Clamp Time For Glue
Tom Watson
time.
I pretty much have a habit of leaving everything clamped up overnight
in conditioned space that is ideally 72/50, or 72 degrees at 50%
relative humidity.
So, for somewhat less than ideal conditions you adjust a little bit.
I worked in a stair shop for about six months and they would take flat
panels out of clamps after an hour and run them through the Timesaver.
I don't hold with that but that is a feeling and it doesn't reference
anything empirical.
When running my own cabinet shop I never took things out of clamps
unless they had sat overnight. That was in the day of mortice and
tenon joinery without additional mechanical help.
When I switched to using pocket screws as a hidden helper on the
joints I would take the clamps off immediately. I know longer feel
that is appropriate for things like doors that will enjoy hig stress
during their lives. It seems to me that they need to sit in situ
until the chemistry is complete enough to give them the maximum chance
of survival.
Many of the glue bottles suggest a clamp time of from 30 minutes to 60
minutes.
It seems to me that a complex glue up, like a dowelled chair, where
you are 'encouraging' imperfect fits to do your bidding have needs
greater than this.
Once again, this is a matter of feel and not backed by data.
I've checked my Hoadley and looked at Forest Products Laboratory but
I'm not finding the definitive stuff that I am looking for.
What I'm interested in is things like shear strength v. time and
tension strength v. time for the typical PVA and A resin glues that we
all use.
If someone can point me to data on this, it would be much appreciated.
Regards,
Tom Watson
http://home.comcast.net/~tjwatson1/
dpb
...
> When I switched to using pocket screws as a hidden helper on the
> joints I would take the clamps off immediately. I know longer feel
> that is appropriate for things like doors that will enjoy hig stress
> during their lives. It seems to me that they need to sit in situ
> until the chemistry is complete enough to give them the maximum chance
> of survival.
>
> Many of the glue bottles suggest a clamp time of from 30 minutes to 60
> minutes.
>
> It seems to me that a complex glue up, like a dowelled chair, where
> you are 'encouraging' imperfect fits to do your bidding have needs
> greater than this.
>
> Once again, this is a matter of feel and not backed by data.
>
> I've checked my Hoadley and looked at Forest Products Laboratory but
> I'm not finding the definitive stuff that I am looking for.
>
> What I'm interested in is things like shear strength v. time and
> tension strength v. time for the typical PVA and A resin glues that we
> all use.
>
> If someone can point me to data on this, it would be much appreciated.
Don't have a reference per se; if there is something fairly readily
available I'd think it would be at the Forest Products Laboratory site.
If it isn't there, must not be easily findable. That would make me
wonder if the basic answer is my thinking--"when it's dry, it's dry".
I have seen some published work (summarized in a FWW article some months
back) on optimal clamping pressures for production woodworking
applications but afaic(an)r(ecall) clamping time wasn't a variable in
the testing. The upshot of that was that pressures far higher than
normally achieved in hand clamping actually produced somewhat higher
strength in testing. But, of course, in most cases the glue joint is
stronger than the wood anyway. The point of this work was pressure for
excessive squeeze out in production work, not mechanical strength, btw.
Of course, the answer depends on the glue specifically and the species
to a lesser degree and the temperature/humidity factors you've already
mentioned.
But, my take is that for PVA glue once it has set up for about an hour
or so in ordinary weather conditions it's strong enough to machine and
if it handles that it's strong enough. I don't think after that point
clamping will have any further effect.
Urethane and other similar chemical bonding as opposed to drying glues
are different and each follows its own regimen. I'd look at
manufacturers' web sites for more specifics on them; most tend to have
additional technical literature. Probably would get a response from
their tech staffs to direct question as well; either reference to
previous work or guidelines for specific applications if provided.
As for the question regarding relying on the glue to make ill-fitting
stuff hang together, glue doesn't work well for that purpose anyway.
Thick glue lines take longer to dry, obviously, but also testing shows
they don't have the strength of nominal-thickness gluelines, either.
How's that for "I don't know"... :)
$0.01, etc., etc., etc., ...
--
Tom Watson
I guess what I'm looking for is something like the old concrete tables
that would show strength over time. This was mostly compressive
strength but the same thinking should apply.
The interesting thing about some of the old concrete stats is that
they thought that final strength v. time was essentially an infinite
program.
When I talk about a joint that I want to 'encourage' what I'm saying
is that I have a 3" stretcher that is dead flat for 2 1/2" but,
because the chair was used after the initial failure, the bottom half
inch has been rounded. I'm not looking for any gap filling help at
that point, and I'm not looking for that half inch to contribute to
the strength of the joint, what I want to know is the tension strength
of the joint, given what I have available and what allowing extra
clamp time does for me regarding final tension strength of that joint.
dpb
> Thanks for the reply.
>
> I guess what I'm looking for is something like the old concrete tables
> that would show strength over time. This was mostly compressive
> strength but the same thinking should apply.
>
> The interesting thing about some of the old concrete stats is that
> they thought that final strength v. time was essentially an infinite
> program.
But concrete isn't glue...or glue isn't concrete. :)
Concrete does continue to cure and change its chemical process through
quite a long period of time. Wood glues don't act like that. Once it
dries (PVA) or cures (urethanes, epoxies) it has reached it's ultimate
strength--additional time, clamped or not, won't matter a whit.
So I don't think you'll ever find a set of data like what you were
looking for.
> When I talk about a joint that I want to 'encourage' what I'm saying
> is that I have a 3" stretcher that is dead flat for 2 1/2" but,
> because the chair was used after the initial failure, the bottom half
> inch has been rounded. I'm not looking for any gap filling help at
> that point, and I'm not looking for that half inch to contribute to
> the strength of the joint, what I want to know is the tension strength
> of the joint, given what I have available and what allowing extra
> clamp time does for me regarding final tension strength of that joint.
...
Not much if anything at all once it has set. If you're pulling the
joint back together to make up for material that has been either
compressed or worn away (or even, to a lesser degree, simply pulling a
separated piece back into position) there's a pretty good likelihood
that same failure will happen again. PVA glue in particular tends to
creep with time, while urethanes and even hide glue don't nearly as
much. To attempt that kind of repair (which I've certainly done as well
altho restoration work isn't a regular portion of what I ever did altho
swmbo did have a period years ago of dragging home a lot of "antiques"
that did work over) unless it is really of value I'd probably go w/ the
urethane and leave it until completely dry. If it's more valuable
piece, and not factory-built, then hide glue would be the choice of
course as it can be reversed if ever became necessary.
--
Tom Watson
thinking is based on what the physical chemistry is when it is 'dry'.
It is also predicated on the defintion of 'dry'.
We know from experience that the squeeze-out is available to be
cleaned off for some time after the joint is set but what of the
'dryness' and 'cure' of the joint itself?
If I glue up a joint that wants to separate because of the mechanics
of the interface, what help may I expect from the adhesive?
This is where NOVA should jump in.
I think he actually took a strength of materials class back in the
day.
On Sat, 30 May 2009 16:48:04 -0500, dpb <no...@non.net> wrote:
>
>Concrete does continue to cure and change its chemical process through
>quite a long period of time. Wood glues don't act like that. Once it
>dries (PVA) or cures (urethanes, epoxies) it has reached it's ultimate
>strength--additional time, clamped or not, won't matter a whit.
>
>So I don't think you'll ever find a set of data like what you were
>looking for.
Nova
> Please don't think that I am being argumentative on this but my entire
> thinking is based on what the physical chemistry is when it is 'dry'.
> It is also predicated on the defintion of 'dry'.
>
> We know from experience that the squeeze-out is available to be
> cleaned off for some time after the joint is set but what of the
> 'dryness' and 'cure' of the joint itself?
>
> If I glue up a joint that wants to separate because of the mechanics
> of the interface, what help may I expect from the adhesive?
>
> This is where NOVA should jump in.
>
> I think he actually took a strength of materials class back in the
> day.
It wasn't me.
--
Jack Novak
Buffalo, NY - USA
nov...@verizon.net
Tom Watson
You lie so bad, dog.
You be an engineer and you had to take this course.
dpb
> Please don't think that I am being argumentative on this but my entire
> thinking is based on what the physical chemistry is when it is 'dry'.
> It is also predicated on the defintion of 'dry'.
>
> We know from experience that the squeeze-out is available to be
> cleaned off for some time after the joint is set but what of the
> 'dryness' and 'cure' of the joint itself?
>
> If I glue up a joint that wants to separate because of the mechanics
> of the interface, what help may I expect from the adhesive?
>
> This is where NOVA should jump in.
>
> I think he actually took a strength of materials class back in the
> day.
So did I, but that didn't cover the subject... :)
The time to "dry" for PVA is dependent primarily on temperature and to
lesser extent RH and what material. Since PVA glues dry by the loss of
moisture from the glue line, it's not a fixed time but dependent on the
external conditions as well as the moisture content of the material and
the amount of glue in the joint. The typical one hour mechanical
strength time is the time at which one can expect the joint to have
dried sufficiently to have sufficient strength for further mechanical
operations. I think almost if not everybody will suggest 12-24 hrs for
complete drying for PVAs.
If you're really concerned about high stress joints I'd definitely
recommend waiting for the overnight just as safe practice but I still
don't think you'll ever find any data that's directly applicable to the
question.
For such applications you might want to consider some of the specialty
glues for laminating, etc., that don't have the same creep properties of
"ordinary" PVA.
Selley products are excellent; it may be somewhat hard to find them
retail altho I've not looked in ages.
http://www.selleys.com.au/Selleys-Aquadhere-Interior/default.aspx
http://www.selleys.com.au/Selleys-308-High-Stress-Wood-Glue/default.aspx
are a couple products you might want to look at.
--
Nova
<snip>
>>>This is where NOVA should jump in.
>>>
>>>I think he actually took a strength of materials class back in the
>>>day.
>>
>>It wasn't me.
>
>
>
> You lie so bad, dog.
>
> You be an engineer and you had to take this course.
>
>
>
> Regards,
>
> Tom Watson
> http://home.comcast.net/~tjwatson1/
I'd would like to be an engineer. I'm a network communications
specialist for what was, at one time, the major long distance company.
Tom Watson
On Sat, 30 May 2009 17:32:02 -0500, dpb <no...@non.net> wrote:
>
>If you're really concerned about high stress joints I'd definitely
>recommend waiting for the overnight just as safe practice but I still
>don't think you'll ever find any data that's directly applicable to the
>quest.
This looks like a good bet for my son's middle school science project
for next year.
Somehow, that seems like a damned shame.
Tom Watson
Tom Watson
are destroyed by relaxing the clamp pressure prior to a certain time.
It is as though a mechanical as well as chemical process were occuring
at the same time and that the mechanical bond was totally dependent on
the completion of the chemical reaction.
I have been told that I have too much imagination for my own good.
Lew Hodgett
"Tom Watson" wrote:
> Shit. For about twelve years I thought you were a PE.
In the future, would it make any difference if I signed my posts using
my business signature:
Lew Hodgett, PE
rather than the more informal
Lew
Tom Watson
PE is of great importance to me.
I've worked with good ones and bad ones but I have not worked with one
who was not available to a logical argument.
That is one of the things that I like about engineers.
Their availability to a logical argument.
Carpenters are half-assed engineers and often produce half-assed
results because they substitute rules-of-thumb for careful analysis.
I know, I'm a carpenter.
When I ask a question about shear strength of a glue line, or
withdrawal strength (tension) on that glue line, I'm asking because I
am outside my area of expertise.
I am hoping that an engineer, or a physical chemist will chime in and
help me out.
It also helps that you are a sailor.
I do not countenance the term 'boater' as it includes far too many
people with whom I would not choose to associate.
Especially the personal watercraft crowd.
It is a great disappointment to me that you are not a woody
traditionalist but I would be interested in hearing your theories on
concrete and fero-cement vessels (I can not bring myself to call them
boats), should you have any.
J. Clarke
If it's a real structural joint where the glue is a stressed member and
doesn't just hold the pieces in alignment I'd go with the old standbys,
Weldwood plastic resin glue or Weldwood resorcinol glue. Understand--they
have no gap filling capability to speak of and they cure _hard_, there is no
flex in that joint, so wood movement will over time break down the bond, but
they will not creep and the resorcinol glue is as waterproof as any adhesive
for wood gets. They're not glamorous and "modern" like the epoxies but
adhesives based on the same chemistry (but British brands, not American) put
legions of Mosquitos over the Third Reich, some of which are still flying
more than half a century later.
Lew Hodgett
"Tom Watson" wrote:
> Lew, you sign your posts any way you want but the fact that you are
> a
> PE is of great importance to me.
Have carried a license since '64 and although there was a great deal
of satisfaction in earning that license, have never had to use it
since I don't do public works.
> That is one of the things that I like about engineers.
>
> Their availability to a logical argument.
Now if you could only get them to make a decision.<grin>
Have yet to meet an engineer that didn't want to screw a project to
death rather than say "enough, time to make some money".
> Carpenters are half-assed engineers and often produce half-assed
> results because they substitute rules-of-thumb for careful analysis.
>
> I know, I'm a carpenter.
>
> When I ask a question about shear strength of a glue line, or
> withdrawal strength (tension) on that glue line, I'm asking because
> I
> am outside my area of expertise.
After graduation, my first job involved working with adhesives.
My chief engineer, an electrical by training, was one sharp guy.
His assessment of adhesives went something like this:
1) Adhesives in tension are about as useless as breasts on a boar hog.
2) Adhesives in compression do little other than restrain lateral
movement. A thin uniform coat is preferred.
3) The real test of an adhesive is in shear. The coating should be
uniform and as thin as possible without starving the joint.
The thicker the joint, the weaker it will be.
As far as clamp time is concerned, more is better.
That was almost 50 years ago, it worked then, it works now.
> It also helps that you are a sailor.
>
> I do not countenance the term 'boater' as it includes far too many
> people with whom I would not choose to associate.
You want an argument, change the subject.
> Especially the personal watercraft crowd.
We do not describe them in polite company; however, Darwin's
observations apply.
> It is a great disappointment to me that you are not a woody
> traditionalist but I would be interested in hearing your theories on
> concrete and Ferro-cement vessels (I can not bring myself to call
> them
> boats), should you have any.
You have to be a masochist to have a woody.
As far as Ferro is concerned, if laid up properly, it, like all
concrete structures will continue to gain strength
ad-infinitem.
The problem is there is no way to test a Ferro hull once it cures so
you basically have a pig in a poke.
You can't get insurance on a Ferro.
Lew
Tom Watson
<sails...@verizon.net> wrote:
>Have carried a license since '64 and although there was a great deal
>of satisfaction in earning that license, have never had to use it
>since I don't do public works.
Still a decent ticket that demands respect.
>
>1) Adhesives in tension are about as useless as breasts on a boar hog.
And yet we often ask them to have an effect.
>
>As far as clamp time is concerned, more is better.
No data.
>
>As far as Ferro is concerned, if laid up properly, it, like all
>concrete structures will continue to gain strength
>ad-infinitem.
>
Is there a trade off between strength and brittlenes?
Father Haskell
>
> My chief engineer, an electrical by training, was one sharp guy.
>
> His assessment of adhesives went something like this:
>
> 1) Adhesives in tension are about as useless as breasts on a boar hog.
>
> 2) Adhesives in compression do little other than restrain lateral
> movement. A thin uniform coat is preferred.
>
> 3) The real test of an adhesive is in shear. The coating should be
> uniform and as thin as possible without starving the joint.
Which is why you use interlocking joints such as finger joints
or dovetails.
> The thicker the joint, the weaker it will be.
Counter by increasing glue area.
Lew Hodgett
> And yet we often ask them to have an effect.
Comes under the heading of poor design.
> No data.
It becomes a function of "green" strength.
'GREEN' ADHESIVE WILL HOLD A JOINT IN PLACE; HOWEVER, MAY BE ABLE TO
HANDLE DESIGN LOAD.
(Hit Cap Lock by mistake.
> Is there a trade off between strength and brittlenes?
I don't have a clue.
A few years ago they had to sink some WWII Ferro boats that couldn't
be broken up even using dynamite.
They sank them some place off the Oregon coast as I remember.
Regards,
Lew
dpb
> Thank you for your response and I do appreciate the thought and time.
>
>
> On Sat, 30 May 2009 17:32:02 -0500, dpb <no...@non.net> wrote:
>
>
>> If you're really concerned about high stress joints I'd definitely
>> recommend waiting for the overnight just as safe practice but I still
>> don't think you'll ever find any data that's directly applicable to the
>> quest.
>
> This looks like a good bet for my son's middle school science project
> for next year.
>
> Somehow, that seems like a damned shame.
>
Well, I'll modify the previous statement somewhat...I think you will
find some data on tensile strength for various adhesives including
PVA--a quick google found several references in various journals. The
nearest I read the abstract for measured strength reduction as a
function of strain rate but in your case the rate is essentially zero.
What I doubt you'll find will be anything about the clamping time vs
strength--since the time is relatively short and it isn't nearly as
complex a chemical bonding process as the concrete example I'd expect
odds are very high that any test joints will have been cured and that
will not have been a variable in the study.
What you might find in studies for commercial applications _might_ be
some information on speeding up curing/drying time via microwave, etc.,
where production times might be a significant factor.
If I were to do any further working, it would be from the standpoint of
that as probably the driving force for the research--what can folks like
the furniture manufacturers get away with when they're gluing up reams
of stock? In general those are fully or nearly fully automated
processes and most probably use enhanced methods to shorten the times.
What, if anything, might be of use to you I've no idea.
I think I'd go back to the original thought I had--send a query to
Weldwood, et al., asking if they have any information on the subject and
the reason therefore. I've had some success w/ them in the past on some
specific applications.
--
dpb
> Thank you for your response and I do appreciate the thought and time.
No problem...
OBTW, I'm an engineer, too, albeit a fairly useless for this stuff
one...NucE/Physics (Nuc Science)... :)
--
Larry Blanchard
> But, my take is that for PVA glue once it has set up for about an hour
> or so in ordinary weather conditions it's strong enough to machine and
> if it handles that it's strong enough. I don't think after that point
> clamping will have any further effect.
I usually take stuff out of the clamps after 30-60 minutes. But I wait
several hours, preferably overnight, before I stress the joint with
further operations. So far I've had no problems.
--
Intelligence is an experiment that failed - G. B. Shaw
DanG
is a bit like wrestling in the mud with a pig . . .. . you finally
figure out they enjoy it.
But on the other hand, the difference between engineer boots and
cowboy boots
/
/
/
/
/
the cowboy boots have the manure on the outside.
--
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)
dgri...@7cox.net
"Tom Watson" <tjwa...@comcast.net> wrote in message
news:6mf325pfvua0uprbt...@4ax.com...
David Merrill
around page 130.
http://www.fpl.fs.fed.us/documnts/pdf1991/river91a.pdf
I had searched FPL for 'pva' and 'clamp time' from this page
http://www.fpl.fs.fed.us/search/index.php
David Merrill
"Tom Watson" <tjwa...@comcast.net> wrote in message
news:825325pusno1qjlh3...@4ax.com...
> snip...
Leon
hold things together while the glue dries, you could use masking tape.
Typically wood glues, PVA are quite strong after 1 hour, strong enough that
clamps should not be needed any longer. In the old days when I used
WeldWood mix with water glue I left the clamps on over night.
For the not "quite right fit" I suspect leaving work in clamps over night
may have some additional benefit "if" the joint starts to separate after 1
hour as you remove the clamps. But if the joint holds immediately it should
continue to hold. Then again it does no harm to leave the clamps on over
night.
"Tom Watson" <tjwa...@comcast.net> wrote in message
news:825325pusno1qjlh3...@4ax.com...
mac davis
I sort of follow the directions on the glue (Titebond)
Clamp for 45 minutes, (I usually do something else for an hour or so), and don't
subject to stress for 24 hours..
This is in part because of confidence in the glue, but mostly because I don't
have THAT many clamps...
mac
Please remove splinters before emailing
PDQ
In news:6mf325pfvua0uprbt...@4ax.com,
Tom Watson <tjwa...@comcast.net> dropped this bit of wisdom:
<SNIP>
>
>
> It is a great disappointment to me that you are not a woody
> traditionalist but I would be interested in hearing your theories on
> concrete and fero-cement vessels (I can not bring myself to call them
> boats), should you have any.
>
>
Haven't hear the word "fero-cement" used in 60 years. Last time I did it was a fellow who worked in iron that was building himself a boat (vessel?) out of concrete.
I asked him why concrete and he replied "Because they said it couldn't be done".
I don't know who "they" was but that sucker actually floated and was about as agile as one of those cars that could go on land or sea.
What's to say, I know he later built one out of iron plate that was a bit faster.
P D Q
Han
news:gvufi8$rdj$1...@news.eternal-september.org:
Reminds me of the mythbusters boat made of newspaper and water (actually
thay made a mold, wetted newspaper to fold into themold, then froze the
whole thing. It planed with the huge MF Evinrude on it. Of course it
didn't last all that long, but the episode was quite interesting.
--
Best regards
Han
email address is invalid
Robatoy
Hey! I got one of those 'mind-eye' thingies... mine needs to have the
batteries recharged. They have a station for that on Manitoulin
Island. (http://www.manitoulin-island.com/)
I tend to think more in terms of long helix, dreadlocks, interwoven
springs, or old fashioned telephone cords.
I don't 'see' the crystalline structures as most of those glues are
gummy and a bitch to shear(sand).
I can see crystalline structures in hide glue, because that shit gets
all cracky and brittle over time.
When in doubt, use epoxy. Uncle Lew has made me see things his way.
I have never had a WEST joint fail, and I have glued up some pretty
goofy dissimilar material joints.
I now use Weldbond for justaboot everything. http://www.weldbondusa.com/
or WEST
Robatoy
Please don't go talking Mozzies. A close friend of mine (best man #2
when I married Angela), eats, sleeps, dreams, Mosquitos. If he finds
out there is a thread about those birds, he'll show up and we'll never
be able to get rid of him... His aunt worked on them in Mississauga,
ON. 2 Merlins and some birch/spruce/glue. Wicked crazy plane.
diggerop
news:Xns9C1C8D736...@199.45.49.11...
Might be of interest
Andrew Barss
: Reminds me of the mythbusters boat made of newspaper and water (actually
: thay made a mold, wetted newspaper to fold into themold, then froze the
: whole thing. It planed with the huge MF Evinrude on it. Of course it
: didn't last all that long, but the episode was quite interesting.
See:
http://www.boingboing.net/2003/06/04/bulletproof-sawdusta.html
http://en.wikipedia.org/wiki/Project_Habakkuk
Pykrete, and Project Habakkuk. Fascinating story.
-- Andy Barss
Phisherman
wrote:
>I was gluing up these chairs today and was thinking about ideal clamp
>time.
...
>If someone can point me to data on this, it would be much appreciated.
>
>
>
>Regards,
>
>Tom Watson
>http://home.comcast.net/~tjwatson1/
I leave my work in clamps for 2 hours or more, but do not work with
the glued piece until the following day. I think the 30 minute clamp
time stated on the bottle is too short. Allowing the joint to slowly
cure undisturbed will give better results, I suspect.
Robert Bonomi
if you ask them.
Having done a little digging in years past, I can summarize (from memory),
but don't have hard facts/details to hand.
"Fully cured" time for most commonly used wood-glues is on the order of 24-48
hours, or longer.
After the glue has set up enough to provide a reasonable 'hold', there is
very minimal benefit in keeping the pressure on.
There are _minor_ benefits from keeping the clamping pressure on for somewhat
longer than the manufacturer-recommended period.
Take the manufacturer recommended clamp time, and do something like triple
it, and you're probably out in the 4-5th decimal place for the share of
ultimate strength you're giving up -- i.e., around .00005 of the 'leave it
clamped for the full curing period' strength. As this is well past the
'stronger than the wood itself' point, that small fraction contributes
-nothing- to the overall project, and you can proceed significantly faster.
Robert Bonomi
bon...@r-bonomi.com
In article <825325pusno1qjlh3...@4ax.com>,
Tom Watson <tjwa...@comcast.net> wrote:
>I was gluing up these chairs today and was thinking about ideal clamp
>time.
>