(08-30-2018, 02:18 PM)titanxt Wrote: Having dealt with heavier cast iron machines, I was wondering about cast iron hand planes. Have you ever seen a hand plane, like a #7 bow or sag if it was stored for a long period partially supported (without the entire length of the sole resting equally)?

Thank you!

Andy

(08-31-2018, 08:38 AM)WoodTinker Wrote: I think this would be a product of heavy weight over a long span over a long duration.

(08-30-2018, 02:18 PM)titanxt Wrote: Having dealt with heavier cast iron machines, I was wondering about cast iron hand planes. Have you ever seen a hand plane, like a #7 bow or sag if it was stored for a long period partially supported (without the entire length of the sole resting equally)?

Thank you!

Andy

(09-03-2018, 07:19 AM)Timberwolf Wrote: ,,,,,,,,,,,,,,,,,,,
Here's a reply from Rob Lee who knows a thing or two about manufacturing.......This is from another WW forum who's name shall not be mentioned....I googled the question..."can cast iron warp" and came up with this...From my own experience I know that gray cast iron can and does warp..In the machine shop where I apprenticed, we made machines for making concrete blocks...We put the C.I.castings to be machined, in a field outside in the dirt, uncovered and exposed to the weather for about two years before we did the necessary machine work..If we machined them before they "seasoned", they warped so badly that the machined parts could not be assembled. ...My personal opinion {altho I don't take my own advice} is the lever cap should be released if the plane is not to be used for a long period.


Rob Lee  
Contributor
Hi -

Grey cast iron can continue to move decades after casting. True - most of the movement occurs early on, and castings were often left to "age" outside - the changes in temperatures remove some of the stresses. Castings can go though a stress-releiving heat treatment cycle as part of the production process.

Keep in mind that most antiques are going to be grey cast iron, and most higher end production is going to be ductile cast iron (invented/discovered in the 40's). These two types of cast iron behave quite diffreently. The basic difference between the two is the form of the graphite in the iron - for grey cast it's flake, and for ductile it's spherical (or nodular). Think of the flakes as fault lines or slip lines in the material - they enable movement. With ductile - the stresses can only release marginally - between nodes of graphite. Here's a useful analogy - think of a crack in a windshield.... if you score a circle around a small crack, it doesn't get larger.... if there are no limits to the travel - the crack can continue - or not. Sometimes being jarred will extend it, sometimes a change of temperature will extend it. Nodular (ductile) iron is the limited crack - grey iron is the unlimited crack.

(What follows is illustrative only....!) When casting iron - the molten metal hardens from the outside first, and the metal shrinks as it cools. As a solid shell forms, it will distort slightly as the core contracts. At a certain point though, the cooled shell is strong enough that additional cooling of the core cannot distort the shell - and the metal hardens with internal stresses - the metal is "like" a solid stretched rubber band - it's in tension. In some castings - you can actually have bubbles of vacuum formed in the material - porosity. In other castings, the shrinking core will cause sufaces to sink. So - you have this sort of eqilibrium where the outer part of the casting is resiting the stresses in the core. Now - a manufacturer takes that casting - and removes the sides and the bottom to establish the working surfaces of a plane. The stresses now begin to express themselves - and the casting moves. Any change in the exterior of the casting could conceivably cause additional movement.... which includes lapping, even decades after casting.

Ok - all of the above is a bit oversimplified - there's waay more to it than that - but in short, grey cast iron can continue to move - ductile iron stabilizes. Changing a surface can release stresses... stresses in ductile are limited, and stabilize quickly, stresses in grey cast iron don't.

Having said all that - I don't think that a .005" convexity at the heel of jointer is going to have much effect at all. If anything - the plane may act a bit "shorter" than it's intended length. I'd have to go back to some of the modelling work we did years ago, but I believe that the tail on a Stanley #7 is too long for the mouth position in the first place...

As long as it works well, the plane is good....

Cheers -

Rob