How To Insert Turret Tags in Tufnol Board
When laying out a
always nice to achieve that professional look to the end result. Of course point to point or hard wiring as
it's called is a technique often used by DIYers, but the layout often leaves something to be desired. An improvement
to the layout and solderability of components can be achieved by using turret tags attached to Tufnol board which is then
used to fix components in place.
The fixing of component boards to inner speaker cabinets can also be a bit of a problem.
Tufnol board / sheet is an insulating material made from paper and glue. It is produced in a number of grades and thicknesses, some of which are extensively used in the electrical industry. It can be drilled, filled and cut and has a good stiffness for component mounting.
Turret tags are small metal, solderable, components which, when board mounted, allow the use of interconnecting wires and fitting of components between them.
(1) Draw your crossover board outline on a sheet of paper and cut to size.
(2) Layout your components on the paper and arrange / re-arrange them to a satisfactory position. Remember that crossover components like inductors should be spaced well apart.
(3) Mark the crossover wire positions on the paper, a small cross or circle, where you want to insert the turret tags. Note: for components with thick wires you should allow enough space to adequately bend / form the connections to the tags, (10 to 15)mm.
(4) Stick the paper onto the Tufnol board to exactly cover the board surface. Sellotape is good because it's transparent. It's also a good idea at this point to mark four corner drill holes for later mounting your board. M3 or M4 holes should be sufficient.
(5)Tufnol is relatively hard and small drills skid / slip over it's free surface so with a small hammer and centre punch mark each drilling position.
(6) Leave the paper in place and drill the holes. Use a piece of scrap MDF or flat wood as a backing piece under the Board. The underside hole edges will otherwise break-away when the drill goes through. Known as break-out, this is not good, as we need a 'good, clean' through-hole for turret tags to fit properly.
Note: (The use of the correct drill size is important for accurate tag fitting. 2.05mm is the specified drill size and these can be obtained from QTA. 2.1mm is usable but less satisfactory).
(7) Remove the paper and re-use on the second board, assuming you are making two. If unusable draw a second outline and repeat the above procedures.
(8) Mark with a piece of tape which board side is to be the component side as it's easily confused.
(9) More easily done with fingers than a drill stand, rotate a small drill (4 to 6)mm between fingers and make a small countersink on each component side hole. Deburr, but not countersink the underside holes, by the same process.
To achieve a satisfactory crossover layout it is useful to plan your component layout on a sheet of paper the same size as your board. Re-arrange the components to achieve a satisfactory mechanical and electrical layout. Remember wires cannot cross each other unless you intend to use the board underside as well. So.....
(10) The tags are supplied with an insertion aid / pillar. On a
scrap of MDF (150 to 200)mm square, drill a blind hole, (6.4mm or 1/4
"), i.e. one that does not go right through and press the pin into the hole with the
drilled recess uppermost. Alternatively, clamp the pin in a vice with the pin recess uppermost.
If you do this you may need to prevent it from twisting.
(11) Insert the turret tag into the pin recess with the turrets facing down.
(12) Keeping the Tufnol board level and with the component side
facing downwards press the board onto the Turret base. The board hole
will be a tight fit and you may need to persevere a little if it's hard
(13) Using a small hammer and centre punch, peen the turret tags base over. Keep the assembly level and strike the punch once. Do not strike the punch more than once or too hard as the turret may split. A little practice may be needed to acquire the correct force.
(14) Repeat the process for all turret tags i.e. until a tag is inserted into every hole.
(15) If you misplace or damage a tag they can be drilled from the underside, (non-component side), and extracted with pliers. However, that particular hole can now no longer be used as the hole diameter or its rim may now be too large for the replacement tag to fit correctly.