Learning to dial in a 4-jaw

Maybe we need a special dial indicator for dialing in a 4 jaw chuck with no numbers(just a white face and a needle). :eek 2:
There are no numbers on the chuck key so why would numbers on the indicator have any importance?:rolleyes:
 
mikey said:
I have a few.
  • Make a mount for your DI that fits on your QCTP. You can make something that fits into a standard tool holder so you can adjust the height to get the tip of the DI on center. This is really important.
  • Use two wrenches to adjust two opposing jaws at the same time; much faster and easier to work like this.
  • Look at centering as working with two pairs of jaws. Turn the chuck and look for the pair closest to the max deviation and adjust those first. Once you get that pair close to center, the other two will be easy to do.
  • Once you're as dead on as you want, go around and make sure each screw has about the same amount of torque on it. Believe it or not, if one is loose that part can move.
  • Be patient. Centering a part accurately takes skill, and skills take time to build. The more you do it, the faster you get.
When I was a baby hobby guy, I remember spending weeks learning to dial a part in. Now I can dial in a part to zero, and I mean zero, in less than half the time it took me way back then. Hang in there.
Click to expand...

I would once again agree with Mikey. Using 2 wrenches will greatly simplify and reduce the time to center a work piece. The only caveat is that for short guys like me it only works for chucks 8" in diameter or less. Trying to reach over a 10" or 12" chuck is more of a PITA than it's worth. As for numbering the jaws it isn't necessary, but does come in handy (especially for us short guys) when using only 1 wrench or when the chuck is disassembled for cleaning.

I can't tell you the number of times I was centering a part and someone started talking to me. It always seems to happen just after adjusting 1 jaw and starting to rotate the chuck to do the opposite jaw. You look over your shoulder and don't pay attention as to whether the chuck has spun less than or more than 1/4 turn. For that reason alone all the chucks and all the jaws are numbered. In addition I have a PULF (made in Poland) chuck that came with the Sheldon lathe. When I first tried it the thing was nearly impossible to adjust within .001" to say nothing about trying to adjust it to .0001" Upon removing the jaws I found they were not in the positions marked on the body. I cleaned them and reinstalled them according to the markings on the body, and it now works perfectly. I'm not sure if it was a problem with dirt, swarf, or misalignment. I do know that now it can be adjusted to within .0001" with no problems.

As for buying additional tooling, it's easy to think that a new toy will solve all your problems. The fact of the matter is in most cases it not only doesn't solve the immediate problem, but rather adds additional problems to the mix. Again I've purchased a number of "used" tools that were all "but new in the box" simply because the original owner bought them convinced they would solve a problem. In reality they didn't and were put on the shelf. Eventually they were sold for a fraction of their original cost because they ended up as dust collectors.

In my shop I tend to over research different methods to resolve a problem. Rather than spend money on something I think might solve the problem I first look for unique ways to use existing tooling and machinery to accomplish the task at hand. This is in all likelihood a product of my experiences at work. I was amazed and sometimes dumbfounded at the resourcefulness of the old German tool & die makers in our shop. Nothing seemed to phase them. They treated every "problem" as a challenge to their skills. Never once did I see any of them fail to ventually overcome a problem. Sometimes it took more than 1 try, but in the end they always succeeded.
 
On the chucks I used during my career I found that for the initial rough-in after mounting I didn't have to read the indicator values, just the swing of the needle. When making an adjustment the movement of the chuck wrench usually is very close to the needle movement. Just tighten or loosen Half of the needle movement. This was using a Starrett back push indicator. Got a Noga indicator mount my last few years of paid work. The best! Wish I had had one for the first 30.
Keep at it. Soon you will find the 4-jaw almost as fast as a 3-jaw and always zeroed out.
 
Not my original process, but I can't find the link:
You are using a DI for this process and the two chuck keys.
1.get as close as you can to center the workpiece.
2. find the lowest point and zero it.
3. find the highest point
4. find the middle point and zero it.
5. now go to the next jaw and adjust to zero
and so forth until you are centered
 
My dad was a shop teacher and taught the 2-chuck key method. He'd marked the face of the chuck next to the jaws with "A1, B1, A2, B2" going around the chuck. Set the stock in the chuck and ran the jaws to loose contact. Used a dial indicator on a mag base (no QCTP's in those days) and swept A1 to A2. Zero'd on A1 and flipped to the opposite side so A2 was at the indicator. Then adjusted both jaws to take A2 half-way to zero. Reset to Zero on A2 and rotated back to A1 for confirmation. He'd get within a couple thousandths pretty quickly, then did B1/B2. For the final adjustment, he'd just tighten one jaw to hit zero.

For square stock, he'd use a couple of methods. One was basically the same as that above, but he had the kid roll the chuck back/forth slightly to find the low point at the indicator. Zero out, pull back on the indicator so it's off the work and rotate the chuck 180. Do the slight roll back/forth to the low point and leave the chuck there. Then do the two chuck key adjustment to half-way to zero.

Other method was to have the student use a square or surface plate and height gauge to scribe the center point of the square stock. Then center punch it by eye. Mount it in the chuck and put a wiggler with a sharp point in the tail stock, engage the wiggler end into the center punched hole. Then use the procedure at the top with the wiggler in the center punched hole, indicator on the wiggler probe shaft to find center. He used this same method for oddball stuff like an eccentric hole.

Once you do it a few times it goes pretty quickly. You'll easily get dialed in within 0.0005" within a few minutes with practice.

Bruce
 
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middle.road said:
From the "Dept of the Easily Distracted & Confused", number the jaws...
Click to expand...
Yeah, the life of a shop teacher, good day was when everyone went home safely. I recall him being frustrated at times with student's test scores. He'd give them a drawing of a ruler in 1/16" grads and label 20 points. Student was asked to write the measurements in lowest term fractions. He put examples right on the test like 8/16 =1/2. He rarely had a student get them all right. We'd wonder how some would ever get through life, but he'd see former students years later and they all finally got it. Can't assume anything when teaching newbies around machinery. Thirty years as a shop teacher and he only had two students suffer minor injuries.

One was a student had drilled a hole in an aluminum shift knob for his car. He used a major diameter drill for a tap drill instead of the correct one. My dad suggested he try filling the hole with lead, then drill and tap. The student washed the knob and had some water in the bottom of the hole. Naturally the water steamed and spattered the lead for a minor burn.

Other student was really lucky. Dad told students to not leave stock beyond the head stock of the lathe. He had some crotch supports for that work, but didn't have the students use them. "Cut the stock so it doesn't hang out". A student left stock out, probably 1/4" or so, and it bent while turning. Dad saw the lathe shaking and hit the master power. The kid reached out to stop the stock before the lathe stopped. He ended up with a pretty good bruise, could have been a lot worse.

Bruce
 
Making a second chuck key is a nice little project in itself. I used an RT on my mill to cut the square end but it can be done entirely on a lathe if you have a milling attachment. Or failing that, some careful file work will do the job.
 
Let me know if you want a printed QCTP indicator holder. I don't mind letting the printer run a bit for you. I might set it up with hot pink filament, depends on the mood at the time... :)
 
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