Where did the knowledge about the capiron get lost?

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AndyT":24lavqmo said:
Another tack on the question of getting no gap between the front edge of the cap iron and the back of the blade...
I've seen this suggested in an old book, though I can't find which one at the moment. The suggestion was to fit the cap iron, then run a bit of hard steel such as the tip of a screwdriver across its edge, deforming the relatively soft steel so that it makes perfect contact.
This would perhaps be most useful to those who don't have perfectly flat backs to their cutting irons.

If I remember correctly, the best description of fitting the cap iron to the blade, was done by our own, Mr. David Charlesworth, in one of his fine books. What made his books so valuable, were the pictures shown at the most opportune time, of the preparation task.

The method demonstrated, was a side to side method of the lip on a stone, sitting on a bench, with the top end nearly touching the bench top. The elevation of the lip end of the cap iron permitted all the metal removal to be concentrated on the area most needing it.
 
DennisCA":2nqj2f4n said:
About getting the cap irons flat to the blade, I've been told that the common method of using a flat surface and making the cap iron itself a truly flat surface is incorrect. The reasoning is that once you tighten that screw the cap iron will bend slightly and you won't have a perfect contact surface anymore. The method I was told use layout fluid to see where the cap iron makes and doesn't make contact when tightened, then keep honing and tuning very, very finely until the contact surfaces mate perfectly.

Dennis, I think you're spot on with your point about cap-iron deflection when the cutter and cap-iron are screwed together. However, I think there's another factor often forgotten, and that's the extra deflection applied by the lever cap (or wedge in a woody) when the cutter and cap-iron are locked into the plane. That pressure, applied to the top of the cap-iron hump, will deflect the cap-iron leading edge forwards, and bend it slightly so that if the cap-iron fits exactly to the cutter back along the mating surfaces, a tiny bird's-mouth will open, and that will obviously fill with shavings and clog the plane to a standstill at the first use.

That deflection under lever-cap or wedge pressure will depend on how thick the cutter and cap-iron are; thicker components are stiffer, and in consequence will deflect less. Thus, the iron and cap-iron in an old woody won't deflect much at all, but the thin cutter and bent-metal cap-iron of a standard Bailey type plane will deflect quite a bit. That will influence two things. Firstly, how much clearance is needed behind the leading edge of the cap-iron to get a true seat in working condition (not out of the plane), and also how close the cap-iron has to be set to the cutting edge to get the 'cap-iron' effect. The thick, heavy iron and cap-iron from a vintage woody will need the cap-iron pushed a small fraction of a millimetre from the edge. So will the thick irons and cap-irond of most modern premium planes. The cutter and cap-iron pair from a standard Bailey plane will need to be set a bit further back to allow for the deflection as the lever-cap pressure comes on.

Maybe rather than worry about measurements, the pragmatic way of getting used to setting up a smoothing plane to get good cap-iron effect is to set it somewhere, try it, reset, try again, and so on. Once you have the set you feel is best, make a mental note of the gleam of light between cutting edge and cap-iron leading edge, and aim for that every time - with THAT PARTICULAR iron and cap-iron. The gleam might well be different for a another double iron pair in a different plane. I'm pretty sure that's how the craftsmen of old went about it - if you'd started talking thous or fractions of a millimetre to Charles Hayward, he'd probably have looked very blankly at you, but he could certainly set up a plane.
 
bugbear":pzaxwmwl said:
condeesteso":pzaxwmwl said:
matt_southward":pzaxwmwl said:
edit: re diamond stones BB, good ones flat but many not I find. Just best to check.

My two DMT stones are flat; I just bought one of the on-offer Trend stones;

trend-diamond-stone-t93971.html?hilit=trend

Following your advice, I will check it (carefully - don't want to abrade a known good straight edge!)

EDIT; thanks for the tip - the Trend is significantly convex (on the coarse side); I Haven't
measured the convexity, since measuring convexity is fiddly.

BugBear

Yup, I got the 5 and I reckon they are generally convex. And they flex a little when using so measuring would be a hobby too far IMHO :)
 
bugbear":1p84yd5s said:
condeesteso":1p84yd5s said:
matt_southward":1p84yd5s said:
edit: re diamond stones BB, good ones flat but many not I find. Just best to check.

My two DMT stones are flat; I just bought one of the on-offer Trend stones;

trend-diamond-stone-t93971.html?hilit=trend

Following your advice, I will check it (carefully - don't want to abrade a known good straight edge!)

EDIT; thanks for the tip - the Trend is significantly convex (on the coarse side); I Haven't
measured the convexity, since measuring convexity is fiddly.

BugBear

I don't know which type you've got, but I suspect the trend stones are made in china due to the fact that they don't say where they're made. The large bench stone sold in the US is, in my opinion, highway robbery. It appears to be a rebadged version of many of the generic steel plate based two sized monocrystalline hones sold on ebay and through various retailers in the states (without the trend label on it) for $30-$50. There have been several reports of the large one being out of flat, and the flatness provided is per inch, which doesn't amount to much if the error is compounding - per inch.

DMT duosharp (the ones with plastic core) and Atomas are the only two hones that I've seen that are consistently flat (perhaps the ezelaps are very close, too, I haven't checked my two with a straightedge - but those were $35 each here, also, made in the US at that price). The chinese hones that are $30-$50 are not, but at least you know what you're getting for the price.
 
(I have done scads of cap irons - from old damaged ones to stock stanleys that look untouched, with an atoma 400 followed by a finer regimen to finish the surface (but without changing geometry).

A freshly surfaced india stone does the job well, too.
 
AndyT":2im1x2s7 said:
Another tack on the question of getting no gap between the front edge of the cap iron and the back of the blade...
I've seen this suggested in an old book, though I can't find which one at the moment. The suggestion was to fit the cap iron, then run a bit of hard steel such as the tip of a screwdriver across its edge, deforming the relatively soft steel so that it makes perfect contact.
This would perhaps be most useful to those who don't have perfectly flat backs to their cutting irons.

Edit: I'm not recommending or condemning this - I've never done it - but as we seem to be writing a collection of all that we know about cap irons, I thought I'd add another little pebble to the tottering cairn.

Andy I do recommend this! What would one fancy? Abrading the back of an iron for a long old time, abrading the cap iron to match? Or accepting the iron as it is, and shaping the cap iron to suit. The cap iron is so soft it can easily be drawn out and shaped and abraded where required.

Perhaps someone with more book knowledge than me could let me know if anywhere it is written that both iron and cap iron must be made "flat ". Rather, the ones I've read it says "tight fit" or the like. I can just imagine in day of yore a young apprentice setting up a first plane. Discovered an hour later trying to make plane iron and cap iron "flat". After some good spirited ridicule the old hand shown how to get a "tight fit" in a couple of minutes using a "tip of a screwdriver across its edge, deforming the relatively soft steel so that it makes perfect contact"

I was going to mention "Modern Practical Joinery" but was beaten to it :).

Although the flattening of both iron and cap iron is a great way to do things it is rather funny that it has become the default position. If something has been lost it's been the advise of those many practical and professional hand tool woodworkers. :ho2
 
Thanks Graham.
I can see the logic too.

A quick rub with a screwdriver versus lots of time fiddling and searching for a stone which stays flat for ever?
For a busy professional, no contest!

But demonstrably, both approaches do work.
 
Yes but,

If the back of the blade is not flat, near the edge, the wire edge will not be nicely honed away. (Assuming a flat stone)

David
 
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