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Cleaning parts by barrelling

(Author: Stephen Brook)

For small brass and nickel parts. Also for stripping paint and rotted zinc plating.

The barrelling machine shown on the right can be used for a wide variety of purposes, from cleaning and polishing small items to paint removal and the de-burring of metal parts. I have used it for cleaning Meccano brass ware and nickel plated parts for the last 15 years and have found it to be very effective. I have also used it for removing paint from small parts. Although this machine is over 15 years old the same model is still available for sale to-day from Beach Lapidary Ltd, Unit 1c, Chapel Lane Works,Westcott, Dorking, Surrey RH4 3PJ, U.K. Telephone 01306 875776. No website but the machine is sold by agents such as www.gemcraft.co.uk and www.stonepolishing.co.uk  

Vaned drum

What the machine will do is determined by three things: the type of barrel, the media used in the barrel and the cleaning or abrasive agent.

Barrel types are plain or vaned, media includes steel pins, ceramic shapes (used for de-burring) and many others such as ground walnut shells used for polishing cartridge cases. The cleaning and abrasive agents are powders which are used in conjunction with the media. If you want to know more about other uses for this machine (including its most popular use which is polishing gemstones) have a look at the instruction

Mixed steel media

sheets on this page and the websites above.

Anyway, back to its Meccano uses. I use a barrel which is 5.5 inches long, 4 inches in diameter and has three vanes in conjunction with 1lb (450 grams) of mixed steel media. See photos. This combination sees to all my Meccano cleaning, polishing and paint removal needs up to a maximum component size of 5 inches x 2.5 inches.

The procedure is as follows:

  1. weigh approximately 8oz (225 grams) of brass or nickel plated parts (don't

    Just a large size, fine mesh kitchen sieve. The best way to use it at the end of each stage of the barrelling process is to press the convex side against the open top of the barrel then gently tip the barrel to allow the water (only) to drain away leaving the parts and steel media inside the drum.

      mix them).
  2. put the parts in the vaned drum together with 1lb of the steel media, a level teaspoonful of Burnishing Soap B (obtainable from Beach Lapidary Ltd) and cold water to about half full or slightly less.
  3. put the lid on the drum (see instructions).
  4. put the drum on the rollers of the machine, as shown in the photograph, and set the machine running for 4 hours using a mains timer.
  5. after 4 hours, empty the dirty water out of the drum, fill with water, agitate and empty the water out again. Half fill with water and add a level teaspoonful of burnishing soap as before and put the drum on the machine for another 4 hours.
  6. this should be sufficient for even very dirty parts. If it isn't, replace the soap and water as above and give it another 4 hours.
  7. empty the water from the drum, pick out the parts and place them on an old

    A hairdryer on a stand which I cobbled together to assist in the final drying process. The clamp holding the hair dryer to the stand is a device used by musical instrument repairers for clamping awkwardly shaped parts together whilst the glue dries. It is also useful for holding the mainspring of a Meccano clockwork motor during motor repairs.

    towel. Use a hair dryer on a stand (see photo) to dry them thoroughly, turning occasionally as with fish fingers.

If you don't plan to use the steel media again immediately it will stay rust free for at least a few days if it is kept in the sealed drum and covered with a mix of  a teaspoonful of the burnishing soap and water. Otherwise dry it very thoroughly.

The final finish should be totally clean (including all crevices) and polished, but not to the kind of high sheen you would get if hand polished with, say, Brasso. Any paint or varnish (many Meccano brass parts are varnished) will have been removed as will any loose (nickel) plating. Sound plating will have been polished. I have not noticed any damage to threaded or toothed parts but if you were to examine them under a powerful lens I am sure that you would find that any very sharp edges had been slightly rounded. One problem you will encounter is that of small bits of the steel media getting themselves lodged in holes, particularly tapped holes and blind holes (e.g. #179 rod socket). They are usually small steel balls and are fairly easy to remove by pushing them out the way they

Instructions page 1

went in with a steel panel pin (a bent one for single tapped bosses) or by using a strong magnet in the case of blind holes. Otherwise, a pair of very fine nosed pliers and a bit of wiggling will usually do the trick. In 15 years I haven't yet found a bit of steel that I couldn't remove (shouldn't have said that, should I?) but if the worst comes to the worst the steel can be dissolved in concentrated acid leaving the brass intact (or so I am told). Obviously, discard any bit of steel that gets stuck. If you don't you can be sure that it will do it again. Any losses in the steel media can be made up with small steel balls and panel pins. Some minor distortion to the thread within tapped holes occurs occasionally. My remedy is to run a 5/32" BSW tap through the hole to clean it up.

Instructions page 2

I haven't tried cleaning parts plated with anything other than nickel, so there is room for experiment here as there is with rust removal. Using an abrasive rather than a burnishing soap will give a much more rigorous action whereas reducing the amount of water in the barrel will give a slightly more rigorous action. As you will see from the above, paint removal is a part of the cleaning and polishing process, so if all the paint has not been removed after the normal 8 hour cycle, just extend the processing time. In the case of painted gears (yes, I have found a few of these) and other parts with sharp or deep crevices, it saves processing time if you pick out the softened paint from the crevice with a panel pin at the first water change after the first 4 hours of processing. 

The drum and other parts are available separately at reasonable prices but the full kit of parts is quite expensive. The motor unit is a fairly simple piece of equipment so could lend itself to a bit of Meccano ingenuity. For those who wish to try, the principal dimensions of the working parts are as follows:

AND NOW FOR THE EVIDENCE OF WHAT IT CAN DO.

My attempts to get the pictures to show in this document have failed but they are available here instead:- www.nzmeccano.com/image-35267

UPDATE - ZINC PLATED PARTS

Having just unearthed from my scrap box a batch of about 50 zinc plated 2.5 inch (5 hole) perforated strips which were suffering from the all too common problem of zinc oxidisation (otherwise known as zinc rot), I decided to experiment with them in the barrelling machine to see what it would do. The strips were covered in a grey powder with occasional brown blotches, so they were just about as bad as they can get and it was obvious that I had no chance of salvaging anything of the original zinc finish so I decided to try to strip them back to the bare steel for subsequent re-spraying.

The 50 strips weighed in at just over half a pound so I treated that as a single load and used the process outlined above with steel media and the barrel half full of water but with an abrasive (Beach Products "Abrasive A") in place of the usual Burnishing Soap "B".

After 4 hours I changed the water and renewed the abrasive then gave the parts a further 4 hours in the machine before inspecting them. By this time, all the discolouration had gone as had patches of the zinc plating revealing bare steel beneath. Another change of water and abrasive and six more hours in the machine resulted in the plating being totally stripped from all but 6 of the 50 strips, revealing a smooth, unpitted steel surface albeit somewhat grey in colour.

The six partially stripped parts can go in with the next batch. The remainder were processed for 4 hours with Burnishing Soap "B" which got rid of the greyness and polished the parts to bright steel ready for re-spraying.

 

R.Chantler      (at 12:27pm, Sun 3rd Jun, 12)

Zinc plating is very cheap at a plating works and they will pickle the parts B4 plating.I have a French
made 10 set and had 50% replated zinc and is far superior to original at reasonable cost.

Jim Perry      (at 9:24am, Tue 28th Sep, 10)

Do not buy from stonepolishing.co.uk this company still owes Beach Lapidary for machines purchased 2 years ago. We are happy for customers to purchase direct from us at Westcott Surrey 01306 875776

Charles      (at 5:21pm, Sun 4th Jul, 10)

If you want to strip the zinc plating (including its oxide), it's easier just to shove the parts in 33% HCl for a few seconds, then wash them. You can find this either in a swimming pool shop (as pool acid), or in a builder's merchant (as Spirit of Salts).

Stephen Brook      (at 11:55am, Sun 25th Apr, 10)

Thank you, Charles. I will be cleaning another lot of parts in the near future, so I will take some before and after photos. I have yet to find a brass part that cannot be cleaned and polished thoroughly by this method including those covered in thick layers of paint and others that are almost entirely black. Bear in mind, though, that badly discoloured parts may require more processing time, 16 hours being the longest I have found necessary. All the gears I have cleaned (about 200)had already seen some use but using the normal 8 hour processing time there is no noticeable rounding of the teeth. On occasion the thread of a threaded boss may suffer some slight distortion but this is easily rectified with a 5/32 BSW tap. Meccano parts aren't close tolerance so there is really no problem but I would think twice about cleaning a part with, say, an exposed 10BA thread.

Charles      (at 5:58pm, Thu 22nd Apr, 10)

Great article, Stephen. Thanks for that. Is there any chance of you doing some before-and-after pictures? How badly tarnished parts can you do? Do you get any significant rounding of the edges of the gears?


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