Wouldchuk":2wjc7otv said:
The particular reason I was interested is as I've an old Bailey No 7 which has a very noticeable highspot just behind the throat.....
Ah - that's definitely a rogue plane! There are others that crop up from time to time with the same fault - I gather it's quite a common failing on the Calvert Stephens 88 plane that Record made for a while. However, lapping probably won't help in this instance.
Inagine a plane with a hollow in the length of the sole, so that the toe and heel are in contact, but the mouth area is clear of the wood (that's also a fault that crops up, usually on newer planes). In this instance, lapping will help, since the two points in contact with the lapping surface are 'high' and need removing. However, it's almost impossible to lap something with only one high spot. Balancing a plane sole on just a high spot is just asking too much; there must be some other part of the plane sole in contact with the abrasive, so that part will be abraded too, even though it's not a high spot. Hence, you end up with a convex-soled plane.
To tackle the high spot with only simple 'home' equipment, try the following. First, check the sole with as good a straightedge as you've got - even quite a short one will do, such as the blade of a 6" engineer's square, to find where the high spot is. Check along the edges of the sole too, since the side webs may well have kept the casting straighter there, so the high point may not extend to the sides. Mark the high spot with something like a Sharpie (or chalk or soft pencil, if they'll take on the smooth plane sole). Then start to address the high spot with a smooth cut file, but be careful which file you select. You want a 'flat' file, not a 'hand' file - the 'flat' ones have a very slight belly in their length which you can see by looking down their length. (They're called flat files because they're used for filing flat, not because they are flat. They usually have tapered, curved sides too, so that you can tell them from hand files - which are flat!) By using the flat file with a bit of finger pressure over the part you want abraded, you can control where you take metal off.
Be a tad careful how you hold the plane in the vice. Plane sole castings are thin, and vice pressure can distort them a little and give false flatness readings when you're checking with the straightedge. It may be better to do the checking with the plane free of vice pressure.
If you don't have a flat file to hand, you can make a pretty good substitute from a stick of (say) 1" square wood, with one (or more!) faces planed to have a slight belly, and then a piece of coarse emery cloth or wet-and-dry glued on.
With the weapon of choice, attack the hump. Go a bit cautiously at first and CHECK FREQUENTLY with the straightedge, so that you can gauge how fast metal comes off. You can pile in a bit more enthusiastically once you get a 'feel' for the job. To start with, DO NOT file anything away from immediately behind the mouth. Do this bit last, if it needs it. What you want ideally is a plane that touches at toe, heel, and around the mouth.
When you get it flat to your satisfaction, you can either leave the sole with abrasion marks, or dress the whole length with fine wet-and-dry wrapped round a block of wood or cork sanding block. That's more for appearance's sake than effectiveness. A careful rub on the float glass lapping plate would clean up the sole surface too, now it's flat; but it's not a really necessary step.
Finally, fit blade and cap-iron, and try it out. Adjust as necessary. With any luck, that's a job you'll only ever need to do once on any metal plane.
Hope that helps!
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