I Don't Understand My Drill Bit Chuck

You could check the accuracy of the square by clamping it to the table so that the long arm is perfectly aligned to the long axis of the table, then see how square the other arm is to the cross axis of the table. If it is out, you could even take a light cut while it's there and it will be square.
 
bill stupak said:
Have you checked your drill bits? I have a spotting drill that consistently drills off center. I suspect the grind might be off. Stu
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Thanks, Stu, but that's the one thing I think I can rule out. Unless lots of bits in two different sets are off.

I've seen this problem before and just changed the X coordinate assuming I got it wrong the first time. The fact that the error was in X and never in Y is a clue that the column is tilted left/right, not front/back, and the fact that the bit looks to be too far to the right makes me think that's the way the column is tilted.

The problem seems to be something that's coming from switching to the drill chuck, and the fact that the chuck requires that I move the head farther up the column is the thing I'm investigating.

Once I have enough coffee.
 
A few minutes ago, I suddenly thought in terms of the angle error rather than the error in terms of thousandths of an inch. I remembered I have an Igaging angle measurement device. I zeroed it on my table and put it on the Z-axis.

AngleError.JPG

0.4 degrees off. A quick calculator shows that if my difference in head height between my center drill and the drill chuck with the small bit I used was 3", it give about the amount I moved the drill bit by eye to center it in the hole.

I might even be able to fix it using this indicator.
 
Great! Looks like you're on the right track. That looks like a nice gauge, but if it were me I would also check it with an indicator and machinist square like the fellow did in the video I posted. I don't know what the rated accuracy of that electronic gauge is, but a dial indicator should be dead on. If nothing else, it's a good backup just to verify.

Good job!
Ted
 
Technical Ted said:
Great! Looks like you're on the right track. That looks like a nice gauge, but if it were me I would also check it with an indicator and machinist square like the fellow did in the video I posted. I don't know what the rated accuracy of that electronic gauge is, but a dial indicator should be dead on. If nothing else, it's a good backup just to verify.

Good job!
Ted
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Not only that, I think there's no particular reason to believe the side of the casting is purely vertical and parallel to the ways. FWIW, they claim the indicator is repeatable to 0.10 degree.

I loosened the four cap screws on the Z-column base and when I prepared to get the mallet and convince it to be in a different position, it was reading 90.00. So I retightened them.

This made me figure my spindle tram will now be off, and I checked it. It was off by over 20 thousandths. So back to my tramming fixture and that took a few whacks with the hammer to convince it to be somewhere else. I stopped when it read off by .002 over 10 inches just to verify the problem I started out to fix was going away.

Clamped a scrap of aluminum to the table, used my spotting drill to mark a hole, then switched to the drill bit in a my chuck and it is visibly centered much better.
 
I think it's fixed.

I clamped the machinist's square to the table (it's a 5" not a 4 - I misremembered) and after a little foolery, got the indicator to sweep the edge over almost all of its range. No error at all.

If I figure it's .0005 (since I'm using a .001" reading indicator, I'm sure I would have seen that) and solve for the angle needed to give that, I find it would have to be .0057 degrees. Much better than it started.

Test_on_Sq_Top.JPG
 
That's great news! At this point you may want to consider acquiring the necessary tools and/or items to align that Z axis dead on. Vibration could cause it to move in the future so it might be a good idea to check it once in a while as you would check your head tram. I can't even imagine if one of my mills had a Z axis that was off. Seems to me it would really compromise accuracy. A nice little 0.030" travel test indicator with adjustable mounting arms and a 6" or larger machinist square wouldn't cost you much, but prove to be very valuable to you in your hobby. I picked up a decent indicator from Shars for around $30 if I remember correctly and it works fine for what I use it for. You can make the mounts/arms yourself if you have a lathe, but they are so cheap on eBay you might want to buy instead.

Just a thought,
Ted
 
Looks like you pretty much already have what you need. Good job!

Ted
 
That angle cube looks like a cool tool, gotta start dropping hints for stocking stuffers this year :big grin:
 
They are cool. If you're trying to put a piece of stock at an angle to clamp down and then trim straight giving an angle, they work great for that.

CuttingTheTapers.JPG

That Sharpie line on the right is parallel to the table, so I cut away most of the stock on the bandsaw and then milled that area in a straight cut on X. Ends up that 16 degree angle.

(Do I need to mention the Angle Cube and that plastic clamp weren't there when I made the cut? And neither was the part you can see the cap screws in?)
 
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