That's interesting information, Penangsang.
Very interesting.
However, I would imagine your teacher is fitting a round pesi to a round hole.
The pesi on this sundang is square.
When we fit a square shaft ( the pesi) to a square slot ( the cut in the ganja) there are unequal stresses at the square cut corners of the slot. The material in the ganja is of small mass, thus the stresses will not be great, however, they will exist, and if that ganja is of layer welded material , we could expect to see any imperfections in welding fail. Especially so when we realise that the sides of the oblong slot are very thin in comparison with the length from the pesi to each end of the ganja.
Still, as I have remarked, the mass is not great, so with perfect fitting, and a press fit of only a few thou, you'd possibly get away with it. Provided you did not go into high orange on the heating.
With a round hole and round shaft (pesi) the same unequal stresses do not occur, but are distributed evenly around the hole.
But then there is still one problem that is insurmountable with traditional hand-tool techniques, and that is the achievement of a tight fit betweem ganja and blade base. I've made a number of keris, and more than a few ganjas. To get a neat tight fit between ganja and blade base is a swine of a job that requires repeated fitting and filing or scraping.
If you want to do a shrink fit you do not have the possibility of achieving a tight fit of ganja to blade base, and anything less is simply not acceptable.
Now, if we consider the blade that is the subject of discussion here, we can see a reasonably close fit, and we can see a very considerable gap between the pesi and the ganja. Anybody who has the skill to hand cut a slot to a tolerance of the few thou needed to achieve a shrink fit, would certainly have the skill to cut that slot so that it fitted closely to the pesi at its top.
Yes, it is possible to shrink fit a ganja to a pesi, but it is not possible to use this fitting method with hand tools and achieve an acceptable fit to the blade base. Most especially so with a square cut pesi and slot.
The crimp method of fitting is where the hole is cut to a press fit on the pesi, and then a punch and hammer is used to tighten the ganja hole around the pesi. I have most often seen this method used in Bugis and Peninsula keris.
The key method of fitting involves cutting a keyway with a very small file into the side of the hole in the pesi, then a small key is made to fit that keyway --- a tiny piece of tapered steel --- which is driven home with a punch, thus tightening the ganja. Sloppy and lazy makers use a small nail instead of a purpose cut key. The best position for the key is at the buntut urang side of the pesi hole.
So to my mind, the question remains:- how is the ganja kept in place?
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