# I Don't Understand My Drill Bit Chuck



## MontanaAardvark (Jun 22, 2018)

I have a Jacobs-style chuck on an R8 arbor for my Grizzly G0704 that is doing something I simply don't understand.  The centerline of the holes seems wrong but the bit doesn't seem to wobble as much as it should.  

I've seen this issue before but dismissed it as an error on my part, but yesterday I saw it again.  The other times, I readjusted the mill to put the part on the centerline and assumed I had gotten the edge zeroed incorrectly.  

I'm making some part for my flame eater engine project and my plan was to cut the outline of some parts and then go back and drill holes in specific locations.  This way the holes will be on the same coordinate system as the outline of the parts and be exactly in the right place.  

Last week, while making the flywheel, I made a holder for a #2 center drill that fits a 1/4" collet and used it to start the holes.  




Then I switched from the quarter inch collet to the drill bit for the big holes at the top, with a 9/32 bit in my chuck and it was visibly off center.  Even my wife commented on it and she doesn't have the eye for small differences I've developed.  If it's visible from a few feet away without a magnifier, it's way off.  

I chose the 9/32 bit almost blindly; it's to clear a 1/4" shaft and allow my 3/8" OD bearings a shelf to sit on.  So as an experiment, I tried switching to a 5/16 bit in my 5/16 collet and it as visually right on the center.  I drilled 5/16 holes.  The other four holes (at the bottom) were a size I didn't have a collet for, so I went back to the drill chuck and visually centered the drill bits.  It was about .015 off.  




So how can a drill bit in a chuck on an R8 arbor not be on the centerline like a part if a collet in the same spindle?  Shouldn't it wobble that .015 or nearly .030 total?  I don't see how it can be as wrong as it seems to be.


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## JimDawson (Jun 22, 2018)

Just a guess, but it sounds like your head is out of tram.  The further you extend the bit tip from the spindle the more error that is introduced.  Years ago I had the same problem and I had to call my machinist neighbor over to figure it out, I thought I was going crazy.


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## MontanaAardvark (Jun 22, 2018)

JimDawson said:


> Just a guess, but it sounds like your head is out of tram.  The further you extend the bit tip from the spindle the more error that is introduced.  Years ago I had the same problem and I had to call my machinist neighbor over to figure it out, I thought I was going crazy.



I thought about that, but then thought that the smaller collets are dead nuts on center with each other so how could the arbor and chuck be different.  

It's something to look at and it means doing something, though.  Beats sitting around not doing anything.


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## RollingPin (Jun 22, 2018)

I had a heck of a time finding chuckless drill chuck for an R8 arbor. Every one that I tried wobbled like nobody’s business. I finally got a 1 piece chuck and arbor for my G0704.


Sent from my iPad using Tapatalk


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## ttabbal (Jun 22, 2018)

Glacern and PM both sell decently reviewed R8 drill chucks. You could also get a straight shank chuck and hold it in a collet. Or even hold the drill bit in a collet if you have a properly sized collet.


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## JimDawson (Jun 22, 2018)

MontanaAardvark said:


> I thought about that, but then thought that the smaller collets are dead nuts on center with each other so how could the arbor and chuck be different.
> 
> It's something to look at and it means doing something, though.  Beats sitting around not doing anything.



Even if the chuck has runout, it will still put the tool bit on the center of spindle rotation.  But the tool tip might scribe a circle rather than rotation about a point.  In other words, the runout has little effect on the hole center.  The hole center will still be on the spindle centerline.


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## Technical Ted (Jun 22, 2018)

I agree to check that the head is trammed in properly... This certainly could cause an issue like you are describing. 

Ted


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## MontanaAardvark (Jun 22, 2018)

So I just re-checked my tramming and it seems OK.  First off, an overview of how I do it.  I don't remember where I got this method.  I have a Mitutoyo .25"x .0001" dial indicator that's old but lives a sheltered life.  This is mounted in a half inch square aluminum bar and doubles as an optical spherometer (I'm a telescope maker and have made mirrors with this).   I drilled a hole for a 1/4" brass rod and hold that in my collet in the spindle.  Because I only have one of these cool dial indicators, I rotate the spindle 180 degrees by hand and flick the indicator once or twice and make sure it's not stuck somewhere by sticktion.  I have to pull the pin up while rotating because it would go into the Tee slots, and then below the table.  

Overview shot with the indicator on the side I need the mirror to read. 



Here's a closeup of the dial when it's on the left:




and when I rotate it 180 degrees (and, yes, the subdial is still on the 0.15).  




That's not quite one tenth (.0001") and the distance between these two spots is over 10" (10-1/4 I think).  It's the way I left it the last time I checked (and that time I moved the headstock slightly) back in May of '17.  

Would this vary if the head was a foot over the table?  I'm not picturing the geometry in my head but I don't have a way to test that available to me.


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## Technical Ted (Jun 22, 2018)

I'm not familiar with that mill. Is it a Grizzly? Does the table/knee move up and down or is the head mounted on a column and that moves the head up and down?

If the later, it sounds like your column is not plumb with your table and spindle. You trammed your spindle in, but if the column is at an angle to the spindle/table then it would shift the center of the spindle to the side when it is raised or lowered.

Ted


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## MontanaAardvark (Jun 22, 2018)

Technical Ted said:


> I'm not familiar with that mill. Is it a Grizzly? Does the table/knee move up and down or is the head mounted on a column and that moves the head up and down?
> 
> If the later, it sounds like your column is not plumb with your table and spindle. You trammed your spindle in, but if the column is at an angle to the spindle/table then it would shift the center of the spindle to the side when it is raised or lowered.
> 
> Ted



That's very possible.  It's a Grizzly, and the head goes up and down on the column.  At one point I had it completely apart to add my ball screws and mounts and all, so it might be that when I put it together, I assembled it out of alignment.  

The biggest machinist square I have is 4".  I have a carpenter's square that gets me to 12" and a framing square that's bigger than that.  

I think I used the 12" square when I put this back together.  How should I do this?


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## JimDawson (Jun 22, 2018)

With your indicator setup it looks like you have a lot of overhanging mass all supported on a 1/4 inch pin.  That could affect your reading.  Not saying it is a factor, but that it could be.

Try checking with your quill both retracted and at full extension and see if the readings are different.  That might be a good indication of column tram.  A good 12'' square and an indicator might be useful for checking the column tram.  Maybe check the square for squareness by laying it on the table and indicate the X & Y, that assumes that your tabel runs square.  Not sure how else you could check the square of the square.


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## Technical Ted (Jun 22, 2018)

I very well could be wrong, but since you trammed the head I'm thinking that the spindle is plumb/square with your table, but the column is not. So, envision that your column is tilted at a 45 degree angle (grossly exaggerated), but the spindle/quill is plumb/square with your table. If you raise the head using the column by 2" the spindle would raise 1" and move 1" sideways in the X direction while the whole time the spindle is still in a plumb/square orientation. So, IMO, raising the quill only up and down might not reveal the problem since you've trammed that in. At least that's my story and I'm sticking to it! 

Anyways, using an accurate square would be one way although if it were me I'd like to figure out a way to use a dial indicator. It's hard not knowing the machine, what the column/ways might look like and what you have to work with. Do you have any large accurate angle plates you could put on the table and use as a square?

Hopefully others will jump in here with ideas.

Isn't that column keyed? Or does it just use bolts to hold it on and keep it properly aligned?

Ted


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## Technical Ted (Jun 22, 2018)

Now that I've been blabbing away something dawned on me that I should have asked up front. How are you adjusting things to tram your head in? Are there separate bolts to allow the head to pivot like a Bridgeport or are you adjusting it by tilting the whole column where it attaches to the base?

When I first read your post I was thinking on the lines of a Bridgeport type machine with the pivoting head.

Ted


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## Technical Ted (Jun 22, 2018)

Is this the mill? http://www.grizzly.com/products/Mill-Drill-with-Stand/G0704

If so, I looked at the manual and it does have a tilting head like a Bridgeport (although different setup), so I'm still sticking to my story! 

Ted


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## Technical Ted (Jun 22, 2018)

How about trying this with your 4" machinist square? A bigger square would be better, but I'm thinking you'll be able to get it a lot closer than it is now... Just make sure when you do this you use the column crank to raise/lower the head (as he does in the video) and not the quill. 






Ted


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## $Bill (Jun 22, 2018)

Technical Ted said:


> How about trying this with your 4" machinist square? A bigger square would be better, but I'm thinking you'll be able to get it a lot closer than it is now... Just make sure when you do this you use the column crank to raise/lower the head (as he does in the video) and not the quill.
> 
> 
> 
> ...


We actually built our own tramming tool and it was a God send...........BB


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## MontanaAardvark (Jun 22, 2018)

I've been unable to get to the HMF for a while, but I think you're very likely right.  

First off, it is the mill you found and posted the link for.  I don't recall any sort of keyway or any other mechanical aid for ensuring the Z axis column is perpendicular to the table, just four large cap screws holding the Z- column to the X/Y base.  

I haven't watched that video yet, since it hasn't been long I could access this site.


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## royesses (Jun 22, 2018)

Technical Ted said:


> Is this the mill? http://www.grizzly.com/products/Mill-Drill-with-Stand/G0704
> 
> If so, I looked at the manual and it does have a tilting head like a Bridgeport (although different setup), so I'm still sticking to my story!
> 
> Ted



Looks like figure 29 on page 31 for the headstock tilt adjustment.
Roy


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## HMF (Jun 23, 2018)

By the way, I want to remind everyone that we have our own VIDEO library where you can post videos without using YouTube:

*https://www.hobby-machinist.com/gallery/categories/member-video-channels.6/*

*available to donating members.*


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## bill stupak (Jun 23, 2018)

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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## Downunder Bob (Jun 23, 2018)

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.


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## MontanaAardvark (Jun 23, 2018)

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



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.


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## MontanaAardvark (Jun 23, 2018)

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.




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.


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## Technical Ted (Jun 23, 2018)

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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## MontanaAardvark (Jun 23, 2018)

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



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.


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## MontanaAardvark (Jun 23, 2018)

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.


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## Technical Ted (Jun 23, 2018)

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


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## Technical Ted (Jun 23, 2018)

Looks like you pretty much already have what you need. Good job!

Ted


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## markba633csi (Jul 21, 2018)

That angle cube looks like a cool tool, gotta start dropping hints for stocking stuffers this year


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## MontanaAardvark (Jul 21, 2018)

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. 




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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## royesses (Jul 21, 2018)

I purchased a Gem Red angle cube from Amazon last year. It has a backlight and is very sensitive and accurate. Also it has a calibration procedure. I had one from Harbor Freight but it was slowwww to respond and no backlight and not very repeatable.

Roy


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