View Full Version : Milling Trouble
07-17-2009, 12:46 AM
I have an urgent need to do a .610 wide slot in 1/4" mild steel plate, but no milling machine, or any experience with one for that matter. I do have a decent HF drill press tho. It's a mid-90's Taiwan made floor model. 16" swing? 1HP motor. It never saw nuthin' but wood until it got to me so it's probably as good as the breed gets.
So I got me a PhaseII X-Y Table from Enco and an #2 Morse 1/2" endmill holder from J&L to see if maybe ..... and so far we ain't doin' to good.
I plan on roughing the slot out with a drilled hole and a cutoff wheel, so all I'll need to do is clean out the sides to the correct dimension, but being like a kid with a new toy I lashed it all up for a little bit of surface milling.
And that's when the trouble started. For some reason the taper's not holding and when it fell out mid cut it was time to say goodbye to my only 1/2" endmill. Another one bites the dust.
After a coat of felt tip pen for marking I knocked the holder in there for a look at taper contact. It's from J&L's "Value" line which explained the Made in China sticker, but gosh, there was lots of missing ink. The fat part was naked all the way around for 3/4". Lots of marks above too. So I'm thinking that's OK, but I could put up a pic if anyone thinks it's necessary.
In hindsight something I'm not sure of is if I should be using a centercut endmill for surface work. The only endmills I have are the ones I've been using on my lathe to rough out for interior work, and centercut's work fine for that. Is it possible that type of endmill is digging in and pulling my taper out?
07-17-2009, 12:59 AM
I hate to be negative,But the drill press is not realy designed for milling. Using a morse taper end mill holder without a drawbar is shakey at best even in a milling machine.You need a new plan:(
The cold harsh light of day.
07-17-2009, 01:07 AM
Two primary problems:
One, a drill press' spindle bearings are NOT designed to take the side loading an endmill produces, and chances are, both that bearing and the quill-to-casting fit is no better than mediocre. When it did cut, you probably got chattering and a poor finish.
And two, do NOT use an unrestrained taper to hold endmills. Without a drawbar or other locking mechanism, the only thing holding the taper into the spindle is friction. That's fine when the force of the work is trying to push the taper deeper into the socket (as in when you're drilling) but with an endmill, if the taper slides or moves even a tiny bit, it "unlocks" completely and goes flying across the room- as you discovered.
Couple this with the fact that the helix (twist) of the cutter tends to try and draw the tool downward- and thus, out of the socket- it's basically inevitable it'll come flying out. You're lucky all you broke was the endmill.
Your drill press almost certainly has no provision to accept a drawbar, and likely can't be easily modified to accept one. Short of borrowing a real mill, or having a pro shop make the cut for you, I'm not sure what your answer is. Die grinder and file work?
07-17-2009, 01:13 AM
Milling with a DP just plain dont work:eek: No Way, No How! the Dp method of holding the drill chuck in - Jacobs taper - is designed to be used with downward force and any lateral/sideways force will cause the problems you have already experienced. Yes, there is an occasional JT on a DP that will stay put for some very light side cutting, but it is risky for the tool, the chuck, and your body - when that chuck with an end mill comes flying out of there, its best to not connect with it.....
Your best, and easiest method to accomplish this job is to 'chain drill' (consecutive side by side holes) close enought to not leave a web between the holes, clean up as best as you can with a hand hack saw, or jig/sabre saw and then file the rest out....
07-17-2009, 01:56 AM
Sorry, but that way is nothing but trouble. My advice, either pack it up on your cross slide and use the lathe (still far from ideal, but doable), or find a friend with a mill.
The Artful Bodger
07-17-2009, 04:10 AM
Ditto to comments regarding drill press unsuitable for milling.
However it is not all bad news. I believe you now have a drill press with an XY table? Use it to drill a series of holes in nice straight lines (i.e. 'chain drill) outlining your desired slot. Use a metal cutting jig saw or hacksaw to join all those holes until the centre bit falls out. You will find finishing with a file will be suprisingly easy as the X Y table has left those holes in nice straight line!
I like to use the smalles practical drill for chain drilling as it leaves less to file!
07-17-2009, 06:40 AM
keep all your body parts attached and forget milling in the dp, for one thing, the chuck is prone to pop out with no draw bar holding it in.
your job however is a piece of cake - same idea as what Bodger says. I'd just layout and centre punch the holes, chain drill along each edge of the slot, hacksaw where necessary and file in the final slot to dimension. A very accurate fit can be made, maybe better than milling, if you have what goes in the slot with you...put a little blue on the piece, test fit along the slot and carefully file of the blue marks. you can take a fit from 'the piece will just barely go in with some force' to 'a smooth running fit with no slop' depending on what you want
07-17-2009, 07:04 AM
Starting a hack-saw in a line of small holes - twice - is going to be a problem.
Mark the the hole out - by hand if you have to - and centre-punch for each hole and drill several holes:
- 2 x 19/64" (0.594") holes in the centre of the slot and 9/64" in from each end; and
- two lines of say 3/16" holes each 7/64" in from the lines at the side of the slot - holes spaced say 7/32" apart.
Use a 1mm (0.040") wide abrasive cutting-off disc in a 4" (or larger) angle grinder and cut between the two lines of holes as far as you can. Finish off with a hack-saw in the slots provided.
Use a wider abrasive disc and a file to finish off as required.
07-17-2009, 09:04 AM
SOME drill presses will tolerate milling.
MANY/MOST will not, and will either spit the part or the tool at you, mill corkscrew patterns instead of straight, etc. etc.
With a taiwan DP, I'd not bother. I tried it, as have most people, and while teh tool stayed in place, and the taper didn't fall out, the results sucked bigtime.
Mill in the lathe. THAT has problems also, big ones, but it will work even on a small lathe if you stay within the limits of small cuts and many passes, etc, etc.