Perfect Miters?
Greg Esres
miters are perfect, some show small gaps on the visible side of the
thicker portion of the profile. I'm curious as to the cause; seems
like my miter saw should be cutting them perfectly. It's almost as if
the ends being joined have edges slightly rounded over. Any thoughts?
Ed Bennett
Hi Greg,
I'm not sure that I can picture exactly what you are describing. But,
I still might be able to help.
Why do you think that your miter saw should be cutting miters
perfectly? Have you gone through some extensive alignment and
precision adjustment procedure or are you just trusting the scales on
the machine?
Here's an article that you may find helpful. It talks about the
accuracy needed to produce tight miter joints. It also talks about
different methods for achieving that accuracy.
http://www.ts-aligner.com/accuratemiters.htm
Even when machines are perfectly aligned and adjusted, it's still no
guarantee that the results will be accurate. Skill is required, even
when using machines. Proper technique and fixturing can make all the
difference. Here is another article that you might find helpful. It
talks about the sort of problems that you can encounter on a table saw
but it shouldn't be a problem to relate the same sort of issues to the
miter saw:
http://www.ts-aligner.com/external.htm
Let me know if you have any questions or need more help.
Thanks,
Ed Bennett
e...@ts-aligner.com
http://www.ts-aligner.com
Home of the TS-Aligner
John Grossbohlin
"Greg Esres" <ges...@boundvortex.com> wrote in message
news:1189732240.9...@g4g2000hsf.googlegroups.com...
Assuming that the saw is adjusted properly it could be that the wood is
slipping slightly as you cut... some sandpaper glued to the fence and/or
using the clamp that goes with the saw may solve the problem.
John
Greg Esres
<<Why do you think that your miter saw should be cutting miters
perfectly?
>>
Well, I guess "consistently" is a better word. Some of them are
perfect; why aren't they all?
<<Have you gone through some extensive alignment and precision
adjustment procedure or are you just trusting the scales on the
machine?>>
I have measured the angles and they seem dead on; however, I'm not
concerned about that. My doors jambs probably aren't perfectly
square, so the miter angles will take some adjusting anyway.
It just seems to me that if you slice two pieces of wood with the same
blade, the cuts ought to join with no gap. Why not?
<<Here's an article that you may find helpful. It talks about the
accuracy needed to produce tight miter joints. It also talks about
different methods for achieving that accuracy.>>
I'll take a look, thanks.
<<Skill is required, even when using machines. >>
Dang!
<<Here is another article that you might find helpful. It talks about
the sort of problems that you can encounter on a table saw but it
shouldn't be a problem to relate the same sort of issues to the miter
saw:>>
I've review that, too.
Thank you sir!
Greg Esres
<<Proper technique>>
Ed, I think your website gave me the clue I needed. It mentioned
possible blade warping on thin cuts. I noticed the edge of my cut
that was rounded was where the blade withdrew *last* from the wood,
where the damping of the blade would have been least with the thin
cut.
When I stopped the blade after the plunge and withdrew it while
stopped, my cuts were clean again.
Thanks!
Greg Esres
<<the wood is slipping slightly as you cut... some sandpaper glued to
the fence and/or using the clamp that goes with the saw may solve the
problem.>>
I've had a hard time figuring out how to clamp stuff with this saw
(DeWalt). It didn't come with a clamp and the fence isn't the ideal
clamping surface. And these flat pieces of trim don't offer much to
grip either. Still, I don't think it's moving. Looks like I had poor
technique.
Thank you
Lee
length ie upper/lower..right side/left sidenews:1189736555.8...@k79g2000hse.googlegroups.com...
Greg Esres
<<don't forget the most over looked thing....the pieces most be the
exact same
length ie upper/lower..right side/left side >>
You mean the diagonals? Yes, I noticed that because I had to adjust
the miter angle of the leg, the diagonal is slightly less than the
header, so the corner juts out a bit. I figure I can shave that off
once the glue dries.
Thanks
Lee
frame if the right vertical is slightly longer(or shorter) it throws off
all the angles. If all is equal and your saw is tuned properly there
shouldn't be a gap in any of the miter joints.....but then again it's not
always a perfect world that's why they make wood filler lolnews:1189739703.8...@g4g2000hsf.googlegroups.com...
Lew Hodgett
The easiiest way to get perfect 45 miters is to build a sled using a
factory corner from a sheet of 3/4 ply.
See Fred Bingham's book, "Boat Joinery & Cabinet making", for details.
Lew
Greg Esres
<< No I mean the length of the pieces you are joining together. Think
of a pic
frame if the right vertical is slightly longer(or shorter) it throws
off
all the angles. >>
Gotcha. Not an issue yet. I can only do one miter at a time, so
there's just a leg and header.
Ellestad
Most chop saws that I have looked at don't hold "picture frame" miter
accuracy when the table is clamped. The near side of the table climbs
(squirms up) when the clamp is tightened taking the table surface out of
square with the fence. That takes the cut out of glue-up precision. You can
still frame a garage with it but . . . My old Porter-Cable stays pretty true
and likewise the Delta version. I've seen some awful examples of this,
though, with Bosch and DeWalt.
The sliding miter saws son't necessarily cut so true, either. Ther're good
for joist cutting, though.
Tim
"Greg Esres" <ges...@boundvortex.com> wrote in message
news:1189732240.9...@g4g2000hsf.googlegroups.com...
DanG
not meeting on the finish surface? Most carpenters set a pencil
or nail under the trim so that there is a slight back cut on the
miter to allow the front face to meet.
If the 45 is not making, you might glue a strip of sand paper to
the back splash and/or table of your miter saw to prevent creep.
--
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)
dgri...@7cox.net
"Greg Esres" <ges...@boundvortex.com> wrote in message
news:1189732240.9...@g4g2000hsf.googlegroups.com...
Dave in Houston
"John Grossbohlin" <nos...@nospam.earthlink.net> wrote in message
news:13ejqkr...@corp.supernews.com...
> Assuming that the saw is adjusted properly it could be that the wood is
> slipping slightly as you cut...
On numerous occasions I've noticed that my DeWalt 708 (slider) tends to
pull the stock ever so slightly as the blade makes it way through the cut.
Or, maybe it's due to the Jessada blade tooth configuration (30 deg ATB).
It could also be the casings themselves. If they are off-the-rack,
store-bought millwork then you can NEVER count on one piece being exactly
the same dimension (on any plane) as the next.
--
NuWave Dave in Houston
Dave in Houston
"Lew Hodgett" <lewho...@earthlink.net> wrote in message
news:13ek23i...@corp.supernews.com...
> RE: Subject
>
> The easiiest way to get perfect 45 miters is to build a sled using a
> factory corner from a sheet of 3/4 ply.
I'd gage the corner angle before I'd trust the plywood.
Greg Esres
<<Maybe I'm not understanding. Is the 45° accurate and it is just not
meeting on the finish surface? Most carpenters set a pencil or nail
under the trim so that there is a slight back cut on the miter to
allow the front face to meet.>>
You got it. But it was only on the thick part of the trim. Now it's
perfect since I changed the cutting technique. However, I was
wondering how to do the "back cut". Nice to know how professionals
are doing it.
Thanks
Greg Esres
<<If they are off-the-rack, store-bought millwork then you can NEVER
count on one piece being exactly the same dimension (on any plane) as
the next. >>
I bought them at a millwork shop, but yes, I've noticed that different
batches seemed slightly "off" from the pieces I had.
Greg Esres
<<Most chop saws that I have looked at don't hold "picture frame"
miter accuracy when the table is clamped.>>
With great foresight (i.e., laziness), my saw isn't clamped or
bolted. :-)
Ellestad
"Greg Esres" <ges...@boundvortex.com> wrote in message
news:1189781741.6...@o80g2000hse.googlegroups.com...
Ed Bennett
People put way too much stock in books and magazine articles. Just
because it's in print doesn't mean it's right.
You really shouldn't trust that the unskilled minimum wage sawdust
jocky at the plywood factory managed to put an accurate corner on one
of the 10,000 pieces of plywood he cut that day. If the corners of
plywood have any spec at all, it's probably on the order of +/- 1/8".
I'll have to add this one to the "Myths and Ledgends" section of the
web site.
Lew Hodgett
"Ed Bennett" wrote:
> People put way too much stock in books and magazine articles. Just
> because it's in print doesn't mean it's right.
MIne works quite well.
> You really shouldn't trust that the unskilled minimum wage sawdust
> jocky at the plywood factory managed to put an accurate corner on
one
> of the 10,000 pieces of plywood he cut that day.
I don't; however, I do trust the automation used to trim 4x8 sheets to
size since it is not a manual labor job these days.
Lew
Leuf
wrote:
Oh come on Ed. You make it sound like there's some kid with a skill
saw that makes the plywood at the factory. The first time that
plywood gets touched by a person is when you buy it. If it's a
typical hobbiest shop and their square says the factory corner is off
then my money is on the $10 square from the Borg being off not the
ply. I do double check when it's something critical like a miter sled
though.
-Leuf
Ferd Farkel
As many subfloors as I've run, I can't say I've ever seen gaps
at end joints where the plywood was off square.
Chris Friesen
> You really shouldn't trust that the unskilled minimum wage sawdust
> jocky at the plywood factory managed to put an accurate corner on one
> of the 10,000 pieces of plywood he cut that day. If the corners of
> plywood have any spec at all, it's probably on the order of +/- 1/8".
The factory edges are not cut by some guy with a circular saw.
The whole process is automated using something called a "DD Saw". Among
other reasons, plywood right out of the press is still pretty hot.
Chris
Ed Bennett
> The factory edges are not cut by some guy with a circular saw.
>
> The whole process is automated using something called a "DD Saw". Among
> other reasons, plywood right out of the press is still pretty hot.
>
> Chris
Yes, yes, yes, I know. I appreciate all of the comments about guys
with skill saws vs the "perfection" of automation, etc.
I've seen how plywood is made. The sheets are gang ripped to width
and then cross cut while in motion. The feed rate of the cross cut
saw (traveling at an angle) in conjunction with the feed rate of the
board determines the squareness of the cut. The factory is staffed
with unskilled workers. The person overseeing the crosscutting may
never have even touched a circular saw in their entire life. I'm
quite sure that they care more about length and width than they do
about squareness. If they track these measurements as process
parameters (a big IF), then these are likely to be checked on a random
audit basis with simple instruments (i.e. tape measure) by more of the
same unskilled minimum wage workers.
A long time ago I heard this same folklore and tried to apply it in my
woodworking. "Use a factory edge as a straight edge, use a factory
corner as a square, etc." I probably read it in a magazine article
written by some journalist who (while pretending to be an expert) had
never touched a circular saw in his life. That's when I learned not
to trust the factory edges (even on furniture grade plywood). They're
good enough for construction purposes (sheathing, flooring, roofing,
etc.). And, there are probably a lot of people who will never notice
a problem in their own work. But, they are far from "perfect" (what
Lew originally said) and don't suit my needs. I also learned not to
take technical adivce from journalists - a lesson that has been
reinforced countless times over the years.
The original poster has related that his problem was being caused by
deflection of the blade when making thin cuts. I could be wrong, but
I suspect that the demands of his work exceed the accuracy of factory
cut edges on plywood. I'm glad he was able to find his solution in
one of my articles.
Ed Bennett
> MIne works quite well.
Your sled? I'm sure it suits your needs.
> I don't; however, I do trust the automation used to trim 4x8 sheets to
> size since it is not a manual labor job these days.
That would be another topic for the "Myths and Folklore" page. Just
because its automated doesn't mean its perfect or accurate. I run a
shop full of automated machines and I assure you that accurate results
still depend on the skill and knowledge of the people using them.
I've hired people to run the exact same programs on the exact same
machines with the exact same fixturing and they still manage to screw
up the parts. Heck, I've even screwed up a bunch of parts over the
years. The machines used to trim plywood to size may be automated but
"perfect" accuracy is not automatic.
Ed Bennett
> As many subfloors as I've run, I can't say I've ever seen gaps
> at end joints where the plywood was off square.
I haven't done so many subfloors (two or three) but I've noticed the
gaps in each one. Not that it matters, it's just a subfloor. I
thought we were talking about woodworking with slightly higher
standards.
Ellestad
plywood of any kind that was reference square - you're not going to cut good
cabinet quality joints basing them on the origingal corners. No supplier
that I have ever dealt with would ever even suggest that their plywood of
any type was "joint square". I find that often the sawn edges are even wavy.
The automated sawing of 4x8's at the factory isn't concerned with making the
edges and corners to joint standards - it is to simply get the sawing done
very fast and cheap!
I agree that you might have problems with cheap squares and straight-edges.
Every time I see a magazine or book showing someone laying out cabinetry
cuts with a framing or rafter square I immediately know that the author
either didn't know what he was talking about or he was dishonest (most
framing squares need some corner peening to reasonably square them up). I
have a fair amount of money in my squares and rules.
Tim
"Leuf" <lege...@dontemailme.com> wrote in message
news:iqmle3pvn6t4i16fi...@4ax.com...
Swingman
> In about forty years of doing this I don't think I've ever found a sheet
> of
> plywood of any kind that was reference square -
Hmmm ... just walked out to the shop and the first three sheets I checked
had all four factory corners that were "Starret square".
In my 45 years of doing this I don't find that unusual/remarkable at all ...
but then I build _lots_ of cabinets out of quality hardwood plywood.
Go figure ...
--
www.e-woodshop.net
Last update: 8/08/07
KarlC@ (the obvious)
Peter Huebner
ges...@boundvortex.com says...
> I'm gluing up some door casings prior to installation and while some
> miters are perfect, some show small gaps on the visible side of the
> thicker portion of the profile. I'm curious as to the cause; seems
> like my miter saw should be cutting them perfectly. It's almost as if
> the ends being joined have edges slightly rounded over. Any thoughts?
Lots of 'interesting' forces brought to bear on the wood and the saw(blade)
when cutting mitres against a fence. I've seen those slightly rounded cuts,
distortion through my RAS climbing on to the wood during the cut or being
forced off its intended direction by grain. Similar effect through timber
climbing up on a mitred table saw blade. (I don't have a mitre saw myself, but
these forces will apply there, too).
Apart from the obvious - adjustment as close as possible - I have developed the
technique that if I cut to within 3/4mm of size first and then do a cleanup cut
to a knife-marked line I get very good results because these forces are largely
reduced or nearly eliminated. I have also found that the cuts made at the >90
degree side in this fashion seem to be slightly superior on my RAS.
Meanwhile, I am avidly reading what others have to say on the subject ;-)
-P.
--
=========================================
firstname dot lastname at gmail fullstop com
Peter Huebner
says...
>
> I don't; however, I do trust the automation used to trim 4x8 sheets to
> size since it is not a manual labor job these days.
>
> Lew
Hmmm. We reclad our shearing shed with construction grade ply a couple of years
back. Some of those sheets were *considerably* off square. Nearly 1/4", some of
them. Didn't matter because we put battens over the joins, but .... ;-)
As an aside: I laid parquet flooring in my old folks' house a few years ago,
and found that even a lot of the 12" sq. prefabricated tiles were out of
square! Had to recut many on the RAS to eliminate gaps. Yeesh. Not sure to this
day how I managed to eliminate pattern creep between the tiles over several
runs, I guess it must've evened out.
Mike O.
>> In about forty years of doing this I don't think I've ever found a sheet
>> of
>> plywood of any kind that was reference square -
>
>Hmmm ... just walked out to the shop and the first three sheets I checked
>had all four factory corners that were "Starret square".
>
>In my 45 years of doing this I don't find that unusual/remarkable at all ...
>but then I build _lots_ of cabinets out of quality hardwood plywood.
>
>Go fig
We find a few sheets of 3/4" hardwood veneer core that are not square
on occasion. It does seem to be related to certain vendors which I
think is related to the quality of their products. Since most of the
time our builders do the purchasing we try to "steer" them to better
quality material which normally means a different vendor.
Mike O.
Ellestad
know that my experience is common with most of the collegues that I have
mentioned this with over the years in my area. I do find that the short base
of a machinist square is too small to reveal many of the problem pieces that
I've encountered (in fact I had a problem with this on some Baltic Birch two
weeks ago - and its getting to be a challenge for my old gray-beard mind). A
24 inch blade helps but . . . I've found sheets with square corners that
were'nt square to each other due to swoops in between. Years ago a couple
friends who worked for the Forest Products Laboratory told me that there was
no particular concern on the part of industry to deliver clean,
square-dressed product assuming that typical handling may likely ding the
edges a little anyway.
Certainly, though, as per your experience I would presume that some
manufacturers, suppliers and yards do better than others. When I bought the
Baltic Birch that I mentioned I asked the kid filling the order if we could
find a few sheets that were "reasonably flat" with a good straight edge ot
two. He said something to the effect of, "We'll see what we've got but it is
what it is, you know." This yard supplies a lot of the area cabinet shops
that aren't big enough to get supplier-direct purchasing.
I envy your resource.
Tim
"Swingman" <k...@nospam.com> wrote in message
news:B_SdnRKkQat9gHbb...@giganews.com...
Swingman
> mentioned this with over the years in my area. I do find that the short
> base
> of a machinist square is too small to reveal many of the problem pieces
> that
> I've encountered
Granted, that's an important point. However, the underlying point that Lew
was making with his "factory plywood corner" suggestion is valid, IME.
One of the best "miter jig" concepts for making frames is the one using a
factory corner from a sheet of plywood and the concept of complementary
angles to alternate the cutting of adjacent parts to insure 90 degree angle
joins.
It is not that difficult to find a corner _square enough for woodworking
purposes_ on a sheet of quality plywood these days, and for miter jig
purposes you generally need a relatively short distance, say 8 - 12 " on
each axis, so the square you use on your actual woodworking projects is
going to be your limiting factor in any event.
That said, I agree that you certainly want to measure with the best
available tool, and not just take it on faith, that a factory plywood corner
is square enough for your purposes.
Ellestad
good fortune to find all that many good corners on the product that I've had
available here - even on supposed high-grade hardwood plywood (although the
price would imply - no pun - that the corners should be pretty good). One of
my good friends was a furniture maker and he ran a hardwood operation along
with his shop. He carried high grade hardwood plywood and Baltic Birch and I
purchased wood from him from time to time. He never felt that his supplies
would predictably have reliable corners and his stuff was generally better
than I would get from the main dealer in my area. I really think from your
experience that quality standards may vary depending on product chanels in
your area. As I said before, I really do envy anyone who can count on the
corners and edges of their raw materials to be square and true.
Tim
"Swingman" <k...@nospam.com> wrote in message
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Ed Bennett
corners varies considerably. Not just from sheet to sheet but it's
not unreasonable to believe that some facilities produce better
quality than others. Maybe one factory has an OCD guy like me who
checks the machinery at the beginning of every shift. Maybe another
factory doesn't bother with it unless it breaks down (or needs a blade
change). I strive to make recommendations that will work for anyone
who applies them correctly. So, I just can't recommend trusting the
accuracy of edges and corners of plywood sheets. If you can verify
that the corner is square, then it certainly would work well on a
sled.