Tolerances.. how tolerant are you?

[Dan Clermont]

I am curious to know what others out there think is acceptable for woodworking tolerances? Do you work to within 1mm, 1/16", 1/32", 1/64"??

My goal is to always be withing 1/32" if at all possible. I get grumpy otherwise

Dan Clermont

 

[nickao]

Well if I am jointing wood I want absolutly no gap. If I can hold two boards up to a light and can not not see light going through, it is the best it can be. Whatever that measurement is, it is the tolerance I need for my work.

I know hardwood moves, but I go for perfect and take what I get. 1/32" is possible and reasonable, 1/64" is better. With the Incra setups I have, at least when the project is first made, the tolerances are at least that tight(1/32 to 1/64). After they leave the shop it is out of my hands.

Of course if I am doing house trim or cabinets the tolerances need not be that tight, 1/32" is plenty good enough. I have seen paint grade trim accepted by some  builders with 1/16" gaps others freak at that and demand the job be trimmed out again.

Once I even told a sub to rip down the exterior trim that had at least 1/2 gaps! The builder stopped me and said caulk it! Boy I felt for that homeowner. That was the last job I ran for that builder.

Nickao

 

[The Dude]

Dan, you have reminded me of a phrase I heard several months ago.  We were doing these French Doors on a 4x4 platform on rollers for a play at my kids theater company.  www.haymarkettheatre.org (there is a plug for a fine group; The Nebraska Youth Theater .  ) and I just could not for the life of me get the jambs to stay square.  After my frustration level reached the boiling point I called the director and said, "dude, I cannot get these doors the way I want them."  He told me to bring them down and let's just haul them in....dress rehearsal was starting and "Frank" the old time "set dude" would fix them up.

After getting them up the freight elevator Frank says...WOW these look great.  My thoughts were "they are awful" because they would not stay square, the doors weren't set right in the jamb....etc....ad infinitum.  Frank brings out some plywood triangles, screws them to the jambs, sprays them black with spray-paint, drapes a curtain over the corners, and proudly states...

"Good enough for Theater!!!"  and sends me away with a pat on the back and a "nicely done."  The night at the show....you couldn't tell a thing.  Two months later at another production they were painted white, and now they are back to black in the wings.

So, thats my story.

To answer your question, I try to go into the "nats a$% catagory" and most the time it is still..."Good enough for theater".

Timmy C

 

[nickao]

Dan, you have reminded me of a phrase I heard several months ago.  We were doing these French Doors on a 4x4 platform on rollers for a play at my kids theater company.  www.haymarkettheatre.org (there is a plug for a fine group; The Nebraska Youth Theater .  ) and I just could not for the life of me get the jambs to stay square.  After my frustration level reached the boiling point I called the director and said, "dude, I cannot get these doors the way I want them."  He told me to bring them down and let's just haul them in....dress rehearsal was starting and "Frank" the old time "set dude" would fix them up.

After getting them up the freight elevator Frank says...WOW these look great.  My thoughts were "they are awful" because they would not stay square, the doors weren't set right in the jamb....etc....ad infinitum.  Frank brings out some plywood triangles, screws them to the jambs, sprays them black with spray-paint, drapes a curtain over the corners, and proudly states...

"Good enough for Theater!!!"  and sends me away with a pat on the back and a "nicely done."  The night at the show....you couldn't tell a thing.  Two months later at another production they were painted white, and now they are back to black in the wings.

So, thats my story.

To answer your question, I try to go into the "nats a$% catagory" and most the time it is still..."Good enough for theater".

Timmy C

Great point Timmy, don't sweat the small stuff!

But if you are charging a client 5000.00 for a 36" piece they will see day in and day out, it better be better than "Good enough for theater" quality. Some people are so critical others aren't. Hiding mistakes is an art form. Isn't wood working  just "fixing your previous mistakes until the job is complete". I find nothing is perfect, but have become adept at making it "look" perfect.

Oh yes,  thanks for the great service!

Nickao

 

[The Dude]

It has always amazed me that when I finish a piece, and there is something that is just "not quite right", perhaps off just the most miniscule (spelling for Matthew acknowledged), my eyes are always drawn right to that imperfection.  Other folks that see the piece would NEVER EVER notice it, but the craftsman that made the piece, can never live it down in their own eyes.

T

 

[tvgordon]

I agree with Timmy, we as the ones who built the piece notice imperfections that no one else would notice (unless you point it out - which I do and my wife says "what are you showing me - you're worried about that?). 

But I still drive myself crazy sometimes (short drive) trying to get the details just right.

Tom.

 

[Michael Kellough]

To answer your question, I try to go into the "nats a$% catagory" and most the time it is still..."Good enough for theater".

Timmy C

When I work on commercials the criteria is to keep the defects smaller than a pixel. Of course it depends on whether the part will have a "closeup". And now with HD the pixels are a lot smaller. All the TV sets have been rebuilt to cabinet grade from theatre grade.

 

[poto]

I hear ya, Timmy. I just finished a piece with some slightly complex joinery that came out pretty well, but not as well as I would have liked (a 500 micron gap where there should have been no gap). The next week my contractor and cabinet maker (who are re-doing my kitchen and bathrooms) came by and looked at it (and said nice things about it) but I could tell they could notice the gap in the joint. They then asked why I wasn't making my own kitchen cabinets. I told them that 1) I'd never made cabinets before, and 2) though I was fully capable of making cabinets, I wanted someone else to make them so that I wouldn't spend the rest of my life seeing that *huge* mistake (whatever it was). If someone else makes them, I probably won't notice that 500 micron gap - or care. You're just too close to it when you have made it.

And in answer to the original post, I aim for perfect joints (at least at glue-up time), but usually have to settle for 100-250 microns.

 

[Fred West]

Oy Timmy, boy did you hit the nail on the head. I work for perfection, agognize about the defects and then am completely surprised when no one else sees that huge gap, gash or other defect that I KNOW sticks out like a sore thumb. ;D Fred

 

[dirtydeeds]

tollerances are dependant upon what work you are doing

on cabinet joints and framed items (like doors) built in units or decorative joints the answer is as tight as humanly possible

in second fix carpentry (trim to 90% of the membership) "show joints" such as mitres and coped joints need to be tight as possible

in other parts of second fix carpentry you hide the variences by creating reveals or shaddow gaps then the eye takes over as your judge

if the second fix work is stained or varnished any visible cut edge or gap is immediatly obvious so we are back to as tight as humanly possible

on first fix work (framing to 90% here) any gap bigger than 2-3mm (1/8 inch) just looks plain sloppy

the same goes for visible structural timber work in big sections

i have never done timber shoring but there will be a stage where an open joint looks sloppy

 

[nickao]

That all sounds right to me.

 

[Dan Clermont]

Wow, I didn't think this thread would get this kind of response.

I guess the reason why I ask is I am known to fret over the tiniest bit of light on an edge when jointing even though if I pulled a feeler guage out I'd be lucky to fit a 1 thou feeler guage between the wood and the square.

After every cut with my TS-55 I pull out my cheap, crappy, flexible square and check for dead square. If you go through all this effort and take your time to correct squareness in the milling stage your projects will have nice tight joints and be perfectly square.

When I handcut a dovetail or make a mortise and tenon or cut a dado I want no gaps, no light, absolutely nothing and I am known to cut a 5/8" dado with my router and then handplane the board for the perfect fit!

Here is the kicker, I am a hobbiest, couldn't care less if it took me all day to build a basic cabinet as long as it is square and the joints are nice otherwise I feel like I've failed. When I do make a mistake I'll leave it to remind me what not to do next time.

I am getting ready for a glue up on a MFT cabinet and my top and bottom when sat together cup about an 1" in the middle. You go through all of this work to make something flat and the man made materials are nowhere near flat. Same thing happened with my daughters bookshelf although I am the  only one that would ever know. Everybody sees past the slightly cupped boards and I did a great job minimizing it.

Thanks for all of the responses. This has been a very interesting thread so far

Dan Clermont

 

[dirtydeeds]

dan

if you want dead square check the diagonals, its far more accurate than checking with a square

theres a tollerance on the diagonal as well

when making a standard door or cabinet door or other framed component the eye cannot see something is out of square if the diagonals are within 2mm AND if its more than 2mm then you will have a bad time fitting it

NOW when you come to hang your PERFECT door then you have to change the tollerances you use and they way you measure them

the measurement is MEASURED

but, the measurement is checked by your eye

if you are hanging a door in an opening, there is no such thing as square, you are entirely dependant on your eye to check for "square" you scribe the door to match the frame [you help yourself by installing the frame square, level  and plumb]

but the frame is rarely as perfect as the door..................  :    thats why old time foremen insist that the guy who sets the frame hangs the door, it doesnt half make you do it right

so you scribe the door to the frame then shoot the door to the scribe line. now the door is the same shape as the frame and because the margin is equal the eye is "fooled" into seeing a straight line even if it isnt

why?

because if the edge of the door is straight and the frame isnt the eye can see the margin varies

finally there are acceptable and unacceptable tollerance on door margins AND the tollerance changes for door types

with any ordinary house door a margin of more than 2mm looks sloppy

on fire doors in the uk, 4mm is the correct margin (we cannot shoot fire doors in because it voids the manufacturers warranty) so we have to set the frames to match the door

a garden gate is different

a wider margin is not only acceptable but is necessary to allow for the greater seasonal movement. and the bigger the gate the bigger the tollerance has to be.

what is the acceptable margin on a garden gate, there isnt one. there just comes a stage when your eye says its sloppy

hope this hasnt bored you rigid  : or totally confused you

 

[dirtydeeds]

as the membership here is mainly north american i had better explain the reason for the old time forman insisting that the guy who sets the frame hangs the door

(when it is my place to do so, i also insist on it because it rewards the guy who installs a good fame with an easier hang)

in older times labour practices where different and the construction sequence was different to modern construction

until after the second world war in the uk a builder normally directly employed all his carpenters and so they had to do first and second fix

(it also means that when you are refurbing older houses, particularly edwardian and victorian cheap mass housing the second fix is diabolical)

the frames were installed immediatly after the walls were built

the second fix wasnt done until the walls were plastered (plaster on brick OR lath and plaster) so doors were hang much later than the frames

hence the foremens' instructions

 

[Corwin]

While I am just a hobbyist and still have much to learn, I had worked as a machinist in my younger days (haven't done that type work in 25 years) and as such I did production work where parts had specified tolerances -- some were as loose as +/- .015", but most were more like +/- .005 or tighter.  Over the years I have read a few articles that discussed accuracy in woodworking, and found differing opinions.  Some very accomplished woodworkers have written that this is wood, and as such a high degree of accuracy is not needed -- and some even do so with a tone that left me thinking that the author felt that it was actually  wrong to attempt a high level of accuracy.  Well, as I have said, I am only a beginning woodworker, but I simply do not accept anyone's opinion that accuracy is not important in woodworking.  Some of these same professionals have discussed how allusive it can be to establish a perfect 90 with various machines.  Seldom does the topic of parallelism come up, well, at least not until you look into guide rail techniques -- I suspect the table saw's abilities in ripping is the reason for the lack of that topic.  My take on accuracy is that it can never be wrong to work towards a higher level of accuracy -- and while it may not be needed in every situation, it is the lack of accuracy, once it gets to a certain point, that can be wrong.  But, that's just my opinion.

In the time I have worked with my Festools, I have had varied results from time to time.  Sometimes I discover why I did not get the desired accuracy and other times I'm left without an answer.  But over time I have been able to improve the tolerances in my work.  Now I am most unhappy if I cannot produce perpendicular or parallel cuts that are within .010" over 4' -- and I am much, much happier when results are within half of that tolerance.  But again, this is not metal we're working with, and I too am rather interested in the responses from members here.

 

[nickao]

Corwin I agree go for the best you can get. Make that 4 ' cut to within .010 and bring it to my house. It may be WAY off. I think you can not find the answer because you did cut the wood accurately and the internal stress of the wood itself and/or environmental factors either immediately or over time changed the results. Especially results to the tolerances you are talking about.

Obviously with hardwoods and soft woods you assume they will change dimensions and therefore build  items with that in mind.
But when you are getting down to .01, even plywood or MDF can show movement. Yes, even plywood can change due to many environmental and/or manufacturing factors.

So when you can not find the problem, for piece of mind just blame it on that and go on. I have been caught in this trap only to find only I could see the discrepancies.

Nickao

 

[Eli]

If you work for the eye as often as possible, the tolerance is self regulating, ie, don't measure at all if you can avoid it.

Wood is not stable. I go for good lookin', not good measurin'. And sometimes fall short.

Favorite quote from above:
"Isn't wood working fixing your previous mistakes until the job is complete."

Rugmakers in the east intentionally tie one knot incorrectly when making a rug, "Because only Allah can create a perfect work". So if my wife ever notices anything, that's the excuse I use.

 

[Fred West]

Hmmm, Eli you go for good lookin, not good measurin. Now is this true throughout your life and if so would your wife even notice if you chose her that way??? ;D : Fred

 

[Eli]

Well, I looked with my eyes and measured with my hands and everything seemed to fit alright...... ;D :

 

[Fred West]

Okay now I am getting the picturehowever, should you and I meet PLEASE just use your eyes. 8) Fred