Fasteners and Sealing
Blind rivet nut is a quick and simple assembly solution
Annemie Van Ocken outlines the benefits of using blind rivet nuts. T
he Tubtara blind rivet nut is a quick and simple system to provide a strong thread in a thin sheet, allowing you to assemble another component with a bolt or screw. The blind installation of the Tubtara - from one side of the workpiece -
is very useful in boxed or enclosed assemblies where there is little or no access from the rear. The Tubtara can be set with a hand or pneumatic tool, a
press or an automatic installation. The majority of the Tubtara applications are still in steel
and corrosion resistance depends on the surface treatment. Dejond’s high quality standard finish is called Zinktop. It is an electrolytic, CrVI
-free plating that guarantees 480hr resistance
against red rust (96hr against white rust). This strong corrosion protection offers a very good internal thread plating which is critical on small diameters and closed end parts. Too heavy plating in the thread reduces the hole size and blocks the bolt or screw. If you need a high corrosion resistant solution, you had
better use a stainless 316 in chloride bearing environments or a 304 Tubtara in atmospheric conditions. In any oxigenous environment an invisible protective film
forms naturally on the surface of the stainless blind rivet nut. In case of damage this layer rapidly restores thanks to its self- repairing properties.
Dejond specialises in cold forming techniques.
If weight reduction is your priority, the aluminium Tubtara can be a good alternative for stainless. This leightweight material is corrosion resistant and there is no extra need for plating. The Tubtara was initially made for thin sheet applications
of 1 or 3 mm, but nowadays larger grips up to 8 or 10 mm are commonly used. If you work with precoated or prepainted sheets, don’t forget to include tolerances for paint or coating when measuring the exact material thickness. The Tubtara will not damage the surface of your workpiece, nor deform it during setting.
Fig. 2. The closed end HX Tubtara with an underhead seal which offers a watertight solution.
Fig. 1. Anti-turn Tubtara: the special head prevents spin out.
As there is practically no loss of material during forging, the production process makes optimal use of the material. This is very costsaving when using expensive materials like stainless 304 and 316. The stainless Tubtara is often the least expensive choice in a life cycle cost comparison.
Selection of the head and shank style of the Tubtara will depend on the required characteristics of the application. A flat head provides a large surface to prevent push out. If the head is not allowed to protrude much above the sheet, the countersunk and low profile heads are a good solution. When you want to avoid the risk on rotation and increase the torque- to-turn resistance, choose between a hexagonal shank and a round shank with special anti-rotation head. Do you need a watertight solution? Then use the closed end hexagonal HX Tubtara with underhead seal. Still one piece of advice: always check the technical
characteristics of the chosen Tubtara and do some tests on the suitable product in the specific application beforehand. l
Enter 39 or ✔ at
www.engineerlive.com/ede
Annemie Van Ocken is with Dejond nv, Antwerp, Belgium.
www.dejond.com
www.engineerlive.com 39
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