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View Full Version : why does the head on a mill/drill swivel?



gambler
05-07-2018, 07:31 PM
and what is an easy way to re-center it?

metalmagpie
05-07-2018, 07:42 PM
Google on 'tram mill-drill' and all will be revealed.

You can tilt the head to mill or drill tilted.

metalmagpie

gambler
05-07-2018, 07:50 PM
Google on 'tram mill-drill' and all will be revealed.

You can tilt the head to mill or drill tilted.

metalmagpie

my mill doesn't tilt, just swivels.

Jim Stewart
05-07-2018, 07:52 PM
You mean rotate around the round column? (Nothing to do with tramming.)

Because the column is round. And obviously, in that case, if you change the height of the head you may need to reset the position accurately.

I use an edge finder and touch it to the edge of the vise or workpiece, change height and repeat. If you don't have an edge finder, the corner of an end mill with a piece of paper between it and the workpiece or vise works.

-js

Tim Clarke
05-07-2018, 08:13 PM
Short answer is that it's cheaper. When I had a round column mill-drill I swore it was to aggravate me. The scenario went like this: I want to center drill, drill, and then ream a hole. Say, 1/2". So, my center drill is 2" long, and the 1/2 reamer is 8". the 31/64 drill is somewhere in between. I have 5" quill travel??? OOOOPS. So, what to do? Saw off the reamer? Say a few choice words? Imbibe in a couple malt beverages? I tried all 3. The solution was to make an extension for my edge finder. I'd zero on a corner, and move to the location. Then when I needed more daylight under the spindle, I'd crank up the head, re-zero the dials on the same corner, and move to the same co-ordinates. End of problem. I gave the extension to the guy who bought my mill-drill, and I don't remember now how long it was.

garyhlucas
05-07-2018, 08:18 PM
The round column allows to rotate the head even off the back of the table which is convenient for drilling long parts. Otherwise the round column is a nuisance. I think the laser pointer fastened to the head to point at a vertical line drawn on a far wall is a pretty clever dodge that can be very accurate if the machine can’t move.

Rich Carlstedt
05-07-2018, 08:37 PM
why does the head on a mill/drill swivel? and what is an easy way to re-center it?

When the head of a mill swivels, it is called a Turret Mill. The reason for it swiveling is to extend the range of the mill.
Lets say your table is 30 long ( X ) and your travel is 18 inches. or +/- 9 inches from center.
If your work was longer then that, say 28 inches, you could mill the extra 5 inches at each end of the part by swiveling the head both left and then right WITHOUT having to re-clamp the workpiece- this is very important for accurate long work. .
Normally these mills have a measuring tape fastened around the column and a mark on the turret so the location can be repeated ( "0").
When you put a square on the table USING THE T SLOT ( not the edge) and traverse the saddle (in/Out) with a dial indicator reading 0-0 on one edge of the square , you have the turret in plumb (square) with the table and that is the true 0 point!
To keep that you have several methods. One method is to drill a hole between the turret and the column and then taper reamer the hole . Then when returning the turret to this point, you tap in a taper pin in the hole. Another very accurate method (IF you do not move the mill !) is to fasten a cheap laser pointer to the head rigidly ( ! ) and so the pointer can have the batteries changed and no movement occurs. Then turn on the lazer and permanently mark the wall across from the mill (far wall) . Then when returning the turret, just look at the wall while you tap the turret into place. Because of the length of the "moment" arm, it is dead on

Rich

Paul Alciatore
05-07-2018, 08:42 PM
Why does the head on a mill/drill swivel?

Swivel is not a very definitive term. Since you are asking about re-centering it, I must assume you mean rotation about a VERTICAL axis, that is rotation about the vertical column.

Not all mill-drills have a round column so not all of them have this rotation. Mine has a dovetail column and there is no rotation except for a slight droop which combines a rotation with a front-back movement, if the gibs are not locked down.

But why do round column mill-drills rotate about the round column. Well, because they can: I mean it IS a round column. But why do they use a round column? That is the better question. In all likelihood, that is because it is the cheapest way to make a mill-drill. Look at the prices of any line of mill-drills. The less expensive ones have round columns and the ones with dovetail or other non rotating columns are more expensive. Pure economics.

The first mill-drills that I worked with were both purchased by companies that I worked for and they had round columns. I guess their bean counters just looked at the prices of the equipment and did not give even a second of thought of the cost of labor to use them. When I purchased my mill-drill one of the first things I looked for was a dovetail column. That was a must. And I love it over the round column ones.

There have been many schemes for keeping these round column machines on the original center when the head is moved up or down. Keys, outboard shafts, laser pointers, etc. You can search for them here and on almost any machining board. And on the internet itself. Frankly, I do not like any of them. Although they can be made to work after a fashion, almost none of them were designed with tight specs and real solid engineering. I suggest that you read the stated results with a suspicious eye.




and what is an easy way to re-center it?