However, like I mentioned earlier, the break is not complete and I'm sure I could theoretically use it in its damaged state for a while. I can just imagine though it breaking and slicing my hand.
I think you're right to be concerned because a hand plane will sometimes be subjected to considerable forces in use (when encountering switching grain or a knot for example).
Obviously you have two options here: repair and replacement.
Making a new tote is actually not that hard given the right equipment and it makes a great little project for the workshop; guides on how to do this are easily found online, some including dimensional drawings to guide exact shaping. However, I'm a big fan of repairing where possible so I would suggest you at least try a repair first.
Repairs on broken plane totes and knobs can actually be very easily done in some cases and, perhaps surprisingly, the handles are no weaker than when new. This is even if only glue is used for the repair, although further reinforcement is easily done and can result in a truly unbreakable handle (see Pinning below).
Your plan to force the break would be exactly the way I would have recommended you go here. If it doesn't easily break you'll get a very good idea of just how strong the tote is as it stands!
I think your first step though should be to strip or scrape off the remaining finish to get a proper look at the extent of the cracks and if there are any more lurking under the remaining finish. While you're at it you should remove the finish from the knob so that when it comes time to re-finish you'll do both and they'll match. At a guess the finish on the knob will be in fairly poor shape so it should come off anyway!
Assuming the handle does break neatly you simply need to spread wood glue and apply clamp pressure to firmly clamp the parts together, ensuring correct alignment. Because of the odd shape of a tote you may want to build a glueing jig to help with alignment. Here's one simple method:
Note: don't do too many dry runs. The fractured surface of split wood is easily damaged and even one splinter out of place can prevent the parts coming together neatly and forming a strong joint.
Now, if you can't get the tote to break using any force you're comfortable applying you can still reinforce this in a couple of ways:
- getting glue to penetrate into the crack;
- pinning with thin brass rod or paperclip wire.
For security I would suggest you use both these methods.
For the glue in this case you'll want to use epoxy for a number of reasons, one of the main ones being that epoxy is a gap-filling adhesive so no clamping is required to close the cracks.
You'll need your epoxy of course, which should be a slower-setting type (15 minutes at least), also a heat gun or hairdrier. You can thin epoxy to make it more penetrant, using alcohol or acetone, but it's better to reduce viscosity using heat as this doesn't affect final strength as thinning can.
First step is to pre-heat the joint with the drier or heat gun.
Now mix your epoxy as normal and spread it over the cracks, then give it a blast of heat. You'll see that it will become very liquid and will naturally sink into the cracks anyway, but in addition to this as the wood cools it will draw the glue deeper into the cracks. This is why you want to use a slow-setting epoxy, as you need to ensure the glue is still not set when this happens.
Apply more epoxy as needed so the cracks appear full of glue and then put it aside for it to partly set. You want to wait for the epoxy to get to a sort of rubbery consistency, when it's very easy to scrape off the excess. Use the side edge of a chisel or the back of a knife for this.
Now leave it to fully cure before you do any further work on it. Wait at least a full day, but 48 hours or longer would not be a bad idea.
Now to pin the joint, first you must carefully pick the directions you want to pin and then drill carefully right through the tote; you want the pins to cross any cracks. Be careful to note where the fixing screw goes so any pins don't intersect it.
Here are two suggestions for how you might pin a cracked tote:
To glue this sort of pin you can use epoxy as well, but superglue can work quite well too. Be sure to scuff the surface of the wire with abrasive paper or Scotchbrite to help ensure a good glue bond to the metal.
Here's a chisel handle repair that I pinned in place in this way: