I've seen this question arise on a couple of discussion groups lately and rather than writing the same things over and over again I thought I'd write a post on the matter.

What to do with pits and/or porosity?

Thanks to modern casting technology, this isn't the common problem it used to be. In the old days it was much more common and holes had to be filled and pieces re-cast on a tediously regular basis. Nowadays it occurs so infrequently that I sometimes forget that the issue crops up occasionally. In fact, it's probably something that should have been included in Chapter 10 of our book which was published earlier this year.

So, what to do if it occurs? There are a number of approaches and there isn't a one-size-fits-all solution. The type and severity of the problem as well as the design and end use of the piece are all factors in selecting a solution.

The first thing I do is try and ascertain the extent of the problem. Have a poke at the hole(s) with a scriber or similar implement and see how bad it is. Perhaps the holes aren't deep, but if there's a cavity beneath the surface, you've got a bigger problem.

If it's severe and you have a mould, get a re-cast. It's not worth your time trying to fix it. Most casters will accommodate you if you bring the problem to their attention.

If you don't have a mould, i.e. this was a one-off or new carving, you don't have that option. Here are some others:-

1. Make it into a master. Finish the casting as best you can, attach a sprue, fill the holes with milliput or similar (Apoxie resin, polyfilla, or even superglue), sand smooth and make a mould. If you need the materials, you can scrap the original casting after. Fast and easy.

2. Laser. Often the caster will have a laser, if not there's plenty of people offering this service. Fairly easy option, but may not solve deeper issues.

3. Drill and plug. Drill a hole, insert a piece of wire, solder in place. Good for deeper problems. Possibly a problem for complex carvings as detail may be damaged by the process and may need to be repaired after plugging by filing, engraving, use of burrs etc. Good for larger holes.

4. Flood. Flood the area with solder. Not my favourite. Make sure the pits are good an clean, so clean them out with tiny burrs, before fluxing. Dangers are flooding detail that will need fixing after. If the piece drinks up a lot of solder, you have deeper porosity. With enough solder you could even fail your hallmark.

5. Replace. Cut away the bad section and replace it. Easy enough on a plain ring shank, but potentially trickier for other pieces; could even require re-carving the section. Not ideal, but in certain circumstances better than starting from scratch.

 Russell Lownsbrough FIPG

19th April 2021

 Click on the images to enlarge

Portable Electric Engraving Tool

These things have been appearing in my social media feeds for some time now, so I thought I'd give one a try, with a view to seeing how it performs with wax.

They're pretty cheap from Ebay and such like, so it could have potential as starting kit for my students and beginners. There's never enough micromotors or pendant motors to go around at college; for a very small investment this could be a good solution.

The one I bought was £26. In the box was the Pen, a charging cable, an instruction leaflet and a box containing a bunch of diamond tools. There was three circular saw tools in the box too, but frankly they look like an injury waiting to happen.

The pen has three speeds, 5000 – 10000 – 18000 rpm apparently. They estimate use time at one hour. I haven't tested for that long yet, but I suspect that will come down significantly depending on speed and work.

It accepts standard 2.3mm shaft burrs. There is no chuck as such, just insert the burr into the end of the pen until you feel resistance, then push more until the burr is gripped by what I assume is an internal rubber chuck.

Press the power button to set it running, again to increase the speed, a third time for top speed and a fourth to turn it off.

I found it quite pleasant to use; it's light and easy to hold. The 16mm diameter is slimmer than most micro drills, coupled with the light weight this gives plenty of control.

It has a little more torque than I was expecting, not that you need a lot of torque working with wax. It works well with standard burrs; I tried a range between 0.5 and 5.0mm and was satisfied with all of them. I preferred the slowest speed. As always the best way to use burrs with wax is to keep a light touch and don't let friction melt wax onto the burr. It even worked with a 1.2mm drill on a 2.3mm shaft, although I could feel it struggle a little at 5mm depth. Drilling a bit at a time worked better. Personally I usually drill with a hand chuck, as it's more controlled with wax, so this isn't a feature that would bother me.

If you have a pendant-motor or micro-motor, this probably isn't something for which you'll have much use, but it's handy for anyone on a limited budget or looking for something super-portable. 

Not sure about the name, maybe Pen-motor?

I'll update this when I discover it's lifespan.

Update: December 2024, it's still working.

 Russell Lownsbrough FIPG

29th December 2022