Hydraulic press support pin size and strength.

[Screwdriver]

If you imagine putting box section in a vice corner to corner and then the same but with a triangle piece.... The box section is much easier to distort/squash than the triangle

I think it's all a bit if a mute point because whatever people do will be many times stronger than needed... But it's good to think about it and not just copy existing designs

Yes but you're never going to apply force in that direction on a press. This is what I was thinking:

If there is an offset to the force being applied and your concern is to support the edge of the C channel, then the angled insert will generate a bending moment around the long side of the triangle. Remembering the whole purpose of using C channel in all designs is to form an unsupported span.

Normally you would want the press to operate close to the vertical edge of the channel (in between the two spans of course) but on occasions where it pushes the far edge (straight down!) this was what I was getting at. It is a moot point because I don't think that is a particularly weak area in most constructions anyway but it's interesting to think what happens under the circumstances. As often as not, there will be a plate between those spans anyway.

 

[E T]

Plus of course, people often want to stick a pin right through the web of the channel, so even a few uprights "boxing" it in in a just few places might be preferable.

I thought about drilling holes in the web for the pins, but dropped that.
I have to lift/lower the table by hand. Having the pins under the table is much easier because I don't have to line up the holes while holding the table up by hand. I can now easily drop it down or lift it up 1 side at the time.

 

[E T]

Yes but you're never going to apply force in that direction on a press. This is what I was thinking:

If there is an offset to the force being applied and your concern is to support the edge of the C channel, then the angled insert will generate a bending moment around the long side of the triangle. Remembering the whole purpose of using C channel in all designs is to form an unsupported span.

Normally you would want the press to operate close to the vertical edge of the channel (in between the two spans of course) but on occasions where it pushes the far edge (straight down!) this was what I was getting at. It is a moot point because I don't think that is a particularly weak area in most constructions anyway but it's interesting to think what happens under the circumstances. As often as not, there will be a plate between those spans anyway.

The main objective was to make the channel stiffer so it would bend less, not specifically to protect the outer edge of the flange.
Boxing it in will have the same effect, but I think that would put more force on the edge of the bottom flange.
In that drawing the brace is at a 45 degree angle. Mine is at a much steeper angle which makes quite a difference I think.
Either way both solutions will work for most applications. I can bend 12mm flat bar with it no problem. That old 8 ton jack is not to happy with that, that's why I put in a heavier one.