Picture of Parallel Leg Vise with St. Andrew's Cross
Leg vise.JPG
  In woodworking and fabricating, a leg vise can be enormously useful.  They offer a large, flat clamping surface on which you can impart a surprising amount of clamping force.  A properly aligned leg vise can hold large workpieces such as doors or 6x6 beams.  But few companies make proper woodworking leg vises or even the hardware for them.  The issue with making a leg vise is keeping the chop (the part that moves) parallel to the bench leg when under tension.  This Instructable features a solution.  

  I make all my leg vises at TechShop.
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Step 1: St. Andrew's Cross

Picture of St. Andrew's Cross
st. peters cross.JPG
the flag.jpg
  On many traditional workbenches the chop is held parallel with a sliding wooden guide which is shot full of holes.  The worker must place a pin in the hole closest to the bench when the vise bottoms-out.  This procedure can get tiresome after a while. 
  Another option is to outfit the chop with a steel scissor-action mechanism which will keep it parallel at an infinitely divisible distance.  This mechanism is often identified as St. Peter’s Cross, however this is a misnomer, as St. Peter’s cross is actually an inverted perpendicular cross.  The X-shaped intersection we see here looks more like St. Andrew’s Cross, which is called a saltire and is featured on the national flag of Scotland.  So I’m calling this St. Andrew’s Cross. 
  You can learn more about Scotland from the books at your local library.

Step 2: You Will Need:

Picture of You Will Need:

Vise screw and nut
2" x 8" x 32" hardwood (for the chop)
36" of angle iron (8 gauge) or thicker
12" of 5/16" metal bar
5/16" bolt
Various nuts, washers, and spacers to fit


Basic woodworking tools (saw, router, chisels, drill)
Basic metalworking tools (metal saw, angle grinder, drill)
ringai2 years ago
Back in the first decades of the 20th century, this is the sort of project that would appear in Popular Mechanics. In fact, they featured a similar build that used flat stock instead of the angle iron. I think the angle iron is a better choice.

I you'd like to find some really awesome DIY woodshop projects, you could do worse than to go back to the those old issue (via google books) and peruse the freaking awesome tips and projects.

Another excellent source of shop projects are the old Fine Woodworking magazines. They had DIY projects such as a shop-built 8-inch jointer. FWW doesn't have many of those sorts of articles anymore. For that you need to pick up ShopNotes magazine.

Shop-Built machiery is not for the faint of heart, nor is it the path for every wood worker. But man, if it trips you trigger to be able to show off a DIY bench tool, then ShopNotes is your guide.

Edgar2 years ago
A note about it went to my Blog:
Edgar2 years ago
A note about it went to my Blog:

Thanks for the posting, great advice! But how does one give "...a patina of iron oxide..."? Vinegar and salt? Is there a link that will explain the details?

tpral made it!10 months ago

Many many thanks for this instructions. Just built it, works like a charm :)

Result here :


would this work if mounted up side down to support the bottom preventing pinchining?

monty3242 years ago
if you also have the bar in the bottom with all the holes in, it can support the chop and allow it to slide more freely. that probbly diddent make much sense so heres a picture of what i mean

When i was getting this picture i found that benchcrafted also make a cross vice now.
Scotttland (author)  monty3242 years ago
I have the same mechanism pictured in the first part of this Instructable.
12mile2 years ago
after i look at project cant back up to main paige?
vincent75202 years ago
Great idea.
But I guess I'm dumb as I don't see how the two bottom ends of the cross slide in their respective channel ? Or the top assembly is enough to keep them in line and in each channel ? I would have thought the whole thing would be somewhat wobbly if not attached to a rail they could slide in.
Nice inst' anyway : we learn a lot both about this system and tricks about making holes etc …
Better than going to the movies on a rainy day, and shorter too ;))
Thanks !
laxbograt2 years ago
This has been a really well done instrucables series.

Just as a side note the small sliding board does more than just stabilize the rotation of the vise it works to use the screw as a fulcrum and add clamping strength. Without it there it won't clamp quite as tight.

I made a traditional woodworking bench a couple years ago and can attest to the benefit of the extra strength.

Also is reaching down to adjust the pin location really that difficult compared to saw, drilling, planing etc...

Just my two cents.
artagain2 years ago
I'll probably make this in a month or so after I finish my beside tables and start work on the bench. Have you encountered any problems or improvements that you can think of? I may add bearings in the angle iron holes. Again, this is perfect. The Benchcrafted stuff is nice but over priced by about 30%.
Scotttland (author)  artagain2 years ago
No issues so far, as long as the bolts are are fitted perfectly but not too tight you shouldn't need bearings. This vise is actually working out better than I expected.
ShaunHill2 years ago
How much to buy one of these off you?
Edgar2 years ago
Long live Scotland, there'a a lot of Portuguese of mixed Scot Blood, and guess what, a lot are Engineers... :)
Here, the MacDonald name, has turned into Maldonado, etc.
Edgar2 years ago
Long live Scotland, there'a a lot of Portuguese of mixed Scot Blood, and guess what, a lot are Engineers... :)
Here, the MacDonald name, has turned into Maldonado, etc.
Purocuyu2 years ago
Simple, and elegant. Nice work.
THIS IS GREAT! Handy for all kinds of big projects.