Commando Mk3 Speedo Gearbox Greasing

With the gearbox out you can apply grease to the ring and turn the ring so the grease gets pulled in, do this several times. You can also unscrew the grease nipple and with a O ring and oil gun squeeze the grease in. But in the end just get the grease gun but you need one with the right fitting or put some cloth over the nipple and the wrong fitting should still be able to insert some grease. But even though I have the right grease gun I still take the gearbox off and apply grease internally, just don't trust grease guns and nipples to work unless there's somewhere the grease can appear as a tell tale.

... already be greased. If you want to add more you can just prise off the thin metal cover on the inside giving access to the gearing components. Usually the nipples aren't Zerk type but simple ones which accept the old-style pompom type grease gun.

In a fit of enthusiasm, I pushed a high-pressure gun onto that small nipple....The mazac housing 'popped'.

I would like to replace the grease nipple on the speedo gearbox on my Mk3 Commando and my Mercury, but do not know the thread size.  It seems the same thread size as the older style nipples on my 1950's frame headstock, but these have nipple ends that do not suit the clip on more modern grease guns.

If it was easier to dismantle the speedo gearbox I would drill out the hole and put in a suitable alternative, but I don't want to risk getting swarf down into the gears.

I shall take note of Richard's advice on the fragile casing!

As an interim measure I modified a long shank clip on nipple so that it would fit into the thread hole, removed the nipple, and then pumped grease into the gearbox.  This reduces the risk of pressurizing the casing.