Tag Archives: Scraping

Scraping the night away

I’ve been trying to sort a problem out with the website which means that I can’t upload photos. Hopefully I’ll get it sorted out soon but in the meantime I’ll just have to do without.

I was brought up with Smart and Brown lathes; my dad has had a Model A for around 50 years and a 1024 VSL for around 20 years. It wasn’t therefore a huge decision what I would look for when I started to put my workshop together a few years ago. The lathe I bought (unseen off ebay) was a Model M Mk2 which was a very nice 4″ swing tool-room lathe from the late 1940’s to the end of the 1950’s.

It looks better blurred...
It looks better blurred…

It was in a pretty poor state and I think it was a long time since it was a cossetted tool-room machine. Undoubtedly shifted to some unswept corner of the maintenance shop to turn spacers on. I made several other posts about the assessment and strip-down but the most significant matter was the slide-way wear. There was 0.010″ over the length which is quite a lot!
I had wondered about grinding and looked into the costs, but it didn’t seem to be a perfect solution. True it would be a lot quicker than scraping but I could see the possibility of knock-on problems. I wanted to keep the original position of the head, which provided the correct clearance arrangements with the feed drive gears at the rear. One grinder I spoke to suggested that they had ‘shaved’ gears to get over this problem. It just didn’t seem like the right answer. Whatever I did I was going to have to re-establish the original height of the saddle once the work had been completed to ensure that the half nuts still centered on the lead-screw, the feed shaft within the apron, and the main traverse gears had the correct clearance with the rack.
So, to cut a long story short, I decided to scrape the slide-ways using a hardened rail sitting on part of the original head location face and the end of the tail-stock slide as a guide. With a clock stand moving along that whilst clocking the front way, I was not only able to see the initial wear but it gave me a basis from which I could start the work, so that I could start to scrape the worst of it out and establish a reasonable state of parallelism before moving to the next stage.
Months of intermittent scraping have followed. A bit here, a bit there. A few weeks ago, I had arrived at the point of being within 0.001″ over the slide-way according to the clock and so I went to blueing the rail and using it directly on the slide-way to establish a better flatness.
Getting there...
Getting there…
Still further hours but at last the front slide is now ‘good enough’ to sit the rail on to start to do the opposite way. There’s a lot of work to come and this is why I haven’t tried to finish the front slide perfectly. When the rear slide is done, then I’ll use a precision level on my datum faces (under the head) to set the bed horizontal and then use some ground V blocks which span the two slide-ways to establish not only the angular alignment to the head face but to ensure, using blue under the v blocks, that the alignment is achieved with faces on the same plane, not just parallel. It’s almost inevitable that after I’ve scraped the rear way, that the two faces will be parallel but not on the same plane. The process to align will mean that at least one of the ways will have to be completely re-scraped again.
Anyway, months of intermittent work ahead but the first stage is complete.