I restored an Alba 2B years ago. The only part which was really worn was the bottom pivot support pin.
I replaced the 2” diameter pin but hadn’t the facilities to do anything about the bushes. Worked fine after.
wish I still had it.
I have a 1A which I bought from a dealer for scrap value as it was minus the pitman arm. It cost me me 10 GBP plus the diesel to collect from 125 miles away.
I fabricated a new pitman arm and modified the bottom bearing to allow the arm to slide on a bronze block. This followed a mod that a fellow model engineer in the village had done to his. I did initially change the motor for a single phase one but quickly reverted back to the 3-phase original. The 3-phase supply is by a home made rotary converter which also supplies the grinders. The mill and lathes all have 3-phase motors each with its own VFD inverter.
The next real challenge I have to solve is making a new horizontal leadscrew nut. The original has been munched at some point as you can see from the photos. This will entail making a suitable ACME threading tool, shaping this part, dilling and threading it so that things are correctly aligned and centred.
The attached photo show its had a dang good bashing at some point. You can also see that there is some special shape to this part that is needed to achieve needed clearance. The circular "pin" section that actually drives the box table horizontally needs to be a very close/smooth fit to minimise backlash.
While I have done a reasonable amount of metric threading I have never done any ACME threads. On that basis I think I will do some practice threads on some simple round first.
But with the xmas holiday season I'm not going to get much traction until early Jan.
I managed to get some time to prove to myself that I could make a HSS ACME threading tool for 6tpi threads and use said tool to internal thread a nut such that it would get a good fit on the Shapers horizontal leadscrew. Overall I think I can call this a success. The boring bar is a bit hacky but seems to be working and so long as a I take things slowly and accept that I need to do 3-4 spring passes for a final depth it looks like things have come out pretty reasonably.
It is worth noting that this test part was already metric threaded so I cleaned out enough to get approx the hole needed. You can see the remains of the original threads in the 3rd pic. However this is really only cosmetic and for testing purposes not relevant.
Update on the acme threading - I had another look at the pics and thought I should clarify the topslide (compounds) position that can be seen. It is CLEARLY not set at the proper angle and that is for a reason, it wasn't used. I treated this more as a forming operation and just controlled the depth of cut via the cross slide. I took things very slowly with 0.1mm depth of cuts and cutting oil. While this is not what you would do in a job shop as it takes some time to get to 2.1mm depth that eventually lead to a nice screw engagement it did work with no noticable chatter on the sides of the thread and nothing I could hear.
Given this was a through hole I was able to use 130 rpm no problems and could probably have gone to ~200. The lathe manual states not to exceed 240rpm when threading to avoid excessive stresses on the leadscrew/half-nut.
Anyway, thought that clarification was probably in order.
More progress on constructing the replacement horizontal leadscrew nut.
Pics 1 and 2 show the prep work on the cast iron round into a rectangle of suitable size. I then drilled a couple of reference points to support setup in the mill.
Pic 3 shows setting up the offset using an alignment bar and DTI.
Pic 4 is after a LOT carefull threading. We have a finished 6tpi acme thread. It's perhaps not as good a fit as I might like but it doesn't seem to have much if any slope down the axis of travel.
Finally finished the leadscrew nut today. After a test fit I discovered there was no value to be gained by rounding the end over like the original. I suspect that was done on the original casting to save material. It is not needed for clearance.
Pics attached ...
#1 to #4 show the initial machining results.
#5 shows the relief cut into the new nut
#6 installed and ready to have the table assembly begin. I have installed the table slide and tested things. It runs super smooth. Very happy.