What is an acceptable gap when using a hand plane?

[tibi]

Hello,

I would like to ask if there is an acceptable gap between the straight edge and the wood when checking along the width of the board when hand planing the face or edge when hand joining the edges for glueing. I have seen many videos on the subject where instructors tell that no light should be visible, but I cannot achieve that across the full width of the board or full width of an edge. When instructors check for the light under their square or straight edge, there is not enough resolution to see if there is actually no light, or the gap is tiny and they consider it to be OK.

For faces of the board, I can get 0,05 mm - 0,1 hollows across the width of a board (e.g. 150 mm) and for edges, I can get similar results, but the line seems to be wavy for me. If the width of the edge is 30 mm, there are one or two places with miniature gaps (below 0,05 mm), but I steel can see light through them.

There is either a bump in the middle across the width, or one side is higher than the other. I have never encountered a situation where the middle of the edge would be hollow.

When I move the square along the length of the board to check the light, the contact point starts usually at one end of the board, then goes to the middle of the edge and then goes either way to one or another edge of the board.

I have almost never found a section, in which I have seen no light under the straight edge, although the gaps were below 0,1 and sometimes below 0,05 mm.

I check the gap with feeler gauges, that can measure up to 0,02 mm (that is 0,8 thousandth of an inch)

This is valid for planing oak, when planing fir, I can get sections where I cannot see any light under the straight edge or square. It may be caused by the softer structure of the wood and that it can be pressed a little to close any gaps.

I would like to ask if my results are good enough and I should put up with it or I should improve my sharpening, plane setup or planing technique to get really no light visible under the straight edge across the whole length of the edge or across the whole width of the board. If I check the length of the boards, I can get a tiny hollow in the middle as well, but I know that this is acceptable if it is not too big and it is not a bump.

The gap may cause me the biggest problem when glueing the legs of a table from multiple boards. I need to glue wider boards together face to face. And having a wavy surface on both sides, although miniature, can have a negative compound effect.

Thank you.

 

[billw]

Trying for absolute accuracy is a deep, dark hole from which you'll never return. A 0.1mm gap wouldn't phase me in the slightest.

 

[tibi]

The problem that most of us are not trained under some very experienced master, who can show us what is good and what is bad. From the youtube videos we get some insight, but there are some gaps where we can only guess.

We can only guess answers to question what is sharp, what is straight and what is flat in the eye of an experienced master.

 

[billw]

The more important thing is what's good enough in your eyes? Sure, I'm sure some of the professionals with years/decades of practice could grab a plane, skim it over a surface and have it perfectly flat in a couple of minutes.

Will what you're making be affected by that much variance? 1mm out on the side of a box might be glaringly obvious, in the leg of a dining table it would be unnoticeable.

In the first piece of furniture I ever made I reckon there's gaps of well over 2mm in places. Do I care? Nope. DId I learn from it? Yup.

 

[Droogs]

If you are not getting it so that there is no light across the face and especially the edge, check the alignment of your blade. adjust it a tiny bit and try again. On an edge move the plane over to the high side of the centre line and take a shaving and see how it is. You will not get perfectly flat of the plane across a face just because of the shape of the blade but you should get perfectly square and flat on an edge

 

[Benchwayze]

Just get it cleaned up. Finish with a scraper if you must.

If you can't get it right, then finish with an adze. (Robert Thompson 'The Mouseman' did so.)

I realised that someone might think I am being sarcastic. Not guilty folks!

Still, hobby woodworkers are not likely to get as much experience as professional hand workers and it isn't going to be easy to reach their standards. Just get it as flat as you can, and as long as it doesn't affect the look and stability of the piece, live with it. The average lay-person won't ever notice it.

And that's good advice from Paul, when making a rub-joint by hand.

John

 

[paulrbarnard]

A trick when edge jointing boards is to plane them both at the same time. That way they will both have the same 'incorrect' angle. When you put the boards together the two incorrect angles cancel out exactly. On the length of the joint it is better to have a very slight dish rather than crown, that is much less likely to show a gap.

 

[tibi]

If you are not getting it so that there is no light across the face and especially the edge, check the alignment of your blade. adjust it a tiny bit and try again. On an edge move the plane over to the high side of the centre line and take a shaving and see how it is. You will not get perfectly flat of the plane across a face just because of the shape of the blade but you should get perfectly square and flat on an edge

This is exactly what I was thinking, If I have slightly cambered blade, then I cannot get perfectly flat face, i.e. I will have waves across the width of the face, even though they will be very small. If my blade is perfectly straight, I will get grooves made by the edges of the blade. So it is a trade off.

 

[Droogs]

yep

Rmember what you want is "flat enough" unless you start using a scraper, but I wouldnet do that usually until the end

 

[tibi]

A trick when edge jointing boards is to plane them both at the same time. That way they will both have the same 'incorrect' angle. When you put the boards together the two incorrect angles cancel out exactly. On the length of the joint it is better to have a very slight dish than crown, that is much less likely to show a gap.

I know about that trick, I must just try it when the total thickness of both boards is more than the width of the blade. But I should get good results as well.

 

[Ttrees]

I don't use feeler gauges but do use some techniques like rocking and pivoting on my bench, and rubbing timbers to gloss the high spots.
See Charlesworth, he explains why a slightly concave surface is superior and something to aim for.

This is what I have used for a good while for checking my bench and shimming it with blocks, I have an aluminium beam but it's not as long as the work, and the overhang from the countertop deflects, but it gets me by.

I used the beam before to level the bench, but was to find out that I had made it concave resulting in snipe like appearance that you would get from a badly set up planer.
Anymore, if I do this, I will make sure to have two lengths of parallel timbers the length of the work if I ever stop using those nice lengths up...

Best you can hope for is to have a good flat bench or planing board which you can be sure that the material won't deflect, getting consistent shavings throughout the board, as deflection of material could be giving you false readings if it may need better support.

Cue puking and snoring from everyone

Tom

 

[tibi]

I have seen all relevant videos by David Charlesworth on his youtube channel and once I will have bought at least the basic toolkit, I will invest into his paid DVDs, too. Also, I want to buy some classic woodworking books, too.

I have ditched my old small table, that was made of very thin steel profiles and was unusable for woodworking and I would like to build small, but proper bench next year. ( I do not enjoy planing during the winter in the garden, as I do not have enough space to build a workbench in my garden shed).
Currently I have attached a small vise to the sawhorse and I sit on the sawhorse so that it does not move when planing. That way I can at least train edge planing and small face planing (up to 150 mm in width) in the meantime until I build a workbench.

 

[David C]

Minute gaps in both length and width are acceptable, and useful.

Try for 0.1 mm which is the thickness of a piece of good printer paper.

I have a DVD on precision hand planing which might be useful. (From my website).

Best wishes,
David Charlesworth

 

[D_W]

This isn't something to measure. Ideally, any gaps you have should be closable with hand pressure. If that's not attainable at first (it'll become easy without even checking for squareness and straightness if you stick with hand tool woodworking - you'll feel both through the plane), then for visible joints where you really care (like door panels on something fine), then you can waffle with those until they're perfect. Otherwise, get some experience and repetition and see how things go.

If you're not using a cap iron already, learn to use it. There may be some people who don't like hearing about that all the time, but it does something extremely critical for hand work - it makes the shaving thickness consistent end to end regardless of grain orientation. That means if the wood feels flat, it's flat. It also means you won't plane something out of flat or plane the ends off of boards if the grain is inconsistent on a board. If you're experiencing tearout of any significance, what happens is that section of wood changes in thickness planed off at a different rate than the rest.

It sounds overly demanding, but working like this is far less demanding instead.

 

[tibi]

Minute gaps in both length and width are acceptable, and useful.

Try for 0.1 mm which is the thickness of a piece of good printer paper.

I have a DVD on precision hand planing which might be useful. (From my website).

Best wishes,
David Charlesworth

Hello David,

Thank you very much for your answer. Your DVDs are on my wish list for some time already so I will definitely buy them and learn from them.

 

[tibi]

This isn't something to measure. Ideally, any gaps you have should be closable with hand pressure. If that's not attainable at first (it'll become easy without even checking for squareness and straightness if you stick with hand tool woodworking - you'll feel both through the plane), then for visible joints where you really care (like door panels on something fine), then you can waffle with those until they're perfect. Otherwise, get some experience and repetition and see how things go.

If you're not using a cap iron already, learn to use it. There may be some people who don't like hearing about that all the time, but it does something extremely critical for hand work - it makes the shaving thickness consistent end to end regardless of grain orientation. That means if the wood feels flat, it's flat. It also means you won't plane something out of flat or plane the ends off of boards if the grain is inconsistent on a board. If you're experiencing tearout of any significance, what happens is that section of wood changes in thickness planed off at a different rate than the rest.

It sounds overly demanding, but working like this is far less demanding instead.

Hello D_W,

Thank you very much for your answer. I am currently using cap iron on every plane that I have except the wooden scrub plane, where I think it is not necessary (and it was not provided by the manufacturer of the plane, too). I make sure that it is very close to the edge of the blade and I do my best to make sure that there is no gap between the blade and cap iron. I did not achieve this 100% at any of my cap irons yet, but I am very close.The tiny gap of 0,1 - 0,2 mm clogs up with small particles of wood and then it seems to work. I have ground and polished the front of the cap iron too. I will try to remove that small gap too, but I think that my cap iron is a little bit bent and no amount of hammering in the vise helped me to correct this.One edge is a bit higher then the rest of the cap iron. I just need to use the stones until I have a uniform line with a slight undercut that touches the blade for clearance.

 

[custard]

In terms of the finished component (ie a wider board made up from edge jointed narrower boards) then no gap is acceptable. Indeed, a visible glue line of any description (except where technical considerations make it inevitable) isn't really acceptable, although sadly it's fairly common in much commercial work. I've seen ugly glue lines even in the fairly expensive furniture sold in Heals for example.

When it comes to achieving invisible glue lines here are a few points worth considering.

Open grained, darker timbers tend to camouflage glue lines, so American Black Walnut for example isn't too demanding in this respect. Conversely, pale, close grained timbers are more difficult. Holly is often regarded as the hardest timber of all for invisible glue lines, but the much more common Sycamore and Maple will run its a close second.

If you edge joint straight from a thickness/planer the best you'll ever achieve is sub optimal glue lines. No matter how sharp the knives and how slow the feed rate they tend to scallop the edge. A freshly honed hand plane is always the route to the very best glue lines.

All glues aren't equal in the quest for invisible glue lines. Epoxy and UF glues (such as Cascamite) have many advantages, but beautiful glue lines aren't one of them. Another problem glue in this respect is traditional Scotch glue, there are so many uniquely good things about Scotch glue, but the glue lines are almost always pretty obvious.

One of the best glues for invisible glue lines is PVA. I know craftsmen and women who insist on using PVA, even when it's far from the best technical choice, simply to achieve the best glue lines. Unfortunately it isn't always possible, a classic example is with lamination work, UF glues are the better choice technically, and sometimes you just have to accept sub standard glue lines in order to benefit from their lack of creep and spring back. Here's a crest rail on a chair that I made, it would be nice if the laminations were invisible, but with the UF glue I used that's never going to be achievable

 

[johnnyb]

don't obsess about 0.1mm. concentrate on making. planing is just a stage in making. everything you make will help to show you what matters and what doesn't matter in the final item.

 

[Ttrees]

@tibi I do my best to make sure that there is no gap between the blade and cap iron. I did not achieve this 100% at any of my cap irons yet, but I am very close.The tiny gap of 0,1 - 0,2 mm clogs up with small particles of wood and then it seems to work.

I find that the only way I can get a cap iron to contact the iron without any gaps,
is focusing on the center of the cap iron when honing the underside...
i.e using something like a stuck down short abrasive strip not as wide as the cap iron is, or the corner of a hone.
Otherwise I end up with a gap at an end.

@tibi I have ground and polished the front of the cap iron too.

50 degrees on the top side is what most folks using the cap iron suggests,
David W has wrote quite a lot about the cap iron, in articles like wood central, and here, and has made quite a bit of youtube content about using the double iron plane, which if you need use the cap iron is one of the only sources that is thorough on the matter.

Not that it's complicated or anything, but its hard for some to let go of some of their fundamental beliefs which they have followed since the beginning.
i.e having tight mouths mostly, but also steep bevels,different frogs, back bevels and so on
See the shavings and choose for yourself and decide.

That's what your looking for if your wanting more information on smoothing,
but you need a bench first and I suggest having a go at finding a top for your sawhorse(s)
A pair of stiff beams jointed and affixed or even clamped to a solid core or fire door to prevent droop, would be an instant bench if you made up some of these plywood risers

Butt it against the wall or similar thing which might be against the wall

Alternatively maybe this video might be of interest


All the best

 

[dzj]

A while ago, I posted pictures of a chest of drawers I made. Hide glue, rubbed joints...There was a visible glue line or 2 on the
inside of the corpus.
End of the world as we know it.