Are there any advantages to fixing half a length of high tensile threaded rod to the rear of the vise & making the nut part of the handle?
Yes, the rod would extend out the front of the moving jaw right where you want to stand.
I thought the orange nut could be flipped and be part of the handle. The screw would be fixed on the right on the end of the vise finishing where the end of the hole in the nut is when closed as the image shows. I’ll sketch something and post in a few days.
Cut away image link - cut away section vise.jpg - Google Drive
I think I see where you’re going with this idea, and I think it could work. The critical part would be how to solidly lock the threaded rod down in the back so that is can’t rotate when the screw is under high tension.
I like how you keep looking at the vise prints trying to come up with alternative designs. It’s fun to think about, and I think this is the first case where if you dive deeper into the idea you may be able to think of some actual possible design advantages. Will it turn out to be better in practice, I dunno, but I can see how maybe with the right goals and design it could be possible.
The first questions to ask; what problem could it solve, or what new design possibilities does it create?
Thinking about your idea I see another issue, the size of the hole would have to be much larger and would weaken the moving jaw. Good idea for discussion.
Valid point, but if the lower opening in the moving jaw box section currently used for assembly could be removed by having the nut machined for the bearings with a modestly stout retention cap on the handle end, it’s possible a clever designer could mitigate some of the strength lost from the larger hole through the end of the jaw.
It could even be argued that by moving the forces closer to the edges of the box section the vise actually gets stronger because it’s not transferring the load through a flat face which can deflect, but directly into the boxed way in compression.
Edit: Duh, it’s the jaws under compression, not the boxed ways you big dumb ape. So that argument of loading the boxed section more efficiently is moot.
My only excuse is being up till 2am caressing, I mean, assembling my Dragon Wagons and checking out the new tooling. I’m not firing on all cylinders today.
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The innermost thrust bearing seems to be sitting on a cast surface which made me initially consider looking at the area.
I don’t think the loss of material from a slightly larger hole would be detremental considering the mass gained from closing up the access hole. The other advantage is keeping all the moving internal parts completely grit free.
Closing up the access hole could only be acheived by loading the leadscrew assembly from the front which is possible.
I considered reversing the nut & screw to eliminate all the machining of the entire leadscrew thread area from material the much larger diameter of the handle ball.
Having the leadscrew at the back, it could be simple high tensile stock threaded rod with a small amount of machining on one end. The nut would remain pretty much the same with some machining to suit the bearings & nyloc nut.
I would consider fixing the nut / bearing assembly to the moving jaw front face with a recessed circlip as it only has a low opening force on it. Very easy maintenance too.
So, based on the actual failure mode that we’ve seen in Jason’s videos, I don’t think the main body of the vise needs a lot of changing. The hole on the bottom of the box section on the moving jaw doesn’t seem to be a weak link in the system.
One thing I’m not sure if you’re considering is that the lower box section is in compression, not tension, so it doesn’t need to have the same cross sectional thickness to have the same strength in this application. Ductile cast iron has almost 2x the compression yield strength as tensile yield strength.
We’ve already seen that the vise handles 7 tons of force of clamping load, and takes a helluva lot of hammering to break the cast base section. So with that in mind, these are my suggestions.
Maybe a higher grade of bolt for the swivel, and increasing the base thickness 25%? Also, @Fireball_Jason I don’t know how much you QC the porosity of the castings, but I notice mine seems to be one of the worse looking castings that I’ve seen people post pictures of. That probably has as much or more of an effect on ultimate strength as making any design changes. Nothing on mine makes me too paranoid, I think, but that’s the only other suggestion I have right now for changes, or thoughts on the vise on how it could be even better at beating the snot out of the competition.
That and maybe a badass pivoting base. 
Good point regarding the thickness at the bottom of the box section. I still think revising the whole nut / screw / bearing setup to load from the front to give them complete protection by closing the hole.
Looking forwards into a pivoting base. Personally my preference is still to change the section to either square box or tube. I see this as a neater solution to a chunky add on “bracket” to allow the present style to pivot and will still allow the use of the existing swivel base. It may be marginally more expensive for a vise with the pivot built in than an expensive custom bulky add on.
A beefy locking sine plate type setup is what I was thinking for a pivoting base.
I forgot there are 3 axes of rotation, I was only considering the plane looking at the front.
I can see tilting the whole assembly including the base up to 90 degrees forward looking from the side, then the vise can be swivelled at any angle on the original base. This will cover all 3 axes by using the original base in several inclinations.
Yup. In fact, building a base like that doesn’t sound too difficult, I may try and make a prototype for the blue 5" forged vise they sell.
It would be a lot less challenging to lock down tight than Big Red at 270lbs…
Definitely some optimization could be done. Specifically I think that it’ll be hard to lock it down very rigidly so close to the pivot, even with 3/8" bolts, but all the other easy solutions are in the way in other areas, so I need to do some more daydreaming to decide how I’d improve the ability to lock an angle without being horribly in the way or require holes through the mounting table.
That’s the type of bracket, nice and simple.
Curved or straight slotted bars may clamp better as they are further from the pivot point.
Or maybe a ratchet type slot for positive locations.
Good call. I put the brace towards the rear to give it more leverage than the front pivot brace design shown in the sine plate pictures you posted. Angle settings every 15°. The front pivot clamp may be unnecessary, but would probably help control any slop in the hinge mechanism, so probably useful.
I bet I can tinker with the hinge and front pivot clamps to make even more room around the jaws, just need to have the top plate above the hinge so the vise plate and vise can cantilever further forward.
That’s it, I could not find any images of a rear pivot design. I tried to describe it with words and gave up. Are you able to post an image where the new base is at 90 & the vise swivelled 90 on the original base? So the jaws are sitting vertical it would really show the full capability of your design. It would be great for holding long large diameter tubes upright.
The 5" vise in the model is just a rough mockup of the actual blue forged vise, I didn’t go all out and make it a moveable assembly, but nothing is in the way of the rotating base functioning. Here’s a picture of the assembly in the 90° orientation.
Maybe I should make one and see what I’d want to make more and sell a few if anyone is interested.