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Help with Milling for newbie

I recently purchased a vertical milling machine.

My problem is that I am having trouble with

1.setting the origin

I set the vice parallel to the mill table using a dial gauge, then I attach an angle bracket to the table at one end of the vice to act as a stop. This enables me to put the small plastic enclosures that I need to mill into the vice in the same position each time. I try to line the mill bit up with the stop for X origin but cannot get it accurate (the cut ends up 1-2mm out). For the Y setting, I move the mill up to the edge of the job but end up marking the job by accident.

How can I set the origin (my x=0,y=0 point) accurately.

2.calculation to make allowance for slot drill diameter.

I am using a 6mm End slot mill bit. When I make a test cut by moving the table 10mm and then measure the cut length, I find that the amount of cut taken up by the drill is only 4.75mm and not 6mm. (I drill down to start the cut (this should have put a 6mm hole in the job), then move

10mm to the right and I should have the 10mm moved + 6mm drill diameter?)

I know about the backlash and ensure when I change direction that I re-zero the dial reading to take out the backlash.

Currently I measuring cuts with the dials on the handles manually (which is very tedious and easy for mistakes), but have ordered some digital scales that should make life easier.

Thanks for any help to get me started.

PS. Is there a web site someone knows of that would show the various allowances that need to be made when making cuts etc. I have purchased a book but it does not mention those details.

Reply to
David
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Congratulations!

There are things called edge finders that work well for this. They have a shank that you chuck into your mill instead of a cutting tool and an end that can be displaced from center. You set the mill up to run slowly and sneak up on the edge of your part with the tip of the edge finder slightly displaced from center. As you approach the part, the flat on the tip of the edge finder will touch the part once per revolution, and more importantly, move a little bit closer to centered. As you approach the correct stopping point, the tip of the edge finder will be almost perfectly centered, so it transitions from touching once per revolution to continuous contact. At this point, the center of the quill on your mill is offset from the edge of your part in this axis by the radius of your edge finder. Zero the dial on that axis of your mill, taking the radius into account. Now move the mill table so that you can approach your zero line on the other axis and repeat the above process. Approach your work in the same direction that you plan to make your cuts so that the backlash in the leadscrews is closed. With the locating arrangement that you have described, you should only have to zero the dials once.

This is probably a backlash problem mostly. Back your table up one full turn of the handle on the axis away from where you want to start your cut. Now return to where you want to start your cut, moving in the same direction that you want to cut in. Stop at the point you want the cut to begin and lower the tool into the work. Complete the cut by moving the table the cut length - tool diameter. Raise the cutter.

Don't re-zero your dial! Make all your dimensioned cuts in the same direction that you zeroed the dial from originally. Otherwise, you will spend a huge amount of time rezeroing and probably still get disappointing results.

Reply to
MetalHead

Explain in more detail how you do this.

A good investment would be an edge finder for $10 or so. It will get you within a half thou.

You're not allowed to use digitals untill you master the dials.

Reply to
Tom Gardner

(snippage)

Well, dammit, Tom. That's a cross for this amateur to bear with an old Burke/Millrite vertical, backlash, and high-mileage eyes. You guys are tough on the novices here.

Garrett Fulton

Reply to
gfulton

"> Well, dammit, Tom. That's a cross for this amateur to bear with an old

It's like my little nephew explaining that he didn't have to learn math, that's what calculators are for. You have "Special Dispensation" but, didn't you believe your mother when she said: "Stop doing that or you'll go blind!"

Reply to
Tom Gardner

I quit when I needed glasses.

Garrett

Reply to
gfulton

I've seen those "Coke Bottle Bottoms" of yours.

Reply to
Tom Gardner

Well, shoot. Coffee all over the keyboard.

Garrett

Reply to
gfulton

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