Coolant drainage on a Colchester Student lathe (square top)

[mhrvol]

This is a plea for help/advice on the above subject. Please let me explain.

1) I have owned the above lathe for well over 20 years and have never regretted buying it from an apprentice-training workshop which had been closed. It is accurate (even in my hands) and has proved excellent for turning jobs that are too large for my Boxford machine.

2) Being neurotic about rust in my (home) workshop, after going to considerable lengths to reduce  atmospheric moisture as far as practicable (incorporating vapour barriers, installing a de-humidifier  etc) I early-on made the complementary decision  to use cutting oil rather than the more common water-soluble oil coolant (aka “suds”). The reason for this choice is that when I first set up my workshop (to build live-steam models) and long before I bought the Colchester, I read a letter in Model Engineer about coolant in which the writer indicated  that, although the proponents  of water-soluble oils claimed otherwise, the oil and the water do in fact separate over time and that this is undesirable in an amateur’s workshop because the water then lies about the machine and can hence cause rust.

3) The problem I have with the Colchester is that the coolant tray (which is integral to the machine) is essentially flat (yes, really) and as a consequence liquid will not flow towards  the drain-hole provided in the tray which should provide the means by which the liquid being used to aid cutting drains to the sump below the tray. Worse, the actual drain hole is only about 1/4” below the level of the tray. Worse still, the pipe to the sump is  only about 1” in diameter and so is rather prone to clogging with swarf (when liquid is brushed towards the drain hole in an attempt to rid the tray of the inevitable liquid pool. This, of course, make drainage even more of a difficulty especially as cutting oil is, of course, markedly more viscous than suds.Yet worse still, the drain hole is  placed directly under the actual lathe bed so that it is not possible to get a sufficiently rigid “drain rod” down the hole in order to poke the swarf clogging the drainage-pipe down into the sump.

4) I feel that I cannot possibly be the first to have encountered these difficulties (which, it could reasonably be argued, are of my own making to a certain extent)  and so would be grateful for any suggestions/solutions as to how I might circumvent them.

5) I would like to thank in advance any who may feel inclined to respond to this request for help.

[simplyloco]

Hi there. Forgive the ravings of an old git, but I don't understand why you have a problem with swarf in the drain pipe. There should be a -usually slightly domed- screen at the coolant exit, thus preventing the ingress of swarf. Secondly, having used a number of Colchester and similar sized machines, the 'flood' of water based coolant necessary to achieve proper cooling in an industrial environment is sufficient to ensure adequate drainage. I can understand your use of neat oil, but you need quite a lot of it to achieve the above.
May I suggest that you fit a drilled washer and open the tap a little more .
Regards
John

[jem]

I have the same problem with my Chinese lathe, but luckily the tray is removable, so I intend to modify it so that it drains well, would it be possible to fibre glass the bottom of the tray in order to give it a tilt so to drain it, and at the same time incorporate a screen to stop the swarf going down the drain hole? Can you drill another drain in the tray perhaps. The trouble with oil coolant is that it clings to the swarf, and so a lot is waisted, and it is expensive!

Best wishes

Jem

[92220]

Why not just use a spacer under the tailstock end feet, to give a slight slope to the tray, or even between the base of the cabinet and the floor? The fact that the bed is not going to be dead horizontal is not going to make a scrap of difference to the quality of turning achievable.

Bob.

[mhrvol]

Firstly, many thanks to those who have taken the trouble to reply: it really is much appreciated that you have taken the time and made the effort on my behalf. I will try to answer the points raised in the order that they were made.

1) Simplyloco asked why I had not used the dome shaped screen at the drain hole to prevent the ingress of swarf. Very fair point. I did use this initially, but found that it impeded the flow of cutting oil into the drain pipe even further when I (necessarily, because of the lack of any draft in the tray) used a brush to pursuade the oil to move in the direction of the dome and hence the drain hole. This is because the dome shape of the fitment raised the exit holes (that is, those holes in the dome itself) still higher above the level of the tray. I tried to circumvent this by making a removeable plug to fit in the drain hole. The plug had holes drilled in its base to allow the oil to pass through it but these had to be of sufficient diameter to allow the (viscous) oil to flow at a reasonable rate. Unfortunately,, because the pipe to the sump is of such a small diameter (about 1”) , the number of holes to get a reasonable flow rate is limited to about four or five and their size is such that smaller bits of swarf can quite easily pass through them when inadvertently brushed into the plug along with the oil and so can quite quickly block the pipe. I think that Simplyloco is correct in noting that cutting oil is a poorer conductor of heat than suds. I recognised this at the outset, but (probably naively) supposed that this might be offset to some extent by lubricating the swarf as it is sheared from the parent metal by the lathe tool and so reduce the friction heat generated . I do, however, recognise that the bulk of the heat generated in the cutting process will result from the energy required to perform the actual shearing. I would much appreciate it if Simplyloco could expand on his point about a drilled washer and opening the tap as I did not understand this ( my fault , I am certain).

2) I will certainly consider Jem’s point about a fibre glass tray. As I mentioned, the tray is integral to the lathe and is not removeable (or at least, as far as I can ascertain). I tried to make a removeable tray from aluminium sheet suitably shaped to ensure that the oil ended up at the drain hole without the need to use a brush in order to persuade it to move in the direction of the said drain hole. This attempt was, however, frustrated by the shape of the lathe bed. My sheet metal skills are nowhere near good enough to fabricate the required topology.

3) In response to 92220’s point about (I think, but may well have misundersttod the point being made) raising the tailstock feet with respect to the tray, I cannot see a way of doing this as the tray is an integral part of the lathe.



Thanks once again for taking the trouble to respond.

[simplyloco]

To use an old English phrase: "What's your bl**dy name?"
1.    You need to replace the domed screen with a flat drilled washer if you have discarded the original one. That will help matters.
2.    If you increase the pump flow - i.e. open the tap- your coolant should flow through the system without further trouble. You might need to put some more         oil in the tank to achieve this result.
Bob was suggesting that you tilt the lathe slightly to encourage the coolant to go down the hole, but if the hole is in the middle of the bed then...

John

[uuu]

Crazy ideas time:

It sounds drastic, but can you drill a hole in the lathe bed above the drain? Not in the actual ways, of course, but in the web between
them. Then you could rod it through more easily.


Could you make the drain hole much bigger and fit a giant swarf trap underneath - rather in the style of a sink waste - that can be unscrewed and cleared easily.


Block this drain and cut another, bigger, and in a more accessible position.


Wilf

[mhrvol]

Again, many thanks for taking the trouble to respond. As before, I'll reply to the points made in the order in which they were posted.

1) John, I apologise unreservedly:I did not think to give my name as it did not occur to me that anyone would actually want to know. When I have seen contributors address each other by name on this and similar sites, I presumed it was because they actually knew each other personally and sufficiently well to be on first name terms. Please put this omission down to my (markedly) limited knowledge of e-etiquette !

I did retain the domed screen as (I'm ashamed to say) I cannot bear to throw anything away. Which is why my son (also a model engineer but, in addition, a professional toolmaker) , says that he finds my workshop untidy and hence rather difficult to work in. Or at least, that's the gist of what he says to his old  man ... Concerning your suggestion of increasing the pump flow , the only tap on the coolant system is that which regulates the flow of liquid onto the work. I try to keep the flow of oil from this tap as low as possible because otherwise the drainage problem causes the depth of oil in the tray to increase further. It could well be , however, ( and probably does) mean that I have misunderstood the point that you are making. You are correct an your remark about tilting the lathe: the hole is in the middle of the bed and so without direction, most of the oil would , I expect, accumulate at one end.

2) Before I started this thread I, too, had (extremely reluctantly) concluded that the only way to improve matters was to make the drain hole much bigger, locate it in a more easily accessible place and just live with the need to brush oil towards it . Lacking the courage to actually make large holes in the the tray, however, I am grateful for uuu's seeming confirmation of my worst fears of what is probably necessary to rectify this apparent design fault in an otherwise excellent lathe. I am , however, uneasy about it because I worry that the mechanical integrity of the support for the lathe bed might be compromised .

Jeff

[simplyloco]

Jeff
I should have made my point a little more clearly. The surface tension of the oil is much greater than that of an emulsion, therefore a greater depth of oil is needed to overcome this tension and allow the spread of the oil into the hole, where it will disappear before your very eyes!
John

[atgordon]

Quite a long time ago, I worked in a production shop that was using copy lathes to make parts for Hewland gearboxes. We had to use cutting oil as per customer spec, but the oil was too gloopy (my term for high viscosity!) and wouldn't flow well through the coolant systems. The foreman added paraffin to the cutting oil and voila, viscosity reduces somewhat and everything worked just fine.

I've always used cutting oil rather than soluble oil in my workshop since I use the lathe infrequently (14"x 40" 5HP), but when used, it works hard. I use Castrol cutting and grinding oil, and it needs diluting 4 parts of oil to 1 part of paraffin for it to flow really well though the flood coolant system. Since paraffin is miscible in oil, the resulting solution looks and feels like a "lighter or thinner" version of cutting oil.

Thankfully, my swarf tray is removable and adjustable, so the headstock end is tilted upwards, so coolant flows towards the perforated swarf catcher that then returns coolant to the sump in the tailstock end leg.

[jem]

On my Chinese lathe, the coolant tray , which is removable, has a small drain box under it, to catch the coolant and then directs it to the pump. Could you put a drain box under your tray outlet, with a filter in it, so that there is no restriction in the top of the tray perhaps? Regarding fibre glass, it does stick very well to paint and metal, so that might still be your way forward, you could incorporate your aluminum tray into it. We used to repair leaky petrol tanks for outboard motor with fibre glass, and they didn't then leak!!!

Jem

[92220]

Jun 25, 2019 20:57:06 GMT mhrvol said:

Firstly, many thanks to those who have taken the trouble to reply: it really is much appreciated that you have taken the time and made the effort on my behalf. I will try to answer the points raised in the order that they were made.



3) In response to 92220’s point about (I think, but may well have misundersttod the point being made) raising the tailstock feet with respect to the tray, I cannot see a way of doing this as the tray is an integral part of the lathe.



Thanks once again for taking the trouble to respond.

Hi.

Ooops!  I didn't make that very clear did I !!! What I meant to say was put a spacer under the tailstock end of the cabinet, to set the whole lot at a shallow angle, which shouldn't effect the operating accuracy.

Bob.