Reconditioning a Relmac lathe

[Lee Roberts]

Ok mate sorry it didnt work out so well, keep going tho you will sort it i'm sure...

Dinner time, SUNDAY ROAST !

[irving2008]

Removing the remains of the 1st attempt was easy - didnt even have to melt it out as there was hardly anything in there, but what was there showed promise - nice n shiney and clean surfaces



So cleaned it all up and re-assembled with a blowhole this time and left it out in the hot sun for 4 hours while I popped down to Argos for a better burner - the new one is 2300W and a much wider burner so it melts the metal in about 6 minutes against 18 or so before.. so much hotter (and you can buy the canisters for it too!)

So the fire-cement appeared to be set, it was rock hard and the whole lathe was hot to the touch from being sitting in 26degC sunshine for 4 hours so thought I'd try again...





As you can see, not a great success

Two mistakes... firstly my impatience, I assumed it had set but clearly was only on the surface and not right through - it needs that 24h or so... and secondly, I made the end dams not from ally foil but from pieces cut from an ally foil dish 'cos its thicker and easier to handle. But to get it round the shaft I cut fringes and bent them over. Big mistake, because it prevented the fire-cement sealing to the shaft properly. As a result when the pressure built up the fringes lifted and allowed the hot metal to spurt as you can see - it was quite a loud bang and fortunately I was standing on the other end... The third pic shows the 'hole' where the pressure built up, probably due to water vapour from the fire-cement. the air blow hole worked ok till it blocked up tho :)

[irving2008]

So we live and learn...

I now had 3/4 of a bearing, but obviously needed to do it again (but hey, I expected this)

Next problem was to get the spindle out to clean up again... now I had a full circle of bearing metal I encountered another problem... the centre section of the spindle is about 2thou bigger than the journals. The soot 'release agent' worked fine, I could turn the spindle OK although it was tight, but I couldnt extract it. It took some serious work with a rubber hammer to get it out. Whether this would damage the bearing surface is hard to say, the pics suggest not (see below).

Next time I might try the oiled paper suggestion instead of soot as this will give more clearance. Also this time I didn't put the foil shim right through to the journal as the first time it seemed to act as dam, but if I did it might allow the bearing to ease when the pinch bolt is undone. Trouble is all the examples I have found on the web are for fully split bearings not side split like these so I don't have any information on this.

Here is a pic of the bearing surface, sooty but smooth, before I chopped it all out again :(.



Here is the bit that goes into the keyway.. a nice impression and shiney too :)




I am wondering whether to put the lathe on end and try pouring into an open well rather than use the pouring hole (if indeed that what it is). It would certainly be less likely to fail. Or maybe I need multiple airholes in both dams that would 'plug' as the level rises so improving the 'venting'. Clearly this is going to take more than a couple of goes

Oh well... lets hope the weather is good next weekend!