Four Tube Knifemaker's Vise

Really handy for holding knives when working on handles. I think most everyone has one of these, but if you are new to knifemaking then put your recycling hat on and make yourself one!



I want to use it in my mechanic's vise or attach it to the face of my finishing bench. This design can be easily converted to mount directly on a flat surface such as a bench or tabletop.


Materials
You will need a couple of feet of pipe or tubing (see below)
3/8" NC hex nut, (4)
3/8" NC x 1" bolt, (4)
5/16" flat washer, (2)
1/4" to 3/8" steel bar or round stock. (6 inches)
Round neodymium ("rare earth") magnet, (2)
4" x 4" block of wood (preferably hardwood), (5 " long)
Paint, your color choice.


Tools
Bandsaw or hacksaw
Bandsaw or hand saw for cutting wood
Welder
7/16" drill bit
3/8" NC tap
Drill bit to match your magnet diameter
Drill or drill press
Half round file
Sandpaper or wire brush
1/2" Forstener bit
Hammer


Pipe or Tubing?




The trick to making a good four tube vise is finding two sections of pipe or tubing where one is a smaller diameter that slips inside another of a larger diameter.

These tubing pieces are from my local dump. They appear to be sections from a screw jack that is used to support beams in the basements of houses around these parts.

When looking for your own tubing you can source some different sizes of either pipe or tubing.

• When working with pipe, the measure is based in the inside dimensions. (How much flow can go through the pipe.)
• When working with tubing, the measure is based on the outside dimensions. (Structural)

For both pipe and tubing, the inside diameter is OD minus (2 times wall thickness). For example, 3" tubing with .125" wall will be (3 - (2 x 0.125")) or 2.75" inside diameter. For pipe, see the schedule table. Schedule 40 is a very common pipe size so I have included it here.




Some convenient sizes of schedule 40 pipe to use are shown in the table. If you look at the ID and OD numbers in the table, you can see that 3-1/2" pipe will allow 3" pipe inside it. Keep in mind that you may have a weld seam inside the larger pipe to grind out before the pieces fit, but with short lengths that we need this seam is a manageable obstacle.




I cut the outside (2.75" OD) pieces to 3" and 4". These are shown as A and B. The inside pieces C and D are cut to 5".



Part D is shaped to fit to part A. I cut the curves out with the band saw and filed the shape to approximately match the outside of A.




I used the belt grinder to clean up the pieces.




I added the holes for the knob bolts to go through. These are drilled to 7/16" for 3/8" bolts.

Note: Some makers optionally cut slots in part C to hold the blade at 90°. I like it to be closed so as to reduce the amount of filings or metallic dust that will settle in the jaws. If course steel dust gets in the jaws you risk scratching or gouging your blade. Always check the jaws and replace if necessary or add some replaceable material like leather or neoprene.



Use a bolt to hold the nut in place for welding. It's like a clamp, but simpler and will help clean the threads in the nut on the way out.



The mounting plate 'E' was intended to be either mounted to the front of my assembly bench or the extending part on the bottom could be dropped into any mechanic's vise. Optionally, you could make this plate in any reasonable dimensions into a flange and bolt the vise directly to the surface of your workbench.




Drill four 1/4" holes in the corners of the base in case you want to mount it with screws.



I cleaned up the welds with a wire brush. After welding, sometimes the nuts can be slightly deformed and hard to run a bolt through. I chase the threads with a 3/8 NC tap and a drop of oil.


Part 2 coming up...

 

Continued

Jaws

For jaws I used a piece of oak that's very closed to the size of the inside of piece C (about 2-1/2" or so)




I traced the outside of part C, then drew a line inside to approximate the inside of of the tube.



After cutting some corners off on the bandsaw I shaped close to the line with the belt grinder. A 36 grit belt chews through pretty quickly.



I marked the middle and ripped it with the bandsaw. Using the belt grinder again I took the jaw faces back about 1/8" each. This will let the jaws open up to 1/4". I mostly make thinner blades, so 1/4" for the opening is plenty. If you are making very thick blades or want to add something like neoprene or leather to further soften the jaws, then take a little more off the jaw faces.


I made two shallow holes with a 1/2" Forstner bit. These are 1" from the end.



I tapped a 5/16" flat washer into the holes. These will allow the knob bolts to press into the jaws without deforming the wood too much. If you want to use another size washer, a slug or a coin you can use a drill bit to match. It's helpful to make it a tight fit.


Two small but powerful neodymium magnets will help keep the jaws in place inside the tubing. I drilled the holes to friction fit and dropped some CA (super glue) in the holes before pressing the magnets in.

Knobs

The knobs are basically pieces of steel welded to bolts so that you can turn them by hand and not need any tools. Three or four knobs can be made to tighten the jaws and moving pieces. Some people prefer a bolt in one side of the jaws and a knob on the other side.




I cut some 3/8" x 1/2" steel into 2.5" pieces.



Squared up on the belt grinder. When they are still clamped, mark out lines for the bolt heads to align with before welding.



Welding a bolt on. Clamp the bolt head down so its in the center of the handle.



For tightening the jaws you can use one knob and a bolt on the opposite jaw or two knobs. Knobs can be anything added to a bolt to increase the force. Some are round with knurled edges, some look like sprockets. Whatever works and is easy for you.




I got this far before getting the paint out.

For paint I had some leftover navy blue and some light machine grey for the knobs. However, with the temperatures well below freezing I used some tricks, well actually I used heaters and an old oven to heat the paint and parts before spraying.





If you make one or have any tips, please let us know.

Dan

 

I would add a slot on both sides of the mouth so a blade can be put in side ways to spine work. this design would work better clamped to a bench top in that way.

 

Yes, I mentioned that in Part 1. I have slots in one of my knife vises. I have found that the slots let a lot of grit down between the jaws especially when doing filework and it's hard to keep them clean. Having the full circle provides some protection, but that comes at the expense of flexibility.