Design of oil grooves in dovetail slides

Let's assume a knee type milling machine with dovetail ways for all three axes. My questions are on the design and machining of the oil grooves in the surfaces of the dovetails. The two horizontal axes are the easiest so let's begin there. The oil grooves will be in the short element - the saddle - and for the table the two flat surfaces are above the angled surfaces.

I've seen two different styles of grooves - a straight longitudinal groove down the center of the flat surface with several short grooves at right angles and extending almost to the edges of the surface, and a zig-zag set of grooves extending lengthwise. Either of these appear to do an adequate job of oiling the flat surfaces of the table ways.

My first question is how to oil the angled surfaces. For the table the angled surfaces are below the flat surfaces. At several locations the flat surface groove can be cut through into the angled surface so that oil can flow downwards. Now, what to do next? Cut matching grooves down the angled surface with what? A cow-mouth cold chisel? A linear groove would not be necessary but the metering unit needs to be large enough to supply both surfaces.

Or it is better to run a separate metered line to a hole through the angled surface from the outside of the saddle? Then the question is how to distribute the oil the length of the angled surface? That is not an easy chisel job for the fixed surface and my first look at machining a groove suggests that a special T shaped end mill would have to be made if a circular section groove is desired. A woodruff key cutter could cut a square corner groove. I don't know if I could grind each tooth of a woodruff key cutter to a radius. That still leaves making the cross cuts with a chisel.

OK, we've worked out the fixed angled surface, but the gib lubrication is another problem. These are tapered gibs so I'm thinking that the best way is to drill a hole through the saddle and into the center of the gib. That hole should be elongated into a slot to allow for the movement of the gib. Oil grooves may be milled in the working surface of the gib from that hole. This appears to be a better method of oiling the gib surface than from the associated flat surface. The gib surface is slightly below the flat way and this is a leakage path which would affect the pressure in the flat way distribution groove and there would be no pressure in the angled surface groove.

On the saddle to knee dovetail the angled surfaces are above the flat surfaces. Can they be oiled by pressure from the flat way? That still leaves the gibbed surfaces which so far appear to be best oiled by a separate line.

Last but not least is the vertical dovetails for the knee to column. Does it make any difference where the oil enters the dovetail - center, top, or bottom? The only way to get oil to angled surfaces is through a separate line to each. Well, that might not be right. The oil is under pressure and could flow horizontally from the flat way into the angled way.

Well, it looks like running separate lines to each surface is going to be the best way, even though it might be more work. That decision then leaves one major question: how to machine the distribution groove down the length of the fixed angled surfaces of the dovetails? The three gibs can be milled in a vertical mill. They are just a bit tricky to hold down.

That about does it for the six sliding surfaces and leaves the three leadscrews. Just drip some oil over them? Drill an oil hole in the nut and feed the oil in there? That makes 9 lubrication points and the Bijur kit for Bridgeports has 9 metering units so I maybe got something right.

What have you guys seen and/or done for lubrication of knee and column type machines? As a friend of mine says, "inquiring minds wish to know."

TIA
Carl

I will answer your question later today as I am headed to an airport now. One thing you NEVER want to do is cut straight grooves into any surface that run parallel to the travel. Rich

Why are you asking such a long question, taking an machine tool design class? You say "let's assume". That sounds like you do not have a machine now and are building one? Or you have a cheap import with out any. What is it?

Yep, that's a long and quite complicated question. I've cut oil grooves in the past in awkward places with little grooving chisels made from old round files, small cut off stones mounted in " pencil grinders ", rotary files/burrs mounted in the same. Most of the time it can be a combination of all three.

Normally you would groove elements that aren't exposed. Don't overdo the grooving. I normally do shallow zig zags if at all possible but I've seen in plenty of straight line grooves with smaller grooves going across at 90 degrees and circles joined up with straight or angled lines.

Don't go too near the edge of whatever it is you're grooving and don't make them too deep. On the knee to column slides/gibs don't take the groove too near the bottom of the ways. 3/4 of the way down is fine. The oil needs to enter from the top of the way/gib. Gravity will do the rest.

Regards Tyrone.

Rich: You got it. I have an import knee and column machine and I would like to upgrade the existing oiling system. It is not metered and not all surfaces are oiled. I have a Cincinnati CountourMaster vertical mill that needs new pumps and meter units. I would like to review the oiling porting and grooves when I do this job. I will relocate the pumps and meters to a more accessible location. I also have a LeBlond knee and column tool and cutter grinder which has oiling felts but I have given some thought to changing to single point pumped lubrication. Because I have three different machine with different requirements I generalized my questions into "just how are these oil distribution grooves/galleries/ports best designed and machined" figuring that this would be of more interest to the forum. Any suggestions from your experience would be most welcome.

Tyrone: I'll grab my Foredom rotary tool and sorta hold a burr near the fixed dovetail surface and see what that looks like. That's the most likely method so far.

Carl

lathehand said:

Rich: You got it. I have an import knee and column machine and I would like to upgrade the existing oiling system. It is not metered and not all surfaces are oiled. I have a Cincinnati CountourMaster vertical mill that needs new pumps and meter units. I would like to review the oiling porting and grooves when I do this job. I will relocate the pumps and meters to a more accessible location. I also have a LeBlond knee and column tool and cutter grinder which has oiling felts but I have given some thought to changing to single point pumped lubrication. Because I have three different machine with different requirements I generalized my questions into "just how are these oil distribution grooves/galleries/ports best designed and machined" figuring that this would be of more interest to the forum. Any suggestions from your experience would be most welcome.

Tyrone: I'll grab my Foredom rotary tool and sorta hold a burr near the fixed dovetail surface and see what that looks like. That's the most likely method so far.

Carl

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Hi Carl, you'll need to create your groove before going at it with a rotary file or burr. They'll skip sideways off the ways unless they have a groove to follow. I used a small 2" dia by 3/16" wide grinding disc to start things off. They're much easier to groove with as the rotation of the disc is in line with the direction of the groove. I bought them by the box full. When the got down to about 1" dia I threw them away.

An old 1/2" round file ground up like a narrow chisel is as good as anything in the hand tool field. With a bit of practice you'll be surprised how quick it is. I could do say a 20" groove by hand in about 10-15 minutes.
Cast Iron is relatively soft and easy to chisel. Get a scrap piece and have a practice first.

I had the 3/16" solid carbide rotary file for smoothing out the groove profile when it was nearly finished.

Regards Tyrone.

Also use a Sharpie magic marker to draw lines first. I would cut diagonal groves in the flats to feed the doevetails so as the table or saddle moves forward and backward the oil goes with the flow, apposed to a straight line, As Tyrone suggested double check where the sliding member sets and keep the groove away from the edge as the pressure will just run out an open to the air hole. One thing to think about. "who will see the grooves"? If they aren't quite perfectly straight who will care?

One rule of thumb is to have more oil apposed to less :-) in machine tools is best, now if we were talking about other types of lubricants less is better...more friction is better...but on machines ...oh well...lol...use your imagination...lol

I have a block of cast iron and I will mill the same size dovetail in it and have a practice go. I have some experience chipping cast iron, just not in the confined space of a dovetail and requiring this degree of care. This is going to take some time and I will report back when I have some results.
Thanks, guys
carl

I have been thinking you should consider installing Rulon 142 or Turcite B on the mill. Also on those cheap import are so far out of alignment they will need to be machined and scraped. Scraping way nearing material is like scraping butter. Plus it's self lubricating. So the location of the oil ports and grooves is not as important. Cheers. Rich

Whilst we are on the topic, and i do apologise if this is considered a bit of a hijack. In the situation that you do have grooves running parallel to the movement of the ways, is there a way to remedy this?

I have a Schaublin mill that seems to have a combination of zig-zags, circles and straight longtudinal grooves. I suppose using rulon or turcite, etc would archive this but would require installation and rescraping, could using liquid setting moglice to fill the groove and cutting new grooves to suit work?

One notable point about the Schaublin is the built in oil pump has no metering vales on the lines. So the closet ports recieve oil first and the furthest ports take much longer. The furthest lines were well clogged on my machine, a hot air gun warmed up the copper tubing to get them to clear with compressed air after an hour of fiddling about with bits of wire, air and solvent. Valves are now on the list.

Static Expansion said:

Whilst we are on the topic, and i do apologise if this is considered a bit of a hijack. In the situation that you do have grooves running parallel to the movement of the ways, is there a way to remedy this?

I have a Schaublin mill that seems to have a combination of zig-zags, circles and straight longtudinal grooves. I suppose using rulon or turcite, etc would archive this but would require installation and rescraping, could using liquid setting moglice to fill the groove and cutting new grooves to suit work?

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For a feature as small and shallow as an oil groove, it would not be easy to assure that a full-length bonded-in filler material would stay where put and not itself become a problem.

I *suspect*, but have no proof, that blocking the entry-end - or both ends, abandoning the intervening gap as a fretting-corrosion "smut" trap might be all that is needed.

Think brass or Copper wire into tiny drilled holes, each pin then upset as a "blind" rivet, then finished-off flush with the load-bearing surfaces.

That said? If a firm as savvy as Schaublin saw fit to include straight lines when they built it? Why mess with that at all?

It doesn't class as a disaster, could have less of a downside than first appears, may even have an upside they understood then, and we do not. Yet.

If the straight lines are interrupted with a circle and the next line is 180 degree's from the other, then that's not as bad as one straight line. Today during class I will take some photo's of a famous vintage English made machine that has one line and show you what I mean. Just because it's a well know builder doesn't mean it can't be improved on. Also I have filled in straight oil grooves with different methods and will write more about that tonight. Have a class in 45 min. Cheers, Rich

Here is the table and saddle of a Beaver Mill saddle and table with straight oil grooves. Kev the machines owner told me it is a 1965 model year and a very popular machine in England. Note the straight oil grooves in the saddle interrupted with circles, but if they had moved the lines to opposite sides of the circle as I said above the table would not have the raised unworn way.

Beaver oil spreaders

My Beaver VBRP Mk2 mill definitely does not have a straight line down any of the oil spreaders, anywhere on the machine. On the table, they are large side by side circles, joined where they touch. The apron is similar.