Short answer
Cyanoacrylates and anaerobics tend to cure inside a bare stainless steel cannula, so use a PTFE-lined needle, a one-piece polypropylene needle or a flexible polypropylene tip. UV-curing adhesives can start to cure inside a translucent hub, so use a needle with an opaque black hub. Choose the gauge by bore, then test on your own adhesive and cycle time.
Two problems, one cause
Most instant adhesives and light-cure adhesives are easy to dispense until they cure in the wrong place. The needle is where that happens.
- Cyanoacrylates and anaerobics tend to cure inside a bare stainless steel cannula. A thin film builds up between shots and the bore closes.
- UV-curing adhesives cure when enough light reaches them. A translucent hub lets light into the fluid that sits in the hub, so it cures there and blocks the needle.
In both cases the fix is the material around the fluid path, not the gauge. Keep metal out of the path for cyanoacrylates and anaerobics. Keep light out of the path for UV adhesives.
Needles for cyanoacrylates and anaerobics
Three families in our range keep bare metal away from the fluid.
| Option | Construction | What it suits |
|---|---|---|
| PTFE-lined needle | Stainless steel outer tube with a PTFE inner tube, threaded hub | Precise placement with a rigid tip; very thin fluids and solvents |
| One-piece polypropylene needle | Molded as one part, no bonded joint and no metal in the flow path | All-plastic dispensing where a long, straight tip is needed |
| Flexible tapered tip | Polypropylene cannula that bends | Edges, corners and finished surfaces that must not be scratched |
The PTFE liner gives the most control with watery fluids, because the outer tube stays rigid. The polypropylene options trade some rigidity for a flow path with no metal at all, and the flexible tip can be trimmed to length on the line.
PTFE-lined sizes
| Gauge | PTFE bore | OD | Overall lengths | Hub color |
|---|---|---|---|---|
| 20G | 0.6 mm | 1.14 mm | 33.5 mm and 45.5 mm | Gray |
| 25G | 0.33 mm | 0.8 mm | 33.5 mm | Pink |
| 27G | 0.25 mm | 0.6 mm | 33.5 mm and 45.5 mm | Red |
The bore figure is the inside of the PTFE liner, which is the size that sets flow.
Polypropylene sizes
One-piece polypropylene needles run from 18 to 27 gauge at 55.2 to 57.7 mm overall.
| Gauge | ID | OD |
|---|---|---|
| 18G | 0.84 mm | 1.25 mm |
| 19G | 0.72 mm | 1.0 mm |
| 20G | 0.6 mm | 0.85 mm |
| 22G | 0.42 mm | 0.75 mm |
| 25G | 0.26 mm | 0.78 mm |
| 27G | 0.21 mm | 0.72 mm |
Flexible tapered tips come in 14, 15, 16, 18, 20, 22 and 25 gauge, in lengths from 1/4 in to 1-1/2 in. Each size has its own product page with the full spec table.
Needles for UV-curing adhesives
Our UV-blocking needles have a Type 304 stainless steel cannula on a threaded polypropylene Luer hub that is opaque black. The black hub keeps light off the fluid waiting in the hub between shots.
| Gauge | ID | OD | Lengths |
|---|---|---|---|
| 25G | 0.26 mm | 0.52 mm | 1/4 in and 1/2 in |
| 27G | 0.21 mm | 0.42 mm | 1/4 in and 1/2 in |
| 30G | 0.16 mm | 0.31 mm | 1/4 in and 1/2 in |
The range is fine gauges on purpose, because UV adhesives are often placed as small dots or thin beads.
Because every hub in this family is black, hub color cannot tell the gauges apart. Go by the printed gauge or measure the bore.
Choosing the gauge
Pick the gauge by bore once the material is right.
- Thin cyanoacrylates flow fast. A finer bore, such as the 25 or 27 gauge PTFE-lined needle, gives more control over dot size.
- Gel cyanoacrylates and thicker anaerobics need a wider bore. Start with the 20 gauge PTFE-lined needle or an 18 to 20 gauge polypropylene needle.
- UV adhesives usually go on as fine dots. Start at 25 or 27 gauge and move finer only if the dot is too large.
Test two neighboring gauges on your own adhesive, pressure and cycle time before standardizing. Our gauge guide covers how bore and length affect flow.
Handling between shots
The right needle slows clogging. It does not stop an adhesive curing if it sits too long.
- Keep idle time between shots as short as the process allows.
- Cap or replace needles at the end of a shift rather than leaving adhesive in the tip.
- For UV adhesives, keep curing lamps and strong daylight away from the syringe and needle while dispensing.
Where to go next
Browse PTFE-lined needles, UV-blocking needles, flexible tips and the one-piece polypropylene needles in custom and specialty.
Replacing needles a customer already uses? Search their part number in our cross-reference, or send it through the quote page. We quote per SKU and quantity.
Questions
Why do cyanoacrylates block stainless steel needles?
Cyanoacrylates and anaerobic adhesives tend to cure inside a bare metal cannula, especially between shots. A PTFE liner or an all-plastic needle keeps metal out of the flow path and resists that clogging.
PTFE-lined or polypropylene for cyanoacrylate?
A PTFE-lined needle keeps a rigid stainless steel outer tube, for precise placement. A polypropylene needle has no metal at all and a flexible one bends and will not scratch the part. Both resist clogging, so choose by how the tip has to reach the joint.
Why does hub color matter for UV adhesives?
UV-curing materials start to cure wherever enough light reaches them. A translucent hub can let light into the fluid in the hub, which cures and blocks the needle. An opaque black hub keeps light out.
How much light does the black hub block?
We do not publish a blocking figure. Test the needle with your adhesive, your curing lamp and your real cycle time to confirm it stays open.
Which gauges are available?
PTFE-lined needles in 20, 25 and 27 gauge, UV-blocking black needles in 25, 27 and 30 gauge, one-piece polypropylene needles from 18 to 27 gauge and flexible polypropylene tips from 14 to 25 gauge. Other gauges can be quoted to order.