Questions about milling spindles

[Hack]

I was looking at a few different mill / drills at harbor Freight this afternoon and had a few questions enter into my mind while comparing them. The thoughts began by remembering how most people will steer you away from milling with a drill press and a x -y table. Why?

Then I thought well, is it because of the spindle taper or bearings? Must be the bearings because it seems as though the drill presses and mill / drills all have the same chuck (except for the R8 ones). Is there that big of difference between the MT and JT tapers as far as milling?

The reason I have heard not to use a drill press is due to the spindle, lack of mass (rigidity) and that it can't produce the accuracy of a mill. The spindles supposedly can't handle the side loads but what about the tooling itself? I got to beleive that a drill press with a good spindle could handle better side fources than say a 1/8" end mill. Is this correct?

Anyway enough rambling. My point is that I see how another CNCzone member has done a very good job using a drill press and cnc ing it and I know that I have a handfull of small parts to mill (basically squaring of some aluminum parts) so does it really require a mill or can I get away with the drill press and an x-y table.. My drill press is a Grizzley 14" Model G7944 with a MT2 Spindle.

[balsaman]

Milling machines have draw bars to hold the taper in, a drill press does not. As a result the taper will fall out of your drill press when subjected to side loads. Also, you can not hold your endmill in the drill chuck for milling. The forces caused by milling will cause the endmill to pull out of the chuck. This is bad.

The fellow who converted a drill here is using tiny endmills and milling brass bar up to 1/4" diameter. He is getting away with a few things because of the very light loads. Many have tried, few have suceeded. Stevie suceeded.

By all means try. Let us know how it goes.

Eric

[ger21]

Like Eric says, the taper will come loose very easy.

[Hack]

Is it the spindle that loosens or just the chuck?

I see both drill presses and mill/drills with morse tapers, I am assuming the drawbar holds the taper (spindle) on the mill / drill, but what difference is there in how the chuck is held or made?

Looking at an exploded view of my drill press, I am seeing the spindle locked in by a nut and below that an arbor. Is this what you are telling me will loosen up? A quick look through the grizzly catalog shows all of the mill / drills with the drawbar, but one .... the G0517. Is this anything other than a drill press with an x-y table on it and if not, how can it be safe?

What determines why a certain taper is say MT #1,2,3 or R8 etc?

Im sorry if I am asking to easy of questions, but inquiring minds want to know

[eman5oh]

The drill chuck will pop right off the taper when you try to use a endmill in it. Also check for play when the spindal is extended any slop will make a lot of chatter.

[Ken_Shea]

Hack,
Tapers have very specific dimensions but the numbers are easier to remember, the bigger the number the bigger the taper, the R8 is not a Morse taper but as pointed out is tightened up by a draw bar and cannot come loose where the Morse taper and Jacobs are a held in place only by friction fit, when drilling vertically you can imagine that they will not come loose but put a substantial and repeated side load on them and there is great potential for coming loose since there is very little surface area on the chuck arbor taper, strictly speaking they are just not designed for anything but drilling.

[HuFlungDung]

Hack,
Compare where the bearings are located on a mill versus a drill. Quite often, there may be 3" to 6" from the end of the quill to the bottom bearaing on a drill press. On a mill, this distance is much shorter, and the bearing is quite a bit more rugged in the mill spindle.

Add the length of the chuck and tool to this already long distance, and you find yourself with an alarming overhang from the nearest bearing support. Its just a simple fact of machining, that excessive overhang = chatter and generally lousy tool performance. If it was otherwise, machines would be built much lighter duty than they are.

[RotarySMP]

The mini mill comes with a MT 3 taper spindle and a drill chuck (for drill with). To mill with it you need to get some collets/ end mill holders / MT shank end mills...

The drill press comes with an MT2 taper and a drill chuck.

The difference in the machines is the hollow spindle on the mill, so you can put a draw bar (bolt) down the spindle to retain the MT3 tool holder, or collet for milling.

You shouldn't use the drill chuck for milling on the mill, because:
1/ the chuck can't grip an end mill tight enough, and it will likely pull down into the work.
2/ The JT taper between the chuck arbor and the chuck is not designed for side loads, and the chuck might walk off.

You shouldn't mill with the chuck on the drill press because:
1/ above
2/ above
3/ The Arbor can walk out of the MT2 spindle.

Rigidity is relative. The all bench mills are not exactly rigid either.

[Swede]

One final issue of mill cutters in a drill chuck (as if there aren't enough already)... a Jacobs chuck (especially a cheaper clone) will have an unacceptably large runout, meaning the cutter will describe a circular motion larger than the actual diameter of the cutter. One always want to minimize runout in any machine. If the runout is excessive, the cut will be ragged, inaccurate, and the cutter itself will be doing most of its cutting on a single flute. This will load the flute and dull or break it. If you dismount a cutter from a jacobs chuck, then remount it, it will be in a different physical position, and I don't refer just to Z. It is the nature of a Jacobs chuck.

Similar in many ways to a standard scroll chuck. Remounting work in a 3-jaw will rarely result in accurate rotation. This is the bane of many new machinists who don't understand this... they turn a part, remove it to test the fit, then remount, and wonder why their tool bit does not have a continuous cut on the work when infed another 0.002".

All this said, it CAN be done, and has been done, for quick setups, very light forces, and with plenty of caution for the safety issues. Don't do it to a part which you have worked on for weeks! The chuck can and will fall out and destroy the work.

Some Jacobs chucks can be body-drilled and secured to the male jacob's taper with a cap screw. It may also be possible to modify the morse taper for a draw-bar. Doing both of these will secure the system. The accuracy issues remain.

Good luck, be safe!

[Stevie]

Yeah the chuck can fall off

It's the size of the cut that makes the difference
I take small cuts; i did try with the 1/4" and took 0.05 cut at 15IPM and got away with it
But it sounded horrible to say the least

My projects are brass or Alum; i would not even think about shoving steel into it; the cutter will pull; or the chuck "WILL" just fall off

I am looking at replacing the whole spindle assembly; i have some nice FAG roller brgs with a 3/4" bore and the outside is just about a match for the inside of the spindle housing (the part that moves in and out)
I can bore the housing in more; and the part of the housing thats a bit big now (0.005") I will use for an oil seal
You know you build something figure its done; but I don't think your ever really finished

Had to just pop back and edit this

The machine as many uses; i have already used it as a tool grinder; made a new D bit out of a busted #78 sized carbide drill; i used a diamond wheel (1" dia) in the chuck at 3000 rpm; then used the rotary axis to grind the diameter needed then simply just created the cutting edges by lifting and rotating to make the D; works good too

The machine was mainly made to drill holes around tiny brass muzzles of guns from model ships/planes
I can and do use it as a mill but with cutters in the 1/16th to 1/32nd range; it make a very nice drill jig for this the other day

The barrels fit into holes drilled in the jig made by the mill; remember the part it drilled is just 4mm diameter; those barrels are just 0.73mm diameter on the end and drilled scale (these drilled on the lathe not on the mill/drill)
Thats a King George V Class 5.25" 50 caliber QF Mk1 turret from the Tamiya 1/350th model kit
I do all the barrels for that and many other kits

[ViperTX]

HACK,

If you can live with the wibble...wobble...noise...then go for it.

[Hack]

Just kidding guys (about the wife thing), but after reading the above posts and "just knowing better" I bought a mill. Told her I had to have it, explained the safety concerns yadayadayada - Had to sell some woodworking tools to pay for it to keep the wife happy but I'm sure I'll be happier (with the mill and the wife)!