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KMB
08-18-2006, 02:30 PM
Hello, I'm new here and this looks like a good place to learn alot of stuff about machining. I have a question about a mill I just got. How good is good enough? I mounted a guage to test any variance in the table and moved the table front to back and side to side and the table only varied from 0.0000 to 0.0015...In my mind, that's good..but then again, I'm no machinist! Any thoughts?

Millman
08-18-2006, 02:59 PM
{{How good is good enough? }} One of the great questions of all time. Search the archives for checking the spindle, table, and everything under the sun. What kind, size is it? Welcome!

SGW
08-18-2006, 03:18 PM
"It all depends." What are you trying to do? Quite likely the accuracy you have will be "good enough" for most anything you're likely to tackle...but only you can know for sure.

There's also the "knowing your machinery" aspect of things. If you know the quirks of your milling machine, and what you need to watch out for, you'll be able to get better work out of it than one might anticipate.

kap pullen
08-18-2006, 03:23 PM
.0015 error sounds very good to me.

How's the tram of the spindle to table?

That means mounting an indicator in the spindle
and sweeping the table with the indicator.

A good machinist learns to compensate for errors
and make parts better than his machine.

If you're making rocket parts, your .0015" may
not be good enough.

For most work, that will be fine.

Kap

Alistair Hosie
08-18-2006, 04:05 PM
Kindest regards from over the pond and a hearty welcome Alistair

lazlo
08-18-2006, 04:14 PM
I mounted a guage to test any variance in the table and moved the table front to back and side to side and the table only varied from 0.0000 to 0.0015...

The test you did measures the local flatness of your table, and your numbers are fine if you're just getting started.

Eventually you'll want to check/adjust the "tram" -- how perpendicular the spindle is to the table, but that's a relatively involved process.

For now, I'd just make stuff. You'll know if you have a problem with the machine alignment. Then post your question here -- you'll find a ton of people willing to help you.

Have fun, be safe!

Cheers,

Robert

KMB
08-18-2006, 04:14 PM
.0015 error sounds very good to me.

How's the tram of the spindle to table?

That means mounting an indicator in the spindle
and sweeping the table with the indicator.

A good machinist learns to compensate for errors
and make parts better than his machine.

If you're making rocket parts, your .0015" may
not be good enough.

For most work, that will be fine.

Kap

That's exactly what I did! I figured it would be a good test for it. I'm making motorcycle and lighting parts, no rockets here!

The mill is an old Maxmill YC-1-1/2VA (Bridgeport Clone)...I can't remember the table size, somwhere around 9x50 I want to say...here is a pic of the same one: http://machinetoolsforsale.com/Pictures/MaxMill_Vmill.jpg

I've done some test cuts with aluminum, and I'm very excited about using it.

lazlo
08-18-2006, 05:06 PM
I mounted a guage to test any variance in the table and moved the table front to back and side to side
...


That means mounting an indicator in the spindle and sweeping the table with the indicator.That's exactly what I did!

To test the tram of a mill, the table doesn't move: you mount a DTI on a horizontal rod like a Zero-It indicator holder, and sweep the DTI in a circle around the table. You'll have tram errors at each point on the clock face. You then adjust the front/back, and left-right "lean" of the spindle to minimize the tram error, which results in the spindle being perpendicular to the table.

What I was implying by "just start making stuff" is that you'll typically see tram errors when you take wide parallel cuts across a flat workpiece -- there will be a ridge between each subsequent pass. If you're not seeing any problems with this, then you don't really need to adjust the tram yet.