Mills and Drills

Can anyone elaborate on the differences between a Drill and a Mill as far as the relative size, placement, and materials when it comes to the chuck, spindle, quill, arbor, collet, bearings, gears, ect.?

In other words, it's obvious that a mill can move the tooling along more than a single axis, unlike the drill press, but I am attempting to get a handle on the *physical* reasons why so many here say that a drill press shouldn't be adapted to mill use.

If these physical reasons can be solved with only small manufacturing changes in drill presses to allow them to become more suited for milling, then does the conventional drill presses unsuitability have to do with the bottom line of the manufacturers or lack of consumer interest responsible for a lack suitable adapers/tooling, or perhaps there are other logistical issues involved?

I've heard about the specific forces that the bearings and so forth would have to take as being a reason for a drill presses unsuitability for milling operations, but it seems to me that a suitable gearing adapter would negate much of these "lopsided" forces.(Probably at the expense of a lot of power).

Also, I figure that since so many of you have been machining for so many years, is there a possibilty that any bad drill press milling experiences are at least in part a result of a lack of availability of suitable adapters and tooling for this?

Anyway, in the meantime I will of course still take the advice of not using a drill press for milling purposes, but only when it comes to metals, because there shouldn't be as much of a problem with plastics like Nylon or Delrin.(But I'll listen to opinions either way). :-)

Thanks a lot.

Darren Harris Staten Island, New York.

Reply to
Searcher7
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The foremost reason is physics.

Basically it has to do with friction.

Bear with me.

Drill presses mostly use a morse taper to mount the chuck to the spindle. Morse tapers are ordinarily considered to be 'self holding' which means the tangent of the taper angle is *smaller* than the coefficient of friction for the materials involved. Here this is of course steel on steel.

What this means is that for axial loads the taper will not come loose from the socket.

You can drill all you want and the forces that try to extract the taper shank of the drill chuck will not do so.

Note the preceeding explaination involves axial loads.

Milling imposes *radial* loads, or side loads to the taper. At this point the relevant angle one compares with the friction coefficient is no longer the taper angle.

Simply put, under radial (side) loads, morse tapers become self releasing. The drill chuck arbor will self-extract from the spindle under side loads.

The other reason one does not mill in a drill press (namely, the absense of a draw bar to prevent the arbor from extracting) is that it typically involves putting and end mill in a drill chuck.

Again the physical sciences rear their ugly heads and the problem here is that the end mill is *harder* than the jaws of the drill chuck. Aside from ruining it for precsion drilling work, an end mill, no matter how tightly cranked down in the chuck, will never be secure for extracting under axial loads.

So what to do? Buy a drill press and modify it to accept a draw bar, and some kind of collet perhaps. By the time you are done you could buy an R8 spindle mill-drill and be done with the thing.

Jim

Reply to
jim rozen

Drill presses built for side forces are called mill/drills. I don't know what kind of adapter you are imagining that would turn a drill press into a milling machine.

Reply to
ATP*

According to :

Start with the lack of rigidity of the drill press's frame. It is designed only to support the workpiece against the axial forces of drilling.

A milling machine has a *lot* more metal in the head, a more rigid column (the best ones don't have round columns, and actually move the *table* up and down with a leadscrew. Even those with round columns have a larger column diameter, to minimize the twist under cutting loads.

The quill (which moves the spindle up and down for drilling type operations) is larger in diameter, and a more precise fit in the headstock, so it will not move sideways under cutting loads.

The mounting of the cutter to the spindle of a milling machine is *not* via a drill chuck. A drill chuck is normally mounted via a taper -- a mount not designed for side loads, as the drill chuck will pop lose and start bouncing around the shop, spinning rapidly, and carrying a sharp cutter with it.

And -- a normal drill chuck is not designed to grip the hardened surface of an end mill shank. (An exception is the diamond grit jaws on one of the more expensive Albrecht drill chucks -- designed for use in a milling machine, and made with a standard milling machine taper (e.g. #40 MTMB, or R8 collet format) shank -- *not* a taper such is used for normal drill chucks.

The bearings in a drill press are designed to handle only the axial (thrust) loads, not side loads.

Gear drives can increase the torque at the expense of speed. So can belt drives. This is *not* the major weakness of a drill press when used for milling.

Milling machines have a *lot* more steel and cast iron which go into their makeup.

There are cheap small tabletop drill presses which can be easily lifted with one hand. The weight of a tabletop milling machine of similar size will probably require a two-hand lift.

A lack of suitable design for the purpose. A *first* requirement for a drill press which is going to be used for milling is a hollow spindle, so a drawbar can lock the end mill holder or collet into the spindle -- to protect against popping the tool holder out from side loads.

And *nobody* is going to make a drill press with such a spindle, as it would cost more, and the machine's frame would still be inadequate for the lateral and twisting loads which milling would apply to it. Making a drill press with such a spindle would simply be leaving them open to lawsuits, which all manufacturers would rather avoid at all costs.

Note that a radial arm drill press *might* be solid enough in some features so you could get away with it -- but none of these weigh less than a minimal floor-standing milling machine, and there is no way that you could get it up to your apartment.

Of course there are problems using it for Nylon or Delrin. You have done nothing to deal with the tendency of the chuck to pop off the taper when subjected to side loads.

And there is still the tendency for the frame to wind up under cutting loads, causing a deeper cut than you intended, and thus increasing the chance that the chuck will pop off.

Yes -- it is *possible* to redesign and manufacture a drill press for use as a milling machine -- and this is exactly what you will get if you purchase a "mill drill". And -- it will be to heavy to get up your stairs. (And -- it will still not have the workpiece size ability of a milling machine so designed from scratch.

Good Luck, DoN.

Reply to
DoN. Nichols

A small mill-drill would be no problem to disassemble and move up a residential staircase. No part of those is as bulky or heavy as, say, a refrigerator.

A really small mill drill, like a Sherline or Taig, could be carried up intact by one person.

Reply to
Don Foreman

2 major problems:

(1) you have side load and interrupted cut on an end mill which a drill press is not designed to take. At best the quill bearings will get beaten out quickly. At worst, the end mill will slip in the chuck, the chuck will come off the arbor, the arbor will com out of the quill, generally at high speed. (2) The lateral location of the drill press head is not rigid. I.e. most drill presses are made so the drill press head and table clamp to the column. Again, not a problem in drilling, and in fact it may even be helpful to allow the drill to seek center. Milling side loads will cause the head/table to shift resulting in part/machine damage and possible operator injury.

If you are bound to try this, or have economic constraints, be sure to keep everything as tight as possible, re tighten the chuck frequently, use slow speeds and don't force anything. In my not so humble opinion, it takes *MORE* skill and experience to successfully mill with a drill press than a milling machine. Of course, by the time you have acquired the necessary skill, you wouldn't do it.

It still beats a file.

Uncle George

Reply to
F. George McDuffee

According to Don Foreman :

But he has multiple floors of narrow staircases, and he has suggested that an appliance dolly will not be practical on those stairs.

But -- he has also said that he has managed to move some pinball games up those stairs, so I don't really know.

Sure -- but I would consider those to be miniature milling machines, not small mill drills. Same for the little mills which Harbour Freight (among others) seems to offer.

But since he wants to do a lot of work with stainless steels, I'm not at all sure that any of these would prove satisfactory. I really think that he needs a place at ground floor level for his machines -- perhaps one of the garages which can be rented.

A small mill would at least let him get some experience, which would enable him to make a somewhat better choice next time around. Perhaps even to choose to find somewhere else to live which would adapt to the machine tools which he really needs. (But then again -- living in New York (Staten Island) is a different kind of life -- and one not well fitted to hobby metalworking.

Enjoy, DoN.

Reply to
DoN. Nichols

Gerry :-)} London, Canada

Reply to
Gerald Miller

Er, how about one of the HF/Sherline/Taig mills (they are real mills, just small) vs. most any radial drill?

Pete C.

Reply to
Pete C.

So basically all necessary upgrades would actually make a drill a mill. :-)

Thanks.

Darren Harris Staten Island, New York.

Reply to
Searcher7

To clarify what I said about the specific(radial) forces not friendly to the conventional drill press, I was addressing the possibility of a "gearbox" placed *after* the chuck that would negate these negative forces to an extent.(That is why I said that it would result in the loss of a lot of power, by virtue of being inefficient). This gearbox would of course have to be made to "fit" the housing in the chuck area. This would have the effect of distributing out the radial loads that account for all the negative things you mentioned. But of course there is still the ridgidity issue.

P.S: I haven't been able to find detailed plans on the internet, so if anyone is aware of any illustrated info concerning the parts and dimensions of these machines, and in particular the work tables(rotary and otherwise), I'd appreciated it.

Thanks a lot.

Darren Harris Staten Island, New York.

Reply to
Searcher7

I was going to pick up a hand truck, but realized that it would add to the dimensional size of the video games I wanted to get up the stairs and around the corners. These machines are as wide as 25 inches, as deep as 34 inches, and over 6 feet tall and 350lbs.(These are maximum numbers).

Ok, so perhaps what I need is a universal base that would perhaps amount to three 100-150lbs sections before being bolted together, and an attachable/detacheable dovetail column which may add another 150lbs. To this would be added the swappable heavy duty "Mill head"(motor housing and all containments). All this would ad up to attain the needed ridgidity.(I can dream, can't I?).

I guess you're right about me getting a small mill for now. The most extreme thing that I will have to do that would be beyond the capability of the Rotabroach I just won on eBay is carve out a 4" diameter hole that is 1/16" deep in stainless steel.(Not all the way through).

If I can establish that I could get that done with something like a Micro-Mark Mini-Mill, then I'd be set for now.(I'd of course need to also get a machine for straight cutting 1/4" thick S.S.).

*** BTW, as far as a drill presses short-comings as a mill, if we apply what was said to a lathe instead of a drill press? Would most of the same issues apply?

Thanks a lot.

Darren Harris Staten Island, New York.

Reply to
Searcher7

According to :

[ ... ]

Hmm ... the 4" diameter will probably call for slower spindle speeds that the Micro-Mark can provide -- and more torque. Especially so because you insist that stainless is your material of choice. I really suggest that you experiment with something like 12L14 steel, and compare how easy that is to machine to what is needed with stainless.

I'd be a *lot* happier if you were not insisting on stainless. And I'm not sure *why* you insist on stainless. If it is inside what you are making, it can be lightly coated with oil, and you will have no problems with rust. If it has to be out where people can handle it, then you might want stainless.

The Micro-Mark probably could make a 4" x 4" *square* pocket fairly easily. Though you might have to make two or three passes with Stainless to get 1/16" deep. To make a round one on a small machine, you would be better off with a rotary table -- *if* the overall size of the workpiece is small enough so the corners will clear the column as it is being rotated.

A lathe is a *lot* better as a mill than a drill press is. The setup is awkward, and the travel is less than you would probably like, but since the spindle is hollow, you can fit a drawbar to hold the endmill in a collet (or in an endmill holder) in place. The lathe is designed for lateral loads. Mostly, the problems are with the orientation of the milling cutter to the work, and the added stuff needed to give a vertical axis -- which is usually not as good as the rest of the lathe.

That said -- model makers, in particular in England, do some amazing milling in a lathe.

Enjoy, DoN.

Reply to
DoN. Nichols

Actually most of the parts in question will be enclosed most of the time but the device will be opened up frequently for adjustments.(I just don't know if S.S. 316L would be over-kill).

For this particular operation the work will be 4-1/2" x 4-1/2".

The lathe as a mill seems to bring with it a different set of problems. One operation will require that I start with a 3/4" rod and *square* one end down a 1/4".(1/2" x 1/2" x 1/2" x 1/2"). This would take some kind of cutter that I'd have to slide the word under.(And that is just one of several "square" parts involved in my first project). That is why a mill-drill is my first choice at this time. It would seem easier to use a mill as a lathe instead.

Thanks.

Darren Harris Staten Island, New York.

Reply to
Searcher7

According to :

I think that it is serious over-kill -- and it might not be the best material for other reasons, such as difficulty hardening it by heat treating..

Hmm ... and the round depression is centered? This could be nicely done by a lathe. Let's see -- 4.5" square means that the diagonal would be 6.36" diagonal, so a 7" lathe could handle it, if it had a 4-jaw chuck which could extend the reversed jaws out far enough.

That diagonal applies to the distance from the cutter axis to the column as well, when working with a rotary table.

[ ... ]

[ ... ]

An end mill in the lathe's spindle (in an end-mill holder) and a milling adaptor replacing the compound to allow vertical adjustment of the workpiece. The square could be accomplished with just this, but what would make it easier would be one of those collet sets which holds

5C collets in either a square (for four sides) or a hex (for six, obviously), which could be held in the vise on the milling attachment and be rotated one flat per pass to produce the desired square end.

That latter depends on the mill. First off, you will need some kind of workpiece holder (like a chuck) to fit the spindle (and a larger spindle is better here), and a good way to hold a cutting tool.

Or -- you could mount the workpiece on a rotary table, and

*mill* the workpiece to shape as you rotate the table.

It would be a lot easier to explain the limitations of each route if you already had experience in using the basic tools, and you're trying to decide which tools to get, so you don't have that experience yet.

Good Luck, DoN.

Reply to
DoN. Nichols

I won't have to worrry about that. But since this is a unque kind of videogame joystick, I'm more concerned with the sweaty hands of a gamer who will have to open up the top to change certain settings. My original concern was involved the ball bearings that would roll against the S.S. plates, but I redesigned it so that there will be no friction to worry about between the chrome steel bearings and the S.S. Wherever there would have been friction between metal parts, Delrin was substituted, so that now the only contact will be between Chrome steel(bearings) and Delrin, Stainless steel and Delrin, and Delrin and Delrin.

Ok. A 4" diameter(1/16" thick) Delrin disk will be placed into that hole.

So I guess that one of the 7 x 10 or a 7 x 14 mini-lathes by Micro-Mark, Central Machinery, ect. would work. So it seems that instead of entertaining what the shortcomings are of a drill for conventional mill work, I should have been making comparisons between a Mill and a lathe.

It looks like I'll be spending a lot of time on the lathe pages at the website for Harbor Freight and Grizzly. :-)

True. But You've taught me a lot. :-) I was just getting ready to get a small mill, but now I will look harder at the lathes.

*** It seems to me that once I account for the 3-dimensional(LxWxH) workspace(maximum size of the work piece),and all tooling, jigs, tables, and adapters for both a mill and a comparable lathe, I should just ask what *can't* be done by one machine that the other one can do.(I'm not really worried about what is "easier").

Thanks a lot.

Darren Harris Staten Island, New York.

Reply to
Searcher7

According to :

[ ... ]

Are these settings necessarily part of the joystick, or could the controls be mounted somewhere else?

So -- just wipe the steel part down with a good thick lube like Vactra No. 2 Waylube (which you'll need for your lathe or mill anyway).

[ ... ]

O.K. Any reason why you can't use aluminum for the square plate? Aluminum protects itself by quickly forming an oxide coating which prevents oxygen from the air reaching it to continue the oxidation.

Since you no longer need it to be a bearing surface (the Delrin is doing that) you should be fine. And a good aluminum (say 6061-T6) is quite nice to machine.

[ ... ]

As long as you can get a milling adaptor for the cross-slide.

Yes -- with the understanding that it will be more convenient to have both eventually.

O.K. Not exactly the best of machines, but probably closer to your budget for the moment.

And -- make sure that you get a 4-jaw chuck for your square and rectangular workpieces.

Remember that my size calculations were based on the assumption that the circular depression (I would not really call it a "hole" at that depth to diameter ratio) was centered. (Pretty much has to be, given the size of the depression relative to the overall size of the workpiece.)

O.K. Understand that I have several of both lathes and mills, in different sizes.

O.K. Sometimes, the decider of whether it can be done or not on the "wrong" machine is more whether the machine is large enough to be "abused" in that way. Also -- what tooling you may have around to adapt it is important.

Good Luck, DoN.

Reply to
DoN. Nichols

Uncle George sez:

"> It still beats a file."

Perhaps someone should have expounded on the method of "milling" whereby one chain drills an outline of the desired part and then does final shaping with files. I'd be a lot safer than trying to mill on a drill press. Supposedly there is a gun factory in one of the "Stans" (packy I think) where they produce modern-type firearms with only files. It must be a real bitch to bore and then cut rifling. Those stanny dudes are very innovative, though.

Bob Swinney

Reply to
Robert Swinney

The mechanical "restrictor" will be part of the joystick assembly itself.

Because in some of these prototypes there is the possibiltiy of having to include a game printed circuit board which would have to be cooled with a small fan. So that would make any lubricant a no-no.

Yes. That and it's light weight is why Aluminum was my first choice. That is until I realized that Aluminum *may not* have the stiffness needed. I can't afford to have the disk warp or flex under pressure because of the tight tolerances and the fact that parts of the 4-1/2" x

4-1/2" may have to be under 1/16" thick.

Actually, in the future I will be working with a lot of this. :-)

And another thought. Perhaps those who have been using lathes and mills for many years would correct me if I'm wrong, but since the lathe is inherently simpler than a mill, mechanical problems and maintenance cost should be lower.

My present budget is in the $400-$600 range, but anything that'll cost more would probably be too big for me and my living situation.

Ok. I'm making a list. :-)

I'll definitely be perusing sites and books looking for unconventional lathe uses.

*** Well, with the same work envelopes and access to *any* tooling(along with a good imagination) I guess that a lathe can do everything a mill can and vice versa. The only thing at that point that would be different between the two are the length of travel of during specifc operations and the speed at which each can be done, all factors taken into consideration.

Thanks.

Darren Harris Staten Island, New York.

Reply to
Searcher7

Ok. I perused the Taig and Sherline sites and found only micro and miniature lathes, which seem way too small for me.

Any other recommendations for a machine for what I need to do would be appreciated.

Thanks a lot.

Darren Harris Staten Island, New York.

Reply to
Searcher7

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