Be kind to a man of very little brain

[Paddy Roxburgh]

Rxh, how do you prep/sharpen the file for scraping?

 

[rxh]

Paddy, I grind the teeth off the end of one face, then grind the end to a slight curve, then take the grinding marks out with a sharpening stone. The scraping action is rather like using a paring chisel but requires rather more force. Lay the file down horizontally with the tip at the point to be scraped, hold the file handle with one hand and press down on the file with the other, lift the handle whilst pushing forward until you feel the edge start to bite and continue pushing to take off a shaving. With a sharp edge you should be able to take off nice little curly shavings. Why not give it a try? It will cost very little and you may find that it suits you more than endless lapping.

 

[Paddy Roxburgh]

Thanks Rxh. Next time I get a banana shaped plane I will definitely give this a go, it is a similar technique to a violin making technique of rubbing on a flat plate with graphite and then planning the high spots that I was shown a few years ago on a course I went on. Currently all my planes are reasonably flat, I got my local saw doctors (North London saws) to grind them on a machine a few years ago, they charged me £25 to set up the machine and £5 for subsequent planes, including squaring up one edge for shooting, seemed like money well spent compared to lapping the soles.
Paddy

 

[bugbear]

...is that I noticed that Paul Sellers makes the point that you should keep the blade and cap iron in place when flattening the sole whereas Chris Schwartz stripped the plane down. My gut feeling is to go with Paul on this.

The helpful people on OLDTOOLS checked and measured on this question. (They did it,
so you don't have to ... )

You do need to have the frog installed and tightened; but the blade, cap iron and lever cap have no significant effect.

This is not true of a wooden plane where the blade and wedge substantially deflect the body.

As AndyT mentioned, I've put quite a lot of effort into this topic;

I believe the approach that I've developed with help from others, and adopted for my own use, is practical, accurate and effective.

my original page, evolved over time
page on the principles
page on the practise, including a montage of progress shots

BugBear

 

[MusicMan]

Bugbear, your web site is very informative. I'm also familiar with the techniques and you have made a very nice job of illustrating and making them accessible. Recommended!

Keith

 

[Cheshirechappie]

...is that I noticed that Paul Sellers makes the point that you should keep the blade and cap iron in place when flattening the sole whereas Chris Schwartz stripped the plane down. My gut feeling is to go with Paul on this.

The helpful people on OLDTOOLS checked and measured on this question. (They did it,
so you don't have to ... )

You do need to have the frog installed and tightened; but the blade, cap iron and lever cap have no significant effect.

This is not true of a wooden plane where the blade and wedge substantially deflect the body.

As AndyT mentioned, I've put quite a lot of effort into this topic;

I believe the approach that I've developed with help from others, and adopted for my own use, is practical, accurate and effective.

my original page, evolved over time
page on the principles
page on the practise, including a montage of progress shots

BugBear

BB's approach is sound. The technique of scraping to a surface plate has been used in precision engineering for a couple of centuries, and was the foundation of machine tool accuracy until the development of high-precision slideway grinders about a generation ago.

Generally, most of the waste is removed by filing, using successively finer files. Scraping is a fine finishing operation intended to remove the 'last thou', and in skilled hands, it can produce flat surfaces with deviations in the order of a tenth of a thousandth of an inch - but that takes quite a lot of time, a very light hand and a lot of practice. For the practicing woodworker, sub-thou accuracy is not really needed.

One advantage of this technique is that it can be quite fast. If the plane is held in one hand and the file in the other, the sole of a number 3 smoothing plane can be taken from a concavity of 6 thou to flat (but file rough) in about ten minutes (I used three-square (triangular) files because their curved faces allow you to attack quite localised spots without damage to surrounding metal.). Subsequent scraping would take a bit longer, but an abrasive papered finish takes about the same as filing. I know, because I've done it. A jack or try plane would take proportionally longer, but still a good bit quicker than lapping on abrasive sheets.

The disadvantage of the technique from the woodworker's point of view is the need for some specialist equipment, most particularly a decent surface plate. All the substitutes mentioned in the previous pages are things that are 'assumed' to be flat. They may be, but there's no absolute guarantee, and any out-of-flatness will reflect in the finished plane sole. The only way to be sure that you're using a flat reference surface is to acquire one of known, certified flatness. The other tools - files and scrapers - are not too expensive or difficult to find, and a tube of marking blue costs very little and will last a woodworker two or three lifetimes. If you REALLY want perfection, those are the lengths you'll have to go to. The lash-ups won't do.

However, you CAN get away with using some of the lash-ups for reference flat surfaces if you use a bit of common sense and expect a decent working plane rather than a perfect one. For all but the most fastidious, that's likely to be quite adequate. The British Standard for handplanes calls for soles to be flat within a maximum deviation of 1 1/2 thou either side a true plane, and most carefully set up lash-ups are likely to be be a bit better than that. They've worked well enough for plenty of woodworkers, and the ultimate test must not be whether a sole is flat to certain engineering limits, but whether the plane cuts wood and produces surfaces as accurate or as smooth as the woodworker requires.

(Edited because my number 3 plane's sole was 6 thou concave, not convex as I originally wrote!)

 

[MusicMan]

"The only way to be sure that you're using a flat reference surface is to acquire one of known, certified flatness."

Not the only way. The first ones were made by Whitworth using his famous test for a plane - take three and check them against each other. Similar to his test for a straight edge. The beauty of this is that you need no equipment other then a scraper and blue, and a dial gauge on a base and arm to show you how close you are.

However, for woodwork, as you say, we don't need to be this fussy. A small, secondhand, used engineers plate is likely to be fine for us. Especially if it is granite, since that chips rather than bends if damaged, so does not leave inaccurate bumps.

+1 for your post, though.

Keith

 

[ED65]

I measured the thickness on both a belt from my belt sander and a piece cut from a roll. Both were over 1 mm thick and I wondered whether, in pressing down on them, even on a hard flat surface, would compress the paper by a few thou thus rendering the flatness of the plate immaterial.

There may be some of that, but however much there is it doesn't appear that this is an issue in practice.

As such, I thought that wet and dry would be a better bet if “stuck” down with water. This is what Jacob and others seem to recommend although there seems to be a debate as to whether to use water or white spirit. Of course others maintain that ordinary abrasives stuck down with adhesive are just as satisfactory as wet and dry.

All of them work. This is a little like in sharpening discussions where people tend to get caught up in debating the pros and cons of their favourite system, going back and forth trying to successfully argue what's best. But a message that tends to get lost in the shuffle is that they all work.

One final thing, before I leave Jacob and D_W to continue their debate, is that I noticed that Paul Sellers makes the point that you should keep the blade and cap iron in place when flattening the sole whereas Chris Schwartz stripped the plane down. My gut feeling is to go with Paul on this.

That is a question I find particularly interesting, given how it is almost universally recommended to have the iron in place so the casting is 'stressed' or under working tension.

I'm sure I'm not the only one who this occurred to: if this is so critical why aren't the irons installed when the casting is ground flat in the factory?

As far as I know even the very high-end consumer planes, where the sole is guaranteed flat to within some minuscule tolerance, the body casting is ground flat by itself. If that isn't quite a persuasive argument that neither the frog nor the irons have to be installed I don't know what is!

However, I think you should have then in anyway. Why not? It's not like the added mass makes the job noticeably more tiring.

P.S. If all else fails, I’ll just have to buy a new plane but that may be the subject of another post next year.

An endless supply of Silverlines await you on Amazon should you want one at very modest cost

 

[Cheshirechappie]

"The only way to be sure that you're using a flat reference surface is to acquire one of known, certified flatness."

Not the only way. The first ones were made by Whitworth using his famous test for a plane - take three and check them against each other. Similar to his test for a straight edge. The beauty of this is that you need no equipment other then a scraper and blue, and a dial gauge on a base and arm to show you how close you are.

However, for woodwork, as you say, we don't need to be this fussy. A small, secondhand, used engineers plate is likely to be fine for us. Especially if it is granite, since that chips rather than bends if damaged, so does not leave inaccurate bumps.

+1 for your post, though.

Keith

Quite true about the comparison-of-three surfaces! However - in geek mode for a minute - there is debate as to whether Whitworth was the originator, or whether it was his mentor Henry Maudslay. It may also have been Whitworth whilst in Maudslay's employ. Whichever - the principle is sound!