Absolute beast. When I first moved down to Penrith from Glasgow in 1985 Penrith Steam Museum was either closed or was in the process of closing and it had some old machinery in it.
Temporarily sited to get it up and running Judging by the paint not being totally worn off under the chuck,this lathe hasn’t seen much use So connected up, let’s unleash the 12,5hp shall we? Absolutely dire. Doesn’t have the power to pull the skin off rice pudding. 0,5mm depth of cut on a 50mm bar of stainless steel and the spindle slows down. A pissy little Myford lathe with 3/4hp would do better. Something is seriously wrong 🤔
Assuming nobody could have used the lathe like this when it was used last 19 years ago,got me thinking. What could have gone wrong by itself?The three phase motor wasn’t trying to run on two phases,as that would be easy to hear. But, I did wonder if it possibly wasn’t switching from star to delta? Contactor out Stripped and cleaned. Like new inside,again backing up the theory it’s hardly been used. The problem persisted. This lathe has three wet clutch packs which are very small for the size of the lathe. Having stood for so long, these clutches could be totally dry. so next port of call, the gearbox. Top cover off Clutches accessible from the back. Duly cleaned with brake cleaner and oiled. Gearbox oil drained and refilled, all 45 litres of it 😳Gearbox oil pump checked,plenty of oil flow to the clutches and everywhere else… And… the problem persisted….🤬
As they say,” assumptions are the mother of all feck ups”. Yep, I will agree with that. Whilst I had assumed something had gone wrong with the lathe by standing so long,I was totally on the wrong track. Assuming somebody with a lathe this big would know how to use and maintain it,was also me on the wrong track. It hadn’t vandalised itself gradually due to non use. The issue had been there 19 years ago when it was last used. All it turned out to be in the end was clutch adjustments. I adjusted up the forward, reverse and brake clutches and full,power returned
First paying job was a set of 700mm tank tensioner wheels that needed a skim Which it coped with ok,but it did highlight other issues….
One thing I had noticed early on, was the chuck was knackered. Pretty strange in that it looked almost brand new,and the jaws hadn’t been machined into or butchered. Given the fact that the clutches hadn’t ever been adjusted,it’s safe to say the condition the chuck was in was directly related to the Neanderthal who had been using it. Consistently over tightening a chuck leads to the jaws becoming bell mouthed. Given I had seen a piece of scaffold pipe next to the chuck key,it’s pretty evident it had been used to over tighten the chuck. The problem with a chuck this size,is that even if you are machining right next to the chuck,it’s the equivalent of having it stick out two inches and it’s not steady at all. The bar pushes away from the tool, you get a finish like a ploughed field and inconsistent depth of cut. So what to do?🤔
A new , decent brand chuck this size will set you back £2k easily. Given the excellent condition of the chuck otherwise, I decided to take a stab at reconditioning it. The main issue you have,is if you want to remachine the jaws with any degree of accuracy, you need to load the jaws up to get rid of the free play in the chuck. Herein lies the problem, as you need to load the jaws the same way they would be loaded as if you were clamping a bar. So stick a bit of round bar in the chuck and tighten it and it soon becomes apparent that the bar is now in contact with the faces of the jaws you need to remachine😕
I’ve seen various bodges people have used to do this from machining a groove into the face of the jaws,tightening a hollow ring into the groove and then grinding through the middle , to drilling holes,inserting pegs and clamping a hollow ring with the pegs. As said,these are bodges,you get by with what you have. I had another idea though….
First of all I clamped a small bar wrapped in paper,switched off Neanderthal mode and tightened the chuck with a bit of mechanical sympathy Definitely bell mouthed, darker witness marks at the back, lighter towards the front of the jaws. The tighter you tighten the chuck, the worse it gets.
So, a bit of measuring and drawing on the computer,and I started making a jig Jig complete and ready to use
And securely clamped in the chuck. This was the only way I could see you could load the jaws up in the required direction and still be able to machine the face of the jaws that needed remachining
