Ideal Dimensions of Vice Clamps

For several months my 90mm Arceurotrade Type 2 vice has been held down to my milling table with step+strap clamps and studding into T-nuts. The clamping has been perfectly satisfactory in most respects, the only objections being that the set-up isn’t very low profile and it permanently takes the clamping components out of service for other purposes.

My plan is to make four vice clamps of the double-step variety, probably held down with cap screws through counterbored holes into T-nuts. I’ve seen numerous videos online of people making vice clamps, but in none of those I’ve seen involving a vice like mine with a horizontal clamping slot does anyone actually discuss how you tailor the dimensions of your clamps to the dimensions of your vice so as to get optimal holding power in the slots.

In my case the slot is 10mm wide [or tall!] and 7.5mm deep, and the slot begins 10mm from the base of the vice. This tells me the tongue that goes into the slot should be at least 7.5mm long and a shade under 10mm thick, but the critical thing I’m unable to decide on is what thickness overall to make the clamp when measuring from the thickest point, i.e. the heel that contacts the table. Clearly an overall thickness of less than 20mm would mean the tongue would be angled upwards when entering the slot and a thickness of more than 20 mm would mean it would be angled downwards, in each case requiring some extra thinning of the tongue for full insertion.

But what will happen in the event that the max thickness is exactly 20mm [the overall length of the clamp being, say, 50-60mm]? Will the downwards pull on a tongue entering exactly horizontally make for a more secure fixing than either of the alternatives as long as the cap screw is closer to the tongue than the heel?

Sorry for my footlingly elementary question, and thanks in advance for any help.

Bill

Valid questions all.

"Ideally" the tongue of the clamp should enter exactly horizontally. But exact is not always easy and it may wear anyway. So the usual plan is to make the clamp slightly too short ( low) at the front and slightly taller at the back so that the tongue points slightly downwards when tightened. Only a few thou difference is needed.

If you imagine the clamp taller at the front, the tongue would tend to push the vice away from itself when tightened, which would not be safe or accurate. If you imagine a large difference it is easier to see the problem.

The tongue should be made slightly too thin for the slot so it does not jam when tilted.

Rod

I’m not really sure of your problem but I use these, although my vice is slightly different. I also have clamps that fit in the holes.

Vic

Certainly going to be secured to the table with those clamps and they are not obtrusive.

Emgee

The clamps need a reasonable heel to sit on the table otherwise they will be compressed into the table. A line contact like those Vic has shown will end up marking the table as some cast iron table are soft. Create a clamp with a heel of say 3mm wide.

Mine are similar to the ones shown but I didn’t make them tapered - I rebated the bottom to just leave a land at the outer end of the bottom surface. Sloped ones will def only have point-line contact with the bed.

Overthinking this. Remember mostly you want the vice not to move. Once that is achieved extra holding is redundant. Its not as if you are going to pick the whole machine, stand and workshop floor via the vice!

Clamp forces needed to hold a small vice in place against practical cuts on typical ME size mills are quite modest. Especially if a thin card / thick paper / thin alloy "gasket" is interposed between vice and table to take up tiny imperfections and, generally, greatly improve frictional grip.

Rule of clamps is slight downwards tilt towards the business end. Small step / nib at the other to contact the table. Ideally step / nib should be about twice as far from the bolt as the holding tip but never less than same distance away as you want force multiplication not reduction. Things need to work with bolts just tight enough not to come undone not need them larrupped up so hard that the table slots scream.

I'd use alloy rather than steel for the clamps (and Tee nuts). Won't mar the table, itty bitty bits of swarf and cut dust get pressed into the alloy rather than the table helping protect it. If you do get over enthusiastic the clamp should bend or threads strip before you hurt the table. Alloy on steel gives a better grip than steel, especially smooth steel, on steel.

Digressing it may be instructive to look at some of the methods used to hold things in place on shapers for a different view on how workpieces et al can be held. Given that shapers and planers really can put a seriously shifting "bonk" on the work when cutting some of the approved work holding methods seem, um, distinctly modest. Hafta say that I'm too chicken to try some of what was apparently industrial standard practice on my little Elliott.

Clive

Bill,

Here's another variation on the theme. I have the 70mm version of the Arc precision vice on my shaper and the slot dimensions are very similar to those on your larger version. To hold it to the table, I made four toe clamps using a piece of 8mm steel rod to act as the pivot, like this:

The clamp itself was made from a piece of 12mm x 25mm steel stock with a 6mm high x 7mm deep cut out at one end to fit in the vice groove. A 15mm long by 8mm wide slot was milled to accept the hold-down bolt. Clamping two together as below, I drilled an 8mm hole along the join about 13mm from the end. The pivot rod sits in this recess and the dimensions gives the slightly nose-down attitude required to hold the vice in pace. Works for me.

The quality of the photos is quite poor - I'm using a phone too close - but you get the idea.

John

I have a slightly different method for attaching my vice onto a jig borer, the table has three radial tee slots so the normal methods do not really work.

This is what I came up with, it is a separate sub base which has location buttons underneath, one button goes into the central hole, the other goes into the front slot. The whole lot is then held down with custom made Tee Bolts.

You will see the vice is held down to the sub base with similar clamps to the others shown previously, and some additional cap head screws act as dowels to make sure it goes in the same place if removed for any reason.

Cap head screws are OK until they fill up with swarf, then it is a pain to have to clean them out before the vice can be removed. So I try and use hex head fasteners and spanners for this purpose if I can.

The vice can be removed and replaced with other tooling such as chucks and collets extremely quickly using this method.

And if I am working on very small parts I just hold a smaller vice in the main one.

Phil

Edited By Phil P on 27/09/2020 11:39:48

I think i have the same Arceurotrade 90mm vice you describe !

Here's the clamps i made for it , they allow clamping from the sides and the ends of the vice as i often want to clamp the vice in both the X and Y axis for different purposes.

Although the contact area with the vice looks very small i have never had it move in use.

It’s not clear in the pictures but the corners are slightly rounded over. I’ve used them on many occasions and they haven’t marked the table on my VMC.

They look good John, I’ve filed that idea for future reference!

Many thanks to everyone who has replied.

The replies have helped me to see what is critical and what isn't. There seems to be a consensus, starting with Rod, on a slight downwards tilt at the holding end. This is the practice I've always followed with the clamping kits I've got, so I suppose there's no reason for vice clamps to be any different.

Clive, I do have a paper gasket between my adjustable angle plate and the table, but I didn't put one in when I installed my vice; I will do so when it next gets moved. I didn't know aluminium was a preferable material for table clamps, though I see the logic of it. Presumably the ubiquitous clamp sets in the £40-£60 range would be prohibitively expensive if aluminium was used. I haven't got any aluminium of a suitable size at the moment but I do have a two foot long piece of inch square brass. I suppose using that would be extravagant, though.

John, your solution is very interesting. I might want to put a flat on the side of the rod in contact with the table, but your experience suggests that's not strictly necessary.

Phil, your base is very elegant and no doubt a big time saver when the vice needs to be re-installed. I note your point about hex head screws being preferable for not acting as swarf traps.

T.B., your end clamps are a great idea. Could you give me the dimensions? Having the dimensions would be very useful even if I ultimately make a different kind of clamp.

I made my clamps from aluminum. The underside is rebated leaving about a 1/4" heel to contact the table. The screw was located as close to the vise as possible.