12" Bench Top Hand Shear

Brooke Clarke 2010 - 2016

Background
Using
Compound Linkage
Related
Links

Fig 1 Overall View

12 Inch
                Bench Top Hand Shear

Fig 2 Linkage

12 Inch
                Bench Top Hand Shear Linkage
Fig 3 Cutting 12" x 14" PCB
 (PS shown incorrectly turned 90 deg.)
12" Shear
                  cutting 12x14" PCB

Background

For years I've been trying to find a way to cut Printed Circuit Boards (PCB) for both through hole and Surface Mount Technology work.  A scroll saw mounted under a work bench works but it has about a 1/16" saw kerf that's wasting expensive PCB material.  A scribe used on both sides of the board (making "V" grooves) takes a lot of time and hurts the fingers.  The 8" Mini Shear Break worked a small fraction of the time.  Tin Snips work but have a very short cut distance so even when going from each side are very limited.  They also bend the PCB material to the point where it might be overstressed.  The Harbor Freight 67256 Multi-Function Tool cuts very slowly with the 67264 diamond blade.  A foot operated sheet metal shear that's about five feet long works but takes up a lot of space and is expensive.

The Enco 130-5700 12" Bench Top Hand Shear cuts 1/16" PCB material like a knife through hot butter and is very easy to control.  The 5" ($67) , 6" or 8" versions may also work well, but I got the 12" ($120) to error on the safe side.  If you know how the smaller units work for cutting 1/6" PCB material please let me know.

The Harbor Freight Throatless Shear item# 38413 is designed to allow making a curved cut and so is not as good a choice as the 12" shear for making straight cuts.

Using

The 12" shear will not stand up by itself.  The factory intended for it to be anchored to something very substantial so leverage could be applied to the handle but it takes a very small amount of force to cut PCB material since the shear uses a compound linkage.  So it does not need to be anchored for leverage but does need to be mounted to keep from falling over.  You also need to have good lighting to see the PCB cut lines and the blade.  The plan is to mount it on a two foot square piece of heave plywood.

With the shear sitting on the floor and a table lamp on the left side and the back leaning against a cardboard box to keep it from falling over I separated a 2.5" x 3.8" ExpressPCB "Mini Board" into 63 (6 by 9)  smaller boards in about 5 minutes.  Note that after making 6 cuts then each strip needs 9 more cuts so 63 cuts for 63 parts.  Note that there is no fiberglass dust like with a saw.

Tried the shear of a stack of paper about 1/2" think and although it cuts the paper easily it does not cut straight.

Sheet-metal will be another test.  Both Brass and Phosphor Bronze.

The "Wheel" shown in Fig 1 can be adjusted up and down and is there to keep a steel plate from lifting when it's cut.  But the wheel is not needed for PCB matgerial.

11 Feb 2010 - I'm now thinking to mount it on my work bench using the thumb nuts so that it can be moved to the back when not being used.  But will need help to lift it.
I tried to get the shadow of the blade to act as an optical guide for cutting, but the lamp is too wide of a light source.  Something like a single LED may work.  Because of parallax the apparant position of the PCB needs to be offset a little to get the cut on top of the 0.006" wide cut lines.  If you know a good way of positioning the PCB let me know.

April 2016 - Separating 12" x 14" panel of 68BA battery adapters, see Fig 3 above. 

Each panel consists of an array of 4 x 9 (26 total) final sized PCBs.  The first round of cuts was to make a cut 12" long separating the panel into sticks 3.5" x 12".

Note although the shear is named a "12 Inch" model the actual cutting length is an inch or two short of 12" so in order to cut a 12" long PCB two operations are required.
First, using a piece of angle iron clamped to the bottom of the drill press table as a guide for a square cut, the PCB panel was cut about 3/4 of the way (about 9") then the board was turned 180 degrees for the next cut.  But before making the second cut the board was sprung so that the cut part of the board can be pushed against the right side of the lower cutting blade.  This has the effect of lining up the second cut with edge made by the first cut.  So it takes two cuts to get through 12" of board. 

It's probably possible to cut a panel 18" by a larger dimension using this two step process.

Compound Linkage (Fig 2 above)

The Handle is a little over 34 inches long and the distance between the handle pivot bolt connecting link top is 2 inches for a 17:1 advantage.  If a PCB is inserted at the back of the shear there is about a 2:1 advantage for a total of 34:1.  But even if a PCB is inserted at the very front it still cuts with very little force on the handle.

Related

12" Bench Top Hand Shear
5C Tool room lathes when working in the Microwave business the shop was full of them
8" Mini Shear Break
Active Storage - shelving and box sizes
Air Tools
Digital-Retro-Turbo-Encabulator
Drill Press used with 5C collets
Electric mains power Generators
Farm Hi Lift Jack
Geodesic Dome Connector Plates
Hints & Tips What Goes Wrong
Lathes for < 1" OD parts (5C collets)
Mini Machine Tools (Lathes and Mills) One of my dreams
Fasteners A page made for my own use with dimensions of common fasteners used for product design and for looking at new ideas for products
Measuring Tools Used mainly for reverse engineering
Pocket Tools
Tumbler - for deburring

Links

K7QOs QRP Lab Notebook - has a chapter on using this shear for cutting PCB material.
He has added a table on the left with a stop that's exactly 90 degrees from the blade.  Handy if you cutting raw sheets.

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