Getting things Square
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- This topic has 17 replies, 6 voices, and was last updated 5 years, 3 months ago by Ecky H.
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Seems I’ve found my weakness, it’s woodworking 😀
Actually, it’s getting things square, or parallel, or whatever it is called.
I was using the square to mark off a straight edge on the end of my workbench worktop as I needed to saw off about 12mm. When I got around to matching up, the lines were out by about 5mm.
I checked all four sides and planed, and checked, and planed a bit more, but it’s still out by about 5mm. The top doesn’t look twisted either.
I’m not too concerned because it’s a big workbench, so a few millimetres out here and there doesn’t bother me (ignorance is bliss). But if I were working on smaller, finer details, that 5mm suddenly because huge.
What do I look for when those knife wall lines don’t match up?
2 June 2019 at 8:11 am #577205I’m assuming you have used the same face and edge to register your square against as you square the line round. So my guess would be that because the top is laminated it isn’t flat so there is a twist between the opposite sides?
Hi Paul
I honestly don’t know. When I look at it, I can’t see any discrepancies. One of the corners does look a little fatter than the other, but I can’t see how that would take it out of square. It would mean the line would just have more to travel (if that makes sense).
Regarding to your “when I got around” my conclusion is that you start on one arris, mark across the surface, “elongate” the mark around the next arris, mark to the following arris and on the last arris your marking lines don’t match.
Please keep in mind that an angle of one degree spreads the sides around 1cm at a distance of around 23″ (57cm). With a 24″ wide and 4″ thick workbench top the overall distance is 56″. That’s as over two times as far as the 23″. That means that an overall deviation of less than 0.25° is sufficient add up to your 5mm spread…
So the strategy is to minimise the repercussions of these deviations.
First of all: test your square for squareness.
Assuming that your square is near enough to square, please be aware that every existing workbench is slightly out of square, no straight edge is absolutely straight, all edges are a bit out of parallel and there’s a tiny little twist and there are undulations in every flat surface.Choose one edge as your reference edge. Let’s assume that it is the upper front arris of your workbench. Then mark two lines from that arris: one across your workbench surface, one across the front edge. My next step would be the marking line on the underside of the benchtop and the last line would start on the end of the first line (at the upper rear arris of the bench top).
That should bring the the ends of the marking lines nearer together on the lower rear arris than the 5mm you mentioned.Hope that helps,
E.
- This reply was modified 5 years, 3 months ago by Ecky H. Reason: adjusting terminology "edge" and "arris" to match the post of @sylvain52
2 June 2019 at 11:22 am #577234You have to choose ONE reference face and ONE reference edge. Make the reference edge square to the reference face. Make a pencil mark on the two of them.
Place your initial measurement mark at the arris between the two references.
Placing the square on this reference arris, trace the perpendicular on the reference edge and the perpendicular on the reference face.
You now have a marking (1) on the other arris of the reference edge. You also have a marking (2) on the other arris of the reference face
Place your square on (1) and mark the non-reference face.
Place your square on (2) and mark the non reference-edge.
You should come close even if the two edges are not parallel or if the the two faces are not parallel.I’ve got a vague idea what is being said but arris, reference edge, face, perpendicular, these are terms I’m not very familiar with. I think I need a video so I can see what has to be done.
How do I tell if my square, is square?
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You must be logged in to view attached files.Seajay, basically your graphic is just 90° away from the things Benoit and I wrote about:
[attachment file=”577249″]If you can ask a precision engineer mechanic, check your square with a “known good” square.
If that isn’t possible, eg. John Heisz made a video about checking and adjusting a combination square: https://www.youtube.com/watch?v=cxrCZd7r6qE
Hope that helps,
E.
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You must be logged in to view attached files.2 June 2019 at 12:54 pm #577251https://commonwoodworking.com/using-registration-faces/
Try doing this exercise!
Thank you all, I’ll look into it.
So, how do I make sure the initial surface is 100% flat, ensuring I can then use that to gauge everything else? I can’t use the combi square because, at this point, I don’t have a 100% flat surface.
One thing I definitely need to get hold of, are winding sticks.
EDIT: If I’m not parallel, would that throw my line off?
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You must be logged in to view attached files.@mark68 you need to watch Paul’s videos. He goes over these things in almost every project. You will need to learn the terminology to ask questions, otherwise it is almost impossible to give help.
An arris is where two planes meet. You could cut yourself on an arris in metal.
Most woodworking pieces have a length and then are wide in one of the other directions and narrow in the other. Think of the vertical part of a door (a stile). It may be 30 inches long and then maybe 2 1/2 wide and 3/4″ thick. We call the wide surface a face and the other one an edge.
So, there are two faces and two edges. We take extra care to make sure one of the faces is flat, straight, and free of twist and, also, make sure one edge is straight, flat, and free of twist. Generally, we make sure these two are perpendicular to each other (square). We call these the reference face and reference edge. Even if you machine your wood perfectly so that all surfaces are flat, straight, and square, you should pick a face to be the reference face and pick an edge to be a reference edge. We put a loopy mark on the reference face that runs towards the reference edge and then put a V like mark on the reference edge.
Every time you put your square on the work, the handle of the square should be on the reference edge or reference face.
Go look at Paul’s earlier videos. These are basics you really need to master. Maybe the tool tote project or the dovetailed boxes? As for getting material flat, look in the tools and techniques videos.
Thanks Ed.
Yes, I watched quite a few videos yesterday and I now know what’s required. Turns out I was doing about 99% of everything required. I have realised I just need to take a little more care and pay more attention to the finer detail. It doesn’t help that I have full blown ADHD. This means, the longer I stay on a task, the faster I tend to work. It’s biological and I’ve learned I have to walk away from a project for a few minutes.
@mark68 keep at it. You’ll get it. Once you see how using just one face and one edge to reference off of works, it will make more sense. You might even want to play with material that is wonky on the other face and edge to see how using one reference face and one reference edge makes those other faces not matter. If you need to strike a line that is longer than your square, you still work from the reference edge, but you hold a longer rule or yardstick against the square to get the reach needed for striking the line.
Paul makes it look easy, but there are a lot of steps and it is easy to miss them when you are learning. Once you get through it a couple times, you’ll understand why things are done as they are and it will get easier.
Just spent about 2 to 3 hours truing up my workbench aprons. Enjoyed.
Funny thing though, when I used my combi square (which is now square due to the handy video link provided by ecky H above – thank you) I saw a thin sliver of light of the same uniform thickness, between apron surface and bottom of the square. Then, I noticed my square wasn’t perpendicular to the apron, so when I made sure it was, that sliver of light all but disappeared.
So I’m not sure what’s going on. Combi at a tilt, there’s that sliver of light, when perpendicular, it’s gone.
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