A method for larger planes (to get them really flat)

[D_W]

I am not one for multi hour techniques to address maybes, but I have figured out over time how to make planes like this very flat in a short period of time, so I'm going to share it. This plane is a norris A13, something I overpaid for and when I received it, it had two very high corners and the others very low. Unfortunately, tehse were diagonals. There was also a lot of wear under the mouth. With as much use as this plane saw, I'm lucky that it doesn't appear to have ever been dropped.

The overall idea here is to file the center hollow in steps - like a thousandth hollow, just a tiny amount, and then lap off the outer ring.

This is my glass shelf lap with the plane on - sorry, i forgot to take a picture of the sole ahead of time, but it wouldn't have shown much.

I put dykem (marking fluid) on the bottom of this plane, let it dry, and then lap it to see where it's high.

Turn it over, put it in a vise and file the spots that lost color on the lap (notice the high back corner - this isn't just a little high - it's probably 2 or 3 sheets of paper high - perhaps a hundredth). This is the swarf from about 30 file strokes.

put pressure on the file like this - push the file in the direction of the plane length. Just doing this will file the sole hollow as the file will flex a little bit under pressure. It's easy. Go slow and ensure you feel the file cutting or you're just dulling the file and wasting your time. Tap the filth out from time to time. If the plane is mild steel (many infills), use a file card to make sure you don't pin the file and make huge scratches in it. The swarf will be little pigtails instead of dust in mild steel.

If you are doing a long cast plane (like a stanley jointer) and are uncomfortable with filing, make a 2x2 or 2x3 inch wood block and work in small sections with coarse PSA machine paper stuck to the block. You cannot get enough downward pressure to lap those planes efficiently, and you will end up relieving the ends a lot, but you can do this technique with a smaller block and the paper will cut much better as it dulls due to the small contact area. This is an effort thing of 10 to 1, I'd bet (BTDT), and the accuracy is far better if your reference source is flat.

 

[D_W]

Every 50 or 100 file strokes (this is probably going to remove material faster than you expect - make sure your file is sharp), re blue the sole and lap it on the reference again to make sure you're not turning high spots to low spots. Keep doing this until you've made a bit of a hollow (only a tiny one) and the outside is becoming the high spots.

when you think you've filed well, use a good straight edge and a feeler (if you don't have those, just go to the lap at this point and lap the rest out) and see what's left. The heel of this plane other than one corner was really high (or low, however you want to say it). because it's only the last little bit and it's the last part out of flat, I'm not going to spend another 20 minute filing the rest of the sole - but you could do it if you felt the need. What you're seeing is right at about exactly 2 thousandths for that short run. No other spot on the entire plane allows a 1.2 thousandth feeler or even feels close to it (this is a starrett straight edge).

For cosmetics and to make sure the edges are not high, I put it on the lap for about 50 strokes and it's done. I turn it over after that and give it a cosmetic sanding with 220 grit.

I tested my reference surface with pressure early on with this straight edge, so it's no surprise. It's a glass shelf on a very deliberately flat planed area, and any little dots of glue or even small shavings or dried drops of finish need to be scraped off before it's laid on the bench to work.

Filthy hands and small blisters - this has taken about 1/2 hour. Lapping would've been agonizing.

I came upon this process with files when making infill planes - it's nice to make a nice infill, but you cannot lap the large mild steel planes quickly (and beating away on them on a lap probably won't result in flat, either). They are like rubber on sand paper. I'd done the small block thing years ago on a few jointers that I was using. I lapped the first one for 5 hours, and the second one was worse than the first and I noticed that a small block cut cast much more quickly than a large lap. Despite being worse, the second plane took less than an hour.

 

[D_W]

The iron is a replacement and in good shape, the cap had a significant amount of wear. I flattened the iron on this same 80 grit lap, ground a primary bevel on it and put it to the turkish oilstone for very cursory initial refinement and to get a working edge.

I then ground the wear off of the front of the cap on this same lap stoned the bottom undercut of the cap and refined the front with a deburring wheel and a buff (this is done in seconds, it beats hand polishing the iron and removes the wire edge.

A turkish stone is like a friable medium fine arkansas stone. they're great for following something that makes deep grooves because they'll cut the peaks mostly off pretty easily and you can get a very quick decent initial edge (right off of an 80 grit lap, even on the back) in just a minute or two. A washita is almost as good at this. Subsequent refinement can just occur in the cycle of use rather than faffing long.

All of this preparation was no more than another 10 minutes (including fixing the cap and flattening the iron, etc).

good performance given the low effort on setting up the iron. The shaving laying on the glue bottle was the one before this one.

I have a desire to be able to do these things well, but in a very lazy way -all of it - the flattening all the way to doing just a little bit of iron prep and letting use and regular sharpening result in any needed further refinement. This is relatively lazy and if you get your lap prep area done properly, you can match any manufacturer's spec in not much time. I lap small cast iron planes because it's usually easy, doing this with them only on infills that I make (to really nail flatness - it's a pride thing when building - trying to match or better what lie nielsen makes - if you can't, you'll find that your newly made infill will not match a LN plane in fine smoothing, and that's annoying).

 

[D_W]

you may look at the shaving and say "what? what more refinement?"

The point of this is just to find the capability of the plane and make sure that on a flat surface it will take shavings like these. This plane is very heavy and won't see many thin shavings.

Sharp and not quite as refined will result in shavings that look like a woven mesh like the one on the glue bottle. Once the edge is refined a bit further, the shaving will look more uniform (it will be more uniform), but ultimate thinness really won't get much less than this (it's some fraction of a thousandth - probably half).

 

[MikeG.]

Or, have a good friend who has some decent engineering machinery, who'll take a sliver off for you on a milling machine.

Seriously, though, anyone who hasn't tried filing a plane will be surprised at how quickly you can remove material. Be cautious, check often, and stop if you start making a mess. You could ruin a plane quickly if you foul this job up.

BTW, you can actually using winding sticks to assess the base of a plane. This can be a useful place to start to give you an over-all picture, particularly if you have (as DW had) diagonally opposite corners as high points, because it is all too easy to then rock on the abrasive and leave misleading marks on the sole.

 

[AJB Temple]

Excellent thread D-W. Thank you. Adrian.

 

[D_W]

Or, have a good friend who has some decent engineering machinery, who'll take a sliver off for you on a milling machine.

Seriously, though, anyone who hasn't tried filing a plane will be surprised at how quickly you can remove material. Be cautious, check often, and stop if you start making a mess. You could ruin a plane quickly if you foul this job up.

BTW, you can actually using winding sticks to assess the base of a plane. This can be a useful place to start to give you an over-all picture, particularly if you have (as DW had) diagonally opposite corners as high points, because it is all too easy to then rock on the abrasive and leave misleading marks on the sole.

This one was wonky enough to rock on the bench in as-received form. It's not a deal killer for me, but laziness causes me to put the plane aside for a while as I don't actually need it for use. But I won't re-sell it like that, either, not even at a loss. This is the most expensive plane I've bought, too - I guess I had dreams of it showing up in a usable condition that matches the price!

If I have a mentor, it's George Wilson (an instrument and tool maker, though I don't work remotely similar to the way he does) - George often tells me that I really won't get to the full menu of things that I'd like to do unless I get a lathe and a mill. I don't want to learn to use them and would probably lose interest and then have them taking up floor space.

but the point about just chasing the problem through the thickness of the sole is relevant, as is a convex plane without twist. The back and forth between the file and reference surface is necessary so that you can actually ensure you're spot working the problem areas with the file. A lap alone is a good way to make it less good with more effort and time.

Most of the planes that I've gotten as drastically bad as this are hard used, though. I think someone walked this one down board edges diagonally for a long time.

 

[D_W]

BTW, you can actually using winding sticks to assess the base of a plane. This can be a useful place to start to give you an over-all picture, particularly if you have (as DW had) diagonally opposite corners as high points, because it is all too easy to then rock on the abrasive and leave misleading marks on the sole.

Separately, I didn't grasp the winding sticks at first - I assumed straight edge across the diagonal, but I see what you mean - this one would've showed on winding sticks, I believe.

But when I check with a straight edge, i check through the length, across the diagonal and then lateral (a bit of overkill).

I don't know what a good straight edge is over there - starrett is pretty much it over here if you're really going to measure 1.2 thousandths on a 15" long surface and make claims about it - they're expensive. it could be done without that, but I'm not sure how I'd have checked the reference as even though it's filthy and crude looking, it's miles flatter than any table saw top I've ever come across. It's my "planemaking" end, but as with all lazy things - I planed the rest of the bench flat when making it. I planed only an area about 3 feet long and a foot wide flat enough for this lap.

 

[Max Power]

If I have a mentor, it's George Wilson (an instrument and tool maker, though I don't work remotely similar to the way he does)

Is that George who used to work at Colonial Williamsburg ?

 

[D_W]

Yes, that George.

 

[Max Power]

I've got a lot of time for George, definitely knows his stuff

 

[D_W]

Ditto that. Wood or metal, by hand or with machines, and formally schooled in classical design and can pretty much draw anything he can dream up freehand.

generous with advice, too.