I recently picked up both a set of forks (for moving pallets etc) and a grapple (a big claw for ripping up roots, moving rocks, etc) for the front of the tractor.

Both are awesome and I wonder how I ever got by without them. But I could say that about pretty much any tractor attachment. Bushhog? 6’ wide lawnmower? Bucket? Yeah. I’ll probably say the same thing about the tractor-mounted snow blower scheduled for delivery later this summer when I finally get a chance to use it.

The claw on the grapple is actuated by another hydraulic circuit, called a “third function valve” which augments the up/down and wrist functions already on the loader. This is an accessory that I would have had installed when I bought the tractor (as well as a set of rear hydraulic remotes) if I knew then what I know now… but I went ahead and had it installed last autumn and then didn’t do anything with it until I got the grapple.

The nice thing about standards is that there are so many to choose from. Believe it or not things are even worse than the situation with pneumatic connectors for shop air (where everyone I know seems to have standardized on IM connectors at least for the small stuff). There are at least three ISO standards for hydraulic connectors.

It turns out that I have what are called Pioneer connectors (in the same vein as Amphenol, Berg, and Cannon connectors), and more formally ISO 7241-1 Series A.

Unsurprisingly, just like compressed air fittings, a 1/2” hydraulic fitting has no dimension that is “approximately a half inch”. They’re sized by what is expected to screw into the back, which in North America seems to generally be NPTF (National Pipe Taper Fuel), but could also be NPSM (National Pipe Straight Mechanical), or SAE J514 “JIC” fittings… or DIN/metric. Or…

NPT pipe is a “trade size”, and while you’re “somewhere in the neighborhood” for the inside diameter of Schedule 80 pipe at least for the common 3/8 to 1” sizes, it has nothing to do with the outside diameter and thus there’s nothing even close on the connectors themselves. Hmmm, ISO standard connectors on a Kubota tractor, sold in the US - wonder if the threads are still NPT or if it’s something metric? The mind reels a bit.

Fortunately the fine folks at Discount Hydraulic Hose have a nifty solution for identifying common connectors - a set of actual-size silhouettes/templates which one can print out and use to identify common connectors. Now all you have to do is figure out the thread… Fortunately they’ve got instructions on that too and a bunch of links to resources. Check ‘em out.