How to check straightness of boards edges?

[SMALMALEKI]

That's not small. That's a big gap.

All you do is note where they are touching, and plane a bit off that area, then offer up again. Keep on offering up and adjusting until there is no gap. I always then like to finish with one complete full-length pass with the plane, just to clean up the face after the adjustments.[/quote]


Thank you for your tip. I’ll try it.
Let me make a simple declaration here.
I know a 2-3 mm gap is too big for edge joining.
But when I was researching on straightedges couple of weeks ago they have a tolerance of 0.5mm/m. In my novice mind it translates to 1mm per 2m. If we imagine the curve is equally distributed and we have two straightedges of two meters then a gap of two millimetres is within the tolerance of straightedges. Am I wrong?
Could somebody educate me please?

Best regards

 

[Jacob]

The whole point of the work bench top when planing is that it forms a solid support for the stuff being planed. If the surface you use to plane on is not flat and true, the stuff your planing will also not be flat and true as the stuff will flex over the undulations. The reason the effort is put into flattening the work bench top is to generate the ‘reference’ surface you put the wood onto to plane.

I will add before there is a barage of comments that the ‘work bench reference surface’ comes into its own after you have flattened one side. It’s an aid to speeding up flattening the other side.

You can achieve a flat true surface without having a flat a true work bench ‘reference’ surface but then you have to faff around swinging the wood etc to find the low and height points.

Jointing a board can be done in a vice, however if the stuff is long it will drop where it’s not gripped. You can place bench dogs to support / travelling steady, but again this also allows the stuff to droop under the pressure of the plane. The best way to quickly joint is to use a planing stop and do it on the work bench top.

Work benches were usually made to be the length of the longest stuff to be planed.....typically doors. So 6’6”~7’ was a typical length. For a small workshop, where hand tools are primarily used for 4 squaring the wood, the bench should be ideally the length of the longest thing you think you will make and no longer.

There is no escaping having to "faff around swinging the wood etc to find the low and height points" though I'm not sure what the "swinging" bit is.
The idea that having a perfectly flat bench and perfectly flat planes will automatically produce perfectly flat workpieces, is illusory. Not least because all four faces of a sawn timber won't be flat to start with and may even change shape as it is being planed. You are just going to have to faff about and use your eyes.
Rule 1. Get into the faffing about habit early! n.b. it will improve with practice!

 

[Jacob]

....
I know a 2-3 mm gap is too big for edge joining.

Not ideal, but if in the middle the boards may be OK if cramped up whilst gluing. Not good if the gap is at the ends - they are are more likely to open up

But when I was researching on straightedges couple of weeks ago they have a tolerance of 0.5mm/m. In my novice mind it translates to 1mm per 2m. If we imagine the curve is equally distributed and we have two straightedges of two meters then a gap of two millimetres is within the tolerance of straightedges. Am I wrong?
Best regards

Don't research straightedges! It'll drive you mad.
Rely on what you can see. If it looks straight then it is straight enough for woodworking purposes.
I use a combi square ruler but I am not going to obsess over it. Have occasionally used the edge of a builders level as a longer straight edge (setting up planer tables etc) or made my own for similar purposes - verifying it is straight by looking at it down the length.
PS a lot of confusion is caused to woodworkers by engineering ideas being brought in. Engineering works to invisible tolerances, 1/1000" etc. Woodwork works to about 1/64" which is about as small as you can see with the naked eye. For most woodwork purposes 1/64" precision is well beyond what you really need.

 

[MikeG.]

The whole point of the work bench top when planing is that it forms a solid support for the stuff being planed. If the surface you use to plane on is not flat and true, the stuff your planing will also not be flat and true as the stuff will flex over the undulations. The reason the effort is put into flattening the work bench top is to generate the ‘reference’ surface you put the wood onto to plane...............

Any chance of reading the thread title, and the OP?

This is about straightening an edge, which is done in the vice. However much you guys who obsess about "reference surfaces" go on and on about them (wrongly), it is an irrelevance when it comes to straightening edges.

 

[Jacob]

The reason the effort is put into flattening the work bench top is to generate the ‘reference’ surface you put the wood onto to plane...............

No. It's just that a reasonably flat surface is generally useful, whether it's for woodwork, pastry, jigsaw puzzles, shove ha'penny, you name it! :lol:

 

[MikeG.]

The whole point of the work bench top when planing is that it forms a solid support for the stuff being planed. If the surface you use to plane on is not flat and true, the stuff your planing will also not be flat and true as the stuff will flex over the undulations. The reason the effort is put into flattening the work bench top is to generate the ‘reference’ surface you put the wood onto to plane...............

Any chance of reading the thread title, and the OP?

This is about straightening an edge, which is done in the vice. However much you guys who obsess about "reference surfaces" go on and on about them (wrongly), it is an irrelevance when it comes to straightening edges.

Deema chose to respond to this with a snarky little PM, rather than in the thread, claiming that if I had served an apprenticeship I would know what I'm talking about (in terms). So I call on those who worship the notion of using the bench-top as a reference face to explain how that makes any difference to putting an edge on two boards, which is what we are talking about here. I'm all ears.

You don't use a vice for preparing an edge, apparently. I look forward to deema explaining this to custard, who has obviously been doing it wrong for his entire professional career.

 

[Jacob]

The whole point of the work bench top when planing is that it forms a solid support for the stuff being planed.

Yes

If the surface you use to plane on is not flat and true, the stuff your planing will also not be flat and true as the stuff will flex over the undulations.

Not if you want it to plane it flat - checked by looking at it.

The reason the effort is put into flattening the work bench top is to generate the ‘reference’ surface you put the wood onto to plane...............

If the stuff you are planing is not flat and true to start with then it could flex on a perfectly flat bench surface and end up planed with a bend. Either way you have to faff about and look at it.
The basic planing process is to flatten the best side, then mark the thickness and plane down to the lines. If you do this carefully you don't even have to look at the back - just the lines. In fact the backs of a lot of trad stuff are often crudely finished where they are out of sight. It's only the edges where they join which matter.

 

[MikeG.]

....... the backs of a lot of trad stuff are often crudely finished where they are out of sight. ......

That's putting it mildly. I've seen plenty of beautiful pieces where the back of the backs were finished just with an adze or an axe. Rough as old boots.

 

[Jacob]

....... the backs of a lot of trad stuff are often crudely finished where they are out of sight. ......

That's putting it mildly. I've seen plenty of beautiful pieces where the back of the backs were finished just with an adze or an axe. Rough as old boots.

I saw a table top where the visible edges and ends of the back where they went over the apron, were all planed neatly to an inch thickness or similar, but the inner bits were hardly touched and really thick, up to 3" or so. Saves labour and makes a much stiffer table top!

 

[AJB Temple]

Jacob and Mike are spot on. I've made a lot of work surfaces and table tops over the years. Perfectly straight has always been irrelevant compared with perfectly mating. Bemused really by what the bench top has got to do with it.

 

[deema]

I clearly haven’t been very clear in my attempts to help and perhaps caused confusion. Custard’s link to edge jointing is a superb demonstration of the standard techniques taught on how to edge joint. One thing that isn’t totally clear in the initial question (to me at least) is how the edges are being planed. If the parts are being laid unsupported across the two saw horses then edge jointing will be very difficult. The technique illustrated in Custards article shows how long pieces are normally placed on a flat surface that supports it and the planning is done by running the plane alone the flat (reference) surface. Any flat surface when making the work bench will do.

Laying the the edge off a piece of ply or MDF sheet is often a good simple way of seeing 2~3 mm of gap on a long length. I suspect you have a gently bowed form created by planing between two saw horses.

 

[MikeG.]

I clearly haven’t been very clear in my attempts to help and perhaps caused confusion. Custard’s link to edge jointing is a superb demonstration of the standard techniques taught on how to edge joint............

Except Custard shows the edge planing (note: 1 "n") being done in the vice, which is the very thing you insist is wrong. As I've said all along, the surface of the bench is irrelevant if the board is in the vice, and if you are edge joining (the subject of this thread), the timber is in the vice. Try to bring a little consistency to your argument.

 

[Jacob]

.... Custard’s link to edge jointing is a superb demonstration of the standard techniques taught on how to edge joint.

Except he uses straight edges. Making two edges each fit the straight edge is more difficult than simply fitting them to each other and missing out the straight edge altogether. He also uses the expression "reference face" which is confusing as the term "face" alone is all you need. A board has a (best) face, a back, a (best) edge and back edge. You get them as straight/square as you can first, judging by eye and square, and then fit them to each other, not to a straight edge.

One thing that isn’t totally clear in the initial question (to me at least) is how the edges are being planed. If the parts are being laid unsupported across the two saw horses then edge jointing will be very difficult.

You couldn't plane an edge on a board simply standing it vertically. How does our OP do it?

The technique illustrated in Custards article shows how long pieces are normally placed on a flat surface that supports it and the planning is done by running the plane alone the flat (reference) surface. Any flat surface when making the work bench will do.

You mean use the bench like a shooting board? Possible I suppose, but tedious. Easier to clamp or wedge them vertically if you don't have a vice. A pair of door props is really handy if you are on site or away from a vice.
Couldn't find a better photo: these door wedges are knocked up in minutes from scrap, or more carefully on a bench. Brilliant substitute for a bench vice. Stand board in one or two wedge props and put far end of board (door etc to be planed), against something solid for resistance to planing efforts.

 

[MikeG.]

Careful Jacob, that door will bow in the middle if you plane it like that unsupported by a reference surface. :wink: :lol:

I just lie a B&D Workmate down, gripping the end of the door in its jaws.

 

[Jacob]

Careful Jacob, that door will bow in the middle if you plane it like that unsupported by a reference surface. :wink: :lol:

I just lie a B&D Workmate down, gripping the end of the door in its jaws.

I'm starting to worry about reference surfaces!
Try the wedge prop. Much handier than a workmate, quicker, and take up little floor space. One will do, two is better. You can lift and move the door or board with the wedges still attached.

 

[MikeG.]

........Try the wedge prop. Much handier than a workmate, quicker, and take up little floor space........

I shall. More importantly, they will protect the floor better than a Workmate. Particularly handy if working on a door with door furniture already fitted.

 

[Sgian Dubh]

I shall. More importantly, they will protect the floor better than a Workmate. Particularly handy if working on a door with door furniture already fitted.

Another option, no better or worse than Jacob's floor resting device, except that it takes up more space I suppose, is to cut a notch out of the end of the horizontal member of a saw horse, or saw horses. Cut one side of the notch perpendicular to the wide faces, and the other at a bit of an angle, say 5 or 10 degrees. Slide the door into the notch, and drop a wedge in place to hold it firm. Slainte.

 

[Doug71]

Sorry for going slightly off topic but for holding doors throw away your wedges etc and get a Magic Gripper, they are brilliant.


http://www.themagicgripper.co.uk/

 

[Jacob]

Sorry for going slightly off topic but for holding doors throw away your wedges etc and get a Magic Gripper, they are brilliant.


http://www.themagicgripper.co.uk/

:lol: :lol: Only £90 a pair!

 

[Sgian Dubh]

The technique illustrated in Custards article shows how long pieces are normally placed on a flat surface that supports it and the planning is done by running the plane along the flat (reference) surface. Any flat surface when making the work bench will do.

I must admit that's a technique I reserve for dealing with thin stock that's to be edge jointed. Basically stuff that's too flexible to be held in the vise without flexing as you run the plane along, e.g., edge jointing a stack of veneers, or perhaps very thin drawer bottoms using a long shooting board made of ply or similar.

Apart from that, I've always used the vise to hold boards to prepare edge joints. If the board's very long you might need additional support at the end furthest from the vise. I have a piece of wood with a couple of steel dowels that drop into holes in the far leg (from the vise) as and when I need it. On the other side of this piece of wood there are a series holes bored that can take a short length of broom handle, and this supports the other end of the long piece.

I'm with others on the preparation of edges for making wide panels in that matching is the aim rather than perfectly straight. I also generally prepare a sprung joint rather than a perfect match, but I make the spring very slight.

A perfectly flat bench is ideal, but I've never found much of a problem if the top is off a bit, although I've also had to work on benches that were badly out of whack - not great, but sometimes you just have to work with what your employer provides. Having said that, after couple of decades of use my own bench had developed a hump across the width, which was a bit of a pain because wide stuff I was working on would rock. To improve it I spent an hour or so fairly recently with a no 7 plane and a sander to get it reasonably flat again. It is certainly an improvement on the humped version but did require a bit of deepening of recesses for things like holdfasts. Slainte.