Replies

1. 
   lat_axe | Dec 06, 2024 01:28pm | #1

   Although I have no experience of making a proper wooden straight edge that's likely to be very accurate and to stay that way, I have made and used many an ad-hoc wooden straight edge, just as a matter of convenience-at-the-time.

   I notice that two main factors are the biggest bugbears: wood type/grain structure and the likely change of humidity such a tool is likely to see.

   Some timbers warp easily, especially if they don't have inherently straightish grain. The best ad-hoc ones I've used have been made of dense old-growth tropical hardwoods of the less swirlygrain ilk. But even those eventually go not-quite-straight in time.

   I've come to prefer metal straight edges of decent (but not ultimate engineering) quality. As long ones cost a packet, I still knock up a wooden one now and then, using it infrequently until it becomes not really straight anymore (a condition not always easy to measure, of course, without another long straight edge). :-)

   But then - how "straight" does it need to be for the task?

   ***********
   I do recall that the nice wooden ones with the holes in have those holes to reduce the effects of warpage. Effectively the holes reduce the width so that part that shows "straight-or-not" is a less wide continuous edge (so less likely to warp) but still give plenty of width to the whole tool for holding and applying it. You can even put your fingers in the holes to apply it.

2. 
   phantomtrapper | Dec 07, 2024 12:47pm | #2

   I think wood selection is probably the main consideration. Its hard to tell through the patina of dirty hands and shop living, but I think mine is mahogany, pretty straight grain. 7/16x44x1 1/2-2 inches as you follow the curve. I've had it 30 years and as a boy in the 50's I remember my dad using it. I don't know if he bought it, made it or even inherited it, I'd have to say its been used for 65-70 years, and never touched up. There are no slots or holes exept one to hang it up and it is as straight as an arrow and as flat as my jointer bed.

3. 
   user-1147207202 | Dec 07, 2024 01:45pm | #3

   Isn't this what MDF is for? I've a number of straight edge and T piece jigs for use when marking up or as router guides, using 6 or 10mm thickness MDF. You could get an eight foot straight edge using the factory edge, and the dimensional stability is very good. I coat with shellac, after writing on the function and fit (e.g. router guide and cutter size) and they last a long time with a modicum of care.

4. 
   sjeff70 | Dec 07, 2024 08:42pm | #4

   I’ve seen a straight edge made of quartersawn maple. Banding or lipping a secondary wood with hard maple.

5. 
   rob_ss | Dec 07, 2024 10:16pm | #5

   No experience as I just make them as needed using a sliding table saw and plywood, but I would pick quarter sawn wood that is quite wide in relation to its thickness for the greatest stability.
   I did have a think about reference surfaces to test with, and came up with a string line as a way to create a perfectly straight reference of arbitrary length, but in truth I'd probably use the factory edge of a piece of MDF as a reference that is 'good enough for woodwork'

6. 
   CharlieFurnituremaker | Dec 08, 2024 03:59am | #6

   https://paulsellers.com/2017/03/making-my-straightedge/

7. 
   lat_axe | Dec 08, 2024 07:48am | #7

   Here's a pontification by a fellow who attempts, with a degree of success, the argument that a wooden straight edge for woodworking is best made at the time (with a jointer plane, for example) for the particular purpose needed at the time.

   https://www.theenglishwoodworker.com/simple-straight-edges/

   One of the comments on this piece, lower down, remined me that .....

   When I plane long board edges to make them suitable for gluing into things like table tops, I check the edge for straightness first by-eye, looking along the edge, at eye-level. as the plank sits in the vise. As I plane the necessary sections to get flatness/squareness, the eye remains the checker.

   Two planks that will be glued edge-to-edge are usually planed together, to make it easier to keep the whole affair flat when the tabletop is formed. (Dead square is not needed, only two matching near-squares that together add up to 180 degrees).

   Once I've got them straight, I swap planes for a shorter item and put that little dip end-to-end, as part of the technique for keeping the ends glued tight when the planks are clamped & compressed to form the tabletop. At this juncture, I put all the unglued planks vertically stacked to ensure that the gaps are right (less than a millimetre in the middle of, say, six foot long planks).

   The eye remains the checker to ensure that the stacked but unglued tabletop is not wonky - the tabletop must look flat-by-eye.

   Only once the thing is glued & clamped do I resort to the metal straight edge to look for any from-the-clamping unstraightness. which is mended with a rubber hammer and a bit of clamp reconfig.