The 918 that did me well for over 20 years
6" Burrell Gold Medal TractorWorkshop Upgrade |
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I have decided to upgrade my workshop so that I can machine most of the larger parts myself. Like my choice of project the upgrade has many twist and turns.
For some time I had been planning to upgrade my lathe. My existing lathe was an early 918 (circa 1986) that has done me well. It was good for work less than 1" diameter and with care could turn diameters up around 4". Beyond 4 inches it became difficult as the lathe tended to stall when a hard spot was encountered.
I wanted digital readout on my lathe and didn't want to repeat the mistake I made with my mill of fitting digital scales and then deciding I should have upgraded the mill first. At around £500 to cost of fitting a DRO is a sizable fraction of the value of a lathe or mill and as the scales are unlikely to fit the next machine would be wasted.
This is where the story takes a big detour. My choice of
machines was still restricted by the need to accommodate them in my
indoor centrally heated workshop. The problem is that while
this is on the lower ground floor on my house, access from the outside
is up some awkward steps, and it has a floor suspended on beams.
My choice was therefor limited in two ways. Firstly a machine needed to either be small enough to get in in one piece or be easily split into smaller pieces. The second and more sever restriction was that I did not want to overload the suspended concrete floor. I could not decide for sure what maximum load it would take but decided that it would not be sensible to load it with the likes of a 1 ton Bridgeport.
Inevitably my attention turned towards far eastern lathes as they offer the best weight to capacity ratio. Here I was making a tremendous compromise as large work needs a sturdy lathe and making a lathe light detracts from its rigidity. I discounted what I call the toy lathes which look like a little lathe on stilts. I was attracted towards the Warco BH600 and decided to pay them a visit. I asked to see the lathe operating and all looked good in the lower speeds. As this would be my only lathe I needed to see it run at its top speed of 1200 rpm. Two things were immediately apparent. Firstly how difficult it was to change speed, particularly if accessed from the rear was restricted and secondly it was very noisy.When I made it clear the BH600 was too noisy I was shown the VS1232 Variable Speed Lathe. This was impressively quite due to it variable speed. Even though I could play with the lathe under power I was not permitted to try the lathe in anger on a lump of cast iron I had brought for the purpose. I was told the lathe did 20 to 2000 rpm in one continuous range controlled by the knob on the front. This implied the motor was effectively direct drive to the mandrel and without a gearbox I could not see how it could possibly develop enough torque to satisfactorily machine up to its 17" gap capacity. As I could get no satisfactory answers to questions relating to the lathe torque at low speed i decided not to buy the VS1232 without answers to this vital question. My best guess is a lathe with this type of drive has a constant torque irrespective of speed selected. Thus unlike a lathe driven through a gearbox the available torque does not increase as slower speeds are selected.
In the end I ruled this lathe out on the grounds of weight as I decided not to chance my luck with its 1/2 tonne weight on my suspended floor. My plans to get a new lathe were in disarray as I was left with no suitable candidates.
After some time I decided to look again at the WM-280V-F Variable Speed Lathe. I initially ruled this lathe out as I did not like the method used to mount the chuck. The chuck backplate is mounted to the mandrel by means of 3 bolts which have to be undone and the chuck prised off. The big attraction of this lathe to me was the weight, at 190Kg as I felt it would be OK on my suspended floor. The top speed of 2000 rpm would be excellent for smaller stuff and its 11" swing large enough for most of the GMT.
I received my VM-280 in November 2008. Initially I was very happy but then I became suspicious that the bed had not been hardened and had been left soft. When I tested the tailstock end of the lathe with and hardened steel scriber I discovered that I could easily scratch it. I spoke to the suppliers technical department who expressed surprise that I could scratch the bed with a scriber. Without too much difficulty it was agreed that my lathe would be replaced.
Over the next few days I spoke to various contacts to try and gauge how hard a lathe bed should be. My brother who has a VM180 was unable to mark his bed using a scriber. All trace of the attempt was easily polished off with a cloth. Over the next few weeks several model engineers I know tired a similar test on their lathes. Some could scratch there hardened bed and some could not! With hind sight at this point I should have called a halt to the exchange of my lathe.
It took some time but just before Christmas my VM280 was exchanged. I installed the first with the help of two retired club members. More accurately I watched as they expertly manoeuvred the lathe up and around my steps and into the workshop and then onto the stand. I wish I could say the same for the "professional" installation of the second. I had planed to tests the replacement prior to installation but given the difficulty of the swap my focus was elsewhere and it was not until I was alone that I tested the bed. I cried. The bed of the replacement VM280 was identical to the first.
My spirits were revived when I received some wise words penned by Kevin
passed to me by Jason. Basically a lathe bed should not be
that hard. This is also confirmed by the tests performed by
other. Various makes of lathes with induction hardened bed
can be scratched with a hardened steel scriber. This is not
true in all cases some can't be scratched. Thinking back to
when I scratch tested the lathe (something I don't intend to repeat!)
the scriber got under the hardened surface which it then lifted from
underneath. I wish I had had some wise council before going
though the hassle of exchanging the lathe!
I now set about fitting digital but that is a story in itself and deserves a separate write up. In the process of fitting the scale I had to dismantle the carriage and lead screw. On reassembly I encountered a number of problems. In several places when I did up the screws moving parts jammed. It would seem that were there were issue with fit the screws had been left slack to get a functioning lathe. In the end I spent more time fettling the lathe than fitting the scales. Now that I have rebuilt the lathe and fitted digital scales it is performing well and I am relatively happy.
My existing milling machine is Sharp II Universal Milling machine. Within its capacity I have found the Sharp to be a good machine. For the work I do I have often found capacity a problem but greatly improved this by fitting a raising block under the head.
A few years ago, at great expense, I fitted digital scales to all 3 axis and greatly transformed the usefulness of the machine. I fitted professional scales which have never let me down. I found this has taken the stress out of machining as I always know where the tool is. The readout has a number of clever functions, such as radius milling, which have proved very useful. I also find the feature to set up the 200 zeros invaluable on complex jobs as I set zeros at each critical position to use as targets and do a dry run to check positions before winding in the Z.
I realised that for the GMT I would need a bigger mill but what? I though of getting a far eastern mill from the X3 stable but did not want to sacrifice the rigidity of the Sharp. The obvious choice would be a Bridgeport but they are big and heavy.
At this point is is worth mentioning that my property is severely restricted in terms of space. I have included a picture of the old Lizard lifeboat station opposite as the house might as well be at the top of a lifeboat slipway. Other that a steeply sloping narrow drive I have no usable outside space. The house is split over 4 floors, the bottom of which accommodates the garage and my workshop. Using another coastal analogy it is like living in a light house. We won't move as we have views over the estuary and countryside beyond so I have to make the most of what I have got.
I seriously though about having a Bridgeport in the house but the investigation of this started a chain of events that would transform the way I use my garage.
Once I realised that having a Bridgeport in the house was a non starter
I looked at housing the Bridgeport in a shed but because of my outside
space constraints this would have to be offside at a friends house.
Shortly after this my thinking was transformed. At present
my garage is used to store my trailer used to transport my 4" Burrell.
If I could get the trailer out of the garage there would be room
for a Bridgeport and more. Eventually I planned to get a van to
transport the 6" GMT and by bringing this purchase forwardI could use this for the 4" Burrell and dispose of the trailer.
I don't like buying though online auction sites so I went to my local dealer Home and Workshop Machinery. In contrast to the welcome I received at Fisher Lane, I was given a warm welcome and offered a cup of tea as I walked though the door. I new they had a suitable Bridgeport in stock and it was not long before I was piling its table with the accessories for the serious work ahead. While the mill was not cosmetically perfect it was clear it was in better state of adjustment to do immediate work than many a new machine. Each time I have purchased a new machine I have spent days adjusting and fettling. This machine was run in and ready to go.
It is surprising how much extra I spent on accessories.
By the time VAT and delivery were added somehow the price
doubled. Well there is no point having a Bridgeport If I cant use
it. In a rash moment I went back before the Bridgeport was delivered to look at lathes.
more.......
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