the Carpentry Way: Joint Decisions                                                          

Joint Decisions

    
I decided to move on from my Oliver 166 16" jointer, and have secured a purchase deposit from a buyer. I'm looking for a slightly wider jointer, a slightly longer jointer, and preferably a jointer with a 4-knife cutter head, ideally Tersa.

Now, at the moment in N. America there is somewhat of a dearth of machines fitting the above description. I look daily, and I look in all the usual spots, and in some not-so-usual spots. The average jointer for sale in North America is a 6" home-shop machine. There's a slightly smaller number of 8" jointers, usually designed in a similar way to the 6" machines, that is, not very well, and then there are a few 12" machines to be had. If I was to hazer a guess, I'd say that less than 5% of what's available are jointers larger than 12", and most of those are 16". A tiny number of 20", 24", and even 30" machines rounds out the picture. The vast majority of the 16" and larger jointers are old hunks of American 'arn ("iron"), some of which dating back 100 years or more, and often having had zillions of linear feet of stock run over them.

Now, once in a while, when I have drool to spare, I head on over to some German heavy metal sites, chock-a-block with ridiculous jointers. It's somewhat akin to a religious pilgrimage. In Germany, the typical jointer is 20", and machines in the 6"~12" size are a distinct minority. I get the impression that the hobby woodworker market there is somewhat small.

As i look through listings of a couple of hundred beautiful jointers, ranging from dirt-cheap to not-so-cheap, I noticed that jointer deisgns vary by more than one would think. After all, when you think about it, the jointer primarily does two basic things:

  1.  Flattens a surface on a board
  2.  With the first surface flat, an adjacent surface can be made flat and square to it

Not much going on really - one would think the physics of this machine had been long resolved. However, looking at jointer after jointer I notice interesting variations in all sorts of things, and not simply color or size. Take fence placement. On the Oliver, and a lot of the older American tanks, the jointer fence is a 100+lb. affair held onto the outfeed table with a pair of large heavy locking screws. Many of the German and Italian jointers also affix the fence to the outfeed table. Here's a couple examples:

Kölle:


Martin T-52:

Quite a few jointers however, have the fence connected to the infeed table side:

Hofmann AHW 500:


Rex:



I could list more makes yet - it appears that the fence attachment to the infeed is the most common one, which I found a surprise.

And then there are jointers in which the fence is supported independently of the tables, in which case the fence pivot mechanism is often centered, more or less, over the cutter head:

Ascom DE 410: 


Schelling A-41:


Panhans:


Kölle AH40:


Kölle seems to have changed their design philosophy from the one pictured at the top of this page with this newer machine. I wonder why?

Baeurle AS510:


Casadei DS510:


Dorna F500:


The monsterous Gubisch AL-4:


Olma:


 RGA FC410:


 Schneider AFK 5:


Now, I think the Japanese also make some sweet cast iron monsters too, you just really don't see them much outside of Japan. The typical Japanese jointer is slightly smaller than the average German machine, typically in the 300~350mm width zone.

How do they situate their jointer fences?

The Matsuda MNT-400 goes for the outfeed table position:


Many Japanese jointers place the fence on the infeed side:

Shimohira HA-300:


Shoda 300:


Love the cast iron 'door' on the left side pedestal on that one.

Takagi 250:


Yasuhara P-350LDX:


And then there are ones with the fence fixed to the chassis, not the tables, like this Taiyō RH-250A:


Though the fence does not attach to the outfeed table, the fence pivot point, the stiffest portion, is on the outfeed side.

So what to make of this? Which different theories are at work, and why? It's got to be something other than patents and limitations that arise that way.

It seems to me than the infeed table aligns the work for feeding to the cutter head, and the longer the infeed table the better. There are several German jointers, and one Japanese model that have 1.8m (6') infeed sides. The inffed table is the one which is adjusted up and down with frequency to change the depth of cut. The outfeed table is generally kept in the same place, which is a hair (a couple of thou) below T.D.C. of the cutter head's knife circle. It is the outfeed table which is most responsible, I think, for creating a flat reference on the stick. So, for the initial jointing of one board face, as the fence is not involved in the process, it really doesn't matter much where the fence attaches.

When performing the second jointing operation, jointing a 90˚ adjacent face to the first, that fence position makes a difference possibly. In this operation, the stick needs to be held closely against the fence, which may require some pressure if the stick is heavy and the board wants' to tilt away from the fence at top or bottom arris. Ideally, you don't want any deflection with the fence at this time, and this is where having the jointer fence attached to the infeed seems to make more sense. And I am jut now coming to this conclusion as I write this.

The disadvantage to having the jointer's fence connected to the infeed is that when you lower the infeed table for a deeper cut, the fence may bottom out on the outfeed table. So, either the fence has to be configured with a bunch of space under its edge along the outfeed portion, or the fence pivot mechanism needs to allow for the fence to be re-positioned. A similar problem happens with the fence attachment to the outfeed table - when the infeed is lowered for a heavier cut, the fence ends up with a fair amount of space under it at the infeed side, and this can cause problems in certain situations.

I think one definite advantage to having the fence attached to the chassis of the machine rather than either table is that the weight and position of the fence can have no effect upon the setting of either table. Depending upon how perfect the castings are for the jointer table supports, a little weight shift here and there can cause a table to slightly tilt or tip.

finally there is one other place in which jointer fences get attached: to the far end of either the infeed or outfeed table. This design is seen on most jointer-planer combo machines and is decidedly a drawback. Such fences, which are often aluminum extrusions come from a company called 'flexomatic', if you catch my drift. I'll never buy another jointer planer machine again for the simple reason that their fence system is crappy.

Thanks for coming by the Carpentry Way. I welcome hearing from readers in regards to which jointer fence design makes sense to them, once any drooling has subsided. Love those big jointers!