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Fixing loose Meccano bosses

(Author: Stephen Brook)

or Put Your Hammer Away

Most loose bosses I have come across do not have a lot of play between the boss and the part it is supposed to be gripping, the boss revolving with respect to the part but not waddling. If, however, the boss is very loose this can usually also be fixed so I will start there.

The first stage in the process is to clean the mating surface between the boss and the part. Soak the joint in methylated spirit, either by using an eye dropper or a clean rag well soaked and squeezed into the joint. Work the boss to and fro with respect to the part several times then dry off the excess with a dry cloth. The meths within the joint will evaporate within a minute or so.

Next, (very loose boss only, remember), screw a STEEL long bolt or screwed rod though both tapped holes in the boss (or, of course, a short bolt if the boss is single tapped), place a small piece of smooth scrap steel against each end of the boss and put it in the vice with your third hand ( a bit of blue tack on each end of the boss helps). Tighten the vice slowly so that the end of the boss holding the part is compressed enough to stop the part waddling with respect to the boss but still able to rotate. Remove from vice, remove bolt, remove blue tak, put Elastoplast on trapped fingers, etc.

So, with the boss still turning on the part but not waddling, put a drop of Loctite 601 retainer on the joint, quickly rotate the boss a couple of times, wipe off any excess then put aside to set. This stuff will start to grab in 20 seconds or so, reach handling strength in about 15 minutes and be fully set in 3 hours. Job done and the repair is permanent and invisible.

Loctite 601 is an industrial adhesive sold by most engineering/model engineering suppliers or, of course, on line. It is not cheap but the tiny bottle seems to last forever. I have had my 10ml bottle for well over 10 years and am still using it. As to strength, I have seen a passenger carrying miniature steam locomotive running around a track with the wheels held on to the axles with Loctite 601 only. Only a blowtorch will loosen it.


It seems that 601 is now hard to find in 10ml bottles (on line, at least) but a near equivalent, 603 retainer, which is claimed to be better still because the mating surfaces do not need to be as clean, can be had for about £6 or £7 for 10ml.  


David Morgan      (at 3:13pm, Thu 31st Mar, 11)

A 3/16"(5mm) Steel ball worked fine for me, Thanks for the idea. I put a steel bolt in the boss and an ali. plate under it.

Charles      (at 10:43pm, Thu 8th Apr, 10)

Yes, I've always used a large steel ball over the peened end and a piece of rusty flexible plate at the other, and a long bolt through the boss (Meccano long bolts are steel, of course). The steel ball spreads the peening into the recesses in the pulley/gear which prevents the boss from slipping again. I've never had the need for any adhesive.

johnfromperth      (at 10:15pm, Thu 8th Apr, 10)

Squeezing a largish steel ball (from a ball bearing) against the peened side of the boss does a good job.
I endorse your comments about putting a screw rod or bolts into the threaded holes in the boss. Otherwise the pressure can collapse the holes in the soft brass.

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