Making Sinker Moulds

Sinker moulds

by Kiwi Hunter

When the wind and rain is lashing at the windows and the sea is far too rough to contemplate fishing it might be an ideal time to whip up a few sinkers After all, if you can’t actually go fishing you can still prepare for your next trip.

To take things one step further why not make your own sinker mould to make the sinkers? An easy-to-make mould for medium-sized sinkers can be made from two pieces of 10 or 12mm flat steel, two short lengths of 10mm round bar, two old file handles and an old hinge heavy enough to do the job.


The dimensions of the mould shown are:-

The three sinker holes are only limited by the size of drill that you are able to use. I have used a 16.5mm drill on the multi-sinker mould shown.

The process

After removing all burrs and sharp edges from the two plates, clamp them together and put a spot of weld on each corner to temporarily hold them together while drilling. If no welder is available then a couple of strategically placed bolts would serve the same purpose, providing they were neat fitting and clear of the drilling of the next process. Once the two plates are fixed as one, the sinker holes can be marked out and centre popped on the edge of the plates.

The finished sinker mould plates

The finished sinker mould plates
The finished sinker mould plates

Determine your required depth or depths if the sinkers are to vary in weight and then drill the pilot holes about one third the diameter of the finished hole. You will only be limited in your size of sinkers by the thickness or size of the plates and by the size of drill available. The mould shown here has a capacity for three sinkers but this could easily be increased if you have sufficient material.

It is important that before you unbolt the two plates or grind off the tacks (welds) that two locating dowels are fitted to ensure the mould comes together perfectly each time it is closed. To do this simply drill through the plates in two diagonally opposing corners with a 6mm drill and countersink on one face only. Now insert a short length of 6mm rod in each hole, ensuring that it has been bevelled either end. Weld the pins into the outside of the plate that has been countersunk. Once again if no welder is available this task could be done by tapping out the dowel hole and fitting a 6mm bolt with the head removed to serve as a dowel. If done this way don’t forget to drill the hole 5mm as this is the tapping size, then drill out the receiving hole to 6.5mm (clearance size) after the two plates are separated.

One more thing to do before separating the plates and that is to fit a fairly substantial sort of hinge to connect the two plates. With the one shown I simply used a heavy duty door hinge with the flanges sawn off and it does the job admirably.

To give the sinkers a more streamlined shape a drilled and countersunk cap can be welded to the top of the mould. This should also be done before the two plates are separated. Once opened up the sharp edges can be removed and the two dowel locating holes can be countersunk to facilitate easier location.

Handles can be welded or drilled and tapped and screwed on if need be and then you’re in business.

Another useful point to remember when pouring the lead is that it is essential that the mould is hot or the lead will solidify before it has completely filled the cavity. I find some copper wire is best to form the sinker eye as this is nice and malleable and is easily obtainable from old electrical wiring. The heavy three-phase stuff is best. Twist this around a phillips screwdriver or piece of rod to form the eye and have it sitting in the mould before the lead is poured. These wire eyes are best held in place by a nail or something similar strung through them while pouring the lead.

Sinker moulds
Diving weight mould

I have included photos of a diving weight belt mould and other sinker moulds I’ve made but as the latter require the use of a lathe to produce and a certain amount of skill that generally only an engineer would have, I don’t intend to go into great detail into the machining process.

Sinker moulds
Sinker moulds, showing top and
bottom pieces

Suffice to say though that a location is essential between the two parts of the mould and the inside surface must be reasonably smooth to enable the sinker to be easily removed. It is also critical that the inside of the mould is tapered over its total length, once again to facilitate ease of removal of the sinker.

A great deal of discretion can be used here to suit one’s particular needs. The basic dimensions of the largest sinker are 120mm long x 34mm diameter, curving from the centre. The idea was to try and make this one as streamlined as possible, both for the drop and the retrieve.

I designed this sinker especially for groper fishing and it weighs in at 830 grams or 30oz. I find this to be a perfect size for fishing with heavy duty traces and large baits from 150 metres deep or deeper.

The range of sinkers shown here would certainly cover most general sea fishing situations, surfcasting excluded. The smaller sinkers from the multi-sinker mould could also be wired together if a hole was drilled in the bottom to allow this. By stringing two or three sinkers together like this a good weight range could be achieved to suit the conditions on hand, ie swell, wind, boat drift, current, size of trace and water depth.

Sinker moulds
Sinker moulds, showing top and
bottom pieces

I like to make my bigger sinkers sacrificial by attaching them to the trace with a cheap lightweight swivel clip. After all, it’s better to lose only the sinker if it gets snagged on the bottom and if I make them it’s by far the cheapest part to lose.

I hope this article contains enough information to motivate some keen fishermen, or for that matter, fisherwomen, to capitalise on that wet windy weekend. Do be sure to use the appropriate safety protection equipment while working, eg goggles, face mask, gloves, etc, especially when working with lead. Please remember that children should be excluded from the area during this process.

Note: Click on images to view larger versions.

Collection of finished moulds and the results
Collection of finished moulds and the results

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Copyright © June 2000, Kiwi Hunter
Revised -- April 2006

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