Page 1 of 5 12345 LastLast
Results 1 to 15 of 63

Thread: How square is square enough?

  1. #1
    Join Date
    Feb 2016
    Location
    NJ
    Posts
    48

    How square is square enough?

    Started on a workbench build recently. Dimensioning 12/4 poplar for the base. Face joint - thickness - edge joint - rip. Pretty standard. I squared my jointer fence to the bed using my 12” Starrett combo square. Similarly, I squared the table saw blade to the table using the Starrett. When all was said and done, I found that I had two 90 degree edges and two edges that were slightly out of square. These pieces are 2 3/4” by 3” and 4” for reference. After thinking it over, and checking all my setups agains, I came to this conclusion - when having to rip thick stock, I typically rip it on my bandsaw, 1/16 or 1/32 oversize, then clean up the edge on the table saw. I know this seems like extra work, and it is, but I hate pushing thick stock over my 2hp table saw and hearing it bog down and struggle. My bandsaw equipped with a 3tpi resaw blade goes right through 3” stock with ease. So I concluded that ripping 1/32” or 1/16” off the edge of a board is causing my table saw blade to deflect away from the workpiece, considering there’s nothing on the other side of the blade to counteract the deflection. To test this, I ripped my workpieces thinner, just by a few thousandths. This time, in an attempt to reduce the amount of deflection, I pushed the stock through very very slowly - ending up with some burn marks - but alas - the piece came closer into being perfectly square. Using my Starrett and feeler gauges, I found that some pieces are out of square by 0.002” over 3”-4”. I’m satisfied with that. I wish it was perfect, but it may just be the limitations of my machines. I often have to remind myself to not become obsessive over chasing “square”.

    Bottom line. 0.002” over 3”. Is that square enough for you?

  2. #2
    Join Date
    Aug 2013
    Location
    Princeton, NJ
    Posts
    6,478
    Blog Entries
    7
    Plane it to size.

    A combo square is not uncommonly out of square, so if you are using that to square your machines then you may be doubling your error.
    Bumbling forward into the unknown.

  3. #3
    You are approaching the practical limit to woodworking measurement. Yes, this would be square enough for me.

  4. #4
    Join Date
    Mar 2006
    Location
    SoCal
    Posts
    20,251
    Generic answer is that if it is square enough for what you are building, it is square enough. Just to confirm your bandsaw ripping protocol . . . You joint a surface flat, then joint a surface square to that. You then put the flat surface on the table of the bandsaw and the perpendicular (square) surface to the fence and rip at the tablesaw. I tend to true-up bandsawn surfaces at the planer using the opposite flat side (that was riding the bandsaw's fence) as my reference surface but, there are several ways to get to where you want to go.

    Even more important in avoiding an endless trip down the black hole of perfection; wood moves. Even if your machines are perfect to a machine-shop level of alignment, the resulting material may not reflect this perfectly ;-) Don't get me wrong. I am one of those guys that aligns to .001" whenever possible. I like to have my machines as close as I can get them. That way I know if there are deviations it is technique or the simple movement of stress release in the material. This is why I (and others I am sure) approach milling material as a multi-step process. I mill to oversize and let things rest. I then mill to final dimensions very shortly before I assembly things.
    "What kind of chump do you take me for?"
    "First class."

  5. #5
    Join Date
    Oct 2007
    Location
    Coastal Southern Maine
    Posts
    301
    I layout all of the boards that I am going to glue into a panel, put the cabinet makers triangle on them, and mark each edge of the joints alternately out/in. I go to the jointer and run each edge away from the fence or toward the fence. This cancels any error that my jointer fence is not exactly 90 degrees.

  6. #6
    The answer is as my new boss saiz “it’s either square or it’s not”.. and I totally agree.

    Out of square compounds. It’s not that hard to make things square unless you are building stuff that kinda trash to begin with. I’ve build miles and miles of cabinets “not furniture” face frame style and it’s out of square slightly like 90% of the time as there’s no real joinery. Just all screws and glue and aligning stuff the best you can by feel and with clamps..

  7. #7
    Join Date
    Jun 2008
    Location
    So Cal
    Posts
    2,634
    I remember a time when was starting out . Nothing was square my saw wouldn’t cut straight or square none of my tools could measure square. My bench wasn’t flat. I couldn’t find a square corner on anything.
    But I endeavored to persevere now my cutoffs and work pieces are pretty good. And if I really try I can make something square big or small.
    Sometimes smaller stuff is harder because I have to use hand tools.
    Aj

  8. #8
    Join Date
    Apr 2013
    Location
    Stone Mountain, GA
    Posts
    594
    I agree with Brian that the planer is a better tool for dialing in the width for this size part. I use the planer for this whenever I can.

    To your general question, is 0.002" over 3" square enough, it depends. It will work for many things, but would be a problem for others.

  9. #9
    Join Date
    Feb 2016
    Location
    NJ
    Posts
    48
    Quote Originally Posted by Robert Hazelwood View Post
    I agree with Brian that the planer is a better tool for dialing in the width for this size part. I use the planer for this whenever I can.

    To your general question, is 0.002" over 3" square enough, it depends. It will work for many things, but would be a problem for others.
    I had thought about using the planer to dimension the width, but the length of these pieces are so close to their finished length, any bit of snipe would be a big problem. I try to rely on hand tools when accuracy is paramount, like in small or delicate pieces. In reality, I could take a few plane shavings off these boards and probably dial them in closer to perfection. The parts I'm working on are for a workbench base, so I think the level of square is acceptable. It just annoys me when I triple check all my machines and end up with anything other than perfect. Like I said before though, it may just be the limitations of my tools.

  10. #10
    Join Date
    Jan 2020
    Location
    Elizabethtown, PA
    Posts
    50
    Quote Originally Posted by Brian Holcombe View Post
    Plane it to size.

    A combo square is not uncommonly out of square, so if you are using that to square your machines then you may be doubling your error.
    While this might be true of a common square from the hardware store, A Starrett square is a precision square. Although dropping one will take it out of square.

    .002" of an inch is less than common machine shop tolerance =/- .005, So I would say it's fine unless your building a space shuttle. Wood moves way more than that from seasonal changes in humidity.

  11. #11
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    52,869
    Ryan, yes Starrrett squares that are kept carefully can be pretty accurate, but please trust that Brian knows what he is talking about when it comes to machine setup including in a machine shop! Check out his metrology thread when you have the chance. A combo square due to its nature can have some variance. I agree that on the wood side it's not such a big deal because as you note, wood is an ornery thing. But cast iron and steel are different and that little bit of variance cane absolutely affect machine setup. A fixed, high quality square is better for that task as a result.

    OP, I also tend to dimension width using the planer.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  12. #12
    Join Date
    Sep 2019
    Location
    Lafayette, CA
    Posts
    368
    How long are the parts? Why not use a cambered hand plane to get them square?

    Wait: who let the Neanderthal in?

  13. #13
    Join Date
    Feb 2016
    Location
    NJ
    Posts
    48
    Quote Originally Posted by Bob Jones 5443 View Post
    How long are the parts? Why not use a cambered hand plane to get them square?

    Wait: who let the Neanderthal in?
    The parts are 24" and 33" long. The parts in question are what I'm calling the "feet" and "shoulders" of the bench base. I have the vertical leg members to mill next, gonna try taking to width in the planer. Even if I get some snipe, the ends will be cut into tenons, so it won't matter.

    My No.4 will lightly touch all the parts before assembly. I could swipe a plane over these parts to true them to dead square, I'll see how I feel when I'm in my shop next.

  14. #14
    Yeah, you shouldn’t trust Brian.

    He is rank amateur at best.

  15. #15
    Join Date
    Jul 2007
    Location
    Inkerman, Ontario, Canada
    Posts
    670
    Depends what you are doing.
    I you skim a 1/16th off on edge on the table saw the blade will deflect.
    If you rip stock for a table top at 91 degrees and flip the next board they fit perfectly.
    If you want "Square" use the jointer.

    Tip:
    If you want accuracy,

    Don't trust anything or anyone...ever!

    Check and verify!

    Don't trust any square or other tool regardless of the price or pedigree, if you can't check and verify it's accuracy.

    For most operations you don't need any tool to check and verify.

    Learn to how to check and reference.

    Mark the face and edge of all of your stock.

    Joint two pieces of stock flat, on the wide face, mark them as faces.
    Joint the edges of both, mark them as edges.
    Place the two faces on the flat jointer table top, place the two jointed edges together.
    If they touch perfectly you have 90 degree edges and your fence is perfectly ninety degrees to your table.
    If not you will see a gap at the top or the bottom that is double the error of your fence.

    If your stock face is wide, place the two edges on the jointer and the two faces together, the error will be even larger.

    No measuring equipment necessary.

    You can obtain a high degree of accuracy with woodworking if you so desire.... but like everything else you have to create the environment to achieve it, and understand the variables.

    Accuracy importance is dependant of what you are doing, how complicated it is, what is dependant on it, and who you are and what you care about.

    Oh yes, and while I'm at it the old "it doesn't matter because wood moves" statement is pure crap. Metal also moves, and so does the granite that they use for all of the ultra high tolerance metrology equipment, like surface plates.

    Use and Care Of Granite Surface Plates – Maintenance Tips

    Cleaning and moisture:

    One of the first principles of use and care of Granite Surface Plates is that you should clean the plate thoroughly. It is important that you dry it after cleaning for 5 hours before testing for tolerance. The choice of cleaning solution is important. If a volatile solvent is used (acetone, lacquer thinner, alcohol, etc.) the evaporation will chill the surface and distort it. So, it is necessary to allow the plate to return to normal temperature before using it to avoid measurement error. In case of water-based cleaner there will be some evaporative chilling. The plate will also retain the water, and this could cause rusting of metal parts which are in contact with the surface. Some cleaners will also leave a sticky
    residue after they dry. This will attract airborne dust, and actually increase wear, rather than decrease it.
    A surface plate should be under constant temperature and with less than 50% relative humidity. Avoid direct sunlight or sudden draughts.

    This is a supersurfacer. Supersurfacers are special machines, they are like a big handplane, they can take a single shaving of 0.001" thick from a board that is 12" wide ( some machines will dress up to 24" wide) Pretty remarkable!
    Well this little puppy is a special supersurfacer, it dresses a face and an edge at ninety degrees!
    So somebody in Japan spent a boat-load of money to build a machine to do high precision woodwork, even though wood moves.

    Some people do accuracy in wood!

    So don't believe all of those who don't and tell you, that you can't.

    RightAngleSupersurfacer5.jpg

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •