Thread: Will 120 mesh silicon carbide grit be useful for flattening plane soles?

Hi Snafuspyramid,

I think it's worth a try on chisel backs and plane irons, both of which are hardened steel, however on the softer plane soles I wouldn't think it would be suitable. Yes, silicon carbide grit will break down into smaller sharp pieces, when used on hardened steel, I would be concerned that on a softer cast iron plane body the bits of carbide would just leave deep scratching, and maybe even get embedded in the softer iron. Although a plane that does simultaneous sanding as well as planing, might be a new invention..

You are aware of course of the limitations inherent in lapping plane soles, and the risk of making the sole convex.

Try it on the blades and chisels and see how it goes.

Regards
Ray

I'll chime in with my usual anti paper-on-glass (or any other surface) method of "flattening", tirade. While it may APPEAR to give a flat surface, I don't believe it can possibly do so. There is just too much movement in the paper, or mesh, and that means inevitable rounding towards the edges. I don't doubt you can produce edges that shave by this method, but try laying them on a flat surface & taking a whisper-thin shaving.

The most practical way to get reasonably flat chisel & plane irons in the home workshop, IMO, is with diamond stones. And even with these, you have to be careful to keep clearing the swarf, which can cause rounding. You will notice it immediately when you proceed to a finer grit size.

I know diamond stones are expensive (I'm talking decent ones - be VERY careful of the cheapies, many of which are far from flat...), but they do last a very long time, and maintain their flatness, unlike stones. An evenly-rounded back on a plane iron isn't necessarily a disater, just a form of back-bevel, if it's even. But it DOES make a big difference to have properly flat backs on chisels, particulary when used for paring.

Larger surfaces like plane soles can be roughed out with paper on a flat surface, but that WILL round edges, so if you want machine-grade tolerances, scraping is the definitive method (but tedious & takes a while to master, which is why I avoid it! ).......

EDIT: Woops, just re-read your post & realized you are talking about grit, not the mesh "paper" I first thought you meant. Lapping with grit on a cast-iron or glass surface has similar problems to lapping on paper stuck to a flat surface, in my experience (I have a Lee Valley iron lapping plate & grits). The grit cuts more agressively at the leading edge, so you will get some rounding, but not anywhere nearly as much as with papers stuck to a flat surface, I've found.

Cheers,

RayG, I can't say that I am aware of the limitations inherent in lapping plane soles? I assume that because of the inertia of the plane body accelerating and decelerating it about the paper will cause it to 'rock' very slightly, giving a somewhat convex surface.

I'm not trying to get a mirror polish, I'm just trying to get the plane soles on old Stanleys reasonably flat (largely removing material from behind the mouth). Near enough is good enough. I suspect that with my current rank beginner status I'd never notice the difference a few microns anyway, if anyone does.

I sort of answered my own question by trying some grit on an old Stanley. Scratched the hell out of it. In fact, it behaved exactly as you said it would, and turned into possibly the world's first sandpaper plane. (No harm done: I sanded it back alright and it's a post-war Stanley #4 someone gave me for free. It's my unhappy test dummy).

While IanW is no doubt correct about diamond plates being the go, purchasing diamond-encrusted plates will have to at least wait until I get a real job (doing a degree).

How about a related question:

Will #120 mesh be suitable for flattening finer waterstones, e.g. King 6000?

Hi Snafuspyramid,

Flattening plane soles is a complex topic, and this particular rabbit hole goes deeper than I care to dig, but I can say that glass isn't generally flat, good granite surface plates are expensive, although I see carbatec is selling small granite surface plates for what seems a fair enough price. Granite Surface Plate : CARBA-TEC

If you do a search for posts on this forum by Mic-d, he has done a lot of work scraping planes, he would be the best one to offer advice.

I'm lucky enough to have a surface grinder, and I've flattened a few on the surface grinder, nice to be able to square up the sides for shooting as well.

Also, have a look at Derek's web site, he has been doing a bit with diamond paste on cast iron for sharpening.
http://www.inthewoodshop.com/Woodwor...mondpaste.html

Of course, the real measure of flatness/sharpness is doing the woodworking....

Regards
Ray

Just my two cents worth, be careful of some of the granite plates as they are not as flat as they claim to be. We ordered one for work and clocked it up in the mill and found that it was nowhere near the 0.001" tolerance as they said so we returned it, admittedly that was around 5yr ago so things may have changed.
Cheers for now Richie

I'll have to do without a granite slab.

Sure, it would be better than 10ml float glass on yellowtongue 50mm benchtop (what I currently have), but would also be $60 more expensive for something I'd only use a few times (I've found glass fine for flattening waterstones and lapping blade backs).

There's always a better way of doing something. Glass seems a good compromise; a number of people whose opinions I've come to respect seem happy with it.

Flattening plane soles is not easy; as others report, it is easy to get a convex sole, as I well know. However I can report on Jim Davey's technique, and Jim has flatttened more soles than ...

Use a long piece of thick MDF, at least one metre, long (not thick) with appropriate grits of _cloth_ backed abrasive (not sandpaper) on each side (starting at 80). Jim does have at least one piece of thick steel plate for this, bugger is very heavy

1. Hold the plane in such a way that the pressure is in the middle of the plane (I assume people are using a plane fully set up with blade etc). Do not pretend you are planing the board
2. Start the plane with the sole a couple of inches over the edge of the paper, and move deliberately (this is not a speed contest) with moderate - even - pressure up and down the paper, going a few inches over the top edge of the paper at the end of each stroke, and finally going over the edge of the paper on the other side. THis keeps the wear on the paper even
3. Keep all strokes even and DO NOT ROCK THE PLANE
4. Pay attention to what you are doing; many people seem to go off with the fairies and wave the plane all over the place, dreaming of a flat plane sole no doubt
5. Repeat until arms fall off
6. When the front and back of the mouth are co-planar with the toe and heel STOP. A straight edge is helpful

If plane sole is concave to begin with it is much easier; if the plane sole is convex to begin with... sell it and get a plane with a concave sole. Often there is a hump behind the mouth for some distance, people have been known to attack this with a belt sander before going through the flattening process; naturally I cannot recommend this, although draw filing with a mill bastard to get the hump down has much to recommend it.

For myself, I keep planes with a flat sole and on-sell the rest!

Cheers
Peter

I am verballing Jim here, so I hope I have the process correct. Any errors are entirely mine etc etc

Might two layers of 7ml glass - slightly wet so they stick together, and clean - resting on a large, marble slab table (about 2' by 4') be sufficient? The table is perfectly flat, as far as my (short) straightedge can tell, as are both sheets of glass.

Also, if wet and dry paper won't be appropriate, might 80 grit red emery sanding belt be better?

I'd like to use what I have available.