Cutting Serrations on Jaw Faces

Customers ask how to cut serrations in the jaw faces. Here’s how I do it.

There are a couple ways of doing it.  One is using a metal shaper, which pushes an angle cutter through the steel.  Or maybe with a Bridgeport type machine you could tilt the head and use the corner of a carbide end-mill to cut the grooves.

I decided to build a fixture.  It holds carbide tipped slitting saws or carbide tipped side mill cutters with a 1″ ID 4″ OD, and range from 1/2″ thick to 3/16.

Serration Cutting-9-2017 (2)

Serration Cutting-9-2017 (1)

I also built a fixture to sharpen the cutters on my surface grinder.  I can get about a dozen jaws cut before re-sharpening.

Serration Cutting-9-2017 (5)

The holder is custom made and I made it long enough to serrate a set of 9″ wide jaws.  I can cut 7″ deep with this holder.

Next I needed an angle fixture to hold all the different fixture plates. I made the angle plate from 1-1/4 thick aluminum, and it is solid.  The fixture plates are designed to hold the jaws at 30 degrees and made so when you are through the first cut then you rotate the jaws to the other side of the fixture plate to finish the diamond serrations.

Serrating 6 at a time (3)

 

Jaw sizes require different pitches and depth of cuts.  The pitch is the difference between cuts.  The baby 2″ jaws have a pitch of .050 between cuts where the 8″ jaws have .125 between cuts and are much deeper of a cut.  I like about .04 square diamond on the bigger jaws where the 2″ jaws have a .020 diamond flat.

Baby Jaws serration cutting

Fixturing for the straight serrations used on Yost and Starrett jaws should be a little more accurate.  Cutting a 6″ jaw and having the jaws just a little cocked will show a crooked serration.  I use pins that the jaws rest on to keep the cuts straight.  The Starrett jaws are shaped like an L, and after cutting the serrations, I remove the material on the back side before heat treating.

Cutting Starrett jaws (3)

The Wilton 6 inch and the 8 x 1-1/2 x 1 inch jaws like the Parker jaws have to be held by a special fixture that I hold the blocks by the back side.

8 inch Chas Parkers (7)

These 8″ Parker jaws first need the serrations cut before carving out the back side for final fitting.

The serrations are obviously an important part of the grip of jaws.  Cut serrations like these are old school and well worth the effort.  The newer style jaws made after the late 1970’s are from powdered metal injected into molds, so the serrations do not have to be cut.  This easier and faster method results in a brittle jaw that chips.  The quality of the newer style will never compare to the jaws built from tool steel by the vise companies of the past.

China Jaws and USA (2)

You can see the difference in a molded set and cut serrations. I do not have to mention which is which because it is so obvious.

 

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Pipe Jaw Building

Making pipe jaws were a challenge in the beginning. I wanted to support the old vises by making these jaws since you can’t find any new ones very easily. My first issue was how the heck do you measure them. I wanted to build these as close to originals as possible since some customers want to replace only one.

Back in my mold making days I had to figure out how to measure shapes that were curved and needed it very accurate. I did this with a microscope attached to my CNC. I like the Skoal scope shown in my picture, which is very affordable.

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I used the readout on my CNC to create points at every intersection.  On this drawing of a Starrett 326 Pipe Jaw, I added small circles at every intersection where it is easy to connect the dots.starrett_326_pipe_jaws

After squaring up the A2 Tool Steel blocks, I rough in the large and small V section where the teeth go, as with this CO Wilton Pipe Jaw. I do this so when I cut the teeth so I am not removing too much material.  It keeps the cutters corners sharp.

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After carefully looking at the geometry created taken with the microscope, it became clear the teeth were rotated at 14 degrees and the teeth are cut at 90 degrees. The vise companies had special cutters made to cut the teeth at one swoop but I cannot afford to have a cutter of this size made or have room for a machine to handle this horizontal cut. Instead I made a special set of jaws to hold the pipe jaw at 14 degrees and use the corner of a 3/8 end mill and step down each cut.

Before I could do that, I needed the geometry and depth numbers so I could program my CNC. Here is a drawing I used for a American Scale Pipe Jaws. Looks more complicated than it really is.a-scale_pipe_jaws

As you can see in the drawing above, I color coded the geometry to help me in programming. After that, I pick up the pipe jaw noted here. When rotating blocks at a angle it becomes more difficult to locate the block. It is helpful to use a 1/2 inch gauge pin held on with a flat magnet and sweep in the pin center with a test indicator. I rotate the indicator 180 degrees then drop the indicator to hit the high point of the pin and rotate the indicator to  find the high spot, set the dial to zero and do the same 180 degrees on the other side of the pin till I have reached a zero reading finding the pin center. You could use a edge finder but I choose an indicator.

I also set the end mill to the top of the pin and that would be my Z-zero. All the numbers on the drawing are taken from the pin center line in the X axis (left to right) and the depth of the cut (Z-axis) is taken from the top of the pin.

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After programming my CNC,  the rest is easy. Using a sharp carbide end mill I cut a roughing cut leaving .005 on the X-axis and .005 on the Z-axis, and then do a finish cut.

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De-burr the entire jaw.  Send to heat treating and harden to 54/56 Rockwell.  Done.

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Vise Jaw Steel and Heat Treating: Why It Matters

A tool is only as good as the material it is made from.  Vise jaws can be made out of just about anything from brass or aluminum to copper or soft steel.  The best material for vise jaws is Tool Steel.

Bronze jaws for a 820 Wilton vise

Bronze jaws for a 820 Wilton vise

There are several options for what kind of Tool Steel to use. I am an Old Timer.  Based on my personal experience,  I would choose  S-7 or A-2.  I believe S-7 is the best choice for Bench Jaws, but I use A-2.  That’s because  it’s easier to find and buy, and it comes in a wider selection of sizes in bar form.  The most important reason I choose A-2 is because it is more stable after Heat Treating.   Out of the oven, most Tool Steels are over 60 Rockwell, which is way too hard and brittle to use.

After the steel is cooled then it must be  placed back in an annealing oven and re-heated to a certain temperature.  For instance, S-7 to 500 degrees and A-2 to 1000 degrees, will take them both down to a tough but less brittle 54-56 R/C.   This means when I weld, or use my torch  flame close to A-2 jaws,  I don’t worry about changing its hardness.

Here is a description of A-2 Tool Steel from Hudson-Metals.com:

steel and old jaws (1)

A-2 Tool Steel Bar Stock

“A2 Tool Steel is a versatile, air-hardening tool steel that is characterized by good toughness and excellent dimensional stability in heat treatment. A2 is intermediate in wear resistance between O1 oil-hardening tool steel and D2 high-carbon, high-chromium tool steel. A2 provides an effective combination of strength and toughness, tool performance, price, and a wide variety of product forms.  APPLICATIONS: Punches and dies, chuck jaws, cutting tools for woodworking, tooling for plastic injection, dowel pins, hammers, industrial knives, and gauges.

The original Wilton jaws built in the early 40’s to late 60’s were very hard. You can find some of these old Bullet Vises around with still sharp serrations even though they are over 50 years old.  See the photo below with two old jaws from the 50’s and the new ones made by WiltonViseParts.  The old ones can still can be used.

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Old jaws next to new jaws.

My Heat Treater and I tested several old jaw sets for their hardness and found they were a consistent 54-56 Rockwell Hardness.  He believed they were made from an Oil Hardening Tool steel like O-1 which is an oil quench.  That was a popular Tool Steel used at that time.  A-2 and S-7 are both air cooled, and that is one reason they are so stable after heat treating. I have made jaws out of O-1, but found they warped more than I liked; about .007 over 5″.  The A-2 shows no sign of warping, so that means the jaw face stays flat and will close  parallel as it should.

When annealing Tool Steel, you can induce an inert gas to keep the jaws from oxidizing.  My Heat Treater likes to use nitrogen. When nitrogen is used at 1000 degrees, and it adds a colorful pattern to the A-2 steel.  Each jaw pattern is unique.  See some examples in the picture below.

If the jaws are made from a good Tool Steel and heat treated to a proper hardness, then they should last the life of your vise.  If you clamp a hard object like a car axle, or tighten down on a hard object like U-joints which are about the same hardness as your jaws, then the serrations will flatten or chip.  Copper Caps not only protect the work piece, but also protect the jaw faces.

3-50 x 750 ser (3)

Colorful 3-1/2 x 3/4 x 1/2 Jaw Set

One thing I tell my customers is that they are buying a Premium set of replacement jaws, and if cared for, they should never need to buy more.