Square jointer/planer cutterheads questions

[KingwoodFan1989]

In the past couple weeks or so I posted a thread asking about jointers, and after the topic of old ones came up a couple or three people mentioned old square cutterheads. I was able to find some info and pics on them but only one or two videos. I'm wondering some stuff about them, though, that I couldn't find.

Someone in that other thread mentioned that they can pull your hand in. Why are they more prone to doing that than a circular head? The corners of square objects still trace out a perfect circle when spinning (think a square blank on a lathe). However, the heads that I have seen in pictures and videos don't look perfectly square...maybe a little bit rectangular even, with the ends of the longer sides holding the knives. Is this what causes the "pulling" phenomenon or is it something else?

The questions have been on and off my mind the past couple weeks, so I thought I'd ask.

[TGW]

When a square head is spinning in a jointer there will be a big gap opening four times per revolution between the table edge and the cutterhead. If something is pulled in there it will be hacked of by the following knife. The protruding corners of the square head are goodat catching stuff and pulling it in there.
So..... if the head catches one of your fingers you are likely to get half your hand pulled in and chopped off. 
If the same accident occured with a round head you will still have half the lenght of your fingers after the accident.

There is a significant difference in day to day practicalty between half lenght fiingers and a half palm with no fingers at all.

Lots of professionals still use square heads but I did early on choose not to. No insurance anywhere in Europe would cover a work accident where a square head is involved.

[WilliamHodge]

In the past couple weeks or so I posted a thread asking about jointers, and after the topic of old ones came up a couple or three people mentioned old square cutterheads. I was able to find some info and pics on them but only one or two videos. I'm wondering some stuff about them, though, that I couldn't find.

I was one of the people that mentioned old machines.

Using old machinery requires training and skill to make the entire machine safe to use. There are a lot of big and cheap machines out there that do not meet OSHA standards. One needs to know how to guard power transmission  and moving parts, set knives, improvise dust collection, and operate a big jointer. The operation is key to safety.

As far as the suction idea goes, I have never seen or heard of that happening. Perhaps someone has done a field test.

[KingwoodFan1989]

When a square head is spinning in a jointer there will be a big gap opening four times per revolution between the table edge and the cutterhead. If something is pulled in there it will be hacked of by the following knife. The protruding corners of the square head are goodat catching stuff and pulling it in there.
So..... if the head catches one of your fingers you are likely to get half your hand pulled in and chopped off. 
If the same accident occured with a round head you will still have half the lenght of your fingers after the accident.

There is a significant difference in day to day practicalty between half lenght fiingers and a half palm with no fingers at all.

Lots of professionals still use square heads but I did early on choose not to. No insurance anywhere in Europe would cover a work  accident where a square head is involved.

Sounds scary! I did have an incident with my 6" Grizzly jointer (standard knives, obviously a round gibbed head) just a few days after I got it and set it up...there was some dust on the table and I wanted to get rid of it, so I pulled the guard out of the way to blow it off...I didn't keep my whole hand on the top and instead grabbed the edge with my fingers wrapped around it. My middle finger is longer than the rest of my fingers, and I felt a little "zing" on one side of the top of my middle finger...needless to say I was VERY lucky my fingers weren't even lower than they were, and I'm sure, based on what you said, if it had been a square head it could have been MUCH worse. It only took off a sliver of skin, but it did bleed for a while and it took several months for the fingerprints there to come back.

[jteneyck]

The above posts cover your question really well.  There are lots of old machines out there.  The really old monsters are often very cheap, but I would never consider a jointer with a square head, no matter how cheap, unless I knew I could retrofit a modern head onto it.  Same thing goes for babbett bearings.  They work fine but if they ever need to be replaced I wouldn't know how to do it and it's not a skill I care to learn.  Happily, there are plenty of used machines with round heads and ball bearings around to pick from.  

John

[KingwoodFan1989]

The above posts cover your question really well.  There are lots of old machines out there.  The really old monsters are often very cheap, but I would never consider a jointer with a square head, no matter how cheap, unless I knew I could retrofit a modern head onto it.  Same thing goes for babbett bearings.  They work fine but if they ever need to be replaced I wouldn't know how to do it and it's not a skill I care to learn.  Happily, there are plenty of used machines with round heads and ball bearings around to pick from.  

John

Yeah, one poster in the other jointer thread I posted described the process of dealing with babbett bearings, and it sounded like a massive pain in the rear. I'd prefer to avoid that. As for the cutterhead, yeah, I'll have to make sure it's able to be fitted with a modern head. On a related note, one of the videos I saw of what I think is a type of square head was one which I will post below. It's an old Porter 12" model that actually had thrown a blade from the old square head. It actually traumatized the previous owner, but thankfully the guy in the video who bought it was able to retrofit a Byrd Shelix head onto it.

[TGW]

I have poured and scrape fitted new babbitt bearings.

I would not loose interrest in a good machine just because it has babbitt bearings.
However

To validate the effort of pouring and scraping babbitt bearings the machine must be well designed and well made and very cheap.
If one has to correct flaws in design or machining AND shift babbitt bearings it will just be too much.
If the machine is expensive the buyer will get no financial reward  from all his work and patience.

Most conversions I have seen from babbitt to ball bearings have been pretty much useless. A good conversion normally requires a lot more effort and skill than pouring and scraping new babbitt.

[KingwoodFan1989]

I have poured and scrape fitted new babbitt bearings.

I would not loose interrest in a good machine just because it has babbitt bearings.
However

To validate the effort of pouring and scraping babbitt bearings the machine must be well designed and well made and very cheap.
If one has to correct flaws in design or machining AND shift babbitt bearings it will just be too much.
If the machine is expensive the buyer will get no financial reward  from all his work and patience.

Most conversions I have seen from babbitt to ball bearings have been pretty much useless. A good conversion normally requires a lot more effort and skill than pouring and scraping new babbitt.

I'm guessing it was you who told me about caring for babbitt bearings in the other thread, right? I remember you posted but I can't be sure. Either way, yes, if it was a REALLY cheap machine AND in good enough shape to where I'd easily be able to adjust everything to be straight, square, and co-planar, then yes, I'd put up with caring for the babbitt bearings. But if it was more than, say, $600 for an old 10-12" jointer in great shape, I'd pass if it had babbitt bearings. I know I might sound like a brat in talking that way, but the description in the other thread of how to care for them (especially the manufacturing of new ones) sounds like a royal headache, haha.

[TGW]

I'm guessing it was you who told me about caring for babbitt bearings in the other thread, right? I remember you posted but I can't be sure. Either way, yes, if it was a REALLY cheap machine AND in good enough shape to where I'd easily be able to adjust everything to be straight, square, and co-planar, then yes, I'd put up with caring for the babbitt bearings. But if it was more than, say, $600 for an old 10-12" jointer in great shape, I'd pass if it had babbitt bearings. I know I might sound like a brat in talking that way, but the description in the other thread of how to care for them (especially the manufacturing of new ones) sounds like a royal headache, haha.

That makes a lot of sence.

A babbited machine must be both cheap and good if it is going to reward it's owner for his extra labour maintaining it.