Beginner lathe

[Pete.]

I think it's more because it takes an understanding of what makes a machine 'straight' to appreciate how precisely it should be re-mounted. Ding the edge of a foot pad just a thou or two and you wouldn't even notice, but then fix it back down onto it's base and you'll put a twist in the bed and start turning tapered parts.

 

[MrFluffy]

Plus the harrison was made for schools and rough job shops etc, its unlikely they would have been set up with a machinists level properly end to end on prepared pads. With the welded stand you could just wheel one into its new home, wind down the jacking screws to get it near enough then hook it up and go. The l5 was never a toolroom lathe, it was more of a robust day to day working tool.
Also, even the best cast iron will creep over time if left uneven and slowly twist itself out of error, the steel reinforced box structure of the original stand is less prone to that. As a result if you disturb the bed to the stand as its carefully shimmed and settled to by the factory, you risk deforming the bed to suit the new position over time when you bolt it down tight.
I had to cut the cabinet up from my first l5, the construction was "robust", 20mm plate in places, 10mm in others and something like 4mm for the majority of it. It's all been repurposed, some of it is my crank jig, some the side plates holding the axle on my chassis dyno build etc. Very very solid item.

 

[MattF]

Cheers chaps. That's finally cleared up their probable thinking on that front somewhat.

 

[tombardier]

some more picks from ebay

http://www.ebay.co.uk/itm/251541711851?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
http://www.ebay.co.uk/itm/181426045096?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

 

[tombardier]

Althought this is what I'd _really_ like!

http://www.ebay.co.uk/itm/201047316670?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648

 

[MattF]

The problem with those barring that second one, IMHO, is that those seem to be one hell of a lot of lathe but with seriously reduced centre distance due to stupidly large headstocks. On a massive machine, all well and good, but surely the headstock doesn't need to be that large on a comparatively small, in relation to headstock size, machine. That's like saying that you have practically every speed and thread pitch available, but you are seriously limited as to what you can turn on it, (unless they have excessively large spindle bores to boot?).

 

[MrFluffy]

Its a toolroom precision lathe, it uses the mass of the headstock to stabilize the spindle to earn the precision bit of its moniker. If it didnt have a massive headstock and the rigidity that comes along with it, it'd be a cooking engine lathe class machine instead.

 

[Hopefuldave]

The 'seriously reduced' Centre distance for.the between centres length is.because they're toolroom lathes, a longer distance between the spindle.bearings adds to the concentricity and accuracy of the spindle (assuming a hefty spindle) and helps 'em hold ten-thousandth on diameter, along with the mass and rigidity of the machine overall - my Holbrook C13 has about the same capacity as a Colchester student/master, but is probably twice the weight (a bit over 2 tons) and is about 2ft between spindle bearings - ok it needed some work (particularly providing 415 3-phase from 240 for the oddball 3-speed motor, hacked VFD takes care of that), but cost me less than a Chinese mini-lathe, has metric and Imperial screw cutting, fingertip power feeds with micrometer stops (with gauge trays for accurate measurements), taper attachment etc. and is a joy to use, silky smooth, you can balance a 2p coin on the toolpost while taking hefty cuts at 2000 rpm...

The model C for ;instance has the spindle drive (5 v-belts from the 2-speed clutch/brake box in the base) carried on its own bearings separate from the spindle (to eliminate vibration), helical back-gear (to eliminate 'gear marking'), pumped oil to the headstock...

Holbrooks get overlooked because nobody's heard of 'em, but they used to say the Colchester on the shop floor.cost as much as the boss's car, the Holbrook in the toolroom cost as much as his house...

 

[MrFluffy]

Here's a more extreme example imho, look at the sheer mass in this around the headstock and toolpost compared to its distance between centres. Its a very popular french brand, les innovations mechanique, though this poor example looks like its spent time in a chicken shed (its for sale for 1200e on leboncoin like this).
http://www.leboncoin.fr/equipements_industriels/663041219.htm?ca=14_s

 

[MattF]

Cheers for the explanation chaps. Just thought it was one of those classic examples of a designer not quite thinking things through, again.

 

[Rig Pig]

Google DSG for a look at what a real lathe!

 

[Pete.]

I recently machined a combustion chamber for a guy's 2-stroke motor where it had been battered by FOD in the engine. Stuck it in a 4-jaw in my Denford lathe and it shook the machine violently even at a lowly 150rpm. Took the chuck out of the Denford and put it in my Monarch (same swing but 1500kg instead of 400-ish). Didn't even tremble.

 

[tombardier]

Another cheapy

http://www.model-engineer.co.uk/classifieds/view_ad.asp?ad=9549

 

[MattF]

Definitely more along the lines of a beginner lathe. The mention of a missing backgear does tend to make one wonder how that has been treat in the past though. It's indicative of slightly less than subtle use, and if they shredded the backgear, (hence the likely reason for its removal), what damage did it do to the spindle etc.

I recently machined a combustion chamber for a guy's 2-stroke motor where it had been battered by FOD in the engine. Stuck it in a 4-jaw in my Denford lathe and it shook the machine violently even at a lowly 150rpm. Took the chuck out of the Denford and put it in my Monarch (same swing but 1500kg instead of 400-ish). Didn't even tremble.

The sheer mass has other uses too then. I'd never paid much attention to toolroom lathe design until the posts above. I'd honestly never appreciated how much difference there was until those differences were mentioned. On a tangent though, why didn't you fix and counterbalance that combustion chamber on the faceplate instead of just chucking it up?

 

[Pete.]

The sheer mass has other uses too then. I'd never paid much attention to toolroom lathe design until the posts above. I'd honestly never appreciated how much difference there was until those differences were mentioned. On a tangent though, why didn't you fix and counterbalance that combustion chamber on the faceplate instead of just chucking it up?

I had to clock it in by screwing the spark plug in backwards, and the dome shape didn't lend itself well to faceplate mount. As it is, I had to go very gently with the cuts as I only had a tenacious grip.

Head, as trashed:


Spark plug to clock it in:



Quick-and-dirt radius turner for the dome:



Repaired head on left, new head on right:



Ironically, the guy fitted the new head and couldn't get the gasket to seal, so ended up using the one I repaired

 

[MattF]

Very nice work there Pete. Like the simplicity of that concave turning tool too. How sturdy was that during use?

 

[Pete.]

Smooth as silk. I only took small cuts but there was no digging in or chatter. Cast ally usually is quite easy to turn though.

 

[MattF]

Looks like it would be quite easy to make a more permanent version of that whilst retaining the simplicity. It's a lot more tempting than some of the overkill designs you tend to see. Yet another thing added to my list of future things to make.

 

[Pete.]

Very easy. Just put an insert on the end of some flat bar and Make a pivot with a slot milled in it for the bar to slide in. A simple clamp and you can adjust for any radius you care for.

 

[MattF]

Cheers Pete. Sounds like the hardest part of making that assembly is the slot, (for those of us without mills or shapers ).