I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok? Also HD had some I frame Jergenson sp clamps 36" that are
competitive with buying pipe and ends for pipe clamp. Are the I frame
clamps sturdy enough to glue up a cabinet with I have never used them
before? I have read that the Bessy clamps are best but at $37 and needing
six they will have to wait.

Thanks
Robert R

"Robert Rushing" wrote in message
...
I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six
clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok? Also HD had some I frame Jergenson sp clamps 36" that are
competitive with buying pipe and ends for pipe clamp. Are the I frame
clamps sturdy enough to glue up a cabinet with I have never used them
before? I have read that the Bessy clamps are best but at $37 and needing
six they will have to wait.

Thanks
Robert R


Not quite the answer you're looking for, but I saw these the other day while
looking for something else.

http://www.rockler.com/ecom7/product...cfm?&sku=10277

Of course I'd already bought mine for Crappy Tire.

"Robert Rushing" wrote in
:

I'm in need of some clamps. I was looking at pipe clamps and have a
few questions. I will be gluing up a small cabinet and need atleast
six clamps. Working in the 36 to 48" range is 3/4 pipe clamp necessary
are will a 1/2 work ok? Also HD had some I frame Jergenson sp
clamps 36" that are competitive with buying pipe and ends for pipe
clamp. Are the I frame clamps sturdy enough to glue up a cabinet with
I have never used them before? I have read that the Bessy clamps are
best but at $37 and needing six they will have to wait.

Thanks
Robert R

There was a recent review on clamps in one of the woodworking magazines, I
believe Fine Woodworking. Worth reading ...



--
Best regards
Han
email address is invalid

My original pipe clamp is 1/2" and more recent acquisitions are 3/4"
and there is little comparison. I was shocked when I saw the 1/2" bow
when in use.

On Sat, 4 Sep 2004 22:33:30 -0500, "Robert Rushing"
wrote:

Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok?

Latest issue of Fine Woodworking reviews all sorts of clamps. The
Rockelrs got high marks.

"Robert Rushing" wrote in message ...
I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok? Also HD had some I frame Jergenson sp clamps 36" that are
competitive with buying pipe and ends for pipe clamp. Are the I frame
clamps sturdy enough to glue up a cabinet with I have never used them
before? I have read that the Bessy clamps are best but at $37 and needing
six they will have to wait.

Thanks
Robert R

HF has 1/2" pipe clamps on sale for $2 for the next couple of weeks. They
had two left when I was there yesterday. They are now in my garage. Can
never have enough clamps.

"Never Enough Money" wrote in message
om...
Latest issue of Fine Woodworking reviews all sorts of clamps. The
Rockelrs got high marks.

"Robert Rushing" wrote in message
...
I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six
clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok? Also HD had some I frame Jergenson sp clamps 36" that are
competitive with buying pipe and ends for pipe clamp. Are the I frame
clamps sturdy enough to glue up a cabinet with I have never used them
before? I have read that the Bessy clamps are best but at $37 and
needing
six they will have to wait.

Thanks
Robert R

"Bob Peterson" wrote in message
"Robert Rushing"
Also HD had some I frame Jergenson sp clamps 36" that are
competitive with buying pipe and ends for pipe clamp. Are the I frame
clamps sturdy enough to glue up a cabinet with I have never used them
before? I have read that the Bessy clamps are best but at $37 and
needing
six they will have to wait.

Jorgenson has a couple of lines of clamps. The Cabinet Master look pretty
good. The others, IMO, are OK, but not as nice as a Bessey F style clamp.
They should do the job though, just not as smooth as the better clamps.
Some of the models have rubber pads, others don't. Coastal Tools
www.coastaltool.com The 36" clamp is $11.95 and the pads are $2.25. OTOH,
they carry the Bessey Tradesman at $14.50 and it has the rubber pads.

They just don't seem to have the fit and finish of a Bessey.
Ed

On Sat, 4 Sep 2004 22:33:30 -0500, "Robert Rushing"
calmly ranted:

I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok? Also HD had some I frame Jergenson sp clamps 36" that are
competitive with buying pipe and ends for pipe clamp. Are the I frame
clamps sturdy enough to glue up a cabinet with I have never used them
before? I have read that the Bessy clamps are best but at $37 and needing
six they will have to wait.

I love the Pittsburgh bar clamps at www.harborfreight.com
which go on sale 3 or 4 times a year (but not right now).
36" is their largest steel bar clamp, or go 48" in aluminum.
Lifetime warranty, I haven't needed it yet.

1/2" pipe is heavy-duty enough because you don't need that
much force if the joint is prepared properly.
http://www.harborfreight.com/cpi/cta...emnumber=37056
Do you have a Harbor Fright store close to you?

$18 for clamps ($2.99 a pop)
$27 for 3 10' lengths of 1/2" pipe at your local pipe supply
Saw them in half and have six 5' pipe clamps for under $50.


================================================== ========
CAUTION: Do NOT look directly into laser with remaining eyeball!
================================================== ========
http://www.diversify.com Comprehensive Website Design

In article ,
Larry Jaques wrote:
...
I love the Pittsburgh bar clamps at www.harborfreight.com
which go on sale 3 or 4 times a year (but not right now).
36" is their largest steel bar clamp, or go 48" in aluminum.
Lifetime warranty, I haven't needed it yet.

I just got a flier from HF which has the bar clamps at half price. $5.99 for
the 36" ones - $2.49 for the 12" ones, etc.. (sale ends sept 27)

...
--
--henry schaffer
hes _AT_ ncsu _DOT_ edu

I see two advantages of pipe clamps over something like the Bessey K-bodies.
First is price. For the price of one 50" Bessey K-body you can probably get
4 3/4 inch pipe clamps and pipe.

Second, with pipe clamps you can alter the length to fit the situation. You
just buy different lengths of pipe and switch them out as needed. I had a
project a few months ago that needed a couple of 8 foot clamps. All I had
to do was buy a couple of cheap pieces of 8' black pipe, take the pipe
clamps off of the short pipes, screw them on the long pipes, and walla.
That also works in reverse. I had another project that needed a lot of
short clamps. I put 2' pieces of pipe on my pipe clamps and used them. But
I still didn't have enough short clamps and wound up having to use some long
40" and 50" Bessey k-body clamps. For that particular project, the length
of the K's was a PITA, and there was no sane way to make them shorter. To
go along with that I must say this. My pipe clamps are for 1/2 inch pipe.
When used on the 8' sections of pipe, they REALLY bent. I had to take some
steps to try and counteract the bend (wedges), but they did get the job
done. A 3/4 inch pipe would have been MUCH better.

So to finally answer your question directly, if you can possibly afford it,
get good quality clamps such as the Bessey K-body clamps. The parallel
clamping action of the jaws is a good thing. If you have/want to use pipe
clamps, get the 3/4". The versatility and price will be good. Or do both.

Wayne




"Robert Rushing" wrote in message
...
I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six
clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok? Also HD had some I frame Jergenson sp clamps 36" that are
competitive with buying pipe and ends for pipe clamp. Are the I frame
clamps sturdy enough to glue up a cabinet with I have never used them
before? I have read that the Bessy clamps are best but at $37 and needing
six they will have to wait.

Thanks
Robert R

The new clamps that Rockler sells are nice. I plan on adding some to my
collection. Look at:
http://www.rockler.com/ecom7/product...=pipe%20clamps

Or go to Rockler.com and type in pipe clamps in the search box. The sure
foot clamps raise the clamps off the workbench and they also have a nice
hanging attachment built in.

On Sat, 4 Sep 2004 22:33:30 -0500, "Robert Rushing"
wrote:

I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok?

No disrespect intended to those who say 1/2 inch clamps bend under
use, but I've not had that experience.

The clamping force necessary to edge glue boards together isn't
anywhere near the amount exerted by 1/2" clamps, so in that
application 3/4" clamps are overkill.

I suppose it's possible to bend 1/2 inch clamps by yoinking hard
enough on them to try to straighten badly out-of-square casework
carcasses, but before I loaded up on 3/4 inch clamps I think I'd spend
the time adjusting my machinery and my technique so that the joints
I'm gluing up are square to begin with.

Fwiw, I've got a rack full of cheaper'n'dirt HF 1/2" clamps that have
done everything I've asked of them. Yeah, they can be frustrating at
times but you can't beat em for bang-for-the-buck.

Part of it's a space issue, too. Since my workbench/outfeed table/
table saw is also my "assembly table", anything I clamp up has to be
moved. Which means it needs to be picked up. By _me._ Know how much
8 pieces of 3/4" pipe, each 4' long, _weighs?_ Add to that the weight
of the project, and it's a lot of damn weight to be picking up and
carefully avoiding hitting things with. Just something to consider.

Michael

If you want to save money on good clamps:

http://www.pennstateind.com/Merchant...gory_Co de=CL

I got a bunch of their stuff and it is all good, expecially the price.

Right now, free shipping on an order of $100.

Be sure and check out thier "web specials" They put stuff on sale all
the time.

I have not bought a clamp in a retail store in years.

Robert Rushing wrote:
I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok? Also HD had some I frame Jergenson sp clamps 36" that are
competitive with buying pipe and ends for pipe clamp. Are the I frame
clamps sturdy enough to glue up a cabinet with I have never used them
before? I have read that the Bessy clamps are best but at $37 and needing
six they will have to wait.

Thanks
Robert R

Clamps bend whether they be Bessie or elcheapo HFs they bend. That is part
of the clamping power of clamps that they bend and create tension in the
clamp. The amount of bend depends on the type and length of the clamp.
Take a bar/pipe clamp and tighten it just enough to barely hold, draw a line
along the bar/pipe, tighten the clamp and watch the deflection from the
line. If a clamp bends too much to use it is either too tight or the wrong
clamp for the job
No disrespect intended to those who say 1/2 inch clamps bend under
use, but I've not had that experience.

The clamping force necessary to edge glue boards together isn't
anywhere near the amount exerted by 1/2" clamps, so in that
application 3/4" clamps are overkill.

I suppose it's possible to bend 1/2 inch clamps by yoinking hard
enough on them to try to straighten badly out-of-square casework
carcasses, but before I loaded up on 3/4 inch clamps I think I'd spend
the time adjusting my machinery and my technique so that the joints
I'm gluing up are square to begin with.

I extend mine using couplings and short pipe lengths.

On Sun, 05 Sep 2004 23:16:24 GMT, "NoOne N Particular"
wrote:

Second, with pipe clamps you can alter the length to fit the situation. You
just buy different lengths of pipe and switch them out as needed.

On Mon, 06 Sep 2004 15:12:10 GMT, "Sweet Sawdust"
wrote:

Clamps bend whether they be Bessie or elcheapo HFs they bend.

Okay, fair enough. This is the internet and I didn't spell it out.
I should have specified "I haven't had 1/2" pipe clamps bend enough to
cause whatever is being clamped to be thrown out of square or buckle
from uneven pressure."

3/4" is overkill. And heavy as hell. Did I mention they weigh a ton,
too?

Best,
Michael "wimpy" Baglio
Who's thinking maybe those spanish luthiers have the right idea by
clamping everything with stick-twisted ropes. ;

Michael Baglio wrote in
:

3/4" is overkill. And heavy as hell. Did I mention they weigh a ton,
too?

Best,
Michael "wimpy" Baglio
Who's thinking maybe those spanish luthiers have the right idea by
clamping everything with stick-twisted ropes. ;

I'll agree that there is a right clamp for most jobs, and using the wrong
one is 'sub-optimal'. I'll also agree that there are a lot of really cool
processes and tools that luthiers use, which would be applicable to the
furniture and jewelry boxes, which make up most of what I attempt these
days.

There is certainly nothing wrong from learning a lesson from 'the other
folks' whenever we can.

Patriarch,
who's thinking there are times when 3/4" may be heavy, but perhaps still
not enough for some projects.

I have been cleaning up my workshop/garage lately. last night I counted up
my clamps.

I have 50 spring type clamps of various sizes, but only about 30 clamps of
other type. Amazing how one accumulates such things over time. i would
never have guessed I had more than 80 clamps.

"Michael Baglio" wrote in message
...
On Sat, 4 Sep 2004 22:33:30 -0500, "Robert Rushing"
wrote:

I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six
clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok?

No disrespect intended to those who say 1/2 inch clamps bend under
use, but I've not had that experience.

The clamping force necessary to edge glue boards together isn't
anywhere near the amount exerted by 1/2" clamps, so in that
application 3/4" clamps are overkill.

I suppose it's possible to bend 1/2 inch clamps by yoinking hard
enough on them to try to straighten badly out-of-square casework
carcasses, but before I loaded up on 3/4 inch clamps I think I'd spend
the time adjusting my machinery and my technique so that the joints
I'm gluing up are square to begin with.

Fwiw, I've got a rack full of cheaper'n'dirt HF 1/2" clamps that have
done everything I've asked of them. Yeah, they can be frustrating at
times but you can't beat em for bang-for-the-buck.

Part of it's a space issue, too. Since my workbench/outfeed table/
table saw is also my "assembly table", anything I clamp up has to be
moved. Which means it needs to be picked up. By _me._ Know how much
8 pieces of 3/4" pipe, each 4' long, _weighs?_ Add to that the weight
of the project, and it's a lot of damn weight to be picking up and
carefully avoiding hitting things with. Just something to consider.

Michael

There are several things that woodworkers never have enough of. Time,
money, wood, space, ideas, tools, etc. And clamps is way up there on the
list.

Wayne

"Bob Peterson" wrote in message
...
I have been cleaning up my workshop/garage lately. last night I counted
up
my clamps.

I have 50 spring type clamps of various sizes, but only about 30 clamps
of
other type. Amazing how one accumulates such things over time. i would
never have guessed I had more than 80 clamps.

"Michael Baglio" wrote in message
...
On Sat, 4 Sep 2004 22:33:30 -0500, "Robert Rushing"
wrote:

I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six
clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a
1/2
work ok?

No disrespect intended to those who say 1/2 inch clamps bend under
use, but I've not had that experience.

The clamping force necessary to edge glue boards together isn't
anywhere near the amount exerted by 1/2" clamps, so in that
application 3/4" clamps are overkill.

I suppose it's possible to bend 1/2 inch clamps by yoinking hard
enough on them to try to straighten badly out-of-square casework
carcasses, but before I loaded up on 3/4 inch clamps I think I'd spend
the time adjusting my machinery and my technique so that the joints
I'm gluing up are square to begin with.

Fwiw, I've got a rack full of cheaper'n'dirt HF 1/2" clamps that have
done everything I've asked of them. Yeah, they can be frustrating at
times but you can't beat em for bang-for-the-buck.

Part of it's a space issue, too. Since my workbench/outfeed table/
table saw is also my "assembly table", anything I clamp up has to be
moved. Which means it needs to be picked up. By _me._ Know how much
8 pieces of 3/4" pipe, each 4' long, _weighs?_ Add to that the weight
of the project, and it's a lot of damn weight to be picking up and
carefully avoiding hitting things with. Just something to consider.

Michael

I have some of each. Got the 1/2" when I was young and broke. I still
find uses for them from time to time. Unless the above description fits
(young and broke) you can use a 3/4 for anything you'd use a 1/2 for but
not necessarily the reverse. I picked up a few 3/4 sets from Rockler a
while back that have the bracket on the back that keeps the jaws level.
I also have a few bar clamps of various types. Have you been thinking
about Besseys? Pipe clamps have the advantage that in an unexpected
situation you can use very long pipes, you can use couplers, you get the
idea. A few are always nice to have around. Other things being equal,
I'd go with the 3/4.

rhg

Robert Rushing wrote:
I'm in need of some clamps. I was looking at pipe clamps and have a few
questions. I will be gluing up a small cabinet and need atleast six clamps.
Working in the 36 to 48" range is 3/4 pipe clamp necessary are will a 1/2
work ok? Also HD had some I frame Jergenson sp clamps 36" that are
competitive with buying pipe and ends for pipe clamp. Are the I frame
clamps sturdy enough to glue up a cabinet with I have never used them
before? I have read that the Bessy clamps are best but at $37 and needing
six they will have to wait.

Thanks
Robert R

Han wrote in message ...

There was a recent review on clamps in one of the woodworking magazines, I
believe Fine Woodworking. Worth reading ...

Just saw it in the rack today: it was FWW, and looked like a very
complete review covering pipe, bar and other cabinet-type clamps,
(even the new blue ones that the blue Borg is selling--Kobalt?). BTW,
I saw those for the first time today also and they look real sturdy,
but I didn't get the mag yet so don't know what the reviewer thought.

Dan

On Mon, 06 Sep 2004 21:56:51 GMT, Michael Baglio
wrote:

On Mon, 06 Sep 2004 15:12:10 GMT, "Sweet Sawdust"
wrote:

Clamps bend whether they be Bessie or elcheapo HFs they bend.

Okay, fair enough. This is the internet and I didn't spell it out.
I should have specified "I haven't had 1/2" pipe clamps bend enough to
cause whatever is being clamped to be thrown out of square or buckle
from uneven pressure."

I have.

'course, those 10 footer 1/2" pipe clamps bow if you just look at them
hard...




3/4" is overkill. And heavy as hell. Did I mention they weigh a ton,
too?

not only that, but they weigh a lot.




Best,
Michael "wimpy" Baglio
Who's thinking maybe those spanish luthiers have the right idea by
clamping everything with stick-twisted ropes. ;

the tighter you get it, the straighter they get...

On Tue, 07 Sep 2004 17:49:58 -0700, wrote:

On Mon, 06 Sep 2004 21:56:51 GMT, Michael Baglio
wrote:

Okay, fair enough. This is the internet and I didn't spell it out.
I should have specified "I haven't had 1/2" pipe clamps bend enough to
cause whatever is being clamped to be thrown out of square or buckle
from uneven pressure."

I have.
'course, those 10 footer 1/2" pipe clamps bow if you just look at them
hard...

10 footers? Yikes, you must moonlight in Plamman's shop. In my
12X16 shop-ette, if I need 10 footers I string a couple of 6's
together. (Like _that_ would ever actually happen, since building
something requiring that much pipe wouldn't actually _fit_ in my
shop.)

Seriously, though, is anyone regularly bending 1/2" pipe when gluing
up tabletops or smaller casework? Iirc, the force necessary to glue
hardwoods together is about 250#/sq.inch, and although I can't
remember what the clamping force of 1/2" pipe is, I think it's
somewhere in the range of "a farking butt-load."

Michael "all figures approximate" Baglio

On Wed, 08 Sep 2004 13:40:36 GMT, Michael Baglio
wrote:

On Tue, 07 Sep 2004 17:49:58 -0700, wrote:

On Mon, 06 Sep 2004 21:56:51 GMT, Michael Baglio
wrote:

Okay, fair enough. This is the internet and I didn't spell it out.
I should have specified "I haven't had 1/2" pipe clamps bend enough to
cause whatever is being clamped to be thrown out of square or buckle
from uneven pressure."

I have.
'course, those 10 footer 1/2" pipe clamps bow if you just look at them
hard...

10 footers? Yikes, you must moonlight in Plamman's shop. In my
12X16 shop-ette, if I need 10 footers I string a couple of 6's
together. (Like _that_ would ever actually happen, since building
something requiring that much pipe wouldn't actually _fit_ in my
shop.)

Seriously, though, is anyone regularly bending 1/2" pipe when gluing
up tabletops or smaller casework? Iirc, the force necessary to glue
hardwoods together is about 250#/sq.inch, and although I can't
remember what the clamping force of 1/2" pipe is, I think it's
somewhere in the range of "a farking butt-load."

Michael "all figures approximate" Baglio



actually, yeah, one reason of many I prefer bar clamps over pipe
clamps is the flex thing. the jaws are shallow- not much reach- and
pipe is less stiff for it's section than I beam or even flat bar. I
mostly build cabinets and for the most part my clamps over 3 foot are
pipe clamps.

snippage
Seriously, though, is anyone regularly bending 1/2" pipe when gluing
up tabletops or smaller casework? Iirc, the force necessary to glue
hardwoods together is about 250#/sq.inch, and although I can't
remember what the clamping force of 1/2" pipe is, I think it's
somewhere in the range of "a farking butt-load."


True that if our jointery is perfect, you shouldn't need much clamping
pressure. But what if you should screw up . . .er. . .I mean if your joints
are a little less than optimal? You just might need a farking but-load of
clamping force. Or if your wood has a slight twist, warp, or cup. Not
everyone can afford the luxury of thickness planers and jointers, etc., and
not all wood is flat and straight.

I cannot remember having 2' or 3' pipe clamps bend enough to be a problem
(using 1/2" pipe), but I have had 4' sections bend a little. And there are
even some possible cases where the bend can be beneficial. For exmple, I
was building a shelf unit that had dadoes cut in the sides and back for
shelves. When I used a clamp across the back of the carcass, it bent and
actually helped to keep pressure on the center of the shelf itself. In
other words, it made sure that the back did not bow outward away from the
shelf. But overall, I would say that the stiffer the clamps the better so
go with 3/4" pipe.

Wayne

On Thu, 09 Sep 2004 16:55:24 GMT, "NoOne N Particular"
wrote:

True that if our jointery is perfect, you shouldn't need much clamping
pressure. But what if you should screw up . . .er. . .I mean if your joints
are a little less than optimal? You just might need a farking but-load of
clamping force.

Or the patience to re-do the "less than otimal" workmanship so
excessive force is unnecessary. To each his own. "If it doesn't fit,
use a bigger hammer" is something it took me a long time to outgrow,
so I really understand.

Or if your wood has a slight twist, warp, or cup. Not
everyone can afford the luxury of thickness planers and jointers, etc., and
not all wood is flat and straight.

In my original reply I was careful to say that I thought 3/4 to be
overkill for "fine woodworking."

We're talking about two different types of building here. If I'm
using undressed lumber that's crooked, bowed, warped and/or cupped,
I'm generally building outdoor play equipment and lawn furniture, not
furnishings for my home.

I've done a bit of that, and I've used the scissors jack out of my car
as a clamp, (or, more accurately, a spreader), too. The right "tool"
for the job, eh?

Michael Baglio
Hope I used enough smileys.

Speaking of 3/4" pipe clamps, HF has the deep jaw ones on sale for $6.

"NoOne N Particular" wrote in message
. com...
snippage
Seriously, though, is anyone regularly bending 1/2" pipe when gluing
up tabletops or smaller casework? Iirc, the force necessary to glue
hardwoods together is about 250#/sq.inch, and although I can't
remember what the clamping force of 1/2" pipe is, I think it's
somewhere in the range of "a farking butt-load."


True that if our jointery is perfect, you shouldn't need much clamping
pressure. But what if you should screw up . . .er. . .I mean if your
joints
are a little less than optimal? You just might need a farking but-load of
clamping force. Or if your wood has a slight twist, warp, or cup. Not
everyone can afford the luxury of thickness planers and jointers, etc.,
and
not all wood is flat and straight.

I cannot remember having 2' or 3' pipe clamps bend enough to be a problem
(using 1/2" pipe), but I have had 4' sections bend a little. And there
are
even some possible cases where the bend can be beneficial. For exmple, I
was building a shelf unit that had dadoes cut in the sides and back for
shelves. When I used a clamp across the back of the carcass, it bent and
actually helped to keep pressure on the center of the shelf itself. In
other words, it made sure that the back did not bow outward away from the
shelf. But overall, I would say that the stiffer the clamps the better so
go with 3/4" pipe.

Wayne