Lathes (Updated 27th January 2017)

Colchester Student Mk.2

Why I bought this, I have absolutely no idea :D It's not as though my Boxford is exactly overworked or incapable of doing the odd jobs I use it for, but I found this Colchester for sale not far from my home so... here it is! It was absolutely filthy, having apparently not been cleaned in several years. The swarf on the bed was inches deep and the splashback required cleaning with paraffin, a scraper and wire wool. It's missing the front electrical panel and the cover panel for the motor compartment (having been converted to single-phase by the previous owner), however the original main motor and suds pump are present, as are fixed and travelling steadies, faceplate and both 3- and 4-jaw chucks. The bed gap piece is installed and even the big spanner for the spindle locking ring is in its storage clips! The bed carries the 'induction hardened' label (and seems to have minimal wear, though it may have been re-ground), the cross- and top-slide handles are the optional chrome items and the micrometer dials have both Imperial and Metric graduations which 'push-pull' under an alloy viewing window. The only really useful thing missing was the thread dial indicator (but see below!). Here's a 'before and after' comparison:

Dual-reading Metric/Imperial feedscrew dials:

I don't think this 4-jaw has seen any serious action...

Right, so some months on when I'd finally got the Student positioned where I wanted it and in some condition as to be usable (oil in the headstock, always a good idea...) I did a few trial cuts and found a strange 'patterning' appearing on turned surfaces, irrespective of spindle speed, feeding manually or under power etc. At first I though the twin drive belts might be 'fighting' each other (one's a bit looser than the other) so I removed one and the marks were still there. I put a DTI on the chuck backplate, chucked a length of 1" steel bar and tried heaving the spindle around on its bearings but without proving any slack or wear that way. Finally I reinstalled the lathe's original 3-phase motor and bingo, mark-free finish. Phew. For a minute there I thought it was going to get expensive. All the original electrical control gear is missing from the Colchester so as a temporary measure I found a spare 3-phase DOL starter in a box of bits and screwed it to the wall next to the lathe. It's only a 3A-rated unit but I won't be taking massive cuts so should stay well within the 5.5A or so that the motor's rated at.

One delight of lathework that I had forgotten since I bought the AUD and VSL was the need to individually shim the cutting tool to correct height. The Colchester has its standard 4-way revolving toolpost which of course needs the tools shimming and that was one of the things that kept me from using it for so long - I could never seem to build a shim stack of the correct thickness; however, much as I'd like a quick-change post for it, the prices for QCTPs of this size are just ludicrous!

I did encounter one somewhat serious issue: when taking a moderately heavy cut, the toolpost could be seen to be rocking! Close examination showed it to be the topslide moving on its base (the part with the rotation degree scale engraved on it) despite all the screws being tight. Oh, they were tight all right: someone had got so enthusiastic with the threadlock that I had to drill them all out. Turned out that surplus threadlock had been forced into the join between the slide and base, holding them apart. With this thin film shaved off and the mating faces polished up, the slide was refitted with new screws and just a modicum of threadlock... at which point much better results were obtained. I don't know whether this cockup was down to the previous owner or the engineering company that claimed to have 'reconditioned' the lathe but clearly whoever's been using it must have been undiscerning about the quality of his work. By way of proof that I 'needed' a bigger lathe than the Boxford, I've used the Colchester to skim some car brake discs that wouldn't fit onto the VSL!

Update 130214:

That temporary DOL starter screwed to the wall was making the place look untidy, as were the gaping holes front and rear where the motor cover and electrical plate were absent. I'd tried emailing Colspares without success so I decided to make my own electrical panel and create some sort of vented sheet to close off the rear. A rummage in dark cupboards turned up a couple of ready-made louvred panels that I'd removed from an outdoor cabinet housing a customer's industrial oil cooler a few years back. The cooler was overheating so I'd replaced the louvres with a big cooling fan and decided the louvres were too useful to scrap! The louvred plate wasn't large enough to cover the lathe's opening but a bit of careful measuring showed that if I attached it to a sheet of alloy, the offcut from the centre of the alloy would be large enough to cover the opening in the front of the lathe and provide the basis for my electrical panel.

The louvred panel looks odd because it's on 'inside-out'; unfortunately I couldn't mount it the correct way around as the motor is in the way!

The original electrical components used by Colchester are long-since obsolete of course, but modern equivalents are available - and quite cheaply as well, thanks to a certain online auction site! I started off by designing a control circuit as I would if it was a for a job at work but it was getting over-complicated with transformers, 24V power supplies and so on so I elected to stick as closely as possible to the original design. This meant using contactors with 415V coils - and as it happens they sell for less than low-voltage items; largely I guess due to the move away from switching high voltages directly in machinery. Some control switches were needed as well but the usual Telemecanique items I work with are only rated for 240V. However Telemec's older switches were designed to work up to 600V and - oh look, some for sale cheaply on Ebay! A couple of snipe bids netted some motor overload units for the contactors and a cheeky 'best offer' got me a panel lamp with in-built 415V step-down transformer [Edit: although it went pop a few months later :( ]. A handful of DIN rail terminals and a 3-phase circuit breaker completed the ensemble which was duly mounted to the alloy plate and wired-up. Total expenditure less than thirty quid. I wired the lathe's suds pump in at the same time; the cabinet interlock switches were left disconnected, however. I don't have a key for the tool drawer (which is interlocked to prevent unauthorised use in a workplace environment) and the only other switch is on the headstock end cover which should rarely need removing anyway. Here's my control circuit (note it provides the necessary 'no-volt release' function for safety):-

...and it looks like this when assembled:

 

I've since bagged a couple of brand-new 415V primary, 9-0-9V secondary transformers that will be ideal for driving a low-voltage worklight - the Student has its original lamp which is currently (no pun intended!) configured for 240V which necessitates it using a 3-pin socket in the workshop; it'd make more sense to tap off the 3-phase since the lathe is using it anyway. An LED lamp will be less susceptible to breakage as well as being brighter for my ageing eyes and costing less to run (though of course anyone who fabricates that sort of argument is conveniently overlooking the cost of converting the thing to start with...!). I've also installed the obligatory Loc-Line flexi hose to the coolant feed, as well as replacing the hardened, brittle plastic pipe that brings the coolant up from the pump. So this 44-year-old Student has a new lease of life, even if its rather-older-than-44 owner doesn't ;o)

Update 270315:

I'd been on the lookout ever since I got the Student for a Thread Dial Indicator but either someone would outbid me or I thought the asking price was ludicrous - plus most of them seemed to be for the Mk1 Student rather than the Mk2. I had a tip-off that a machine tool company up in Tyneside was breaking two Mk2s so I called them up but both lathes had either been sold complete or were picked clean. Based on the information on www.lathes.co.uk I figured that Colchester had probably not altered the fundamental design of the TDI between the models so I decided to take a punt on a TDI for a Mk1. A bold bid on Ebay netted one and, with bated breath I bolted it to the Student's carriage (the knurled nut was already there) and hit the start button. I needn't have worried: sure enough there's no operational difference and the TDI works fine. Its gear is in good shape so with the muck of decades cleaned off it is ready for action!

Yes, I know it's the wrong colour: you lot want the moon on a bloody stick sometimes! :D

Incidentally, if you wonder which marks to choose when threading and are puzzled as to why the lathe has no data plate to help you, the user manual does have the information hidden away in the chapter on thread-cutting... but blink and you'd miss it! Essentially, for even-numbered Imperial pitches (e.g. 12 tpi) you can engage the leadnut on any mark. For odd-number pitches (e.g. 13tpi) engage only on numbered marks and for fractional pitches (e.g. 7 and 3/4 tpi) engage only on number 1 mark. For Metric pitches you can't use the TDI but instead have to leave the leadnut engaged and run the lathe backwards to return to the start of the cut.

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Boxford VSL500

My first machine tool was a 1920s lathe by Mellor, a long-gone company that was based in Huddersfield. That was replaced by a slightly more recent version of the same thing, then in 2004 I decided to take the plunge and bring my workshop kicking and screaming into at least the 1960s :) - so I bought a 1972 Boxford AUD. I'd had it less than a year when I found myself drooling over a Boxford VSL500 on - you guessed it - Ebay. The seller had a number of Boxfords that he'd bought from a school in Retford; one he'd kept for himself and the rest he was selling on to recoup the outlay of having been persuaded to buy them as a job lot! In the event he did very nicely out of it; the first of two VSLs sold for £1800 which is about top whack for an absolutely mint, hardly used example. These were good, but not THAT good. I knew I could sell my AUD for more or less what I'd paid - I'd put a reserve on to make sure - so I thought I'd chance my arm (by now suffering from lathe envy!) and put in a bid on the second VSL. To my surprise I 'won' the bidding (at less than half the price of the first VSL) and made the trip to Retford to collect my new toy. As it's an ex-school machine (the bed has a casting date of December 1977) it has of course done no real work, although several of the controls were seized, having evidently been neither used nor lubricated. The gearbox in particular was nigh-on impossible to operate until I'd spent a couple of hours squirting oil over the moving parts and working the levers. Fortunately the bedways, leadscrews etc. had been kept at least splash-lubed by the cutting oil and the spindle bearings are sealed-for-life so no issues there. The VSL is often regarded as the dog's-danglies of the Boxford non-CNC range. As well as having increased spindle bore it has the 'L00' fitting on the spindle nose which gives more positive location for chucks etc.; T-slots in the cross-slide to allow use as a milling table; and the pièce de resistance, continuously-variable speed control of the spindle. This was pre-inverter drive days of course, so they achieved it by having a system of expanding and contracting pulleys that are controlled by a dial on the front of the machine. Winding the dial clockwise forces the pulleys to change diameter so the ratio between them changes and the spindle speeds up. The whole thing is propelled by an enormous 3-phase 415v motor. Changing that for a single-phase would, whilst not impossible, be an engineering challenge given the arrangement of the speed-change mechanism (as well as sacrilege!) so I opted to leave it in and fit an inverter. Now most inverters take in 240v from a wall socket and output 3-phase... but at 240v. This means rewiring the motor windings to suit (not difficult) with an attendant reduction in the power of the motor. I turned to Ebay... and found a single-phase in, 3-phase at 415v out inverter. It wasn't cheap but by heck it's good. It was only the second time I'd ever worked with an inverter but I quickly realised that if I reinstalled the 3-phase motor to my Perrin mill, I could run that from the same inverter. A box on the wall now houses the inverter along with sundry contactors etc. to switch between the two. I still have the 3-phase motor and coolant pump that I removed when I converted my Bridgeport mill to single-phase, so when I get bored I might swap them back and have the 1ES running from the inverter as well! Anyway, the VSL:

Note DRO for the Perrin at right; it's magnetic so can be positioned to suit the job. You can see the size of the VSL's motor in the following pic! The double-ended shaft allowed factory fitment of an electromagnetic spindle brake, not fitted to this machine as it was apparently an expensive option to have on a school lathe! Unfortunately it does make the VSL slightly longer than was my AUD and I had to rearrange a few things to make it fit the workshop. 

 

I've found that chucks etc. with the L00 fitting don't come along on Ebay very often. However a year after I bought the VSL, I happened upon the same Ebay seller listing a 3-jaw chuck. I got that for less than I thought it'd fetch (less than the seller hoped for too!)... the irony being that it may even be the original one for my lathe as he had several of them to start with and even admitted that some more tooling 'happened to turn up'. Hmmm. Anyway, a week or so later I found an ex-Harrison L00 faceplate for sale about 40 miles from me; I 'won' that auction and when I went to collect it the seller produced an L00 catchplate as well. It was a bit rusty so I haggled and got it for an additional few pounds. A couple of years previously I'd been given a brand-new 3-jaw 'Bison' chuck that had a plain-bore backplate fitted. Of course it wouldn't fit either my old Mellor or AUD so had languished in a cupboard, gathering rust (to my annoyance). I cleaned it up, machined a register on the 'new' catchplate to take it and to my surprise it works AND is accurate! Funny how these things work out, and proof that you should never throw anything away. The chuck-on-a-catchplate can be seen in the photo of the lathe above.

Metrology Equipment

If you buy a lathe you soon realise that you can't just rely on the handwheel dials to tell you how much metal has been removed, you need something a bit more accurate. A micrometer, let's say, or at the very least an Aldi digital caliper :D Yeah, so did I, sorry. Anyway, ignoring all the cheap stuff that's around now, there's a mass of old micrometers etc. for sale at auction sites and so on and a lot of it can be had for buttons... especially if it's Imperial (i.e. measures in inches rather than millimetres). Over the years (starting with a Kennedy dial caliper) I've picked up a few such instruments (sometimes for free!). Of course the difficulty is in knowing whether or how accurate old kit might be once its had years of use and abuse in industry; luckily for me the company I work for set up an in-house Metrology lab so I have access to a range of reference standards by which I can check that my own instruments are spot on - or at any rate, good enough for my purposes. As it happens a biking mate works in the same industry and a few months ago was tasked with clearing out some old stores. In some long-locked cabinets he found an entire car boot-full of micrometers, calipers, DTIs and other kit that he was told he could have as it was all past any use to his company! Having asked for help identifying the instruments he sold nearly all of them on Ebay except for a couple of things that he gave me as I'd expressed an interest. In particular were two blade micrometers and a partial set of Imperial gauge blocks which are of course the basic system for calibrating Metrology instruments. I used the company's reference set of (UKAS-traceable!) gauge blocks and micrometers with 5 decimal place resolution to create a table of dimensions for my own blocks and suffice to say they are well within the tolerances I'm ever likely to need. Spanning 0.1001" to 4", even allowing for the missing blocks there are enough to create useful reference points.

Anyway, the instruments themselves; of course the de facto standard is set by Mitutoyo these days. Once upon a time Moore & Wright were high-end makers although their standing seems to be a bit less these days. Even so their older kit can still be perfectly serviceable and accounts for most of my instruments:

M&W 0-2", 3-4", 4-5" and 5-6" Micrometers

M&W 25-50mm and 75-100mm Micrometers

M&W 0-6" Depth Micrometer

M&W Combination Gauge

M&W Protractor

Mitutoyo 1-2 " Micrometer

Mitutoyo 0-25mm Blade Micrometer

Mitutoyo Series 500 Digimatic Caliper 300mm

Mitutoyo 209 Dial Caliper (for hole diameter etc.)

Assorted Mitutoyo & Starrett DTIs

Draper 0-1 " Blade Micrometer

Unbranded lever-action DTI

Kennedy Dial Caliper

Assorted Chinese Digital Calipers

Matrix Gauge Block (partial) set

Assorted Mitutoyo Gauge Blocks to 20mm

Assorted Micrometer setting pieces to 5"

Pair of precision lathe TIR setting pieces

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