Metal Twin Screw Clamp (no Lathe, No Mill)

This type of clamp is usually made of wood and used in woodworking.
The flat jaws and adjustable angle allow great clamping power and whole contact area, while preventing the workpieces from being damaged, even if the pieces have no parallel surfaces. It can be used flat as a regular vise for drilling small parts, or standing up to hold thin pieces. It’s also possible to hold it in a vise to raise the working height.

I wanted to make a full metal version of this, to help me in metal working.

This version is made with common workshop supplies. It does not include left threaded rod. Only regular tap and dies are needed. The downside is lesser opening speed. But it provides extra clamping strenght with the mechanical nuts.

BLUEPRINT AVAILABLE IN .PDF BELOW

MATERIALS:

• Ø12mm Mild Steel Rod (~120mm)

• 20x20mm Mild Steel Bar (300mm)

• M8 Threaded Rod (~400mm) (I'm using A2 stainless steel)

• 2x M5 Nylstop Nuts (also A2)

• M5 Screw (for step 5)

• 4x M8 Nuts + 2 washers (instead of handles)

TOOLS:

• Hacksaw

• Files

• Emery cloth

• Drillpress

• Cordless Drill

• Ø5,5mm drillbit

• Ø6,8mm drillbit (for taping in M8)

• Ø8mm drillbit

• Ø12mm drillbit

• M8 tap

• M5 die

• Bench grinder {or} Angle Grinder

• Countersink bit

• Caliper

• Scriber

• Square

• Needle nose pliers

  
  

• Cut 2x 200mm lengths of 20x20 bars
• Scribe both parts and centerpunch (check the .pdf for dimensions)
• Drill both 8mm holes
• Joint holes with a rat tail file
• Finish the groove with a small flat file
• Turn your piece by 90° and drill the 12mm hole
• Countersink
• Cut the wedged jaw (you can cut wedges on both, but I prefer to keep one jaw flat for better support, see example at the end)

The nuts are 20mm long, but it’s more convenient to make both at once by cutting longer pieces, like 50, 60mm long for better handling.

• If you want a nice finish on the ends, tighten the cylinder in the drill press chuck, place a piece of emery cloth on your drill press table, and sand it flat (start with a coarse grit like G40, then G80).
• Mark and centerpunch 10mm from the edge on both sides.
• Clamp the piece in the drillpress vise horizontally (easier with V jaws).
• Drill 6,8mm holes along the diameter.
• Thread in M8 with the tap.
• Clean the piece with a emery cloth strap.
• Mark and cut 20mm long pieces from both ends.
• File straight and use the drill press technique again to have a nice finish.

Before going any further, check how it fits in the mobile jaw holes. Use a simple M8 screw to see if it pivots. If it doesn't, use emery cloth.

• Use the same techniques as described above for the nuts, but drill a 5,5mm hole instead of 6,8mm.

• Then, before moving the piece, change your bit for a 8mm and drill just a few millimeters deep.
• When both ends are drilled, take out the piece and file the other side flat.
• As before, mark and cut 20mm from both ends.

• Use a drill and a grinder (bench or angle grinder in a vise) to reduce the diameter of the threaded rod until it is Ø5mm.
  (you can use a bearing to hold and push the rod more easily on the grinder)

• Use a M5 die to thread the end of the rod

• Mount one M5 Nylstop nut on a screw with a counter nut and place in the drill chuck
• Turn it against your grinder to make it round.
• You can make it smoother by rubbing it the same way on emery cloth.

All the pieces are ready, you can assemble them.
Traditionally, this kind of clamp has an handle on each side, but I prefer to have both on the same side, you’ll see why in the example below.

• Place the cylinder nuts in the top jaw, then screw the threaded rods through.

• Place the cylinder stops in the bottom jaw, then pass the small end of the threaded rod through it.
• Screw the screw stops, by holding them with needle nose pliers (you might add some threadlocker if it doesn’t hold by itself).

• LUBE & PROTECT
  Being made of mild steel, jaws and nuts may rust if you don't treat them.
  I am using Rustol Owatrol as rust inhibitor, but some WD-40 or simple oil also works.

You can make handles, I didn't already. But I figured out that using nuts + counter nuts on the end of the thread rods makes me able to tighten harder with a wrench. Or use a drill with a socket to maneuver it quicker.

On your drillpress, your workbench, another vise... There is plenty of uses for this clamp.

Both screws on the same side allows to place the clamp vertically, and thus, the flat bottom jaw rest properly and doesn't risk to tilt.

Obviously, that project would have been way more easier to achieve with a lathe and a milling machine, but as you can see, one can do a lot with elbow grease and ingenuity. I hope this will give you motivation and ideas.

Please ask if you have any question.