Triform & Bulb-T Rivet
Aluminium triform rivets for wood, plastics, plasterboard and insulation materials, and Bulb-T open rivets with an EPDM washer for blind fixing.
About the Triform & Bulb-T Rivet
Triform rivets are pop rivets for soft materials like timber, plastics, plasterboard and insulation: the body splits into three as it sets, spreading the grip on the blind side so the material is not damaged. Ours are aluminium dome head triform rivets in 4.0 and 4.8mm (#54 to #68), plus a Bulb-T aluminium open rivet with an EPDM sealing washer, 7.7 x 27.7mm, for sealed blind fixing. Choose the type and size above; the guide below covers rivet numbers, grip range and how they compare with standard pop rivets.
Also called rivets for plastic or Bulb-Tite style rivets.
Features
- Dome head triform rivets, aluminium 5154, sizes #54, #56, #58, #64, #66 and #68
- Triform body splits into 3 parts during setting
- Bulb-T open rivet, aluminium 5056, 7.7 x 27.7mm, with EPDM washer
- AA code: aluminium shell and aluminium stem
Applications
- Riveting plastics and timber (triform)
- Sealed blind fixing with an EPDM washer (Bulb-T)
Rivets for plastic, wood and soft materials
A standard pop rivet sets by flaring its shell behind the work. A triform rivet's body instead splits into three parts during setting, leaving a large surface area on the blind side so the material is not damaged. Hobson lists triform rivets for wood, plastics, plasterboard and insulation materials, which makes them the rivets for plastic and the rivets for wood that people look for.
Ours are all aluminium (code AA: aluminium shell and aluminium stem) in 5154 alloy, with a dome (truss) head.
The Bulb-T is a 5056 aluminium open rivet, also with an aluminium stem, a dome head and an EPDM sealing washer. Hobson publishes no data sheet for it beyond its dimensions: sold as 7.7 x 27.7mm, with an 18.8mm head, gripping 1.5 to 9.5mm.
Triform rivet sizes: what #54 or #68 means
Triform rivets use the same numbers as pop rivets: the first digit is the diameter in 32nds of an inch (5 = 4.0mm, 6 = 4.8mm) and the rest is the maximum grip in 16ths of an inch (4 = 6.4mm, 6 = 9.5mm, 8 = 12.7mm).
Triform grip ranges are wider than a standard rivet with the same number, and the bodies are longer: a #54 triform grips 3.2 to 6.4mm and is 18mm long, where a standard #54 dome rivet grips 4.9 to 6.4mm and is 10.8mm long. Use the triform figures below, not a standard rivet chart.
#64
First digit = diameter
Measured in 32nds of an inch: 6/32 inch = 4.8mm.
Shortcut: 6 × 0.8 = 4.8mm
The rest = maximum grip
Measured in 16ths of an inch: 4/16 inch = 6.4mm thick.
Shortcut: 4 × 1.6 = 6.4mm
So a #64 (also written 6-4) is a 4.8mm rivet for material up to 6.4mm thick.
| Digit | Inches | mm |
|---|---|---|
| 3 | 3/32" | 2.4mm |
| 4 | 1/8" (4/32") | 3.2mm |
| 5 | 5/32" | 4.0mm |
| 6 | 3/16" (6/32") | 4.8mm |
| 8 | 1/4" (8/32") | 6.3mm |
| Digits | Inches | mm |
|---|---|---|
| 1 | 1/16" | 1.6mm |
| 2 | 1/8" (2/16") | 3.2mm |
| 3 | 3/16" | 4.8mm |
| 4 | 1/4" (4/16") | 6.4mm |
| 5 | 5/16" | 7.9mm |
| 6 | 3/8" (6/16") | 9.5mm |
| 8 | 1/2" (8/16") | 12.7mm |
| 10 | 5/8" (10/16") | 15.9mm |
| 12 | 3/4" (12/16") | 19.1mm |
| 14 | 7/8" (14/16") | 22.2mm |
| 16 | 1" (16/16") | 25.4mm |
| 20 | 1-1/4" (20/16") | 31.8mm |
Triform and Bulb-T rivet size chart
Measure the total thickness of everything being joined and pick the rivet whose grip range covers it. The #56 and #66 (3.2 to 9.5mm) and the #58 and #68 (6.4 to 12.7mm) cover the widest spans, 6.3mm each. Select a row to open that rivet in the selector.
Every triform and Bulb-T rivet we carry, in mm. Triform figures from Hobson's Rivet Dome Triform sheet (240102DYK); Bulb-T figures from Hobson's dimensions; its size is as Hobson sells it. Pack is the minimum order quantity. Tap a number to show it in the selector above.
| Size | Type | Diameter D | Grip range G | Body length L | Head H | Pack |
|---|---|---|---|---|---|---|
| #54 | Dome triform, 5154 aluminium | 4.0 | 3.2 to 6.4 | 18 | 8.0 | 1000 |
| #56 | Dome triform, 5154 aluminium | 4.0 | 3.2 to 9.5 | 21 | 8.0 | 500 |
| #58 | Dome triform, 5154 aluminium | 4.0 | 6.4 to 12.7 | 25 | 8.0 | 500 |
| #64 | Dome triform, 5154 aluminium | 4.8 | 3.2 to 6.4 | 18 | 9.6 | 500 |
| #66 | Dome triform, 5154 aluminium | 4.8 | 3.2 to 9.5 | 20 | 9.6 | 500 |
| #68 | Dome triform, 5154 aluminium | 4.8 | 6.4 to 12.7 | 24 | 9.6 | 500 |
| 7.7 x 27.7 | Bulb-T, 5056 aluminium, EPDM washer | 7.7 (as sold) | 1.5 to 9.5 | 27.7 | 18.8 | 100 |
Triform, Bulb-T or a standard pop rivet?
- Triform: timber, plastics, plasterboard and insulation materials, per Hobson, where you want the load spread on the blind side.
- Bulb-T: a large aluminium open rivet (sold as 7.7 x 27.7) with an EPDM sealing washer under an 18.8mm head, covering 1.5 to 9.5mm in one size.
- Standard pop rivets (open, sealed, multi-grip and peel) for sheet metal and general work: see the pop rivet page.
- Rivet nuts when the job needs a thread in thin material.
How to set a triform rivet
- Clamp the parts together and drill straight through both. Hobson's triform sheet gives no hole size, so drill to suit the 4.0 or 4.8mm rivet body and try it on an offcut first.
- Fit the mandrel into the nose of a blind rivet tool and push the rivet into the hole until the head sits flat.
- Squeeze the tool until the mandrel snaps off. The body splits into three behind the work.
- Check the head is tight and flat.
Triform rivets in Adelaide
Allmat supplies triform and Bulb-T rivets, pop rivets and rivet nuts to builders, fabricators, shopfitters and trade across Adelaide and South Australia. Add them to a quote with the rest of your fixings, and we will price the lot.
Rivets for plastic, timber and sheet
Triform and Bulb-T rivets, pop rivets and rivet nuts are available to order from Allmat for builders, fabricators, shopfitters and trade across Adelaide and South Australia. Order through Allmat, we pick and pack it, then click and collect from the Allmat yard or have it delivered to site.
Goes with
Questions
What rivets should I use for plastic?
Triform rivets. Hobson lists them for plastics, wood, plasterboard and insulation materials, because the body splits into three during setting and leaves a large surface area on the blind side instead of damaging the material.
Can you rivet into wood?
Yes, with a triform rivet, which Hobson lists for wood. Pick the size whose grip range covers the total thickness: 3.2 to 6.4mm (#54, #64), 3.2 to 9.5mm (#56, #66) or 6.4 to 12.7mm (#58, #68).
What does #54 mean on a triform rivet?
A 4.0mm diameter rivet (5 x 0.8) with a maximum grip of 6.4mm (4 x 1.6). A #54 triform grips 3.2 to 6.4mm.
Are Bulb-T and bulb tite rivets the same?
Bulb-Tite is another maker's trade name. Ours is Hobson's Bulb-T: a 5056 aluminium open rivet with an aluminium stem and an EPDM sealing washer, sold as 7.7 x 27.7, gripping 1.5 to 9.5mm. Compare the diameter and grip range with what your job calls for rather than the name.
What size packs do triform rivets come in?
The #54 comes in packs of 1000 and the #56, #58, #64, #66 and #68 in packs of 500. The Bulb-T comes in packs of 100.
Where can I buy triform rivets in Adelaide?
Order through Allmat. Order ahead by phone on 1300 03 03 63 or send your list for a quote, then click and collect from 25 Kapara Road, Gillman, or have them delivered to site.
Triform & Bulb-T Rivet: sizes and finishes we supply
7 lines by type and finish. Pick one above for its product code, pack sizes and dimensions.
| Type | Finish | Sizes | Lengths | Lines |
|---|---|---|---|---|
| Dome triform | Aluminium | #54, #56, #58, #64, #66, #68 | - | 6 |
| BULB-T rivet open EPDM washer | Aluminium | 7.7 | 27.7 | 1 |
Data sheets and documents
The documents for the product you choose are listed with the selector above. Here is every Triform & Bulb-T Rivet document from Hobson Engineering.
All Triform & Bulb-T Rivet documents (4)
Data sheets and technical data (1)
Did You Know flyers (1)
Guides and articles (2)
Need them in bulk?
Add the sizes you need to your quote, or send us your list and we’ll price the lot and supply it with the rest of your order.
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