Mill drill from scratch....kinda'

[ZINOM]

Hi guys, I took the mill head off my three in one a few years back and use it as a dedicated lathe now.

I recently started giving some thought to making some sort of column and base for it and putting a quality positioning table on it to have an extra mill around, and also for my own edification.

My quest now becomes one of finding some source of iron castings that might be suitable for slapping the head onto and securing the base to....oversimplification, I know.

I know a smallish engine block can be used, I've seen an excellent example from one of our members, I guess regular old steel could work too, my problem is I dont have much in the way of scrap for a project like this.

Could the "column" be made of 4' steel pipe with a stout flange welded to it?...could said pipe be filled with concrete to help give it rigidity?

In the abstract, the idea sounds possible, but I'm sure there are plenty of factors to consider that haven't occurred to me yet.

John

p.s. I was thinking of a variable speed motor, maybe from a treadmill....no?

[darryl]

Using an old engine block seems like a good idea. One cylinder could support the column, and the empty spaces filled with concrete, including the column itself. I would be inclined to find a cast column though, as from a drill press, instead of a less accurate steel pipe. Concrete will stiffen the block and the pipe, best to use a standard or slow set, not fast setting concrete. This could be a challenging project for the number of details requiring attention. For instance, how do you intend to raise and lower the head?

[ZINOM]

Thanks Darryl, the head itself has a threaded "column" within the major casting that will allow me to raise the head 3" once it's all bolted to the new support/column....not a lot of travel, but it was pretty good when it was on the lathe so I'm sure I'll get use from it again.

I don't know much about pipes, but I was wondering if there is commonly available cast iron pipe that would have a thick wall and maybe have the integrity I'm looking for.

John

[G.A. Ewen]

ZINOM,
3" is not much, you will ether be shimming all the time or you will not have enough clearance. Having the milling table on a vertical slide will make the machine a pleasure to use. You could make the vertical slide with square ways quite easily. Just a suggestion. I look forward to seeing the finished product.

PS. you could write it up for publication. I bet others with 3 in 1 machines would be interested in a knee mill.

[This message has been edited by G.A. Ewen (edited 12-14-2003).]

[CCWKen]

Filling the column with concrete doen't add much "stiffness". It may absorb some vibrations but adds little to flex strength. If you want a stiff column made from tube, weld angle iron inside of it.

Drill 3/8 or 7/16" holes down three sides of the column about 4-6" apart. Insert the angle iron and plug weld the angle to the tube. Use Tig, Mig or Arc and air cool each spot. Work alternatly around the tube. Grind and finish off. You'll be able to just about lift a car with the column.

[jcurrell]

Go with a sold ground shaft colmb it will give a good finish to start from.

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[ZINOM]

I don't think I need a nice finished column as the head won't be traveling up and down on it....it'll just be holding it like the lathe head-stock used to.

I know 3" isn't much, but I figured with 3-4" of spindle travel, and my ability to raise or lower the head 3" I should have a little workability....certainly not ideal, but not terrible.

I was also wondering if I should look for some steel square tube....I saw a supplier carrying 4x4 and 5x5 with 3/16, and 1/4 wall respectively......I thought I may be able to call a local sign erector to see if I could get ahold of a short length of scrap.

What about mixing lead shot or bb's in the 'crete mix......don't laugh, I'm feeling my way around with this one.....I thought it might give some weight if nothing else.

Thanks for the replies guys....bear with me, I'll probably need more help haha.

John

[darryl]

Ok, so you don't need the column to be smooth, just rigid and weldable. It might make some sense to start by seeing what kind of x-y table you would get to use. Some of these are downright scary in regards to accuracy and rigidity. No point in making the ultimate in column and base if the table is going to be rubbery. Weld something up, and have a method in mind of aligning the table base with the column, like mount the table on short threaded studs. You could weld the studs to the base, to keep them rigid, and use nylock nuts to keep things from getting loose.
Sounds like you'll end up with a good drill press, one that you CAN use for some milling, and one where you get to actually align the table to the spindle on. A square structural steel tube might be easier to work with to weld angle iron table supports and bracings to, and possibly some flat plate, to keep the structure as rigid as reasonable. You will need a method to mount the mill head accurately to the column.

[G.A. Ewen]

My personal experiance with welding and machine tool building is that they don't mix. Every time you weld two pieces of steel together there is a certain amount of distortion no mater how careful you are. As far as filling square tubing with cement to reduce the transmission of vibration I don't know - it might work.

Not trying to be a wet blanket or to stifle creativity, just MHO.

[darryl]

I have filled steel tubes with concrete and found that it does increase stiffness, maybe not by a lot, but it does. There is less springiness to it, but it's no substitute for strength in the metal. If the metal is going to stretch, it will, and loses contact with the concrete. Even so, you still have the damping effect of the extra weight, and the concrete will still prevent the pipe from changing cross-sectional shape, which is part reason why the pipe collapses. With the concrete fill, more of the metal is involved in resisting the stretching forces, while the concrete takes up much of the compressive forces.
Good point, GA about the metal distorting when welding. I wouldn't expect to be able to weld up an assembly in perfect alignment. I suppose it would be an advantage to be able to reheat the entire structure to release stress after fabricating, but it's still going to need some way of adjusting an attachment afterwards, such as an x-y table. I imagine that the assembly will settle in time, as well, so readjustment after a while might be a good idea.

[gunsmith]

If your looking for a stiff column that is cheap, try a hydraulic cylinder from any kind of construction equipment. They are very heavy wall and do not flex. Usualy found in a dump for free. For a good table get flywheels from trucks (big trucks) and for weight you can stack and weld them until nothing will move them. For a mounting flange use a 3" flange from a steel gas line. These are used in the oil and gas industry at refinery type places. I've seen them in dumps also. Good luck and send picktures when your done.

[darryl]

Hmm, I wish there was a dump like that around my town.

[ZINOM]

Yeah, I doubt I'll have that kinda luck....but I'll check around.

John

[jcurrell]

The important thing in useing welding in machine tools is to start with metal thick enough to machine the surfaces after welding.

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[ZINOM]

Darryl raised a good point, I think it makes sense to arrive at which xy table I might want to use and build around it and the mill head.

I have the "phase II" on a drill press now, and it makes the drill press SO much more useful.....but it doesnt have the accuracy, or usability that I'd like to have.

Enco carries a bigger one that looks better...for $119, it's the model# bn201-2536......I've done some web searches for positioning tables and found a lot of expensive laboratory type stuff.....any sources other than Enco that I should check out?

Thanks,

John

ps, I think I'll try to go the route of bolting together as much as I can.