Getting coolant to drain from the table

[Graham WhartonParticipant @grahamwharton]

I have fitted a coolant system to my round column style mill. I have fitted a drain to either end of the table, in the trough at the end of the Tslots. The drain holes are at the same level as the base of the troughs. The drain holes are reasonably large at 3/8BSP fitted with 10mm straight through hose fittings, with 10mm I/D hose running about 1.5 metres back and down to the coolant tank. Coolant tank is about 1 metre below the table.

When I run coolant at a fairly fast rate the table fills up and doesnt seem to drain very well. I can see into the coolant pipes and there is only a trickle going down the pipe even though the coolant level is above that of the pipe entry. I can get, maybe an inch deep of coolant and there is still poor flow.

Occasionally the drain pipe will fill with coolant to the point that it syphons down and clears the table in about a second, then seems to repeat the same thing. Table fills up, pipe syphons the table clear very quickly, gurgles as it empties, syphon stops, table fills and the process repeats. Other times it just seems to stick with a piddly flow out of both of the pipes.

Having the table overflow when the table in central is fine as it just spills over into the drip tray, but when the table is off to one side, the coolant will overflow onto the floor.

I can of course reduce the coolant rate down to the point where i'm putting it on at the same rate that it flows out of the table, but sometimes for chip control I just want to flood the heck out of it.

So, whats the trick to get coolant to drain through a reasonably small bore pipe with little or no head of pressure to get it going. Shorter pipe? Larger bore? Smaller bore? U bend/pipe routing to promote syphoning?

Anyone played/tweaked with things like this?

Thanks for any help

Graham

[Graham WhartonParticipant @grahamwharton]

[Neil WyattModerator @neilwyatt]

Larger bore (increase bore by 2X increase flow by 16 x)

Longer pipe – once full of coolant the increase 'head' at the exit will result in greater flow by 'pulling' fluid down the pipe.

Neil

[Graham WhartonParticipant @grahamwharton]

Thanks Neil, It doesn't seem to be the size of the pipe bore that is limiting the flow. If i look at the inside of the pipe, it is mostly empty, there is a small trickle of coolant flowing down one edge of the pipe. Occasionally the pipe does fill to the point that you get the pulling effect, in which case it empties the table almost immediately, then goes back to a trickle.

If i remove the pipe the coolant flows out of the table better. Its only when I connect the pipe that it can slow to a trickle. Actually Ive just had a thought. The outlet of the drain pipe is below coolant level in the coolant tank, so once the troughs in the table fill up with coolant I have a bit of an air lock in the drain pipe. I never achieve enough pressure at the top end to force the air down the pipe and out of the bottom, and for some reason the air in the pipe doesn't bubble up the pipe and exit the top. It just stays occupying the pipe not allowing the coolant to flow.

I'll give it a go tomorrow with shorter pipes that don't exit below the coolant level, and also longer pipes to see if it promotes the syphoning effect.

Edited By Graham Wharton on 27/11/2014 21:30:06

[Graham WhartonParticipant @grahamwharton]

Ive just been out to the workshop and adjusted the pipes as they enter the coolant tank. I secured the pipes so they feed out above the level of the coolant. This has improved things vastly. and now It clears the table very quickly due to the pulling/syphoning effect regardless of the coolant rate that I throw at it.

Graham

[Paul LousickParticipant @paullousick59116]

Hello Graham,

I have a similar set-up on my mill and also found that coolant does not like flowing thru small pipes. It tends to only run down the inside sides of the tube and not fill them if the length of the tube is long. (about 1m). With a short length of tube (200mm) it flows OK. I think that there must be a capillary action which is restricting the flow. Problem solved by feeding the short length of small tube attached to the mill table into a larger tube diameter tube which drains to the coolant pump.

Paul.

[ChrisHParticipant @chrish]

Graham, I also have a round column mill and have fitted the table with one drain so far, with a 15mm copper pipe draining from a hole the bottom of which is only just below the level of the bottom of the end trough. The fall to the tank is only about 8-10inches and about 2 ft horizontally but the drain pipe does end at just below the top of the coolant tank, well above the tank level. Even so, the rate of drain is very slow, enough for a modest coolant feed but not a flood, not sure how to speed it up other than improve the pipe run layout. Will be interested if you manage to get a drastic improvement to see how you did it.

Chris

[Graham WhartonParticipant @grahamwharton]

Here's a picture of the table with drains.

Here's a shot of the the table drain pipes as they go down the back of the mill. You can see they almost go horizontal just before they go into the coolant tank.

And here is a shot of them at the tank, secured just above the coolant level.

And a couple of videos of it draining at full chat.

[ChrisHParticipant @chrish]

With further thought I wonder if the drain pipe requires an air vent a couple of inches downstream from the connection to the table to aid the flow? Might try that.

Chris

[Graham WhartonParticipant @grahamwharton]

I did think about that, but I think doing that will stop any syphoning effect as once the coolant fills a section of the pipe and starts sucking coolant down the pipe with it, it will suck in air through the vent and you will loose the syphon.

It would appear that the combination of a reasonably long tube, possibly with the horizontal section at the outlet from the table and not having the lower end under water has done the trick for my setup.

Do your pipes go straight down from the table, or horizontal. Mine come out horizontal. You can see the section just at the outlet start to fill up, then the pipe goes full bore with coolant, which then starts to fall down the pipe. Once it starts going it just sucks all the coolant from the table under its own weight. With the lower end under water, the top end of the pipe never seems to achieve full bore, i just get a sow trickle as it forces its way past all of the trapped air.

Graham

[Graham WhartonParticipant @grahamwharton]

I think if your pipes are large enough bore to not need a syphon effect to get them going (mine are only 10mm bore), the air vent idea may work. I read that some people fit tee pieces at the outlet of the table with the tee pointing up to the air. It acts as a vent and also somewhere to blow the air line. When they block up with swarf.

Graham

[davebParticipant @daveb17630]

Standard pipe fittings restrict the flow. On all of the machines I have owned, the table drain was just a straight metal tube screwed into the table drain hole with as large a bore as possible. Any sort of plumbing or gas elbow will impede the drainage. It's difficult to see but you appear to have a reducer to fit your drain tube, eliminate the reducer and use a bigger tube.

Dave

[JonParticipant @jon]

My thoughts exactly Dave, wait till he has created some debris that will constantly block the exit hole up.

Did same on an RF25 think I used 3/8"bsp males running mm bore with 1/2" bore tubing. That permananently and repetitively kept blocking up.

Gone larger bore silicon tubing it flexes, on current mill. Both ends feeding in to drip tray via silicon hose from fittings in the bed ends 19mm bore. My guaze idea didn't work. From there a 3/4"bsp with 19mm ish bore filter/collector with hard plumbed 15mm copper tube to tank. Debris and swarf is the problem.

Decent lathes run guaze or mesh in to a debris collector then 1" bore to tank. Difference is they don't flex and are stationary. No guaze the 1" bore pipe will soon block up as on current lathe.

[mechman48Participant @mechman48]

Try rerouting you tubing to have a vertical drop as close to your table as possible as it seems that you have a fair near horizontal run to the back of your column, in one shot it appears that the left hand tube seems to have a slight rise before it drops over the back of the column… making it higher than the table… negates the syphon effect… leave the drain tube ends above the level of the tank otherwise you're trying to overcome atmospheric pressure on top of the suds level, so without any added pressure / decent syphon drop your suds stay where they are… … you can only give it a try … don't forget to add a filter of sorts before suds enters the tank  (  apologies for granny & eggs implication )

George

Edited By mechman48 on 28/11/2014 11:33:59

[ChrisHParticipant @chrish]

My pipes have a gentle slope down from the table. I am also using neat cut oil at the moment. I would have liked to put large pipe in but the problem would be in the making of the hole into the table, getting a 15mm hole to suit the copper pipe elbow used meant starting with a half inch hole and then Dremel grinding it out larger to fit. Where do you get silicone pipe, or is that just another name for clear unreinforced type flexi hose? Ensuring the hose does not put in a restriction itself by kinking is sometimes a problem too I find. I do think a bigger bore pipe/hose would be better, but it's the fitting of it

Chris

[Boiler BriParticipant @boilerbri]

Try taking the ends of the tubes out of the liquid at the lowest point so the air being trapped does not have to come back up the tube.🎅

Bri

[JonParticipant @jon]

The flexi reinforced hose don't really flex unless its warm and after time tend to get hard. Right pain that bore on bead blaster.

Good cheap source for 1/2" bore is hose pipe but wont be clear. Silicon tube available on ebay but again a colour though there are some opaque stuff around. Try and look for the thinnest wall tube, it will flex easier. I wouldnt recommend the 1" or 3/4" bore due to flexibility but fine for some movement without kinking.

Assuming your 15mm copper is a ferrule sealed in with 1/2" bore. This will be fine until debris gets in to the pipework and stops the flow. Some form of easy clean filter before that can be put back in/on easily.

[ChrisHParticipant @chrish]

On my mill table I drilled 1/2in hole and then opened out until a 15mm copper pipe would just fit in, then sealed it with Araldite and secured/reinforced with an epoxy metal filet around the outside. I then placed a mesh filter across the hole to stop the swarf going down the tube – the filter is very easy to keep clean by a wee brush but of course it's a function of the beast that it does restrict flow a bit. Mesh choice is a tricky one, too fine a mesh and flow is restricted a lot, too coarse a mesh and it doesn't stop the swarf. I'm not sure I have it right, I think it could be more coarse, but it's not too far wrong! From the 15mm outlet pipe I changed direction with an elbow then straight into a reinforced ½in hose down to the tank. The pipe exits at the top of the tank into a wide bore (relatively) return which again has a coarse plastic filter sitting in the hole which provide very little if any restriction due to the area of the filter relative to the size of return pipe and flow. I'm not sure I have any syphon effect in the drain pipe but it sort of works if I don't wind the coolant flow up too much but I need to improve the system as I would like more coolant flow at times.

Chris

PS is it just me, but when I press 'Return' on the keyboard on this post the curser goes back to the beginning, not drop down to the next line? Is this a function of any recent upgrade, never used to happen before?

[Nigel McBurney 1Participant @nigelmcburney1]

On my Adcock and Shipley universal mill the pipe from the table is about 19mm ,it does not go down into the cast base tank,it drains onto the top of the tank and then runs down into the tank via a perforated sheet cover ,so that any swarf carried in the soluble oil is kept out of the tank.There is also a second pipe which drains from the centre of the table through the knee and easily blocks,perhaps the table pipe pipe is an operator mod,at least it works

One thing thats a bit odd is if you look at old photos/catalogues of milling machines around 1910/1930 a lot of them have open ended tee slots,so some lubricant must have run out the end of the table.Must have been a bit messy,unless the drainage channels in the table slope towards the centre ,but it would not take much for it to overflow if swarf built up ,in one photo there is a coolant pipe feed and a drain pipe from the knee, so a pumped supply of coolant was built inI expect the operators soon stuffed the open ended slots with rag. The open ended slots are shown in Brown and Sharp and Cincinnati books on milling.

[Bodgit Fixit and RunParticipant @bodgitfixitandrun]

Why not try using domestic draining pipe 30 or 40mm diameter. Route this down to the tank and feed your small bore flexible pipe into this. You then have a natural vent in the pipe route and it can sit just below the coolant level which then negates splashing. The small bore pie only has to go in by about 25mm so much less is required.

[ChrisHParticipant @chrish]

That may not be a bad idea Bodgit !

Chris

[Boiler BriParticipant @boilerbri]

My curser does the same on my ipad .

Brian

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