Answer Summary
GRIFFIN 1866 Ltd 100% Natural Silk bead cord comes in 13 sizes, from No. 0 (0.30mm) to No. 16 (1.05mm). The right silk cord size is the largest diameter that passes through the bead hole twice with slight resistance. This guide walks through the full GRIFFIN size chart, how to measure a bead hole accurately, which sizes suit pearls versus gemstones versus glass, and the six sizing mistakes that cause the most damage on the bench.
Table of Contents
- Why Cord Size Matters More Than Length
- GRIFFIN Size Chart No. 0 to No. 16 Explained
- Measuring a Bead Hole Accurately
- Pearls vs Gemstones vs Glass: Size Picks
- When to Size Up for Knotting
- Common Sizing Mistakes That Ruin a Necklace
- Glossary
- Related GRIFFIN reading
- Frequently Asked Questions
Why Cord Size Matters More Than Length
Most beginners worry about cord length and pay no attention to cord diameter. That is the wrong priority. A card of GRIFFIN Natural Silk bead cord is always 2 metres, enough for one standard necklace or two bracelets. Length is fixed. Diameter is the decision that actually decides whether the finished piece works.
Two things go wrong when the silk cord size is off. If the bead cord is too thin, the knots between beads sit soft and loose instead of firm and flush. They shift around, the spacing reads uneven, and the necklace wears badly. If the bead cord is too thick, it forces through the drill hole under pressure, and that pressure starts a slow abrasive action against the nacre or stone over time. Neither shows up at the bench when the piece is brand new. Both show up in wear.
The rule for picking silk thread for jewellery making is straightforward: choose the largest diameter that passes through the bead hole twice, in both directions, with slight resistance. Not freely. Not with force. Slight resistance.
GRIFFIN Size Chart No. 0 to No. 16 Explained
100% Natural Silk has been GRIFFIN’s flagship product since the company was founded: Mastery since 1866, The Best of the Best of triple-twisted bead cord, with a stainless steel needle attached on every 2-metre card (Triple Twisted, Needle Attached). GRIFFIN Natural Silk and NylonPower are made in 13 sizes. The numbering is not consecutive. The gaps reflect calibrated diameter increments tuned to each weight category of bead.
| GRIFFIN Size | Diameter | Best For | Typical Bead |
| No. 0 | 0.30 mm | Seed pearls, micro freshwater | 2 to 3 mm |
| No. 1 | 0.35 mm | Very fine freshwater, seed pearls | 3 to 4 mm |
| No. 2 | 0.45 mm | Small freshwater pearls | 4 to 5 mm |
| No. 3 | 0.50 mm | Fine freshwater, delicate gemstones | 4 to 6 mm |
| No. 4 | 0.60 mm | Standard freshwater, light gemstones | 4 to 6 mm |
| No. 5 | 0.65 mm | Medium freshwater, most glass | 6 to 7 mm |
| No. 6 | 0.70 mm | Akoya pearls, standard gemstone rounds | 6 to 7 mm |
| No. 7 | 0.75 mm | Standard Akoya, medium gemstones | 7 to 8 mm |
| No. 8 | 0.80 mm | Larger Akoya, heavier gemstones | 7 to 9 mm |
| No. 10 | 0.90 mm | South Sea, large baroque freshwater | 9 to 11 mm |
| No. 12 | 0.98 mm | Large South Sea, heavy gemstone rounds | 10 to 13 mm |
| No. 14 | 1.02 mm | Large South Sea, baroque strands | 12 mm+ |
| No. 16 | 1.05 mm | Oversized South Sea, Tahitian | 14 mm+ |
GRIFFIN High Performance bead cord comes in 10 sizes: No. 0 through No. 10 (0.30mm to 0.90mm), white colour only. The fibre is ultra-high molecular weight polyethylene (UHMWPE), triple-twisted. The hard specification: 22 N tensile strength at size No. 5 (0.65 mm). For heavy gemstone work where the bead cord needs to be stronger than any silk thread size can provide, UHMWPE is the specification.
Measuring a Bead Hole Accurately
The fastest method needs no measuring tools at all. Take two adjacent GRIFFIN bead cord sizes and pass each through the drill hole of a sample bead from your lot. The size that passes with a slight drag is the right one for that bead.
When you need an actual measurement, a bead reamer gauge or a set of wire gauges works fine. Pass each gauge wire through the drill hole until you find the largest diameter that enters without forcing. Match that to the GRIFFIN diameter chart: the silk cord size whose diameter is closest to (and no larger than) the measured hole diameter is your starting point for the bead cord double-pass test.
One important note about drill hole variation. Natural gemstones and freshwater pearls are drilled individually, and hole diameter varies even within a single strand. Use a bead from the middle of the strand for the sample test, not one of the end beads, which are often drilled slightly larger to take the clasp attachment cord.
Tip: always buy one card more than you think you need when trying a new bead lot. If you test on a sample and discover mid-strand that the next bead in the sequence has a narrower hole, you want a spare card of the next size down on the bench rather than having to stop the project to order one.
Pearls vs Gemstones vs Glass: Size Picks
The bead type changes the sizing approach because it changes the risk profile at the drill hole.
Freshwater pearls. Drill holes are typically consistent within a matched strand, but vary considerably between suppliers and grades. Strand quality matters: high-grade matched strands have tighter hole tolerances. For most standard freshwater rounds in 6mm to 8mm, start by testing GRIFFIN No. 6 (0.70mm) and No. 7 (0.75mm).
Akoya pearls. Higher consistency than freshwater. Drill holes are tighter and more uniform. Test No. 6 (0.70mm) and No. 8 (0.80mm) as your starting bracket for 7mm to 8mm Akoyas.
Dense gemstones (haematite, lapis, pyrite). Hard drill hole edges work as an abrasive surface against bead cord during wear. For these materials, GRIFFIN High Performance bead cord is the right specification, not Natural Silk or standard NylonPower. The fibre is ultra-high molecular weight polyethylene (UHMWPE), 15 times stronger than steel by weight, anchored to a 22 N tensile strength at size No. 5 (0.65 mm). UHMWPE resists the abrasive action of hard-edged drill holes far better than any organic fibre.
Softer gemstones (rose quartz, amethyst, aventurine). Drill hole edges are less hard than metallic minerals but still abrade over time. GRIFFIN NylonPower is a practical choice here. It is engineered for higher tensile strength than standard nylon bead cord (4.2 N at size No. 5, 0.65 mm), giving better abrasion resistance than silk thread for jewellery making at equivalent diameters.
Glass beads. The most consistent drill holes in the bead world, made to tight tolerances. The silk thread size selection is straightforward: use the double-pass test and pick accordingly. No. 5 (0.65mm) or No. 6 (0.70mm) covers the majority of 6mm to 8mm glass rounds.
Crystal beads. Cut crystals have very precise drill holes, often slightly smaller than equivalent diameter glass. Test No. 4 (0.60mm) and No. 5 (0.65mm) as the starting bracket for standard 6mm crystal rounds.
When to Size Up for Knotting
Knotting between beads shifts the sizing calculation slightly. When you knot between every bead, the cord has to hold a firm, compact overhand knot that sits flush against each bead face. A cord that is marginally too thin for the drill hole will still pass the double-pass test with slight resistance, but the knots it produces will be slightly loose.
The test for knotting suitability is separate from the hole test. After identifying the right bead cord size by the double-pass method, tie a test overhand knot in the cord and look at the profile. A well-matched silk cord size produces a knot that is round, compact, and roughly the same diameter as the gap between two beads pressed together. If the knot is soft, wispy, or visibly smaller than that gap, size up one increment.
For pearl knotting specifically, GRIFFIN Natural Silk is preferred over NylonPower at equivalent silk cord sizes because of silk’s knot behaviour. Silk holds a tight, rounded overhand knot more consistently than nylon thread at the same diameter. The triple-twisted construction (which produces the cord’s distinctive Z-Twist behaviour) is what creates that consistent knot profile.
Common Sizing Mistakes That Ruin a Necklace
Mistake 1: using one size for an entire collection. Pearl lots and gemstone lots vary between suppliers, between grades, and even between orders from the same supplier. Test the silk cord size against a sample bead from each new lot rather than assuming the same size that worked last time still works.
Mistake 2: testing only one pass through the hole. The cord has to pass through the drill hole twice for knotting to work. A silk cord size that passes once but jams on the second pass leaves you with a non-functional strand.
Mistake 3: using silk thread for jewellery making on heavy gemstones. GRIFFIN Natural Silk is an organic fibre. It is the right choice for pearl knotting and light to medium gemstone work. For dense stones, the drill hole abrasion rate will eventually cut through silk. GRIFFIN High Performance bead cord exists for that reason.
Mistake 4: forcing the cord through a tight hole. If the cord needs force to enter the drill hole, the hole is too small for that bead cord. Forcing creates nacre microcracking at the drill entry point that is invisible at first and becomes a fracture point after months of wear.
Mistake 5: choosing the silk cord size by diameter number rather than physical test. The size chart is a starting reference, not a substitute for the bead test. Hole diameters on natural materials vary. Two strands labelled the same size can need different bead cord sizes.
Mistake 6: not accounting for doubled cord width at clasp terminations. The cord passes through the clasp loop and back through the first bead twice at the end of the strand. The total cord width at those points is double the single pass diameter. Confirm the doubled cord still passes through the end bead with slight resistance before starting the strand.
Glossary
Z-Twist: the direction of fibre twist in GRIFFIN Natural Silk. Triple-twisted in a Z direction, which produces a round, stable cord profile and the consistent knot behaviour the brand is known for.
Triple-twisted: a manufacturing method in which the cord is twisted three times during production. Used across GRIFFIN Natural Silk, NylonPower and High Performance to give the cord a balanced, kink-resistant structure.
Double-pass test: the practical method for picking a bead cord size. The right cord is the largest diameter that passes through the drill hole twice with slight resistance, not freely and not under force.
Drill hole abrasion: the slow cutting action that hard bead edges exert on cord during wear. The reason heavy gemstones need UHMWPE rather than silk or standard nylon.
Key Takeaways
The right silk cord size is the largest GRIFFIN bead cord that passes through the bead hole twice with slight resistance. Test physically against a sample bead. Do not rely on the size chart alone.
GRIFFIN 100% Natural Silk cord comes in 13 silk cord sizes from No. 0 (0.30mm) to No. 16 (1.05mm).
For dense gemstones with hard drill hole edges, GRIFFIN High Performance bead cord (UHMWPE, 22 N at No. 5) is the right specification. Silk thread for jewellery making is not appropriate for haematite, lapis lazuli, pyrite or similar hard minerals.
For knotting applications, size up one increment from the minimum passing size if the test knot looks loose or soft against the bead face.
Never force a bead cord through a tight drill hole. Forced passage creates nacre and stone microcracking that leads to breakage in wear.
Looking for the right cord for your next strand? Browse the full GRIFFIN bead cord range at griffin1866store.com or request a sample card to test against your bead lot.
Frequently Asked Questions
- What silk cord size should I use for 6mm freshwater pearls?
- For standard 6mm freshwater pearls, test GRIFFIN silk cord size No. 5 (0.65mm) and No. 6 (0.70mm). The right size passes through the drill hole twice with slight resistance. No. 6 is the most commonly used silk cord size for 6mm to 7mm freshwater strands.
- What is the difference between GRIFFIN Natural Silk and NylonPower in terms of silk cord sizes?
- Both products come in the same 13 silk cord sizes and 21 colours, with an integrated bead cord with needle on every 2-metre card. Natural Silk is 100% filament silk, the traditional choice for pearl knotting. NylonPower is 100% synthetic, engineered for higher tensile strength than standard nylon bead cord (4.2 N at size No. 5), and the vegan alternative.
- Can I use GRIFFIN Natural Silk for gemstone beads?
- Yes, for standard weight gemstones such as rose quartz, amethyst, jade and aventurine. For dense, heavy gemstones with hard drill hole edges, such as haematite, lapis lazuli and pyrite, GRIFFIN High Performance bead cord (UHMWPE) gives better abrasion resistance and significantly greater tensile strength.
- How do I measure a bead hole without a gauge?
- The practical method: pass two adjacent GRIFFIN bead cord sizes through a sample bead. The larger size that passes with slight resistance is the right silk cord size. No measuring tools needed for this test.
- Why does GRIFFIN Natural Silk use Z-Twist?
- GRIFFIN Natural Silk is triple-twisted during manufacture, which produces the cord’s distinctive Z-Twist behaviour. The construction gives the cord its round, stable profile, consistent knot behaviour, and the tangle-free handling that makes it the professional standard for pearl knotting.
- How many colours are available in GRIFFIN Natural Silk and NylonPower?
- Both lines are produced in 21 colours. In 2026, GRIFFIN expanded the Natural Silk range with two specialty lines, Rainbow Silk and Neon Silk (the latter including UV-active colours), available alongside the standard 21-colour Natural Silk and NylonPower lines.