"Alan" wrote in message
...
Can you explain how tensile strength is tested now?

The methods of test are described in the wood handbook (FPL) in the
appropriately-named chapter. It's the one I keep referencing in hope that
we can agree on it's being common ground.

I have a question...would you say that a
firm fibre would be potentially easier to cut than a softed fibre that
may deform more easily?

Basic turning principle that the fiber to be cut should be supported by its
fellows. Thus "turning down hill" and turning down grain. Means the softer
cuts easier.


Why must you try to talk down to people? My point was that the
difference would be minimal. Please tell me what the difference in
temperature will be between the timber and the tool tip. Also, I'd
like to refer to the source of this information if you can provide it
please.

A heat sink in the form of the tool, resistance to heat flow in the wood
means the tool is heated well, the wood, hardly. That plus the undeniable,
that the tool remains in contact with wood, while any section of wood is
only briefly - and less briefly if you follow the faster is hotter theorem -
in contact with the metal, should be enough to understand that the wood
doesn't heat in normal cutting.


I'm sorry, if I want to apply a wax finish...heat builds up faster at
a higher speed when pressure is much the same for all speeds used.
This seems to be a commonly expressed opinion and I can't fault it in
"use".

You're mistaking lack of cooling for friction heating. Look at the
information in reply to heat sinking, and consider how much less time the
_same_ wood has to cool when you're friction polishing.


I know you tend to turn at slower speeds than most (from your
continued mention of flying bits of wood (or similar)), but in spindle
turning I find it imposible to accept that the tool could be moving in
and out as you turn to an extent that results in a visible (or of
interest) loss of circularity. I am sure I would not be turning items
out of round in spindle work. Just work out what the tool's
reciprocation rate would need to be for a spindle turning. I find it
hard enough to accept this as a significant issue with bowl turning.

Get yourself some calipers and try it. Simple enough experiment, really.
Press to just the first point of squirm (caused by differential cutting
resistance!) on one section, hold tool distance on another, then see what
results you get. If you skew along the cut with an edge held like this (/
or \), you'll get a better "average" of grain differences, and so a more
rounded piece. Oddly, that's the planing conformation of a skew chisel.
Almost as if they knew how to get the best average, and thus the best round.
Of course, other factors make it more significant in bowl turning across the
grain. Greater centrifugal force distorts the bowl, greater resistance when
grain is picked up rather than peeled, difference in the coefficient of
friction on end versus long grain, jumping the hard latewood ridge between
two areas of earlywood as you come across the bottom and so forth. That's
what makes for chatter - the wood flexing / tool moving. It's a relative
thing. The less tool force applied in the direction of the natural flex,
or the less flex permitted, such as with a steady, the better. Pressing
with the gouge is one reason why folks resort to scrapers to even surface
and circularity. Some increase speed, of course, but unless they back off
the radial force, that just makes smaller chatter patterns.

I don't want to burst any ballons, but you seem to be saying you know
everything...a dangerous position to adopt.

Now who's talking down? You have demonstrated a lack of understanding which
is not conducive to good turning, and I am attempting to ease your way by
getting you to think. Things won't be as much of a mystery to you if you
understand the principles which limit what can or cannot happen.

You may have noted I
don't simply accept everything and this includes your frequent broad
brush strokes about how you've looked at the physics and the
equations..Similarly, attacking someone that challenges your lecture
does not impress me. You make many statements, and intimidate in
order to have them accepted. You commented on the heat sink effect of
the tool, again I ask, what the difference in temperature will be
between the timber and the tool tip. Also, I'd like to refer to the
source of this information if you can provide it please.

I'll get the lab right on it. Let me know how near to the edge and how
insulated from the tool I'll have to get to satisfy you. Of course, if you
can demonstrate that wood conducts or acquires heat anywhere near the rate
of HSS, I won't have to. You'll find information on the thermal properties
of wood in the same source I keep referencing.

Thanks for the ad hominem. As they are generally just a fig leaf for the
ego, designed to avoid concession, perhaps you've gained some understanding,
as uncomfortable as the source may have made you. I will continue to answer
the questions you pose to the best of my ability and knowledge, even when
they're not questions at all, but foundationless assertions.