Be kind to a man of very little brain

[Student]

It is with some trepidation that I venture on to a forum where the topic of capirons generates 240 posts in 10 days. However, here goes

Both Paul Sellers and Chris Schwartz have videos on You Tube about how to flatten the sole of your plane. Both use abrasive sheets stuck to granite plates. Chris Schwartz uses a cut up belt from a belt sander and Paul uses pieces cut from a roll. The question is "if you are using thick abrasive sheets, what advantage does a granite, or float glass, plate have over a thick piece of plywood or MDF"?

To avoid any notion of starting a sharpening debate, I am not looking for answers that say they shouldn't be doing it that way and the best way is ???. Whenever I see sharpening threads, I am always reminded of the quote about any set of experts. Ask 10 experts for the correct way to do something and you'll get 11 different answers.

 

[Wildman]

answer is a simple as a flat smooth surface in all directions.

 

[Beau]

A thick sheet is probably parallel so thickness should not have much influence. Flat is flat whether it's granite, glass a thick MDF or my choice a machine bed. MDF unless well braced might flex when working the plane over the abrasive. Whatever you use I would recommend using a straightedge to check the granite, glass, MDF etc and also check the results you are getting.

 

[Droogs]

it all boils down to how anal you want to be about flatness. the glass and grantie will be truely flat and level over a great distance than the mdf or ply, they are also likely to be more stable and less likely to warp over different temperatures and humidity ranges

 

[D_W]

PSA aluminum oxide roll on a long glass run if you're going to do more than a couple, but the glass run has to be on a flat surface because it will flex.

I've never used MDF or ply and can't speculate what they might be like, but I would limit use of such things to situations where they are checked flat against a known flat rule, etc, and backed well. They should be fine if that's the case. I would also limit use of that to fairly small planes.

The advantage of a long glass shelf is that a glass shop will have such a thing for a cabinet, it will be float glass, and it won't cost much. From experience, a piece of custom glass here (to your specifications), float and tempered is about $90. A shelf 8x42 and of 3/8th or 1/2" thickness is about $20 - it's not tempered, but one tends to be careful with such things.

I'd advocate spending the money to use something other than MDF or ply so that you have something you can use for a whole array of things in the future. You will find uses for a good lap, in plane making, refurbishing irons, etc, and if it is long, it will be 10x as useful.

Use PSA paper that is stuck down, anything not stuck down tight will dub and that is unsightly and will be a problem at some point when you are looking for aesthetics (in making a fine quality plane) or flattening something (like a plane iron - where dubbing is a serious problem).

 

[Carl P]

Some time ago Zeddedhed posted a link to a video of someone making a plane sole exceedingly flat by scraping - I have a couple of planes I'm going to have a go at with this method in the New Year, as it seems a better method.

https://www.ukworkshop.co.uk/forums/hand-plane-restoration-tune-up-t92398.html

Cheerio,

Carl

 

[AJB Temple]

For those who want to do this on granite, Waitrose are currently selling quite large and reasonably thick granite boards or place mats about 18" by 12" for around £15. Might be ideal for sharpening / flattening.

 

[Bm101]

I use glass shelves I took out my kitchen cupboards that we were scrapping. Seem to work ok enough to get a sharp edge. Micrometers don't really feature in my life. Then again... what do I know.

 

[ED65]

The question is "if you are using thick abrasive sheets, what advantage does a granite, or float glass, plate have over a thick piece of plywood or MDF"?

Possibly nothing. If the plywood or MDF are flat they're flat. But you can't assume they are, you must confirm it. And if you're really anal about how flat the plane must be when you're done you need to make sure they are not able to flex when in use.

Incidentally a typical kitchen countertop is often perfectly flat enough for this purpose, although of course using it might come with a whole different set of difficulties if SWMBO catches you!

 

[ED65]

Some time ago Zeddedhed posted a link to a video of someone making a plane sole exceedingly flat by scraping - I have a couple of planes I'm going to have a go at with this method in the New Year, as it seems a better method.

I saw that posted on another forum a while ago and I don't think it's really a starter for the average bloke. The main thing is scraping is only really a viable technique if the sole is crowned, which seems to be relatively rare. And there's a much simpler way to deal with that: use a mill file.

For those who don't have a file or aren't confident doing something like this with one, you can remove a crown successfully with the right lapping techniques.

 

[D_W]

I use glass shelves I took out my kitchen cupboards that we were scrapping. Seem to work ok enough to get a sharp edge. Micrometers don't really feature in my life. Then again... what do I know.

Unless they're fairly old, they're probably float glass, anyway.

 

[Graham Orm]

it all boils down to how anal you want to be about flatness. the glass and grantie will be truely flat and level over a great distance than the mdf or ply, they are also likely to be more stable and less likely to warp over different temperatures and humidity ranges

+1

 

[Jacob]

If you have a good solid impermeable surface like glass, marble , steel, the best way to stick the abrasive is to use cheap paper wet n dry, not cloth backed, and just flood it with white spirit. That's enough to hold it down once it's flattened. No glue needed.
Cloth backed won't stick or lie so flat- Sellers and Schwartz are making it more difficult than it need be.
If it's a long plane then use 2 sheets. Store the sheets between boards so they stay flat.

 

[AndyT]

According to what I have read on here before, glass used for shelves is normally toughened, rather than just being annealed like ordinary window glass is. Apparently the toughening makes it measurably non-flat.

I'd have thought that on the scale we are dealing with here, an offcut of mdf would be flat enough. I think it's logical to say that if you have three pieces stacked up in a pile and they all touch across the whole surface, and if you can flip over the middle one without making any gaps, then the middle one must be flat.

A bit like a 2D version of the three straight edges method. Ok, I know you can't see all the way across the surface, but combined with checking with a good straight edge and a bright light, it would be good enough for me.

Having said that, there is of course a practical problem that as you can't rub a plane sole on a flat surface and make it concave, any errors in your technique will tend to make it convex. (BugBear has explained this several times.)

 

[matthewwh]

It might be wise to first assess whether your plane needs flattening. Opening up one face of a casting carries with it a small risk that you will alter the tensions within it and set it moving. In the same way it's generally recommended to plane a bit off both faces of a board rather than just one, but with a handplane casting you can't do that.

Placing the plane on a reasonably flat surface like a kitchen worktop and trying to get a sheet of ordinary printer paper (about 4 thou) under it should reveal a lot about its condition.

If it does need work, you only need to get the toe, bit in front of the mouth and heel in the same plane. If it's concave between them but they all touch, that's fine. If it's slightly convex over its full length, then that too is fine for most work.

What you don't want is the toe and heel touching and the mouth up in the air, a condition that is reasonably rare but causes the plane to go from not cutting at all to suddenly hacking great chunks out when you reach the end of the board.

The other valid case for doing it is on a smoothing plane when you are producing very fine work and need to be able to feel the difference between nothing and a sub-thou shaving. In this case you are better off starting with a new plane and very carefully lapping in the last thou or so of flatness.

 

[MusicMan]

+1 for Jacob's comment. Paper wet-and-dry emery sheets flooded with white spirit holds them well enough with surface tension, and will be significantly flatter than cloth or sheets stuck with adhesive. Wet-and-dry paper works MUCH better when wet, and white spirit won't rust your tools.

Keith

 

[D_W]

+1 for Jacob's comment. Paper wet-and-dry emery sheets flooded with white spirit holds them well enough with surface tension, and will be significantly flatter than cloth or sheets stuck with adhesive. Wet-and-dry paper works MUCH better when wet, and white spirit won't rust your tools.

Keith

You don't want sheets with adhesive. You want rolls with adhesive - paper backed, stuck to a clean dry flat surface. They will cut faster, and you can vacuum or magnet the metal swarf.

 

[Racers]

Can't say I would be happy flooding stuff with white sprit doesn't seem safe to me.
I clamp mine down and stretch it tight.

Pete

 

[custard]

The question is "if you are using thick abrasive sheets, what advantage does a granite, or float glass, plate have over a thick piece of plywood or MDF"?

Plywood, even top quality Baltic Birch Plywood, is rarely flat. Plus even if it's flat today any change in humidity may mean it's not flat tomorrow.

MDF, especially good quality moisture resistant MDF from a top manufacturer, may be flat provided it's been properly stored at every point throughout the distribution pipeline. But just leaning it against a wall means it adopts a bend which quickly becomes permanent.

And neither ply nor MDF (nor indeed glass in the thicknesses you or I are likely to have access to) are stiff enough to withstand the pressures you'll exert flattening a plane sole.

Flatness, at least at the engineering levels that stop plane sole flattening becoming an exercise in futility, is a rare and expensive property.

 

[MusicMan]

Custard, what you say about improvised "flat" substrates is true. However, small engineering surface plates are not tooooo expensive on eBay. I have two cast iron and one granite, ranging from 12"x12" to 18"x18" and they were in the region £20 - £30 each. One of them I do use for metalwork marking but one I keep in the wood shop and use it for planes and chisels and the occasional measurement.

Of course, having three means that I could check them against each other and make them all perfect. If I could pick them all up.

Keith