Rebuilding a SuperRelm Lathe

[irving2008]

A thread to document the potential rebuild of my SuperRelm lathe... I need to decide how much I want to do this instead of spending £400+ on a new minilathe or a 1960's Boxford or similar.

The SuperRelm, c1915, is a classic early C20th English flat-bed lathe with the heastock and bed cast as one piece. It is an 8.5 x 24, so considerably bigger capacity than most minilathes, with an MT3 spindle bored 20mm and an MT1 tailstock.



The rebuild will need to cover:

• Sorting out the saddle, which binds about 32cm from the heastock end of the bed, but is loose enough to rock slightly about 5cm out;
• Sorting out the top- and cross-slide leadscrews and nuts which are badly worn with a turn of backlash plus the cross-slide has 4mm of movement!
• Sorting out the cross- and top-slide gibs to remove binding
• Sorting out the plain spindle bearings to improve accuracy
• Replacing the flat-belt pulleys with a v-belt (not sure about this one)

I think thats the order to do it as each will make the lathe more usable

Here is the saddle stripped down, and a close up of the dovetail and gib (with the vertical retaining plate removed). The saddle is disconnected from the apron so that I can assess how well it fits the dovetail. There is no rocking on the dovetail as far as I can tell.



The saddle binds around 32cm from the headstock end of the bed and loosens up around 5cm out. I marked out every 2cm from the headstock end and measured the width of the bed using the saddle as a guide to keep the digital calipers square. The results show that the bed varies in width from 102.95mm to 103.36 with the low and high points as suspected. Its hard to tell on which face the wear is however a parallel placed on the rear face shows no gap while placed on the lip of the dovetail shows definite high spots. The dovetail face itself seems flat though (how would I check this?). The saddle has no relief at the point of the dovetail; I am wondering whether to mill one there so that the face of the dovetail takes the load and not the lip... or should I hone down the lip?

The steel gibstrip itself is banana shaped by about 0.5mm at the ends so that could do with a new one being made up. Would bronze or brass be the better option? I am tempted to machine a tapered gib and do away with the four gib screws. There is plenty of metal in the saddle to accomodate one. I would also incorporate a saddle lock which this doesn't have.

The top- and cross-slide leadscrews I shall replace by some 10x2G lefthand trapezoidal screw and make new nuts out of some 1" square brass bar that I have... I could buy a tap (at £36!) or use some spare leadscrew to make a tap (JohnS has kindly offered to do so and get it hardened, when and if I get some stock to him). I might make up some delrin nuts initially to make the lathe usable. The leadscrew will have a 6mm spigot turned on the end to join it to the screw extension and handle assembly - more on that later. There is a limited diameter to allow the top slide to traverse over the cross-slide screw extension which will run in a brass bearing but I want to find a way to incorporate two 8mm ID, 15mm OD thrust washers to control endfloat and also a micrometer dial calibrated 0 - 200.

As you can see the saddle has some t-slots and these will provide the means to mount a boring spindle to rebore the bearings in situ. Options are here to repour the bearing and rebore or to bore oversize and fit bronze sleeves, but I am not sure about the wear of the spindle on the bronze, which is harder than the plain babbit bearings....

Am I mad to contemplate this?