Old Jointer Accident Story

Jointers can send fragments of metal blades flying like shrapnel. You're lucky if all you get is a good scare. March 27, 2012

I had a scary accident in the shop today. An employee was setting the knives on the big old cast-iron planer, probably from something like 1910. A valuable piece of equipment because it's so heavy we use it to get flat sides at right angles to each other on big boards for harvest tables, and then use our planer on the opposite sides.

At any rate he had the knives set to his satisfaction, and tested it by running a block of hickory over it a couple times to see if it left little ridges. Happy it didn't, he went for one more pass and the thing exploded in his face. He's certain he had the knives tightened in hard, but clearly he must not have. It ripped off an inch and a half of the leading edge of the in-feed table and shot it like a spear past him, 10 feet, and halfway through an inch-thick poplar door. He says he felt it ripple the fabric of his shirt on the way. About a third of one of the knives is missing it must be part of the shrapnel I see everywhere. No one hurt, but I thought I'd post this as a reminder, to myself among others, that we deal with powerful, dangerous equipment.

Forum Responses
(Cabinetmaking Forum)
From contributor J:
Thanks for the reminder. We all need a wakeup call once in a while.

From contributor M:
Thank God no one was hurt. If your guy is experienced it is hard to imagine he would forget to tighten the knives. Maybe the backer plate (I forgot what it is called) failed from a century of tightening the bolts? We use Tersa heads on everything and I think they are a lot safer; no bolts.

From the original questioner:
Could be. Hard for me to imagine as well he's inclined if anything to overtighten rather than under. We need to examine the wreckage to determine better what happened. It was one of those accidents that left us so shaky we just called it a day and walked away.

From contributor M:
Old shapers without locked-in cutter blades are the worst. I had a raised panel cutter fly off some years ago. It went right through a wall.

From contributor I:
Glad everyone was okay. I don't blame you for just calling it a day. When something like that happens and you're shaky, it could lead to another incident.

From contributor E:
Sounds like he was very lucky! So was this a planer, or a jointer? The way you described his passing the wood over I'm guessing you meant jointer. And that it's old enough to be roughly 100 years old I'm guessing it probably also has its original, outdated, and by today's standards, unsafe head.

Unfortunately not everyone that owns them is aware that many older style heads are much more dangerous than the modern gibbed heads in today's machinery. Not to say they can't be used safely with a lot of caution, but the risk is so much higher, why would you want to?

I don't know if your machine is repairable or not, but if so I would obviously recommend replacing the cutterhead. A good quality modern jointer will work every bit as well and safer too, so may be a better option?

From the original questioner:
Yes, I mispoke - a jointer, not a planer - guess I was more rattled than I thought by the accident. I've got Tersa blades on a much smaller Inca jointer/planer (it came with them), and I bought a Tersa kit for my big planer. Should've done the same for this big old jointer, but I worried about the interface because of the age. I'm not mechanical enough to be sure I could install it effectively if it didn't arrive already fitting. Also I didn't like the price of Tersa kits, although in retrospect that pales for sure compared to serious injury.

From contributor K:
A similar incident occurred on my friend's old American jointer some years ago. It had a clamshell style head, two knives held onto flats on the head with semicylindrical caps and bolts. We guessed that the threads had failed due to overtorquing, but had no way to verify the hypothesis. He had a tech repair the table damage and fit a newer gibbed cutterhead to the babbit bearings. The machine is still in service, but I think he retired the shorts he was wearing as he crawled across the floor to hit the kill switch. I don't trust heads like that, and I always rotate again through my jointer knives after setting them to be sure they are tight.

From contributor R:
Did he have the wedge shape piece in backwards? (Sorry, but I can't recall its proper name - gibb?) Many years ago on a shaper head one of my men put that piece in backwards. Now it's company policy to have some look at the head before pressing start.