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Old 12-07-2009, 12:16 AM   #1
Twmaster
 
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Default Truing square stock in a 4 jaw independent chuck?

I'm scratching my head here. I have some 1" square I need to work on. Cannot quite wrap my head around how to indicate this so it is trued in the chuck. Each time I try to rotate the part the indicator ends up physically moving making measurements pointless.

A search of google was useless.



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Old 12-07-2009, 12:39 AM   #2
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Default Re: Truing square stock in a 4 jaw independent chuck?

This has been discussed before but poblaby the easiest way is to locate the center and center punch then indicat in on the punch mark with a pump center. the other way is to retract the plunger of the indicator as you turn the piece and you may want to set a little level on top to keep things square.
You can often get close just by eyeballing it in turn the chuck by hand and bring a bit close to the part then turn it 180 degrees you will se a gap adjust out 1/2 the gap then turn 90 degrees repeat until close then finish with above methods.
tin



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Old 12-07-2009, 01:04 AM   #3
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Default Re: Truing square stock in a 4 jaw independent chuck?

D'oh! Pump Center.....

I was just looking at those on Tallgrass Tools web site a day or two ago...

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Old 12-07-2009, 02:46 AM   #4
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Default Re: Truing square stock in a 4 jaw independent chuck?

Quote:
Originally Posted by Twmaster
D'oh! Pump Center.....

I was just looking at those on Tallgrass Tools web site a day or two ago...
Lacking a pump center, you can make do with a regular dead center trapped between the tailstock and the pop mark and indicate off that. The Bogster and others posted that one here a long while back.

Here's a few of the old threads:
http://www.homemodelenginemachinist.com/index.php?topic=6407.0
http://www.homemodelenginemachinist.com/index.php?topic=5034.0
http://www.homemodelenginemachinist.com/index.php?topic=596.0 (the center-in-center trick is at the end of this one)
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Old 12-07-2009, 04:40 AM   #5
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Default Re: Truing square stock in a 4 jaw independent chuck?

Why not just stick it in the 4 jaw and tighten down the jaws a bit, now bring the tip of whatever tool you have in the toolpost, up towards the square bit. Start to rotate the chuck by hand and watch the square corners in relation to the tooltip.
Adust the 4 jaws as nessesary, until ALL the 4 corners are just touching the tooltip, when that happens, it's dead centre.

Try it, you wont believe how simple it is to do, until you give it a go.

Oh, dont bother with any dial indicator, not unless you dont like the thing, it's a good way to ruin them, by trying to true up a bit of square with them.

Mark

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Old 12-07-2009, 05:36 AM   #6
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Default Re: Truing square stock in a 4 jaw independent chuck?

There is the simple old method.
The indicator tip needs to be as close to on center as possible.
With the tip against one flat rock the chuck back and forth to find
the low spot and zero out the indicator. Pull the needle back to clear
the piece and rotate it 180° Lower the tip to that flat and again
rock the chuck back and forth to find the low spot.
If you indicate to the 4 sides low spots the stock will be centered.
If the stock is too big to clear the indicator needle by puling it back,
mount the indicator on the cross slide and move it back out of the way
to rotate to the opposite side.

Rick

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Old 12-07-2009, 05:52 AM   #7
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Default Re: Truing square stock in a 4 jaw independent chuck?

Quote:
Originally Posted by mardtrp
Oh, dont bother with any dial indicator, not unless you dont like the thing, it's a good way to ruin them, by trying to true up a bit of square with them.
Mark
Howzat?
Been truing square in a four jaw with the DI for years. Haven't hurt one yet.
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Old 12-07-2009, 12:53 PM   #8
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Default Re: Truing square stock in a 4 jaw independent chuck?

i agree with rake 60 use the indicator as he says i always set my indicator that is on my surface gage on the carriage then move it back out of the way.there will be times that just getting close will not be good enough and doing it this was you will be right on center every time. i have never damaged an indicator in30yrs +doing it this way
. good luck

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Old 12-07-2009, 03:34 PM   #9
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Default Re: Truing square stock in a 4 jaw independent chuck?

Make a "flapper" for your DI as shown here...

http://www.homemodelenginemachinist.com/index.php?topic=3820.msg39062#msg39062

and you won't need to worry about damaging the instrument.

I made mine so it was one-screw-detachable from my regular 4J centering fixture.

Don't be tempted to center using the edges of square stock. Work off the flat surfaces. The edges are often dented and damaged.

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Old 12-07-2009, 08:55 PM   #10
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Default Re: Truing square stock in a 4 jaw independent chuck?

Thanks again gang. Lots of reading. Great ideas! I just happen to have a coule of centers I can use temporarily until I can make a pump center.



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