Flattening a worktop

[phil p]

Hi,

I bought a second hand bench last year, nothing flash, however it has a hardwood top which has a slight bow in the middle.

It’s only around 1-2 millimetres deep but I would like to get rid of it if I can.

I’m only a DIYer so it doesn’t have to be that precise so I was wondering if it could be either planed out or belt, disc sanded?

Any advice for the best (easiest) way to do this?

 

[Rich C]

Yes you could plane it out, a nice long plane will give a better result.

 

[Jacob]

Hi,

I bought a second hand bench last year, nothing flash, however it has a hardwood top which has a slight bow in the middle.

It’s only around 1-2 millimetres deep but I would like to get rid of it if I can.

I’m only a DIYer so it doesn’t have to be that precise so I was wondering if it could be either planed out or belt, disc sanded?

Any advice for the best (easiest) way to do this?

One way to flatten surfaces is to lay on a straight edge and mark with a pencil all the points where it is close to and/or touches the surface. Then plane off the marks and around them, preferably with a long plane. Then repeat.
Disc sander would do.
Or in brief: identify and mark the high points/areas and remove them.

 

[phil p]

Hi,
I only have a small hand plane therefore would an electric planer do making very thin passes and finish off with the sander?

 

[Jacob]

Hi,
I only have a small hand plane therefore would an electric planer do making very thin passes and finish off with the sander?

They'll all do it but it depends on operator's skill! If you keep monitoring your progress with a straight edge and marks, you get better at it.
Another useful tool is a hand-torch with a focussed beam - it shows up dips and hollows if you shine it across a surface.

 

[eribaMotters]

If it is only 1 or 2 mm I'd be tempted to leave it unless you are 100% certain you can get it perfect.

Colin

 

[Jacob]

If it is only 1 or 2 mm I'd be tempted to leave it unless you are 100% certain you can get it perfect.

Colin

Well yes I agree. I doubt my bench has ever been that accurate!
Trouble is there's a big cult following for super flat "reference" surfaces etc which make perfect sense, but in fact you can do perfectly well without them!

 

[Adam W.]

A crown in a bench top tends to make the work skate about, which I think is a complete drag.

 

[Jacob]

A crown in a bench top tends to make the work skate about, which I think is a complete drag.

A dip is good then! Keeps the workpiece "cradled"?

 

[phil p]

Hmm,

Food for thought if it doesn’t have to be that flat, I might just leave it as chances are that I could make it worse.

Thanks for all the info.

 

[Adam W.]

A dip is good then! Keeps the workpiece "cradled"?

Depends on if you use your bench top as a reference surface to make flat work, I guess.

 

[Ttrees]

A crown in a bench top tends to make the work skate about, which I think is a complete drag.

Not a problem if it's a very small one say less than 1/64" on something like a 7 or 8 foot bench, as material deflection plays a part in something of this length.

A dip is good then! Keeps the workpiece "cradled"?

And if you use the bench cuz ya don't have a surface planer, that dip will
make the work hinge/pivot from the ends, even if one has nose dived off the ends!.

Not a good way to preserve as much material compared, as the ends are better
to have the excess, as the work will stand on itself without pivoting/seesawing about in the middle.
And there's loads of traditional suggestions to have a sprung joint.

Tom

 

[Adam W.]

1/64th is half a mil. We're talking 2mm, which makes a bit more of a difference.

 

[Ttrees]

Hmm,

Food for thought if it doesn’t have to be that flat, I might just leave it as chances are that I could make it worse.

Thanks for all the info.

Sounds like a safer option to me, as with only a single plane I'm guessing you don't have that much experience using it for cabinetmaking, should say tearout be of concern for one, it could pull out chunks as deep as you intend to go down if the wood is like iroko.

This is a hump in the middle isn't it, and not a dip?
If a dip then simply shimming might be well worth it
Seeing as it's timber, it's likely thicker than this top, and only needing a single point
under the middle.

But it sounds the opposite case
I question what you have used to make such an assertion, and am guessing you have a decent enough straight edge
I only bought one recently as I kept using my long stock up.

The edges can be flipped around or over instead, and should give one some sort of an idea of flatness, say should both decide to move in the same banana fashion,
then flipping one around would make this extremely obvious.
(doubling the error)

But I needed to test it first

Tools involved
Long plane is much easier, and likely a good understanding of the cap iron.

A calipers, not for reading measurements, i.e could be done blindfolded, you can feel a lot better than you can see, on even the cheapest thing for a tenner in the middle isle.
I like the non digital ones like below.

And a long reach lamp for the job.
These ones were made in Italy is the sticker is to be believed, and seem to be hard to find, should none secondhand about then seemingly slightly smaller ones for a tenner
are available if you look for "territal" lamps, in eikeas warehouse.

May seem fancy, shoot me down, but I doubt anyone would think this kit is that over the top financially wise, and is stuff that one would use everyday.

Tenner for the lamp, which is absolutely nessecairy anyway.
Fancy calipers probably twice that, should one not have a cheaper one knocking about.
A pencil gauge would get one there but slower.

A long plane makes this easier, but not necessary, just have to be more careful.
Checking eliminates as much need for an only somewhat trustworthy tool,
as in, if one isn't used to using hand planes, it ain't just a case of a hand plane making things automatically flat, no matter the length.

David Charlesworth's teachings is just about the best info you will find regarding
working to fine tolerances.

All the best
Tom

 

[Inspector]

Phil post a couple pictures of your bench. You might be able to shim or adjust the bow out depending on how it is constructed. I would not bring a power plane near the bench as they munch wood like there is no tomorrow and you are likely going to make it a lot worse. I would leave it alone for the time being and do a little reading on using your hand plane and getting it sharp. Then after a little practice on a bit of scrap, plane the high places by hand. It will give you the best result and teach you a lot that will benefit you down the road when you may want to clean up the top again or work bigger projects. Getting a surface flat with sanders is also not an easy skill to master and it is of course dusty.

Pete

 

[Jacob]

Sounds like a safer option to me, as with only a single plane I'm guessing you don't have that much experience using it for cabinetmaking, should say tearout be of concern for one, it could pull out chunks as deep as you intend to go down if the wood is like iroko.

This is a hump in the middle isn't it, and not a dip?
If a dip then simply shimming might be well worth it
Seeing as it's timber, it's likely thicker than this top, and only needing a single point
under the middle.
View attachment 133106
But it sounds the opposite case
I question what you have used to make such an assertion, and am guessing you have a decent enough straight edge
I only bought one recently as I kept using my long stock up.

The edges can be flipped around or over instead, and should give one some sort of an idea of flatness, say should both decide to move in the same banana fashion,
then flipping one around would make this extremely obvious.
(doubling the error)
View attachment 133111
View attachment 133108
But I needed to test it first
View attachment 133107

Tools involved
Long plane is much easier, and likely a good understanding of the cap iron.

A calipers, not for reading measurements, i.e could be done blindfolded, you can feel a lot better than you can see, on even the cheapest thing for a tenner in the middle isle.
I like the non digital ones like below.
View attachment 133109

And a long reach lamp for the job.
These ones were made in Italy is the sticker is to be believed, and seem to be hard to find, should none secondhand about then seemingly slightly smaller ones for a tenner
are available if you look for "territal" lamps, in eikeas warehouse.
View attachment 133110

May seem fancy, shoot me down, but I doubt anyone would think this kit is that over the top financially wise, and is stuff that one would use everyday.

Tenner for the lamp, which is absolutely nessecairy anyway.
Fancy calipers probably twice that, should one not have a cheaper one knocking about.
A pencil gauge would get one there but slower.

A long plane makes this easier, but not necessary, just have to be more careful.
Checking eliminates as much need for an only somewhat trustworthy tool,
as in, if one isn't used to using hand planes, it ain't just a case of a hand plane making things automatically flat, no matter the length.

David Charlesworth's teachings is just about the best info you will find regarding
working to fine tolerances.

All the best
Tom

On the other hand - you can easily tell if a piece is straight enough by sighting down it. Woodworkers don't generally need straight edges.
You can easily tell if it's twisted by laying on winding sticks and sighting over them.
"Fine tolerances" is for engineers. 1/32" is about as fine as a woodworker needs to go, though things may be adjusted to fit each other with much closer tolerances resulting, without measuring anything at all.
PS in any case wood moves. A longish piece may be laser straight after planing, but have a dip and a twist of several mm by the following morning. It doesn't matter - the assumption is that it will be pulled into line during the construction of whatever it is. Hence important to get the sides all square and parallel to each other even if it goes a bit bent.

 

[Ttrees]

@Inspector Indeed that is sound advice
I coulda mentioned that my shims are seasonably adjusted...
should this be an issue with the construction of the bench/something causing that bowing.

Coulda also mentioned that I have some sort of an idea of the errors on my new beam.
As its very difficult to get a true reading on anything convex.
Should one know how flat their straight edge is, and the bench is quite flat and made well,
then one could leave the perimeter alone and work the bump out of the center,

i.e a straight edge which will give a slightly sprung joint, will hinge from the corners of the bench, (when close to flat)
making it possible to reference off of each corner,
should everything be bang on, floor, base, top thickness,
then it is possible to use winding sticks to have an idea of twist or other error.

Tom

 

[Jacob]

@Inspector.......
then it is possible to use winding sticks to have an idea of twist or other error.

Tom

You can use winding sticks and squint for straightness on stuff resting over a couple of boulders!

 

[Ttrees]

So you're saying that you'd start planing the top, just cuz one of them boulders rolled about?
Should it be some Flintstones style bench and not made on the Labby rock?

 

[Jacob]

So you're saying that you'd start planing the top, just cuz one of them boulders rolled about?
Should it be some Flintstones style bench and not made on the Labby rock?

No but what I am saying is that the "reference surface" is the one you are planing, not another one on the bench etc.