The idea for the table-Top Scissors came from a discussion I had at work with a colleague in the workshop. We were talking about things which could be motorized, and for reasons only known to him, he said scissors.
So I got to thinking on how best to do it......
Step 1: Materials & Preparations
There are two different cutting actions, one which moves an entire blade forwards to cut the paper, and another, the one we are interested in, rotates a blade around a point at one end. The rotating action is identical to cutting with scissors and with a bit of jiggery-pokery we should be able to get as much control from the cut as you can with a pair of manually operated scissors.
I'm going to be using an old Epson M147B thermal receipt printer as the donor for this project, any receipt printer will do so long as it has the correct cutter. We'll need to strip the machine and remove all the fun parts. The two main items are the mechanical cutting blade and the fixed blade.
Scissors are sharp. Please avoid cutting yourself. Blood will stain wood, clothing, and your reputation. Take care, and keep any rocks away from the scissors.
Parts used from the Printer;
- The mechanical cutting blade.
- The fixed blade.
- The power switch.
- One large gear.
- One small gear.
- One Extension Spring.
- 12v-24v DC Motor Controller (link).
- 2 x 4-Pin sockets (link).
- 2 x 4-Pin plugs (link).
- 2 Meters 4-Core cable (link).
- Wood Stain (link).
- Various Screws.
- 1 x Compression Spring.
- Electric Hand Drill.
- Electric Hand Jig-Saw.
- Sanding Block.
- Needle Files.
- Screw Drivers.
Searching on Google for the motor's model number (FK-180SH) brought up a datasheet detailing the motor's power specifications. Using this information I selected a 12-24v DC motor controller.
Video at the end....
Step 2: Prototyping
By altering the angle of the main cutting blade, by lowering and raising one end, we can adjust the cutting stroke. To do this we need to find a suitable hole to fit a pivot for the cutting blade assembly, and design a mechanism for mounting the cutting blade.
I decided to use cardboard to prototype the basic design before cutting any shapes from wood.
1 | The cutting blade works by running its edge against the fixed blade. Firstly we need to position the two blades so that when the cutting blade is at the uppermost part of its movement it will have performed the longest cutting stroke. To help with the design I have placed the fixed blade, and the cutting blade on a bit of paper and drawn around their outlines.
2 | We need a find a pivot point on the cutting blade assembly which we can use to adjust the cut stroke. There is a conveniently placed hole near where the blade rotates in the assembly. I will be using this hole as the pivot point.
3 | Rotate the blade assembly down to its lowest point, using the hole as a centre of rotation. Take a measurement of the total height, allowing for room at the top where the cutting blade will protrude above the table top. Take a similar measurement for the width.
4 | Cut from cardboard a piece using the measurements just taken.
5 | Take additional measurements noting the position of the pivot hole, and the area where the motor protrudes above the assembly. Transfer those measurements to the cardboard and cut out the relating areas.
6 | So that the assembly can rotate we need to expand the cutout. Using a compass & ruler draw an outline of the area needed to be removed. Cut this excess card out and check the movement of the assembly.
We will use the cardboard template as a guide when making the first wood part. Once we have the cutting blade assembly mounted to the wood panel we can then begin to build up the table around this mount.
Before continuing on make sure you are happy with the cutting blade assembly's range of motion, that there is enough over-hang on the width & height of the card and that the blade will extend far enough above the top to give a clean cut.
Step 3: Cut Away
By sheer coincidence the pivot hole in the cutting blade assembly matches perfectly to a spring-loaded screw used to hold down CPU heat-sinks in Laptops. Using a spring loaded screw will keep the cutting blase assembly pressed firmly against its mount.
2 | On the opposite side to the cutting blade assembly glue a matched wood panel, this will help hide the motor assembly. I have clamped it between two clamps, and a workbench (I only have two clamps!).
3 | The highest point on the cutting blade assembly is a screw and bracket which holds the motor in the assembly. I have measured an area on the backing plate which needs to be cut out so the assembly can rotate correctly. I began by drilling several holes, and then finishes the cut-out using needle files.
4 |Drill through and enlarge the bolt hole for the pivot so that the securing nut will sit level with or below the line of the panel.
Step 4: Smoothing the Cutting Blade Assembly
1 | Using a flat needle file, or a Dremel with a course sanding drum, grind away the raised areas until they are level with their surroundings.
2 | Round off any sharp edges.
3 | Cut off and smooth down any excess casing from the assembly.
4 | Check the cutting blade assembly sits flush against the mount.
Step 5: Building Up the Blade Mount
1 | Mount the cutting blade and measure the distance between the blades edge and the mount, also note the space above the cutting blade assembly. You will need to make a blanking plate to fill this area. I used two strips of the same plywood which the mount is made from and glued them together, and then stuck them to the mount making sure that all the edges align correctly.
2 | Next we need to cut recesses into the two strips we glued before so that the cutting blade assembly can rotate. I have used a Dremel with a course sanding drum attached. If you had a router that would work too. I used a hacksaw to cut the areas where the cutting blade mechanism extended above the top of the mount. Some careful measuring will be required to get it all to fit and function correctly.
3 | To be able to move the cutting blade assembly up & down (adjusting the cutting stroke), I'm going to be fitting a locking handle to the front of the mount. The front of the mount needs shaping to match the arc of the cutting blade assembly. To do this I simply mounted the cutting blade assembly, held a pencil against a spacer block on the side of the blade assembly and rotated it. All I had to do then was cut outside of the pencil line with my jigsaw. The cut was smoothed and finished with sandpaper.
4 | The back will hold two jacks, one the DC input, and the other is a 4-Pin socket for running power down to the motor controller in the foot pedal and then back again to the motor. I have glued a back plate onto the mount. Using a bit of guess-work, and a conveniently sized washer I have marked up a hole for the socket. Using a small drill, and later a needle file, I have cut the hole out to fit the socket. Above this I drilled another hole for the DC socket.
5 | The blade mount needs closing up; I created a matched panel by drawing around the blade mount and then cutting out the shape to match. Using sanding paper will give a more precise finish.
Step 6: Supporting the Fixed Blade
Before we begin we need some rigid plywood to build with. If you already have thick plywood (8mm or more) you can probably skip steps 1 to 7. I only had 3.6mm Birch Plywood available at the time.
1 | Begin with two equally sized plywood boards. I have picked their size with guess-work on the approximate shape and size I want the C-Shape to be. The plywood I have has one good side, and one not-as-good, we'll glue to two not-as-good sides together, obviously. I have laid the two boards side-by-side on a table. The two smaller parts at each end are for balance.
2 | I don't have a fancy press to hold the boards together, but what I do have is an old coffee table, and the centre section from the dinning room table. Apply glue to one of the boards and smear it around to cover the entire side.
3 | Put the two boards together and align them approximately with each other.
4 | If you don't have a centre section from a dinning table something similar will do, the important part is that it is flat, and won't bend. Lay the heavy flat object (dinning room table centre section), on top of the two boards. Try to be as careful as possible as you don't want to upset the alignment of the two boards.
5 | Pile heavy stuffs on top. Again be careful not to alter the alignment. A little bit off is ok, too much and you will waste a lot of wood later.
6 | Wait. For the glue to dry (I left it overnight).
7 | Dismantle your impromptu press, wonder at your conjoined wood boards and marvel at your new plywood panel.
Note: Old shoes and holey old trousers are not a prerequisite of panel making.
Now that we have a solid panel to work with its time to prepare the C-Shape.
8 | Using the mount for the cutting blade assembly as a starting point, I have drawn out a C-Shape on the plywood panel. It is important to make sure the gap in the opening of the C is set to the right height, and width, for the fixed blade. I used the edges of a large washer to mark a radius on the corners. The size of the C-Shape is down to your own choice. I went with a length of 10cm, and a width of 4cm.
9 | Confirm your measurements.
10 | Using your favourite saw cut out the C-Shape. I used a hand operated electric Jig-Saw to cut out the ruff shape. I used a sanding block, needle files, and my Dremel to shape to the pencil lines.
11 | Take the cutting blade assembly cover that you made in step 5, check it is positioned on the corrected side, and then glue it to the C-Shape.
12 | Check the C-Shape assembly lines up with the cutting blade assembly mount.
13 | We will be using four counter-sunk screws to hold the fixed blade support to the cutting blade assembly mount. Taking care with your measurements drill four holes for the screws remembering to counter sink the holes. Because the rear top corner of the cutting blade assembly mount didn't provide much error for margin I left that hole until last. While the other three screws were in, and after making precise marking I drilled the final hole. To make sure I had a perfectly vertical hole I fitted my Dremel into a drill-press attachment.
14 | While the two parts are screwed together go around the edges with a set-square and check all the corners are as they should be. If you need to make any adjustments, and I did, I found it best to use a sanding block.
Step 7: The Cutting Blade Assembly Adjustment Knob.
1 | Begin by drilling two holes, spaced as widely apart as possible, into the cutting blade assembly at the opposite end to where the pivot will be.
2 | Cut threads into the newly drilled holes. I used some screw to cut the threads, the metal isn't very hard but it does take a bit of strength and control to do.
3 | Shape a lump of scrap plywood to fit on the end making holes for screws to attach it to the cutting blade assembly.
4 | I went digging through the screw-pot at work and found what looked like the perfect knob. I drilled a hole in the wood block to take the screw-end of the knob. Make sure to drill the hole slightly smaller than the thread so the bolt/knob/screw will cut a thread into the wood.
5 | We need to make a bracket with a guide. The bracket will press against the front and secure the cutting blade assembly in place when the knob is tightened, the guide will stop the bracket moving around when we make adjustments. The design of this bracket and guide is not fixed, just make sure it clamps against the front when the knob is tightened.
Step 8: Attaching the Fixed Blade to the C-Shape Support.
The fixed blade will sit on a mount protruding from the C-Shape. We will use the spring in the wood to keep the fixed blade pressed up against the cutting blade.
Consider, for a moment, a pair of manually operated scissors and examine their blades, you will notice a slight outwards bow. This bowing of the blades helps to concentrate maximum force at a single point of contact. The effect of which is a far better cut than you could achieve with straight cutting blades. To replicate this effect we will need to angle the fixed blade to the cutting blade, we can do this by sanding an angle into the fixed blade mount.
1 | Create a block of wood to which you can attach the fixed blade. You will need to make sure that it will push the fixed blade past the cutting blade and that the two blades are not inline with each other. We will use this overlap to help press the two blades together.
2 | Before gluing the block to the C-Shape, or drilling any holes place the block and the blade against the C-Shape. They should press together at one end, and there will be a space at the other. The wood block will need to be sanded down so that there will be no gaps at either end. I found the difference, over a 5cm length, to be approximately 1mm. I used this measurement to angle the block. You can see this angle in the first photograph.
3 | The blade has several holes already in it, I will be using two to screw it to the block. When drilling the holes make sure to angle the block so that the holes go at 90 degrees to the fixed blade. If you don't do this the screws will not sit flush against the blade.
4 | Glue the block to the C-Shape.
5 | Attach the fixed blade to the C-Shape and assemble the Table-Top scissors.
6 | Check the movement of the two blades. The two blades should only contact at a single point at any given cutting blade position.
7 | When you are happy with the alignment mark up the square edges on the C-Shape and round them off to match the other curves on the C-Shape.
8 | Test the cutting motion by connecting the motor controller. I found that the fixed blade would slip off the cutting blade and the mechanism would jam. To fix this I elongated the rear screw hole and lowered the back end of the blade. You can see this slight angle in one of the photos.
If everything is setup correctly you should be able to cut paper....
Step 9: Building the Base.
1 | Using the same technique from Step 6 I glued two panels together and made up a rigid board.
2 | I made a measurement of the bottom of the cutting assembly. In the centre of the board I drew the shape just measured of the base of the cutting assembly.
The exact design of the base is upto you. I kept the same 4cm width used in the C-Shape but I did away with the rounded corners and went for an angular X design.
3 | Draw your design onto the board.
4 | Cut it out.
5 | Sand down to the pencil lines.
The cutting blade mount will have two screws through it, holes need to be drilled into both the base and the mount. Check where you hope to drill the holes and make sure there will be enough clearance. I decided to use a block of wood, sat behind the 4-pin socket. The block will help hold the socket in place and give the screws something to screw into.
6 | Drill two holes into the base, and two matching holes on the cutting blade mount. On the underside of the base counter-sink the holes.
7 | Shape a wood block to sit tight against the 4-pin socket in the cutting blade mount. Drill two holes in the block matching those in the base and the cutting blade mount. Check that the screws you plan to use will screw into the holes drilled.
8 | Assemble the Table-Top Scissors, check that all the parts align correctly.
Step 10: The Foot Pedal | Gearing the Knob.
The motor controller has a small potentiometer with a knob on it. As the knob is too small to turn with your feet we need to make an alternative mechanism to rotate the pot. Using a series of gears and linkages we can make a pedal box to rotate the potentiometer, and to house the controller board.
1 | Remove the knob from the potentiometer.
2 | At the top of the knob, approximately 2mm from the end, cut the top off. There should be a little sleeve that comes out, it will have ridges on the inside which match those on the stub. Measure the outside diameter of the sleeve.
3 | Take the smaller gear and drill out the centre hole to match the diameter of the sleeve from the knob. Check the sleeve will fit inside.
4 | Using a small needle file cut down the inside of the smaller gear to create a slot, repeat this on the opposite side.
5 | Make similar sized slots in the sleeve, check the two match by putting the sleeve into the smaller gear.
6 | Make a small bar to fit between the slots.
7 | Slip a plastic washer over the knob's spindle.
8 | Place the small gear onto the spindle.
9 | Down the gap in the spindle slide the small metal bar so it fits in the slots.
10 | Push the sleeve down the spindle so it aligns with the bar.
11 | Place another plastic washer on the spindle.
12 | Press the assembly tight with your fingers.
The gear should now be held tightly in place. The there should be no slipping when the spindle, or gear, rotates.
13 | Rotate the knob to the maximum position is either direction.
14 | Place the larger gear against the small gear so the cogs mesh. Make note of the gears positions in relation to each other.
15 | Rotate the knob to the maximum opposite position. Make note of the movement of the larger gear during this rotation. The smaller gear will rotate approximately 270 degrees, the larger gear will move a smaller amount.
16 | Allowing for errors cut the larger gear down so there is ample gearing available for the smaller gear to complete its rotation. Make sure to keep the centre intact as we will need this when we come to mount the gears.
17 | Measure the distance between the centre holes for the larger gear and the centre of the smaller gear.
18 | Transfer these measurements to a bit of wood and drill holes to match the shaft for the knob and the larger gear's centre.
19 | Fit the geared knob, and the larger gear.
20 | Check the movement of the gears and knob. The knob should go through its full 270 degree range without coming off the larger gear.
Step 11: The Foot Pedal | Making the Mechanism
1 | Begin by squaring off the wood used in the previous step. Leave at least a 1cm border underneath the smaller gear.
2 | We want a solid base for the foot pedal so I used off-cuts from the X-Shaped base we made in step 9. Begin by sanding and smoothing down the sides of the base plate.
3 | Cut a groove into the base plate so that the gear assembly will stand upright in the groove.
4 | Attach a hinge to the base plate at the opposite end to the groove.
5 | Using another off-cut from the base, or a spare bit of wood if no more off-cuts are available, and match its width to the base plate. This will be used as the foot pedal.
6 | Attach the foot pedal to the base plate using the hinge.
The foot pedal will need to be spring loaded so it will reset when you take your foot off it.
7 | Find a suitable spring, the one I used is about an inch in length.
8 | Mount the spring to a wooden spring seat. I used a small screw and a washer to hold it.
9 | The spring seat will be glued to the base plate, but you will have to find the optimum position for the spring. The foot pedal will need to rest on top of the gear assembly and just very slightly compress the spring. When you have found the sweet spot glue the spring seat to the base plate.
The next few stages will require a fair amount of guess work, and jiggery pokery. We need to connect the larger gear to the foot pedal, and spring load the larger gear to help it return to it's original position when you foot is taken off the pedal.
10 | Remove the larger gear from the gear assembly. Drill a hole at each extreme into which a screw will screw into.
11 | Make a linkage approximately 1.5cm in length. Drill two holes at each end, make them larger than the screw so the linkage will be free to move. Attach the linkage to the larger gear.
12 | Use the small extension spring taken from the printer, attach it to the larger gear.
13 | Cut down the foot pedal so the end does not hit against the gear assembly when fully compressed.
14 | Refit the larger gear to the gear assembly.
15 | Measure and cut a 1cm wide strip to match the arc of the larger spring. Glue this strip behind the larger gear to help support it.
16 | Glue a strip of wood to the foot pedal so that the linkage will align to the larger gear.
17 | Onto the base plate glue a small block to which the extension spring will attach.
18 | Connect up the gears, springs & linkage.
19 | Check the mechanism works.
Step 12: The Foot Pedal | Enclosing the Internals
1 | Measure the height of the foot pedal, measure the length from the back of the base plate to approximately 2 cm past the foot pedal. Cut two measured wood boards, these will be used as the sides of the pedal box.
2 | To the right side (opposite the gears) we will attach the motor controller. I cut four small corner blocks from scrap. Placing the motor controller onto the side I marked in pencil where I wanted the motor controller to fit. It is important to allow room for the side to be attached to the base plate at the bottom, and to leave space for any wires that will connect to the controller.
3 | Glue the four block mounts to the right side panel. Place the motor controller onto the mounts and mark screw holes.
4 | Once the glue has dried on the mounts, drill screw holes, if you have a depth gauge on your drill you should be able to avoid drilling all the way through the side of the panel.
5 | The two sides will be attached to the base plate with screws. Drill two holes on the right side and match them up to the base plate.
You may find that the foot pedal knocks against some of the components on the motor controller board as the pedal is pressed down. If this happens simply notch out the foot pedal until there is enough clearance past the controller board.
To keep the gear assembly in place we will be using long screws. The screws will come from the left side, through the side panel, through the gear assembly board, and into the base plate.
6 | Drill two long holes which will be used to hold the gear assembly & the left side in place. I have added a third screw to give extra support toward the front of the left side.
7 | With the two sides in position, and the foot pedal at it's highest position, measure from the front of the left side panel to the top of the panel following along with the angle of the foot pedal. Also take note of the inside gap between the two sides.
8 | Cut a top panel to match the measurements.
9 | Position the top panel so that it rests on top of the foot pedal, slightly pressing it down. Take note of its location and mark holes on the two sides for screws. Leave 1 to 2mm protruding at the front.
10 | Drill two screw holes per side.
11 | Fit the top panel, in pencil mark the two sides where the top of the top panel runs.
12 | On the top panel draw in pencil lines which mark the sides.
13 | Dismantle the enclosure.
14 | Cut the sides along the lines to match the angle of the top panel.
15 | Cut the top panel to match the angle of the sides.
16 | Reassemble the enclosure, remembering to sand any rough edges.
The final two panels, the back & the upper panels will be made as a single part. On the back will be an opening for the 4-Pin socket.
17 | Measure the internal space at the top of the enclosure. Cut an upper panel to match.
18 | Measure & cut a bracket which will glue to the underside of the upper panel. I made mine from spare wood from the base. The bracket will need to support the upper panel and the back panel.
19 | Drill a hole in each side panel for screws to go into the rear support bracket. Make matching holes in the bracket.
20 | Measure the back of the enclosure, make sure to measure from the outside of the two side panels as the back plate will overlap their edges. Mark & cut out the back plate.
21 | The upper panel and the bracket need to align correctly to the back plate. Check your measurements, and glue the two panels, and the bracket together to make a rear cover.
22 | Drill screw holes at the bottom of the rear panel and into the base plate.
23 | Check the rear cover fits correctly, then remove it again.
24 | Position the 4-Pin socket on the back of the base plate. Check that it will not hit against anything and them measure its position in relation to the bottom and side of the enclosure.
25 | Mark and then cut a hole on the back panel for the socket to come through.
If you find your measurements are off, you might need to cut away some of the base plate. Like I did.
During testing I found that the larger gear moved off of alignment if pressure was too quickly removed from the pedal. Investigating the problem showed the larger gear twisted slightly causing the gears to disengage, so to stop this happening I made a bracket. The bracket doubles up as a back-stop for the 4-Pin socket, and as a guide for the larger gear.
Step 13: One Last Hole
Another fluke, or consequence of my subconscious genius, you decided, is that the switch's depth is almost identical to the thickness of the C-Shape support. So we're going to cut a hole in the C-Shape and mount the switch in it.
1 | Fit the cutting blade assembly into position. Check for available space, and that the cutting blade assembly will not catch on the switch. Take note of the switch's intended position, and the switch's size.
2 | Mark a hole on the C-Shape using the measurements from stage 1.
3 | Cut out the hole marked on the C-Shape support in stage 2.
4 | Put the switch in the hole in the C-Shape support cut in stage 3.
5 | Assemble the Table-Top Scissors & The Foot Pedal, and check that all is well.
We're nearly done, but before we can cut the finish line there are still a few things to do. Firstly we need to stain the wood, and secondly there is the wiring to complete. Before we do this now is a good time to check that all the mechanics work, and that there are no missing screws, bolts, or springs.
To do this build up both the Foot Pedal and the Table-Top Scissors and check over your work before continuing.
Step 14: Finishing
1 | Strip down the foot pedal, set aside all but the wooden parts.
2 | Smooth down all the wood surfaces with a fine grained sand/glass/emery paper, or similar.
3 | Paint.
4 | Leave to dry.
Next the Table-Top Scissors, which will be blue, with a green base.
5 | Strip down the Table-Top Scissors, set aside all but the wooden parts.
6 | Smooth down all the wood surfaces with a fine grained sand/glass/emery paper, or similar.
7 | Paint.
8 | Leave to dry.
Step 15: Interconnectedness
The plugs come with their own instructions, and it was noted that the largest diameter cable they could be used with was 6.5mm. However the diameter of the 4-Core Cable I had, and the only one I could find, was 7.1mm. I checked the cable against the socket, and they are mismatched, just like the instructions indicated they would be.
Luckily, I have a plan.
1 | Cut off around 8cm (3") of shielding off one end of the 4-Core cable.
2 | Slip an 8cm length of 8-10mm diameter heat-shrink over the end of the cable, position the heat-shrink approximately 2 cm back from the end of the cable. The heat-shrink should overlap some of the cable's shielding.
3 | Heat the heat-shrink so the heat-shrink shrinks over the cable.
4 | Repeat stages 1, 2 & 3, at the opposite end of the cable.
The cable's diameter should now be small enough to fit inside the plug assembly.
Follow the instructions that came with the plugs to complete your cable.
Step 16: Building the Dream
1 | Attached the knob mount to the cutting blade assembly.
2 | Fit the cutting blade assembly to the cutting blade assembly mount.
3 | Cut and solder the cutting blade motor wires to the 4-Pin Socket.
4 | Install the DC socket into the back of the cutting blade assembly mount, include a connector for the switch.
5 | Fit the switch into the C-Shape, wire and add connectors to the end.
6 | Attach the Cutting Blade Assembly mount to the X-Shape base.
7 | Connect the switch and screw the C-Shape to the cutting blade assembly mount.
8 | Install the fixed blade to the mount on the C-Shape.
9 | Fix the adjustment knob and guide to the front.
10 | Check the switch is in the off position.
Put aside the Table-Top Scissors.
11 | Assemble the gear mechanism, install it into the base plate.
12 | Add the hinge & compression spring to the base plate.
13 | Wire in the 4-Pin socket to the motor controller.
Depending on how you wired the cable you might have to swap the polarity on the socket.
14 | Attach the sides, taking care with the wires when doing so.
15 | Install the back plate making sure the 4-Pin socket correctly sits in its hole. I used some foam pads to help keep it in place.
16 | Plug the cable into the Table-Top Scissors & into the foot pedal.
17 | Plug in the 12v DC supply.
18 | Ready your foot.
Next we'll power it up!