Getting crazy here , holes drilled off center - please help!

dimbmw · Aug 4, 2018

Hi everyone

I am a newbie trying hard to figure out what the heck is going on here. I have a cnc converted Sieg X2 mini mill with ball screws.

Here is the problem - I make a hole in a piece of aluminum (either drill or mill), then I try to indicate it with the micrometer, and the hole is off center by about 0.1 mm on Y axis and 0.5 mm on X axis.

I checked everything. Gibs are tightened, no play in anything. Backlash is compensated. Everything looks good.

It is driving me nuts, I am fighting with this piece of crap for a week, and no progress.

What can cause this weird thing?

Please!?

moonlight machine · Aug 4, 2018

dimbmw said:
Hi everyone

I am a newbie trying hard to figure out what the heck is going on here. I have a cnc converted Sieg X2 mini mill with ball screws.

Here is the problem - I make a hole in a piece of aluminum (either drill or mill), then I try to indicate it with the micrometer, and the hole is off center by about 0.1 mm on Y axis and 0.5 mm on X axis.

I checked everything. Gibs are tightened, no play in anything. Backlash is compensated. Everything looks good.

It is driving me nuts, I am fighting with this piece of crap for a week, and no progress.

What can cause this weird thing?

Please!?

You said it, Piece of crap. Toss it in the scrap skip and get a real mill.

dimbmw · Aug 4, 2018

moonlight machine said:
You said it, Piece of crap. Toss it in the scrap skip and get a real mill.

I know it is a crap, but I need to know the reason why the damned hole drills off center?

DDoug · Aug 4, 2018

Please, for the love of god....
try cnc zone. com
or here:
Home Page - Projects and Articles on Our Forum! | The Hobby-Machinist Forum

dimbmw · Aug 4, 2018

So basically the simpliest experiment I’ve done to eliminate as much causes as possible was this: I set just set x=0, y=0 above the spot where I intended to drill. Then I took a spot drill, slowly deeped it into the aluminum, and then just lift it up, not moving the table, so x and y were still at zero on the DRO. Then i took a 0.0005” starlet micrometer, and tried to indicate the hole just drilled - and it was off center.

Milland · Aug 4, 2018

No offense to you, but this is a forum meant for professionals, with professional-grade equipment. So when someone says take it to a forum meant for hobby machines, they're not trying to insult you, but point you to a group that's better oriented towards your needs.

Saying that, what you're likely facing is an "off-perpendicular" condition, where your Z-axis is not square to the X-Y tables. That means that unless your combination of drill length and indicator point length are the same, there will be an offset due to the spindle shifting as it rises, in your case in both axis.

If you set up a precision square on the table, then rotate it four times at ninety degrees and indicate the vertical surface each time, you'll see that the indicator shifts as you raise and lower the spindle. That's showing the off-perpendicular error of the vertical axis.

Try out the other forums mentioned, you'll probably find them better for your needs.

Bobw · Aug 4, 2018

2 possible things.. (that I can think of quickly).

Your X and/or Y are not square to your Z. (head nod maybe).. And by the way, its an indicator,
not a micrometer...

I'm going to make a guess that the tip of your indicator is not at the same gage length as
your drill.. I'd bet my left nut (my favorite one) that if the indicator tip is at the same
gage length as your drill, you would be pretty close.

2nd thing.. Just flat out flex of the machine. OR the drill just wandering off doing
its own thing. POS drills on floppy machines have a habit of doing that.

moonlight machine · Aug 4, 2018

dimbmw said:
So basically the simpliest experiment I’ve done to eliminate as much causes as possible was this: I set just set x=0, y=0 above the spot where I intended to drill. Then I took a spot drill, slowly deeped it into the aluminum, and then just lift it up, not moving the table, so x and y were still at zero on the DRO. Then i took a 0.0005” starlet micrometer, and tried to indicate the hole just drilled - and it was off center.

How do you indicate a hole with a micrometer? Starlet, is that a chinese brand?

dimbmw · Aug 4, 2018

Bobw said:
2 possible things.. (that I can think of quickly).

Your X and/or Y are not square to your Z. (head nod maybe).. And by the way, its an indicator,
not a micrometer...

I'm going to make a guess that the tip of your indicator is not at the same gage length as
your drill.. I'd bet my left nut (my favorite one) that if the indicator tip is at the same
gage length as your drill, you would be pretty close.

2nd thing.. Just flat out flex of the machine. OR the drill just wandering off doing
its own thing. POS drills on floppy machines have a habit of doing that.

I figured out that the column is clearly not perpendicular to the table.

It appears that the problem is that the spindle axis is not parallel to the column. So after I trammed the spindle by shimming the column’s base, the column became not square to the table.

I don’t think this mini mill has anything to adjust the parallelism between the spindle head and the column. Just a bad machining of the parts I guess.

I am wondering if I should restore the squareness between the column and the table and just sacrifice the squareness between the spindle and the table?

dandrummerman21 · Aug 5, 2018

if you drill a piece of stock and you are off center .1 mm (.004"), just move the table .004 and make another part?

Do you need a good part or are you just drilling holes to see what this awful thing can do?

Just pick up an old american made drill press, you can probably hold location tighter than you are now, for less money than you will put into this harbor freight junk.

Or am I missing something?

dimbmw said:
I am wondering if I should restore the squareness between the column and the table and just sacrifice the squareness between the spindle and the table?

Take a hammer to it and bang on it until it is square?

crazygoat · Aug 5, 2018

Whats the old saying about a fool and his money?

Mechanola · Aug 5, 2018

Spindle can be unperpendicular, spindle bearings can be wandering, drill can be of uneven angles, aluminum can be moving, vice can be wiggly, speed and feed can be over the hill, direction of rotation can be wrong, flutes build-up can happen, chuck can be less than discussible—wait, how do you chuck your tools?

EmGo · Aug 5, 2018

If we have to go back to basics, drill with a center drill first then make sure your drill is properly sharpened. Uneven flutes and bad sharpening can make drills wander a lot. If it's anything you care about, you need to spot drill it first. You can get a gage for checking drill bits quite cheap. You need one.

dimbmw · Aug 5, 2018

dandrummerman21 said:
if you drill a piece of stock and you are off center .1 mm (.004"), just move the table .004 and make another part?

Do you need a good part or are you just drilling holes to see what this awful thing can do?

Just pick up an old american made drill press, you can probably hold location tighter than you are now, for less money than you will put into this harbor freight junk.

Or am I missing something?

Take a hammer to it and bang on it until it is square?

Problem is i need to mill out a pretty complicated part, having bearings on both sides. I need to mill one side and then flip over, indicate the hole (and thus zero my X and Y), and mill the second side. Of course my bearings are supposed to be against each other. With such a mill I am having hard time to make holes concentric.

Hammer is a good idea , i really want to destroy this crap with the hammer

it is not harbor freight, it is LMS... but looks like not much of a difference

dimbmw · Aug 5, 2018

EmanuelGoldstein said:
If we have to go back to basics, drill with a center drill first then make sure your drill is properly sharpened. Uneven flutes and bad sharpening can make drills wander a lot. If it's anything you care about, you need to spot drill it first. You can get a gage for checking drill bits quite cheap. You need one.

I used a center drill, of course.

crazygoat · Aug 5, 2018

dimbmw said:
Problem is i need to mill out a pretty complicated part

Why would you even expect to be able to do this on the that POS?
Oh wait. I know. You fell for the magical 3 letter be all,do all code, didn't you.

litlerob1 · Aug 5, 2018

Mechanola said:
vice can be wiggly,

Is that a thing? I hope that never happens to me. (Wiggly)

OP, I think you need to invest in a CNC grinder for your Drills, that'll solve all your problems.

R

DDoug · Aug 5, 2018

Where's Machtool these days ? He would be all over this.

Maybe turned into "MAch3Tool".......

EmGo · Aug 5, 2018

litlerob1 said:
Is that a thing? I hope that never happens to me. (Wiggly)

Nice try. If it never happened to you, you wouldn't know what it was. Popsicle sticks and duct tape.

Or in an amergency, your fingers never get soft

litlerob1 · Aug 5, 2018

What are the tell-tale signs that you might be getting "wiggly"? I'm thinking not a good wifi connection, or old age. Maybe reminiscing using a complete POS Machine to Drill a hole, might cause some shivers---but wiggly??

R

Getting crazy here , holes drilled off center - please help!

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