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Article: About Bolts & Screws for Loudspeakers.

A DIY'ers Guide to Loudspeaker fittings and fasteners.

  Amongst the vast number of available fixings, QTA systems have selected a few which are useful for Loudspeaker construction. Most popular are screws but depending upon cabinet material and access, bolts may be better. MDF, the material of choice? is constructed from wood fibres. It is easily split when screwing it's edges and needs pilot holes. In addition, the faces are hard and difficult to screw without pilot holes. Repeated use of screws can strip the wood leaving useless holes. Bolts compress the material but need rear fitting access or the use of accurately-aligned wood inserts. So.........Choose carefully.

Screws Pan Head
(1) Bitumastic Damping Sheet

Pan Head. Mild steel. Better grades are case-hardened and have hard tips. Available in cross-slot and / or Posidrive / Phillips heads. Finish is usually Bright Zinc Plated, known as a BZP finish. Other options include Chemi and Oil finish, known as Chemi-Blacked. Occasionally a spray paint finish is used. Many other varieties are also available in different materials including Stainless Steel and Brass.

Woodscrews Cap Head
2) Cap Head Woodscrews

Cap Head Woodscrews. Similar in design to Woodscrews in that they have a sharp cutting thread. The head however is designed to be used with a steel hex key, hex head screwdriver or similar. Available in limited lengths and size. The most useful sizes for driver fixings are M4 and M5. The larger size is best suited for large bass drivers. Available in Chemi-black or BZP finish.

Assorted Lenght Button Head Bolts
(3) Button Head Bolt

Usually High Tensile steel or Stainless steel, often supplied in self colour. The heads have a hexagonal recess which requires an Allen key or hexagon Bit to tighten. Some are available with  Chemi-Black finish. Note: Chemi-black finish is a 'cosmetic finish'. In a damp environment it WILL eventually corrode.

Assorted lengths of Cap Head Bolts
(4) Cap Head Bolts

Same material toughness as Button Heads, Note: Bolts usually have (20 - 25)mm threaded body length only. If you find you need a longer thread, carefully select the correct Bolt length. Bolts with a fully threaded body are known as SET Screws, NOT Bolts. Also available in a variety of materials and finishes. The most common are natural self finish or Chemi-black. Stainless varieties are used widely in plant for the food industry.

Hard Nylon Bolts with Nylon Washered Nuts
(5) Nylon Bolts

Made from hard Nylon. Being non-ferrous and therefore non-magnetic they are useful for fitting Air Cored and Ferrite Cored Inductors without influencing their magnetic properties. They have only moderate strength, and should not be over-tightened as they will stretch. Available with Washered Nuts i.e. integral nut and washer or with separate washers and nuts.

Assorted Washers, Standard steel, Shakeproof and Wavy
(6) Assorted Washers

Two basic types, Plain and Shakeproof. Plain washers can be of type A or B. This defines the outside diameter relative to the internal diameter. Type B have greater load-spreading ability because they are larger in overall diameter so..... But not here. Subsets of Shakeproof are Spring, Crinkle and Wavy. Wavy washers are only available in Stainless Steel. Crinkle can be defined as Internal or External which defines the location of the teeth. We have internal. See the Pic.......... There are many others but......

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