How big can I go with a machine vice?

The direction of the cutting forces when milling are not always along the feed axis. Consider an endmill cutting conventionally along the x-axis. If the width of cut is shallow (say less than 10% of cutter diameter) then the forces will be mostly along the x-axis. But if we now increase the width of cut to 100% of the cutter diameter then the direction of the cutting force for a single tooth will start along the x-axis, move round to the y-axis and then back to the x-axis but in the opposite direction. So how should we orientate the machine vice?

I've never had a problem with work moving in the machine vice on the vertical mill. I have had a couple of wobblies on the horizontal mill with ambitious depths of cut. A 5hp 4-pole motor geared down to 60rpm produces a torque of 596.8Nm. At the edge of a 100mm diameter cutter that translates to a force of 11936N. You need a pretty large clamping force to resist that!

Andrew

Unlike most folk here I leave the swivel base on. I like the ability to clock the vice true when needed although my usual method of pulling it back hard against the studs before tightening in stages usually gets to around a thou or two in 4". My vice slots aren't that accurate relative to the jaws but tweaking the swivel easily took care of that. But I have a Bridgeport with plenty of vertical room.

For a non swivel vice I'd seriously consider flipping it over, clamping to a bar accurately aligned with the table and machining the slot sides true to each other and to the jaws. Make a T shape clamping "washer" with the lower part of the stem fitting nicely but not too tightly in the table slots and the upper part a similar fit in your re-worked vice slots. The pull back when tightening technique should then get you alignment accuracies rather better than mine. Not quite up to a well fitted key but close and far easier to shift.

I like my pair of the Vertex VJ-400 110 mm x 180 mm vices **LINK** . Basically a mechanical screw version of a lower end hydraulic vice they can be set to three different maximum openings. Normal vices are pretty much square capacity so a 110 mm / 4" jaw width vice opens to around 110 mm / 4". The VJ-400 goes out to 180 mm / 7" if need be so combining the lighter weight of a 4" vice with the ultimate capacity of a 7" one. Obviously it hasn't got the grip of a true 7" vice but I've always found it enough when needed. Generally I find it gets used pretty much as a 5" nominal vice. Relatively expensive now and lacks the fancy Kurt style angle lock anti jaw lift device but I find it a good performer.

Hafta say I'm more than a little skeptical about the practical behaviour of all the fancy automatic anti-jaw lift systems. I figure the benefit is ore due to being on a well made, or well fettled, vice.

As far as weight is concerned didn't Chick, the One-Lok people, use an alloy base at one time. I've long been tempted to try my hand at a home brew version.

If you want something bigger at, possibly, a more affordable price maybe the adjustable planer vice published in Popular Mechanics **LINK** would be a useful source of inspiration for a home build. Looks quite amenable to bolt up from lumps construction. Getting the working faces of the jaws dead square to the base looks to be the only part needing extra care.

Clive

Seeing as there are only 2 sizes of Versatile SG vice listed, the 6" is going to overhang by about 8", I think this makes it a bit big for your table, however the work envelope of the 4" seems a touch on the small side.

I have an RF45 type mill, so same depth table, and rather liked the adaptability of the versatile SG and seriously considered one, I ended up with the 120mm type 2 precision, it still has the multi position usability and has a good wide opening, though loses the multi position jaws. I have not regretted my decision, the width, jaw depth and clamping capacity all seem to be in the Goldilocks zone for my machine and use.

One option I have seen used is to consider having two identical vices, depending on what you make this can be very handy and means slightly smaller ones can be considered.

At the museum, we have a large drill mill which has 500mm X travel, and a Tom Senior light vertical with a slightly smaller bed. 100mm vises are about the optimum size, and we have a pair which can be used together, but we also have one of ARC's 5" vises which opens much wider than the smaller ones. I think the 5" is the biggest that fits without being too big, and the swivel base is only used very occasionally. A 6" vise would be too big and too heavy for my liking.

Edited By old mart on 26/05/2020 14:10:03

I am the proud possessor of a modern Abwood 6 inch milling vice. A really superb bit of kit if I say so myself.

There is just one very minor drawback, I simply cannot lift it onto the milling table. This does have the advantage that the vice will stay in pristine condition.

Andrew.

That was part of my reasoning in getting the two Vertex VJ-400 types. If I needed to hold something long spanning the two vices would work fine.

The three opening settings give me pretty much the holding ability of a 7" vice in something little more than a normal 4" vice size. For most of my use its effectively a 4" jaw x 5" opening vice. I have a larger 6" vice should I need a wider jaw but have never needed it since I got the Vertex vices. But if I'd got an ordinary 4" jaw one odds are the 6" would have been mounted the first time I needed more opening and just stayed. So in many ways I agree with the folk who have settled on the 6" one as a good compromise. But a conventional 6" is considerably heftier and I'd miss that extra 1" of opening for enough odd jobs.

Clive

Edited By Clive Foster on 26/05/2020 14:20:00