Mechanical Part Guide

The following may help you navigate the most common mechanical parts we use from the lab supply. Note: the McMaster-Carr purchasing links frequently include downloadable CAD models to import into SolidWorks.

Clevis Pins, 1/4 Inch

Clevis pins may be used as pivots, shafts, and locking pins. They feature a flanged head at one end and at the other a cross-hole through which a cotter pin may be inserted for retention. These are commonly found in low-speed joints which don’t require speed or precision.

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Description: clevis pin, 1/4” diameter, 1/2” nominal length, 5/16” usable length
Location: Hardware Drawer 13
Part Number: 2442


Description: clevis pin, 1/4” diameter, 1” nominal length, 13/16” usable length
Location: Hardware Drawer 13
Part Number: 2444

Description: clevis pin, 1/4” diameter, 2” nominal length, 1-13/16” usable length
Location: Hardware Drawer 13
Part Number: 2446

Description: clevis pin, 1/4” diameter, 3” nominal length, 2-13/16” usable length
Location: Hardware Drawer 13
Part Number: 2448

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Description: cotter pin, hairpin shape, to secure 1/4” clevis pin, 3/64” wire diameter
Location: Hardware Drawer 13
Part Number: 2450


Shoulder Screws, 1/4 Inch

Shoulders screws have a smooth precision-ground section and a threaded end with a smaller diameter. These are intended as rotational shafts to use with either either the bushing bearings or ball bearings. The shoulder is 0.250 inch diameter, the thread is 10-24, and the head is a 1/8 inch hex socket. They will rust if wet.

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Description: shoulder screw, 1/4” diameter x 1” length shoulder, 10-24 threaded end, alloy steel, used as axle
Location: SHELF-B-5 : Shoulder screws, bearings, & bushings kit
Part Number: 1554


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Description: shoulder screw, 1/4” diameter x 1-1/2” length shoulder, 10-24 threaded end, alloy steel, used as axle
Location: SHELF-B-5 : Shoulder screws, bearings, & bushings kit
Part Number: 1548


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Description: hex nut, #10-24, zinc plated, for shoulder screws
Location: SHELF-B-5 : Shoulder screws, bearings, & bushings kit
Part Number: 1588

These #10-24 hex nuts fit the threaded end of the shoulder screws. The nominal width is 3/8 inch.


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Description: washer, for #10 hardware, zinc yellow chromate plated steel, 1/2” outer diameter x 0.220” inner diameter
Location: SHELF-B-5 : Washers Kit
Part Number: 1610

These washers fit over the threaded end of the shoulder screw but not the shoulder.


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Description: spacer, nylon, unthreaded, 1/2” outer diameter, 1/4” length, for 1/4” screw size, off-white
Part Number: 6047

These spacers are especially suitable to adjust the effective length of shoulder screws, but may also be used as thick washers.


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Description: washer, for 1/4” hardware, zinc chromate plated steel, 0.734” outer diameter x 0.312” inner diameter
Location: SHELF-B-5 : Washers Kit
Part Number: 1608

These washers fit over the shoulder section of shoulder screw.


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Description: shaft collar, for 1/4” shaft, one-piece clamp-on
Location: SHELF-B-5 : Shafts, collars, & couplers kit
Part Number: 1542

Clamp-on collars can be used as high-load axial constraints on shoulder screws or plain shafts.


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Description: shaft collar, for 1/4” shaft, set screw type
Location: SHELF-B-5 : Shafts, collars, & couplers kit
Part Number: 1552

Set-screw collar can be used as light-duty axial constraints on shoulder screws or plain shafts.


Bushing Bearings

Bushings are robust bearings with reasonable precision and low friction. They are made of a low-friction material on which steel shafts can easily rotate or slide. Bushings can be directly pressed into laser-cut holes.

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Description: bushing bearing, for 1/4” shaft, SAE 863 Bronze, 5/16” OD, 1/4” Length
Location: SHELF-B-5 : Shoulder screws, bearings, & bushings kit
Part Number: 1570

The bushing has a nominal outside diameter of 8.0 mm; a hole drawn as 7.8 mm in laser-cut 6 mm plywood will yield a snug press-fit.


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Description: bushing, for 1/4” shaft, flanged, SAE 863 Bronze, 3/8” outer diameter x 1/4” length x 1/2” flange outer diameter
Location: SHELF-B-5 : Shoulder screws, bearings, & bushings kit
Part Number: 1562


Ball Bearings

Ball bearings are more precise than bushings and can handle higher loads and speeds. They are generally used in pairs, spaced as widely as possible, typically with a shoulder screw used as a shaft.

Description: ball bearing, for 1/4” shaft, 3/8” outer diameter, shielded, flanged
Location: SHELF-B-5 : Shoulder screws, bearings, & bushings kit
Part Number: 1584

These are made small and thin by using small light-duty bearing balls.


../../_images/ball-bearings-1_4-inch.jpg
Description: ball bearing, for 1/4” shaft diameter, 5/8” outside diameter, shielded
Location: SHELF-B-5 : Shoulder screws, bearings, & bushings kit
Part Number: 1534


../../_images/ball-bearings-1_4-inch.jpg
Description: ball bearing, for 1/4” shaft, 3/4” outside diameter, shielded
Location: SHELF-B-5 : Shoulder screws, bearings, & bushings kit
Part Number: 1550

Note that these have both a larger diameter and thickness.


Dowel Pins

Dowel pins come in wood, plastic, or metal. Wood pins are typically used to connect wooden parts. Plastic and metal are typically used as pivots or to precisely locate parts.

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Description: wooden dowel, 1/4” outer diameter, 1-1/2” length, fluted, chamfered ends
Location: Hardware Drawer 13
Part Number: 1573

The pin has a nominal outside diameter of 6.4 mm; a hole drawn as 6.0 mm in laser-cut 6 mm plywood will yield a tight hammer-in press-fit.


Description: wooden dowel, 5/16” outer diameter, 1-1/2” length, fluted, chamfered ends
Location: Hardware Drawer 13
Part Number: 1575

Description: wooden dowel, 3/8” outer diameter, 1-1/2” length, fluted, chamfered ends
Location: Hardware Drawer 13
Part Number: 1577

M3 Metric Fasteners

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Description: screw, M3 x 6mm length, socket cap, button head, 18-8 stainless
Location: SHELF-B-6 : M3 Kit
Part Number: 1832


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Description: bolt, M3 x 10mm length, button head, stainless steel
Location: Hardware Drawer 8
Part Number: 1829

These are a good length for mounting a NEMA17 stepper motor onto a 6mm panel.


Description: bolt, M3 x 20mm length, button head, stainless steel
Location: Hardware Drawer 8
Part Number: 1828

Description: bolt, M3 x 30mm length, button head, stainless steel
Location: Hardware Drawer 8
Part Number: 1826

Description: screw, M3 x 40mm length, socket cap, button head, 18-8 stainless
Location: SHELF-B-6 : M3 Kit
Part Number: 1822

Description: bolt, M3 x 50mm length, button head, black-oxide alloy steel
Location: SHELF-B-6 : M3 Kit
Part Number: 1820

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Description: M3 x 16 screw, plastic, slotted cheese-head
Part Number: 6051

Plastic screws are frequently used to mount electronics. These fit through the Arduino mounting holes.


Description: washer, M3, 18-8 stainless steel, 7mm outer diameter x 3.2mm inner diameter
Location: SHELF-B-6 : M3 Kit
Part Number: 1836

Description: nut, M3 x 0.5mm pitch, 5.5mm width, 2.4mm height, zinc plated steel
Location: Hardware Drawer 8
Part Number: 1838

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Description: threaded insert, M3, screw-to-expand, uses 5/32” drill hole
Location: M3 Kit
Part Number: 1825

These inserts can be pressed into a 4.0 mm wood or plastic hole to provide a precision M3 threaded hole.


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Description: spacer, nylon, for M3 screws, 3.3mm inner diameter x 4mm length
Part Number: 6053


Sheet Metal and Wood Screws

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Description: screw, sheet metal, self-tapping, blunt, #4 x 1/2” length, Phillips
Part Number: 6057

These screws have sharp threads which can cut into an undersized wood hole.


Motors and Actuators

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Description: small hobby servo, 4.8–6V, no-load speed 60º in 0.12 seconds, stall torque 1.2–1.4kg×cm, 9g mass, clear blue, SG90
Location: Motor and Mechanism 4
Part Number: 1896


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Description: hobby servo motor, large, metal output spline, LKY62
Location: Motor and Mechanism 4
Part Number: 1899


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Description: gearmotor, brushed DC motor, 6V, 4mm diameter x 25mm length shaft, no load 130rpm drawing 100mA, 1kg*cm load 100pm drawing 0.45A, stall at 3.6kg*cm drawing 1.8A
Location: Motor and Mechanism 4
Part Number: 1931

We have purchased slightly different variations of this motor. Some have a pair of M3 threaded mounting holes spaced 17 mm apart, some spaced 15 mm apart. The boss is 7 mm diameter.


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Description: hub, for 4mm shaft, with M3 tapped holes, 2-pack
Part Number: 6049

These hubs are the only practical way to mount a load on the small gearmotors with 4 mm shafts. More details: Pololu 1997 Motor Hub Drawing, SolidWorks model.


Misc. Components

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Description: spring kit, assorted compression and extension springs, 200 pieces
Location: Craft 2
Part Number: 1518

They may be useful as countersprings to provide return motion, as energy storage, or as shock mountings.


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Description: marbles, ~5/8” diameter
Location: Craft 4
Part Number: 2391

Traditional glass play marbles.


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Description: steel ball, 3/8” diameter
Part Number: 6055

Intended to be used as freely rolling marbles or as three-axis pivots.


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Description: O-ring, oil resistant, hardness durometer 70A, Buna-N material, fractional width 1/8”, size 223
Part Number: 6059

O-rings are commonly used for creating pressure-tight seals, but are included here as high-quality elastic bands for making ball bumpers, tires, or round belts.


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