A PEBBLE SHOOTER TUTORIAL Making a pouch to band attachment rig with a vice screw mechanism
Introduction (updated tutorial version following design changes)
A vice (USA = vise) is normally used for the purpose of keeping materials in place securely between a set of “jaws” or other means to facilitate processing these with various tools. The freely rotating vice screw pushes or pulls back the “jaws” via a connection to a fixed non-rotating unit: the pulling motion is what is particularly useful for a pouch to band mounting rig.
Essential tools (NB - all indicated dimensions are metric)
Safety items: protection gloves, safety glasses, hearing protection plugs, dust protection mask.
1. A ruler, a protractor, and a 90-degree angle tool. 2. A power drill, a drill stand, a drill vice, and a jigsaw. 3. A table mounted vice (US = vise) 4. Drill bits for wood in the following sizes: 3, 4, 8, and 12 mm. 5. Drill bits for metal (steel): 2 mm and 3 mm. 6. A countersink drill bit for wood screws. 7. A tap and die set (6 mm steel rod screw threads and tapping for a 4 mm screw section). 8. A center punch for drilling metal. 9. Metal and wood saws. 10. Screwdrivers in various sizes. 11. Nut wrenches. 12. Wood rasp and files (flat and round). 13. Metal file. 14. Sandpaper and wood finishing substances. 15. Other tools deemed appropriate for the project.
Essential materials:
1. A 20 x 30 cm sheet of Baltic birch plywood (18 mm minimum thickness ideally). 2. A section of beech wood rod 50 x 30 x 20 mm. 3. 8 mm threaded steel rod (25 cm) 4. 6 mm stainless or carbon steel rod (two sections of 20 cm length each) 5. 8 mm nuts and metal washers (8 units of each) 6. 6 mm nuts and metal washers (8 units of each) 7. 1 Tee (T) nut (8 mm inner threading, 10 mm outer diameter) 8. Steel cap nuts (4 units in 6 mm, 1 unit in 8 mm). 9. 1 mechanical 4 mm screw. 10. 2 wood screws (5 mm diameter, 50 mm length). 11. Other accessories deemed appropriate for the project.
1 – Band rig tutorial (updated) / Pebble Shooter / Slingshot Forum USA / September 2019
A view of the completed rig
Stage 1 – MAIN WOODWORK
Measure, saw, and drill holes for the following structural elements as shown in the diagrams.
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Fixed mounting block A
The vertical separation between the clamp holes and upper surface increases spring tension.
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Mobile mounting block B
Fixed structural block C with an 8 mm T-nut (below)
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Stage 2 – METAL WORK AND VICE UNIT
Use a metal saw to cut the following to the indicated lengths:
8 mm diameter threaded steel rod:
One section with a length of 23 cm.
Ensure smooth ends using a metal file and sandpaper.
6 mm smooth stainless or carbon steel rod: **
Two sections with a length each of 24 cm.
Using a tap and die set, cut a 3 cm long thread at both ends of both 6 mm steel rods sections.
A. The vice (vise) rotation unit – a relatively simple mechanism:
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The rig vice mechanism – key parts and function
Image A - the assembled unit.
Image B – The 12 mm hole is where the end of the threaded rod rotates freely.
6 – Band rig tutorial (updated) / Pebble Shooter / Slingshot Forum USA / September 2019
Image C – The vice block unit is connected to block B via two 5 x 45 mm wood screws.
Image D – The vice block unit attached to the sliding mounting block B
7 – Band rig tutorial (updated) / Pebble Shooter / Slingshot Forum USA / September 2019
Making the vice unit – please refer to the images for clarity
1. Cut 1 section of beech wood (hard wood) with the following dimensions: 5 cm length, 3 cm width, and 2 cm thickness (see image A, page 6)
2. Mark off the exact center of the wood section, and use a fine nail to prepare the drill hole.
Using a power drill mounted in a drill stand:
3. Place the wood section inside a drill vice, and drill a 12 mm hole to a depth of 9 mm, followed by a perforating 8 mm hole, continuing from the initial 12 mm hole (“necking down”).
Objective: This will allow the 8 mm threaded steel rod section to rotate freely inside the 12 mm hole, while being held back by a 4 mm “stopper” screw section to be inserted at the very end of the 8 mm threaded rod (see step 6 below).
4. Place a metal washer with an inner size of 8 mm and an outer size of 12 mm inside the 12 mm hole of the wood unit (image C, page 7).
Objective: this will reduce friction as the “stopper” screw rotates inside the unit as mounting block B is pulled outwards under elastic tension (band ends) when the turning wheel of the jig is operated.
5. Drill a 4 mm perforating hole on each side running parallel to the main 12 mm to 8 mm hole of the vice unit, which contains the rotating section of 8 mm threaded steel rod. Allow for at least 6 mm between the edge of the wood block and the 12 to 8 mm hole (image A, page 6)
Objective: two 5 x 45 mm** long wood screws connect the vice unit with mounting block B (image D on page 7). (** wood screw length will depend on plywood thickness used).
6. Drill a perpendicular 3 mm hole (image below) using a 3 mm metal drill bit through the end section of the 23 cm long section of 8 mm threaded steel rod (drill app. 3 mm from the tip).
7. Using the tap and die set, cut 4 mm threading for a mechanical screw section inside this hole.
Objective: the 4mm screw will stop the freely rotating 8 mm threaded rod section from falling out. Alternative method: insert a piece of 3 mm metal rod inside the hole with the help of glue.
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Final steps: drill a non-perforating 12 to 8 mm hole in mounting block B, and insert an 8 mm steel washer inside the 12 mm section of the hole to reduce friction. Align the vice block unit with this hole, and drill marking holes for the wood screws via the 4 mm holes in the vice block to ensure exact placement. Separate both units, and complete drilling of the 4 mm holes in mounting block B. Insert the 8 mm threaded steel rod with the 4 mm “stopper” screw in the vice block, check for free rotation, and attach the vice block unit to mounting block B (see images C and D on page 7).
A. Assembly of the vice mechanism and testing
Assemble the vice unit components as shown in the images. Ensure perfect alignment of the rotating threaded rod between mounting block B and the T-nut in structural block C. Start by sliding mounting block B on to the rails. NB- it helps to screw structural unit C on partially to the threaded 8 mm rod via the 8 mm T-nut prior to connecting structural unit C to the 6 mm steel rod sliding rails.
B. Assembly of the entire rig for testing prior to final steps
Refer to the images below when assembling the various parts for the purpose of ensuring that the entire rig operates smoothly prior to total disassembly for sanding & varnishing (optional step).
Adding the metal strengthening supports to the structure: place these as shown on the image below, and mark the center of the holes of these supports with a fine felt tip pen for drilling non- perforating 3 mm holes (4 mm wood screws). This will ensure accurate placement.
Image 1 – the basic structure of the pouch to band mounting rig without the vice unit.
Image 2 – the fully assembled rig: mounting block B slides freely on the 6 mm steel rods.
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C. Making the turning wheel for the vice mechanism
1. Using a compass, mark a 6 cm diameter circle on a piece of Birch plywood. 2. Mark the center (the compass hole) of the circle for drilling. 3. Drill an 8 mm hole in the center of the circle. 4. Using a jigsaw to cut out the wood wheel and shape it using a wood rasp and file. 5. Mark off lines at regular intervals on the side of the wood wheel (see image). 6. Saw along each line to 1 mm depth, and then proceed with filing grooves to 4 mm depth.
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7. Place an 8 mm nut on the outer section of the 8 mm threaded rod, slide the wood wheel on to the rod, and then add an 8 mm cap nut. Tighten both 8 mm nuts to hold the wheel in place securely for it to rotate the vice mechanism.
The Key advantages of this pouch to band mounting rig design:
A. Progressive tension - The main advantage of the vice mechanism approach is a progressive and precise setting of tension on the band ends using a turning wheel that is perpendicular to the fixed and moving screw sections of the rig.
B. Higher clamp spring tension - the vertical separation between the mounting block holes and the upper surface of each mounting block unit increases spring tension (pressure) of the clamps, thus ensuring that both the pouch and the band ends to be connected are held in place very securely. The mounting block holes (“windows”) allow for a very precise placement of the pouch and band ends to ensure perfectly aligned pouches for either over-the-top (OTT) or “through the forks” slingshot styles.
A set of spring-operated clamps (hardware store) needs to be purchased, as these are inserted inside the mounting block holes to hold the pouch and band end in place.
FINAL PAGE – your comments and constructive criticism about this tutorial are welcome.
Your notes:
11 – Band rig tutorial (updated) / Pebble Shooter / Slingshot Forum USA / September 2019