shattered segmented cutters

[joe maday]

i was searching/looking around the internet and came across a blog that showed damage done to a jointer by the blades and lock bar becoming loose and taking a chunk out of the infeed table. That lead me to wonder.... if the same or similar danger exists with segmented carbide cutters. I know they are brittle and prone to cracking/chips, but are they "soft" enough that if they were caught between the cutterhead/other cutters and were jamed against the infeed table ....would it take a bite or damage the table or just crumble further.
Any ideas or any experiances???

[Mel Fulks]

I don't think it is possible for a PROPERLY installed knife to loosen and fly out of a jointer. Don't know about inserts.

[Peter Quinn]

I'm with Mel on this, never seen or heard of jointer knives leaving the head if properly installed, doesn't seem likely or remotely possible if the gibs are correct for the head and all is snug. Loosening? Think about how many screws are involved in even just a small jointer head. Not going to happen. More likely they knives were not installed properly, somebody now has something to talk about.

I have a byrd head, the chips are not thick enough to get lodged easily between the infeed edge and cutter head, I'd guess they would just bounce right on by, but I'd also guess they would have to hit something ferrous and fairly hard to chip, or a good chunk of stone to shatter. So I avoid jointing granite. I'm not hearing anything about carbide failures at any great rate on these heads. I do know that if you let orangoutangs rotate the inserts, and fail to clean out the torx heads properly, and over torque them with the wrong size driver, and fail to clean out the seats.....performance suffers. You might even try to blame the concept for these short comings....I worked for a guy that did.....luckily tersa heads solve those problems for the mechanically disinclined, and they don't come out of the head either unless you want them to.

I'd love to examine the original link.

[glenn bradley]

+1. I have seen jointers where this has occurred but, I have also seen drill press tables with holes drilled in them instead of using the one provided, people without thumbs from misusing a tablesaw and scars around the throat of a bandsaw table from careless blade installation or saw maintenance. I'm sure a loose piece of carbide at 3500 RPM would be ill advised as well but, I'd rather be careful and just not find out ;-) It is no secret that the tools we work with are dangerous if safety procedures are ignored. This includes improper setup, installation, wiring, and maintenance. Like any dangerous item designed for safe use, they are safe if used properly.

[joe maday]

In the original blog about a knife coming out of the cutterhead and breaking the infeed table was identified as not being tightened enough to begin with. My question was , if a carbide cutter became damaged ( by hitting a nail for instance) and shattered, could it damage an infeed table in a similar way or are the cutters too brittle to damage a table, I will try to find the original post/blog. it was a powermatic jointer I belive.

[joe maday]

Turns out that my memory was bad ,.... it was the out feed table that was broken/chipped when the knife slid out of the cutterhead. Here is the article/post:
Extra major bummer with a praise. - by b2rtch @ LumberJocks.com ~ woodworking community (http://lumberjocks.com/topics/40359#reply-477310)

[Mel Fulks]

Looks like the old : "these knives are too hard to change. Think I will just stick knife back in and sell this thing. New guy will have to change them".

[Jamie Buxton]

...I'd love to examine the original link....

There was a thread on SMC perhaps five years ago. I've just searched for it, and didn't find it. The poster had pics of his Hammer A3-31 in the jointer mode with the front of the infeed table chipped and cracked. Apparently the gib screws had not been properly tightened, and the knifeholder had come flying out when the machine was running. Fortunately, he was not injured. The pics were real ugly and scary.

[Jeff Duncan]

Many jointers went to replaceable sections surrounding the cutter head years ago. I don't know why for a fact, but my best guess is so that you wouldn't have to replace the whole table in those situations? The metal used in those areas is softer and so can be cut or scraped instead of shattering like cast iron. Meaning if your jointer has those sections you shouldn't have to worry about a chipped insert causing any trouble. Even if you don't have the replaceable sections, an insert is so small I don't think it would cause anywhere near as much damage as a long section of HSS knife and gib. Think about a gib coming loose while spinning at 3500+ rpm's and it's pretty scary. At the beginning your going to have part of the knife gib still retained in the head as it's hitting the table:eek: A tiny bit of carbide on the other hand coming completely free is just not likely to do too much damage to the tables.

At least that's my best guesstimate for what little it's worth;)

good luck,
JeffD

[Rick Potter]

I posted on Sawmill once about this happening. After my father died, I gave his Craftsman 6" jointer to my son in law, Don. When dad had it, he never had any trouble with it, and I never gave it a thought.

When Don turned it on to use it, a blade came loose (or out, don't know which), and took a 3" wide chunk out of the infeed table, thankfully not hurting anyone. We junked the jointer, and he bought a DJ20.

While I will never know for sure why it happened, I suspect that at some point Dad decided to change blades and never finished the job. When he got sick many things were unfinished, and years later Don was given the jointer.

Moral of the story? When you buy a used tool, especially at an estate sale, check everything before using it.

Rick Potter

[Chris Fournier]

I posted on Sawmill once about this happening. After my father died, I gave his Craftsman 6" jointer to my son in law, Don. When dad had it, he never had any trouble with it, and I never gave it a thought.

When Don turned it on to use it, a blade came loose (or out, don't know which), and took a 3" wide chunk out of the infeed table, thankfully not hurting anyone. We junked the jointer, and he bought a DJ20.

While I will never know for sure why it happened, I suspect that at some point Dad decided to change blades and never finished the job. When he got sick many things were unfinished, and years later Don was given the jointer.

Moral of the story? When you buy a used tool, especially at an estate sale, check everything before using it.

Rick Potter


I would agree but go one step further and say that you should check every new tool new and used. Mistakes happen.

[Peter Quinn]

I would agree but go one step further and say that you should check every new tool new and used. Mistakes happen.

I have received new insert shaper tooling from a top manufacturer with explicit instructions to "break this tool down, remove every insert, clean off the oil, remove any manufacturing grit, replace the knives, torque everything properly. The user assumes all responsibility to insure the tool or tooling is set up properly. Definitely break down and reassemble the cutting head or business end of any new or new to you tool, always. I've bought or brought home lots of used equipment, everything gets a complete tear down, belts adjusted, everything set to factory spec prior to pushing the green button. Especially if it comes from my Dad! I love him dearly but he is the king of half finished projects...guess that makes me the prince? And new stuff requires the same, usually for assembly and cleaning purposes, but at the least to make the user familiar with its condition.

We have a rule at work....all truckers strap and tighten their own loads. No exceptions. Stuff comes flying off your truck going down the road, you are responsible. Now lots of guys load things on lots of trucks, but the driver of the truck has to be the last to check the load before they turn the key. This is basic shop stuff for any shop. Inspect every tool you use before turning it on, if you don't know how to do that, learn it or leave it off. Or wear armor.

[glenn bradley]

In the original blog about a knife coming out of the cutterhead and breaking the infeed table was identified as not being tightened enough to begin with. My question was , if a carbide cutter became damaged ( by hitting a nail for instance) and shattered, could it damage an infeed table in a similar way or are the cutters too brittle to damage a table, I will try to find the original post/blog. it was a powermatic jointer I belive.

Ah, sorry, I was a little off base there. I would think if a carbide insert broke off it would do much less damage than a HSS knife but I would rather not check that theory :) The inserts are small and carbide is brittle. The knives are larger and HSS can take quite a beating and remain in one piece.

[Tony Leonard]

Not a jointer, but for reference anyway...


I have the Byrd head in my DeWalt 735 planer. I have had several inserts break. Not sure why. I've been very careful about torque, cleanlieness, etc. No "bad" wood, etc. Anyway, no damage that I can tell. The chunks that come out are small. I doubt they even hurt the dust collector much.

Tony

[John Piwaron]

I have the Byrd head in my DeWalt 735 planer. I have had several inserts break. I've been careful about torque, cleanliness, etc. No "bad" wood, etc. no damage that I can tell. The chunks that come out are small.

Tony

When you say the inserts broke and "chunks" came out, do you mean that one or more whole inserts disintegrated or is it simply a matter of an edge becoming chipped?