40 holes and set silver clecoes
to be later drilled out when everything is in place.
Sometimes I will start with a #30 if the plans call
for a 1/8" rivet. Also, if the #40 holes somehow get
slightly misaligned, overdrilling with a #20 will get
them aligned again without any "snowman" holes. FWIW
Jay in Dallas
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admin(at)arachnidrobotics
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| Posted: Sat Aug 12, 2006 8:45 pm Post subject: Pilot Holes |
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You're correct in your reply, but you're not giving the members of this list enough credit. : ) Two flute bits would not be my first choice, although they work just fine as you have mentioned. If one's rivets are "wallowing", I would say you didn't use the correct rivets in the first place. As you mention, the design allows for slightly oversized or out-of-round holes.
At any rate, a better bet for drill bits would be the one below. It's simple a 3 flute bit with a 118 Degree tip instead of the standard 150 Degree tip. Three flutes tend to cut a smoother hole, and the 118 Degree tip prevents the bit from 'walking' out of place. MUCH faster than drilling pilot holes.
[img]cid:part1.05060608.01030504(at)arachnidrobotics.com[/img]
But then again, there isn't anything wrong with drilling pilot holes if you don't mind it. I think this is just a case of there being at least two ways to skin a dead cat. Same goes for airplanes...
Mark Sherman wrote: | Quote: | | Quote: | --> Zenith-List message posted by: Mark Sherman <msherman95632(at)yahoo.com> (msherman95632(at)yahoo.com)
Tom H.
Drilling a pilot hole for accuracy of position is only
half the reason for a pilot hole. A two flute drill
will drill a triangle shaped hole until the drill's
lands are into the hole. This is difficult in sheet
metal because it is so thin, you usually end up with a
less than round hole and oversize. That is part of
the reason Zenith uses the cs rivets, it fills the
oversized hole with rivet material and then forms the
head. Drilling a pilot hole first lets the next size
drill produce a much rounder and more accurate size
hole. All this makes for a better fit and stronger
joint for the rivet.
Do you have to do this? Nope, it's your airplane. You
can fill those oversized out of shape holes with
rivets all day long. And then the next time you hit
some turbulence wonder how many rivets are wallowing
around in those oversized holes.
Mark S.
701/912S
Painting in CA
I always found drilling a pilot hole was like
digging a post hole a little too small, then going
back to dig it the right size. If you're careful with
a drill, you won't be off more than .010". If you
notice that, you're FAR too much a perfectionist to be
building this plane. LOL
Do Not Archive
Jaybannist(at)cs.com (Jaybannist(at)cs.com) wrote:Bill, You mentioned that you
have never used silver clecoes. I have found (upon
advice from ZAC) that a #40 drill bit is a lot easier
to control accurately than is a #30 or, especially a
#20. All the predrilled holes in the kit are #40. I
nearly always drill #40 holes and set silver clecoes
to be later drilled out when everything is in place.
Sometimes I will start with a #30 if the plans call
for a 1/8" rivet. Also, if the #40 holes somehow get
slightly misaligned, overdrilling with a #20 will get
them aligned again without any "snowman" holes. FWIW
Jay in Dallas
__________________________________________________
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