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Paul Alciatore
07-05-2007, 12:22 AM
I have several projects that need some milling work and no real mill in my new shop. So I got busy on a table for my SB. This is just a 3/4" piece of 1018 CRS with a lot of taped holes in it. Machined a button to fit the SB cross slide mount.

http://img.photobucket.com/albums/v55/EPAIII/PixA.jpg

Here's my first cut with it, in progress:

http://img.photobucket.com/albums/v55/EPAIII/PixB.jpg

And the finished cut:

http://img.photobucket.com/albums/v55/EPAIII/PixC.jpg

The vertical dimension is established with spacers. I bought a couple pieces of flat ground stock and rolls of steel shim stock. Cut out a stack of 2" and 4" long spacers. With only four sizes of stock I can get within 1 or 2 thousanths. I plan to use aluminum foil if I need finer adjustments.

I am also working on an angle plate with a vertical X-Y slide and vise. But I needed this simple table to make some of the parts for that.

Evan
07-05-2007, 01:18 AM
That will do the job well. It's amazing what can be done on a lathe. I built a milling machine with a SB9. :D

R W
07-05-2007, 03:08 AM
A great idea, could also be used to mount parts for boring.
Would you be able to give more details re mounting to the cross slide.

matador
07-05-2007, 03:26 AM
Give that man a cigar!I like your thinking,Paul.
If I didn't already have a mill-drill,that would be a useful alternative.It will be better still when you get the vertical slide done.Cheap and cheerful,and it does the job.:D

Your Old Dog
07-05-2007, 07:43 AM
I have to say I like it better than any other lathe milling attachments I've seen. I have one that I got at a yard sale and it's junk, vibrates like crazy as not enough mass. Yours look like it will work great and a low tech answer to the problem. Nice job!

Evan
07-05-2007, 08:30 AM
I have to say I like it better than any other lathe milling attachments I've seen.
But,,, but,, mine is bigger! It also has lots of holes in it! (not shown in pic as not yet drilled). [grin]

With fly cutter:

http://vts.bc.ca/pics/34face3.jpg

Here it is milling a fan pulley for a treadmill motor.

http://vts.bc.ca/pics/sheave1.jpg

I also have two other such tables for different type jobs. This one is a 1 1/2" thick chunk with a variety of holes.

http://vts.bc.ca/pics/mill06e.jpg

Then there is the more conventional milling attachment, but a bit beefier than the commercial ones.

http://vts.bc.ca/pics/mill4.jpg

I actually find I don't (didn't) use the full blown attachment very often. Nearly all the milling can be done with the tables and they are more rigid by far. Paul's is also the nicest I have seen, mine included.

pcarpenter
07-05-2007, 10:31 AM
That is indeed a nice milling table. I suppose there is some limit to how wide you want to make it as it gains a lot of leverage that way. Otherwise, I have to say a design like that is better than most as it leaves some room to use real clamps.

I really don't know the answer, so am proposing this question in hopes of a real answer. I have a mill and don't see myself doing this, but I have to wonder about the loads presented to the spindle bearings on the lathe and how they compare to normal turning loads. I know there is plenty of milling that has been done on lathes, but I would think that those with plain bearings (especially) might be prone to more wear doing this. While plain bearings are perfectly acceptable in a lathe, they are not so popular in milling machines...at least not today. A plain bearing is really a hydrodynamic bearing that relys on maintaining an oil film on which the spindle rides. Given that, there is some point at which that film is broken down by lateral forces on the spindle.

The spindle oil used is pretty thin (intentionally) so that it will flow and create that continuous oil film. I guess the question is just how much side pressure the spindle can take before you break down this film and begin to wear the bearing material.

Paul

Evan
07-05-2007, 10:59 AM
but I would think that those with plain bearings (especially) might be prone to more wear doing this.

Plain bearings will take higher loads than any other sort. They are probably best suited to this type of use on a lathe. The reason is that the bearing area is extremely large compared to any other bearing type and the load per sq inch comparatively low within the bearing. The reason they aren't used in milling machines is because they have a "squish" factor.

pcarpenter
07-05-2007, 11:07 AM
While load per unit area is much smaller (assuming a good bearing to journal fit), the durability of the bearing material is also much lower. A ball in a bearing race has greater force applied to a smaller area, but the materials are quite hard while babbit material on the other hand is intentionally very soft.

I think the real critical issue must be that you not exceed the point at which the film breaks down or the babbit would not last long. I just didn't know what that point is in a non-pressure oiled plain bearing.

You can argue that internal combustion engine crank journal bearings see huge force, but their hydrodynamic bearings are fed oil under pressure. Remove that oil film maintained by pressure and they are trash in a matter of minutes.

Paul

Evan
07-05-2007, 11:24 AM
Babbit relies on a matrix of soft metal that contains very hard metal crystals. It is the hard crystals that are the wear points in babbit, not the soft metal. In the case of the SB9 lathe there is no babbit, the bearings are hardened precision ground steel on cast iron. In either case it is extremely difficult to cause the bearings to make contact when rotating. It is this principle that is used in Squeeze Film Dampers that are used to stabilize and centralize the shafts of very large power turbines. The plain bearing in a lathe spindle is essentially a form of squeeze film damper and as such can take loads that would turn a point or line contact bearing to dust.

http://www.kmcbearings.com/products/dampers/sq_dampers.html

[edit]

BTW, if you drop oil pressure to zero in an engine it won't be the bearings that fail first. The pistons will seize in the bores long before the bearings give up.

Willy
07-05-2007, 03:58 PM
BTW, if you drop oil pressure to zero in an engine it won't be the bearings that fail first. The pistons will seize in the bores long before the bearings give up.

On the contrary, a plain shell type bearing relies on a hydrodynamic wedge of oil to keep the bearing journal out of contact with the bearing shell. In a roller bearing equipped engine, which requires very little in the way of lubrication, yes the pistons will seize long before the bearings fail. In a plain bearing engine however, it is a matter of seconds before the bearings spin upon loss of oil flow.

As long as this hydrodynamic wedge remains intact there is virtually no contact between the journal and the bearing itself. This is why one of the in most common cause of bearing failure is frequent starts, at which time this wedge of oil has not yet been established. Once the flow of oil is returned to the bearing and the oil wedge is reestablished there is very little if any wear. I have seen plain type bearings that have been in non-stop service for 75 years, in an electrical power turbine, which still showed the machining marks from when it was first made.

It is this wedge of oil which allows the pain type shell bearing to carry enormous loads. The bearing shells in plain type bearing are quite soft so that any hard solid impurities in the lubricating oil will be embedded in the shell rather than scratch the journal causing it to wear.

Sorry Paul, not to hijack your thread, nice addition to your lathe.
I'm sure it is a lot more rigid than than an entry level mill as well.

Evan
07-05-2007, 04:25 PM
In a plain bearing engine however, it is a matter of seconds before the bearings spin upon loss of oil flow.
However, before that happens the engine will no longer be rotating, usually.

I have had engines fail due to loss of oil. In all cases the piston(s) seized before the bearings. In one case I was riding a Yamaha going fast down the highway. This was a bike with oil/gas mix, no injection. I suddenly realized that the exit I wanted was right there in front of me so I had to slow down, quickly. I made the mistake of fully closing the throttle and in about two seconds the engine locked tight as the piston seized from lack of oil as the fuel was cut off. It was an interesting ride with the back tire locked solid at 60 mph. After it cooled down it started and ran fine, no apparent damage to the bearings.


The bearing shells in plain type bearing are quite soft so that any hard solid impurities in the lubricating oil will be embedded in the shell rather than scratch the journal causing it to wear.
As we are concerned about the ability of the South Bend 9 inch lathe to withstand side loads I will point out again that the plain spindle bearings are not shell bearings. They are hardened steel on cast iron.

I will also reiterate that babbit isn't all soft. Nickel babbitt in particular contains very hard metallic crystals in a matrix with tin. All babbitt alloys rely on the soft metal to hold the crystals of very hard metal in place. It is the hard crystals that provide the bearing surface.

Al Messer
07-05-2007, 05:04 PM
Very nice jobs! I made a stiff angle plate that is bored to fit under the tool post and is clamped down by it. So far, I've been able to get by with it, but maybe, just maybe, there will be a good used Clausing Mill in my future!

Willy
07-05-2007, 06:13 PM
However, before that happens the engine will no longer be rotating, usually.

I have had engines fail due to loss of oil. In all cases the piston(s) seized before the bearings. In one case I was riding a Yamaha going fast down the highway. This was a bike with oil/gas mix, no injection. I suddenly realized that the exit I wanted was right there in front of me so I had to slow down, quickly. I made the mistake of fully closing the throttle and in about two seconds the engine locked tight as the piston seized from lack of oil as the fuel was cut off. It was an interesting ride with the back tire locked solid at 60 mph. After it cooled down it started and ran fine, no apparent damage to the bearings.


Exactly my point. Unless it is a throw away weed eater engine, all two cycle engines utilize roller bearing lower ends because they operate without the benefit of a full flow oil system. Only a roller bearing could survive under those kind of conditions. Try that with a conventional lower end and the bearings would spin in the case or on the shaft within seconds. Or better yet, if you have money to throw away, and I'm sure you don't, dump the oil in your pickup and drive to town. I can guarantee that there will be plenty of oil still flying around to lube the pistons and cylinder, but not enough to save the crank and rod bearings.

Multi viscosity oils, swinging oil pickups, oil accumulators all point to the need to keep this fluid layer established. Without oil on the bearing it soon will have metal to metal contact. Check with some of the local engine re builders in the forestry sector and see what they say will happen to an engine that did not have the benefit of a low oil pressure shutdown system when an engine was operated at an extreme angle and was starved for oil...it won't be pistons and liners they're replacing.

Mind you a plain type bearing on a lathe operates under much lower pressures, but still requires lubrication to survive.The bearing on a lathe is huge in comparison to an engine bearing, it takes only a very small amount of lubricant to keep the shaft and the bearing apart. An oil impregnated bushing is a classic example of how little oil is rquired...you can't even feel the oil film. Or cast iron come to think of it, also a very good provider of lubricant, not only because of it's open and porous grain structure that retains lubricant but also because of it's ability to provide a dry graphite lubricating function. Hence it is usually a first choice for cylinder liners in industrial engines.



I will also reiterate that babbitt isn't all soft. Nickel babbitt in particular contains very hard metallic crystals in a matrix with tin. All babbitt alloys rely on the soft metal to hold the crystals of very hard metal in place. It is the hard crystals that provide the bearing surface.


I won't argue the fact that the material and function of a straight babbitt lathe bearing is vastly different than say a tri metal engine bearing whose first layer next to the crank journal is babbitt, followed by copper, and then a steel backing. the main function of the babbitt layer is particulate embedability, not lubrication.

Evan
07-05-2007, 10:05 PM
Exactly my point. Unless it is a throw away weed eater engine, all two cycle engines utilize roller bearing lower ends because they operate without the benefit of a full flow oil system.
I am quite sure the Yammer didn't have a roller bearing crank. Those were pretty primitive bikes back then in the sixties.

I'm sorry, but experience tells me that the bearings are much less sensitive to oil pressure loss than the cylinders. There is still oil in the system and bearings and they don't suddenly wipe dry like the cylinders do. When an engine seizes while running it is because of lack of oil to the cylinders, not trashed bearings. An engine will still turn with spun bearings. Had a Suburban that did that once. It still ran but made one hell of a noise. But when the oil pump broke on my Morris Minor the engine stuck tight. Had no warning because it had no gauges or idiot lights.

I'm not saying the bearings won't be damaged. They probably will. They won't be the immediate cause of the failure of the engine to operate in most cases. Stuck pistons will.


the main function of the babbitt layer is particulate embedability, not lubrication.

No, the main function of the babbitt is to act as a bearing. The copper liner is a compatible material that will bond to the babbitt as well as the steel shell. The function of those layers is strictly to support the babbitt layer. Without the layer of babbitt there is no bearing. It's all about lubrication.

J Tiers
07-05-2007, 10:29 PM
Babbit bearings have been used in milling machines for a hundred and fifty years, back to the first milling machines, which I actually saw dated to 1809 or so, making it even longer.

But, a babbit bearing will nearly always be larger for the same bearing capacity than a roller or ball. And it will typically have a maximum speed rating lower than the ball or roller.

The ideal bearing does not allow the babbit or bronze etc to touch the shaft. However that happens at startup and shut down, which probably take more wear out of the bearing than hundreds of hours running.

Evan
07-06-2007, 01:15 AM
Yep, but I don't think they were used much in vertical spindles due to lubrication problems. Also, because of the oil layer the spindle is free to move about under load a small amount. Still, plain bearings are extremely tough and are still widely used. As for the SB9, Paul has nothing to worry about. I have been milling on mine for years and the bearings are fine.


But, a babbit bearing will nearly always be larger for the same bearing capacity than a roller or ball.

Perhaps. However, the plain bearings in the SB9 headstock are more compact than other bearing systems. It's not just the headstock either. All the bearings on the SB9 are plain bearings except the spindle thrust bearing.

Paul Alciatore
07-06-2007, 02:46 AM
Not to hijack the thread back, but in answer to R W's request for more info on the mounting, here's an edited version of my drawing.

http://img.photobucket.com/albums/v55/EPAIII/TableEdited.jpg

I cut it back to show about 1/4 of the table and the mounting button for the SB cross slide. The button is fastened to the bottom of the plate with four M5 SHCS and the assembly is mounted on the cross slide in exactly the same manner as the compound. I did have to replace the square head screws with SHCSs as there was no clearance for a wrench under the table.

Another neat advantage of this table is that it will allow milling or drilling on the end of a long workpiece. Even with a full sized mill/drill at work, I have had to resort to manually drilling holes in such parts in the past as there was no way of mounting the work under the spindle. I could easily clamp a 10 foot long part on the table and work on the end. Well, with some outboard support.

As for rigidity, it does sit quite well and movement is smooth. I am finding that when milling the slot in the picture I had to use a fairly slow feed or I would get vibration. The direction of the cut (front to back or back to front) did not seem to make any difference. I would be interested in Evan's experience here. Or anyone else who has done milling on a SB or other lathe.

An interesting advantage of this table is the ability to drill or mill the ends of a long work piece.

Evan
07-06-2007, 03:21 AM
The main thing Paul is to avoid making cuts that tend to lift the table. The other important consideration is that the cutting action should oppose the lead screw motion rather than "help" it.

One problem I forsee in your design is that the mounting via the compound mount won't be able to withstand cutting forces at the extremes of cross travel. It will allow the table to rotate since the grub screws can't provide enough holding action. The alignment of the table to the headstock is critical and some means needs to be provided to keep it aligned. With my tables I mount them via the two 5/16" bolt holes provided in the top of the cross slide when the compound is removed. In the case of my milling attachment I use a couple of "ears" as well that have set screws that bear on the rear of the cross slide apron as in this pic.

http://vts.bc.ca/pics/mill3.jpg


An interesting advantage of this table is the ability to drill or mill the ends of a long work piece.

Yep.

http://vts.bc.ca/pics/34face2.jpg

R W
07-06-2007, 06:00 AM
Thanks Paul, for the extra information, hope to build somthing similar for my
SB10L.
Regards,
R W

Willy
07-06-2007, 06:13 PM
Again Paul, my sincere apologies, Iím sure that it was neither Evanís nor my intention to draw focus from your excellent thread. However as Iím sure you are aware this group does go off on a tangent now and then in order to validate a point.
We can hypothesize and speculate till the cows come home as to what blows up first, but until someone is willing to donate a variety of engines to the cause....two stroke, four stroke, water cooled, air cooled, plain or roller bearing, it will be merely conjecture. As an aside, all of the motorcycle shop manuals I have from the sixties show roller bearing lower ends on all makes of two stroke engines.
One thing I believe that we can all agree upon is the ability of the South Bend headstock to tolerate such loads with ease. As you, Evan and numerous others have demonstrated, with a little ingenuity one is only limited by the level of his imagination, not the machine.
Thanks for sharing Paul, keep up the good work.
Willy

Paul Alciatore
07-07-2007, 12:59 AM
Willy,

No need to apologize. I was only jabbing at you guys in fun. I read and learned a bit from your discussion. I have been with the group for some time and have seen many of the antics that go on here. I like it; well, most of it anyway.

As for Evan, he and I have traded blows before and probabily will again. I don't take it personally and I don't think he does either. I think it helps to sharpen both of our minds. I was well aware of his work on the SB and it is part of the inspiration for my table and some of the other mods I am thinking about. I marvel at the amount of things he seems to get done. And at the amount of 7075 aluminum he can afford.

Evan,

I have only made a few cuts so far and have seen no tendency for the table to rotate. I think I had seen your brackets before and appreciate your reminder. If I find that I need them, they shoud be very easy to add.

One thing I have noticed is that the depth of the mounting hole on the SB cross slide is very close to the height of the mounting button. It may actually be a little shorter on mine and that would mean that the button may rub on the dovetail or the bottom of the compound (or a milling table) may ride a bit above the top of the cross slide. I wonder if this may be the responsible for some problems, possibly your rotation.

Evan
07-07-2007, 01:22 AM
I haven't had rotation problems as I anticipated that in advance and ensured it wouldn't happen. I vaguely recall that somebody else did something similar as you for a milling attachment on a SB9 and did have problems with rotation. On mine the brass fitting for the cross feed nut protruded a slight amount so I filed it flush so I could bolt it down tight to the cross slide. I use a gasket of 600 grit sand paper between the table and the slide for extra grip.

heavysteamer
09-22-2007, 08:53 AM
I know there is plenty of milling that has been done on lathes, but I would think that those with plain bearings (especially) might be prone to more wear doing this. While plain bearings are perfectly acceptable in a lathe, they are not so popular in milling machines...at least not today. A plain bearing is really a hydrodynamic bearing that relys on maintaining an oil film on which the spindle rides. Given that, there is some point at which that film is broken down by lateral forces on the spindle.

The spindle oil used is pretty thin (intentionally) so that it will flow and create that continuous oil film. I guess the question is just how much side pressure the spindle can take before you break down this film and begin to wear the bearing material.

Paul

Hendey used the same type spindle bearings in their lathes and in their milling machinnes. They used ring oilers in both.

J Tiers
09-22-2007, 09:52 AM
I have a vertical attachment with plain bearings, and it has operated very well indeed.

However....

The main problem with lathe milling is the very narrow "footprint" of the cross-slide on the tiny lathes we generally talk about. (the saddle on a larger machine may weigh more than the whole SB-9). You can put a large table on top, but that footprint is the basis, and adds a lot of flexibility/limberness.

Most 3rd party practical milling attachments seem to add a lot of mass, presumably to lessen the looseness/flexibility issues with the crosslide. The MLA stuff is rather heavy-appearing, Paul's big steel plate looks like it weighs 20 lb or so, and even Evan's is chunky, although I seem to recall it is aluminum. (the Atlas and the S-B it was copied from are not very heavy).

Has anyone used a milling table which is bolted to or supported by the entire saddle width including the wings?

A number of larger machines have t-slots in the saddle wings which allow securing work to them.

In principle, on a smaller machine one could at least support the corners of the table on the wings with jackscrews, although you would need to use the vertical slide only. To use the crosslide motion during milling you would need a more complex system for allowing the supports to move. But the base would seem to be a lot more stable with the wider "stance".

AJL
09-22-2007, 09:52 AM
Paul, I agree with Evan. Go ahead and mill all you want on the lathe. It won't hurt it a bit. I've been milling on mine for twenty-five years and things are fine. The same bearings, just new oil once in a while. Andy Lofquist