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Best trick to adjust lathe serrated jaws quickly?

MachineAmateur

Plastic
Joined
Jan 11, 2021
Hi,

I have been wondering how the professionals handle adjusting the CNC jaws which have serrated back edges for locking. There is no position indicators on my jaws and it often takes about 4 tries before they are in a correct spot when changing the diameters of stock. Do you have some sort of gauge to find the right spot at first try?
 

pcasanova

Hot Rolled
Joined
Mar 14, 2008
Location
vacaville ca
I use the depth rod or whatever part of the caliper to measure the depth of the t-nut, then make a note
of measurement to rod diameter for future ref.
 
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DouglasJRizzo

Titanium
Joined
Jun 7, 2011
Location
Ramsey, NJ.
I use a simple 6" scale. Once bored correctly, I scribe the sides of the jaws to line up with the markings on the face of the chuck. I also stamp the corresponding chuck jaw position number on each jaw so it always goes back in the correct place.
 

cnctoolcat

Diamond
Joined
Sep 18, 2006
Location
Abingdon, VA
Use a medium-power cordless impact driver to tighten and loosen your chuck jaw bolts...saves a lot of time.

You can double-check bolt torque on occasion, make sure the impact driver is repeating.

ToolCat
 

Fancuku

Cast Iron
Joined
Dec 7, 2018
I have a database for my soft jaws. The diameter they were cut to, the depth they were cut to and where they sit in the chuck (how much in or out from chuck OD).
I ain't wasting time trying to figure out where they are going to sit in the chuck. I pull out my folder and look it up. One minute, done.

If we are talking hard jaws, I activate the offset of a boring bar and jog it to the diameter of the part I need to hold it, bring the bar near the chuck and put the jaw in just above the tip of the boring bar.
 

Philabuster

Diamond
Joined
Jul 12, 2006
Location
Tempe, AZ
For hard jaws, I have chucking diameters marked on the jaws. I line up the mark to the outer most serration on each jaw and lock it down. Saves a lot of time. The 1/2" diameter mark lines up at the inner most serration on the jaw.

For soft jaws, I put a punch mark at the outer serration where the jaws were cut last. If I need to move the jaw in or out the next time I use them, I count from the punch mark X serrations and then punch another mark in the jaw.
 

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Mtndew

Diamond
Joined
Jun 7, 2012
Location
Michigan
Hi,

I have been wondering how the professionals handle adjusting the CNC jaws which have serrated back edges for locking. There is no position indicators on my jaws and it often takes about 4 tries before they are in a correct spot when changing the diameters of stock. Do you have some sort of gauge to find the right spot at first try?
Call up a boring bar in MDI, tell it to go to X5.0" if you're holding on to 5" diameter stock, handwheel it to about 1/8" away from your jaw face, install jaws.
To double check that the jaws are concentric to each other, simply count the number of serrations that are sticking out. Easy Peasy.
 

MachineAmateur

Plastic
Joined
Jan 11, 2021
Thanks for the answers, many ways to skin the cat it seems! Using the lathe tool with MDI as an indicator is intriguing, have to try that one out. This necessitates a tool with correct diameter which is not always the case though. Perhaps i could create some sort of stick protruding from specific location of the tool changer and with dedicated program (diameter as an input) it would indicate the jaw edge based on machine coordinates.

Dedicated steel rule sounds simple and effective too. These are hard jaws and have no markings at all, even the chuck face is missing any OD references.
 

ViktorS

Aluminum
Joined
Apr 26, 2021
My way to do it is as follows..
Over the years I have collected short cut-off pieces of the most common diameters that i use, and have them placed at a shelf close to the machine. I use that as reference and use a hex wrench to snug up the jaws and spin the chuck by hand to verify before tightening with impact tool.

To get all jaws to the same position I count the serrations above or below the master jaw in the chuck. Also, I always mark the jaws with the jaw number ofcourse.

Usually when I cut softjaws I cut them with one serration above the master, so that way in 75% of the cases I just slap them in and go after a quick verification with a cut-off piece.

I only have one set of hardjaws, and those are an uncommon diameter for me so I rarely use them at all. Almost all material I buy is centerless ground, so running that in softjaws is no issue.
 

guythatbrews

Cast Iron
Joined
Dec 14, 2017
Location
MO, USA
I just use a combination square head and scale. Set the stickout to 1/2 chuck diameter plus 1/2 stock diameter. Hold it on the opposite side of the chuck from the jaw. That's for a 12" chuck it might be tough on a great big chuck. Pretty easy and quick.

Use a medium-power cordless impact driver to tighten and loosen your chuck jaw bolts...saves a lot of time.

You can double-check bolt torque on occasion, make sure the impact driver is repeating.

ToolCat
Yeah use an impact wrench. I use pneumatic but cordless would be great.
 

doug925

Titanium
Joined
Nov 21, 2002
Location
Houston
Hi,

I have been wondering how the professionals handle adjusting the CNC jaws which have serrated back edges for locking. There is no position indicators on my jaws and it often takes about 4 tries before they are in a correct spot when changing the diameters of stock. Do you have some sort of gauge to find the right spot at first try?
Use MDI and tell a known tool to go to the diameter needed to chuck on -.150" or +.150" if chucking on the ID.

Then bring your tool up to the jaws and move them in or out until even with your tool tip.
 

doug925

Titanium
Joined
Nov 21, 2002
Location
Houston
This necessitates a tool with correct diameter which is not always the case though.

We leave T1 as a V or Dnmg finisher, T2 WNMG ruffer, T3 Part off, T12 is normally the reset tool.

Why change tools every time? It's just money out the window....
Doug.
 

MachineAmateur

Plastic
Joined
Jan 11, 2021
We leave T1 as a V or Dnmg finisher, T2 WNMG ruffer, T3 Part off, T12 is normally the reset tool.

Why change tools every time? It's just money out the window....
Doug.

All i have is a 4 position tool changer..:) With shims and all. Especially if boring is needed, the natural directionality is different and forces to remove even the main tool. Not great but acceptable for hobby use.

I tested this method and it works wonders, it is enough just to have any tool next to the jaw and eyeballing the correct locked position from there.
 








 
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