Modifying Tools as Dapping Tools

Dapping tools are punches with a ball shaped end. As they are used to dome metal discs and making halves of beads they are sometimes called doming punches. They are usually used with a dapping block, a square or rectangular block of steel or wood which has perfect hemispherical indentations in different sizes.

As with most commercially produced tools dapping tools are compromised in their shape and function by the logistics and economics of machine tool production of tools. One should really consider most commercially produced tools as blanks which one has to reshape and work with to get a more useable tool from. Engraving tools are a case in point.

Commercially made dapping tools are clumsy, heavy and uncomfortable to use in the hand. They are same thickness as the sphere on their end. They look the way they do because it is cheaper and easier for an automatic lathe to turn them out that way: from the round stock. In the larger sizes they are not pleasant to use. They are also made from soft mild steel so that the lathe tools do not dull as quickly. You may have noticed how commercial dapping tools get dented rather easily. To make a better tool one can use a ball bearing.

Rumor has it that ball bearings may be internally stressed and can explode when heated so lets believe the rumor and grind a flat spot onto one part of the ball bearing. This simultaneously relieves stress and provides a better contact area to braze a rod or piece of key stock (non-hardenable square steel rod readily available in hardware stores) or drill rod onto. Even after brazing the ball bearing is harder than the normal dapping tool.

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What goldsmiths call soldering is really brazing, same flux, use any material that melts lower than steel as a bonding agent copper, brass, silver, gold etc-I use brass. To braze it together cut the rod to length, set up with clamps so that the end of the rod rests on the flat spot ground on the ball bearing and use a fluxed strip of your brazing alloy. Use a thick borax white paste flux. Heat the heavily fluxed steel parts up a lot until they glow orange and then braze them together. Air cool and remove flux residues by running hot water over the tool. Polish off any oxidation scale with Fabulustre®. To keep scale to a minimum paint a slurry made of hand bar soap and water onto it before brazing. ‘Steelies’ (children’s ball bearing marbles) from flea markets are cheaper than when called ‘ball bearings’.

Another option are old fashioned door hinge pins which have beautiful balls on one end.

One can apparently obtain ‘ball valves’ as seconds from pump and liquid flow control companies. They are stainless and seconds can be had inexpensively. These are available in very large sizes and are like a sphere on a rod.

A bought dapping block is best to use. Inexpensive brass ones from India for the smaller sizes can be had from companies like TSI.

End grain of a tree trunk (best is hardwood) can be used for a kind of dapping block. Make a dent with the tool you want to use and then it works fairly well. Note that when using a hammer one sometimes makes a dent into wood because you then have an exact fit between hammer and wood to shape metal sheet with.

Freeing discs stuck in a dapping block can sometimes be difficult. If one places a latex surgical glove over the dapping block while in use discs tend to pop out easily. Rubber dam material also serves very well in this regard. Note that bulk users of expensive dental rubber dam material are physiotherapists and aerobics instructors who buy similar material in large rolls to make stretching tools for their clients to use.

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Remember too that when dapping one should use a dapping tool one half to three quarters the diameter of the hole being used and that one should tip the disc being dapped to an extreme angle as one taps the tool into the block and rotates the disc. This rapidly daps the disc and also allows one to make a smaller dome than would otherwise be possible. This in turn solves the problem of too great a decrease in dapping hole size which can without this technique result in domes with scarred sides.

Lead blocks are really good for shaping metal on and in particular for stamping ring insides on without distorting the ring. Any traces of lead left on tools or transferred to precious metals may eat into them when they are next heated. Skin contact with lead is also not a good idea. Tin or typemetal can also work reasonably well without as much health hazard. One can however wrap the block in a latex surgical glove or in rubber dam material when storing and using it. This prevents contamination very well.

By Charles Lewton-Brain - Copyright © Charles Lewton-Brain 1994-1997
Excerpt from "Cheap Thrills in the Tool Shop"
All rights reserved internationally. Copyright © Charles Lewton-Brain. Users have permission to download the information and share it as long as no money is made. No commercial use of this information is allowed without permission in writing from Charles Lewton-Brain.
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