locating holes and tool center

stoneaxe · Jan 8, 2020

Making an end mill holder-- it was first bored in place in the machine spindle,(on horizontal axis ) then reamed to size with a fixed reamer held in the table vise.

To establish the reamer on hole center, first, the reamer was secured in a vise with the shank indicated in within a couple of thou of parallel with the tables travel.

I ran the table forward so the reamer shank was parallel,but not touching, the OD of the endmill holder. Then took the space between them, plus half the diameter of the holder and reamer shank, and used it for a zero point. Did the same on the vertical axis. Purely a math solution.

Nevertheless, the end of the reamer was about .005 off center.
Maybe it was an accumulation of error, or perhaps the reamer shank was not dead straight, etc- finally I put an indicator on the end of the reamer, and zeroed in the movement (with the end having chamfer, it would move when entering the bored hole.) This may have been a mistake, if the point where the reamer was held in the vise was on center, and the "off center" at the hole entrance was because of a slight bend in the reamer shank.

Anyway, the hole was successfully reamed. I think flex was my friend.

The point of all this, is the question-

Using a measuring device, what is the way to locate the hole center in the spindle, and the same point on the table/vise/reamer setup? I could easily locate either one of them, but the indicator needs to move to locate the other, losing zero in the process.

TeachMePlease · Jan 8, 2020

You attach your indicator to your spindle with in Indicol, a Noga, or a Mighty Mag...

13engines · Jan 8, 2020

After aligning your vise square to the machine as you normally would, mount a dial test indicator in the spindle or on the rotating part of it with a mag base and directly indicate in the flutes of the reamer by rotating the indicator tip over the flutes opposite their cutting direction, and move the table and column until you have the least indicator movement. Another simple way is use a pointed edge finder mounted in the spindle, place the tip of it in the hole on the end of the reamer and mover the table and column until the tip and shank of the edge finder become perfectly aligned. (The quick and dirty method.) Then re-mount your end mill holder and have at it. You could do the quick and dirty method to get you super close, and finish with the indicator if so inclined.

Dave

AlfaGTA · Jan 8, 2020

Mount the boring bar in the vise instead of the reamer....Set to center height and bore to size by moving the table in the "X"
No centering needed...the hole will be cut on the center of rotation automatically!
Cheers Ross

GENERALDISARRAY · Jan 8, 2020

TeachMePlease said:
You attach your indicator to your spindle with in Indicol, a Noga, or a Mighty Mag...

Gravity

its not just a good idea, its the law.

stoneaxe · Jan 8, 2020

Got it. Thank you all.

stoneaxe · Jan 8, 2020

GENERALDISARRAY said:
Gravity

its not just a good idea, its the law.

This comment is a mystery to me. Exactly how does it bear on the conversation?

Booze Daily · Jan 8, 2020

Your spindle is horizontal. The indicator will droop when rotating it.

eKretz · Jan 8, 2020

stoneaxe said:
This comment is a mystery to me. Exactly how does it bear on the conversation?

I believe that is a terse mention of indicator sag.

Edit: beaten to the punch by the Booze man.

michiganbuck · Jan 8, 2020

Holding something in a spindle for boring I like to mark the spindle and the part so it might be put back into the spindle at the same clock place, match up so taking away any possible wobble in the spindle..
Drilling a part I like to spot the part center with a tool bit because a drill can spot off center..even a center drill can start off center with not having a tool bit start.

Boring a part it will be dead true to the axis of the machine spindle center line..but if the machine taper has an issue that will show up in the part.

One way to get away from machine spindle bore or chuck wobble is to turn and bore the part, then part-off the whole part..agree you cant do that with a long thin part.

The reamer follows the hole, gravity won't make it cut a new path.

When you bore a something and then turn it 180* the spindle or chuck wobble will show up in the something. Agree if the spindle ID is perfect and the bore started at center the something will be good.

13engines · Jan 8, 2020

GENERALDISARRAY said:
Gravity

its not just a good idea, its the law.

Along these lines - I have limited experience with horizontal spindles and after years without, have only recently gotten back to owning a lathe. So I ask... can those with experience tell me in general terms how much indicator droop can you expect from an Interapid Dial Test Indicator with properly tensioned joints and held by the post in say a collet extension or chuck mounted in the spindle? This would be a suitable setup for roughly up to a 4" bore or boss.

Same question same indicator mounted off the end of an Indicol adjustable extension rod or Noga Mag base or similar? (For larger features or difficult situations.)

It's just I can't imagine people running horizontal mills or lathes always adding a fudge factor or living with so much uncertainty when indicating something in on these machines. Are extensions just flat out not used?

I will admit that just yesterday locating X on a lathe Z axis live tool bore, life got so much easier when I went from a Noga mag base extensioned setup to a chuck held fixed collet. I"m sure it didn't hurt that I also changed from a tenth to five tenths indicator, but even when I went back for fine tuning experimentation things were still easier.

Dave

eKretz · Jan 8, 2020

Keep it short and stiff and it won't be much. Use a Noga base with a foot long arm and one might see a couple thousandths sag. There's no uncertainty if you know what to do to eliminate it. (The uncertainty, not the sag). For a Noga type setup, the base can be stuck to a solid piece of steel, indicator zeroed and in as close as possible to the orientation as it will later be used on the machine. Simply invert the block of steel and you'll see the sag right on the dial.

In a lathe this is pretty easy. Chuck up a piece of stock and stick the indicator on the chuck, registering on top of the part. Zero it. Then rotate the spindle 180° and see the sag right on the dial.

13engines · Jan 8, 2020

eKretz said:
In a lathe this is pretty easy. Chuck up a piece of stock and stick the indicator on the chuck, registering on top of the part. Zero it. Then rotate the spindle 180° and see the sag right on the dial.

Ah yes I see. Good point. Thank you.

Ha... that's the trouble with being self taught and mostly working alone. No one there to occasionally slap sense into you with the simple ways to solve a problem. If you don't happen to read about them you have to figure them out for yourself, which doesn't always occur on day one of any said problem.

Dave

Gundraw · Jan 8, 2020

Am I the only one that uses a Co-Ax indicator for this kind of stuff? You have to be careful to avoid cosine errors, but I have always had good luck with my import setup.

as9100d · Jan 8, 2020

I probe all circles now [emoji23] the other ways take too long.

Sent from my Pixel 3 using Tapatalk

eKretz · Jan 8, 2020

To be honest, it's not much of a concern out in the shop on a mill. I really paid no attention at all to indicator sag in most cases. Sometimes it's necessary, but most of the time if something really needed to be "right there dead nuts" I would just dial in the work then cut a spot and physically measure how far off location the spot was and compensate.

TeachMePlease · Jan 9, 2020

eKretz said:
To be honest, it's not much of a concern out in the shop on a mill. I really paid no attention at all to indicator sag in most cases. Sometimes it's necessary, but most of the time if something really needed to be "right there dead nuts" I would just dial in the work then cut a spot and physically measure how far off location the spot was and compensate.

Also for most "Close enough" work, if you're zeroed on 3 sides of a supposedly round object, you can more or less "ass"ume that the 4th quadrant is zeroed as well.

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