Adventure With a 4-Jaw Chuck

[Nyala]

Probably about 15-20 years ago, my Dad quit using power tools and gave them to me. These included a South Bend Model C lathe. Dad was a professional machinist and completely rebuilt this lathe, including hand scraping of the ways. Nice lathe, especially for a beginner (I had machine shop classes in High School but that was in the 1960s). The lathe came with a 3-jaw and a 4-jaw chuck, and a wheelbarrow load of machinist tools. The lathe was given to my Dad by a company that wanted him to make some small parts for them in his retirement.

I muddled around for a while with the lathe and made some small parts but a job change and a move in 2012 put a stop to machining for about 5 years. Everything sat unused. In 2017 I retired and started to get back into machining and bought a Precision Matthews PM-25MV bench-top milling machine. I started watching YouTube videos, and still do. I made a number of projects and have more in the works.

However, in all this time I have never used a 4-jaw chuck. I watched YouTube with presenters saying tighten the highs and loosen the lows, while spinning a chuck by hand and showing an indicator needle spinning wildly about and me not being able to determine what was a high and what was a low. It was just a spinning needle on an indicator. I stuck with my 3-jaw chuck.

2-years ago I bought a PM-1236 lathe. Wow, what a difference from the small South Bend. The South Bend was severely under-powered and I could bring it to a stop with only about a .015" DOC in aluminum. This new lathe came with a lot of accessories and marveled at its capabilities. It had a 4-jaw chuck, which I promptly put in a drawer and left it there. It stayed there for almost 2-years, unused.

About 2-3 months ago I wanted to make a new machinist hammer. Easy, right? I decided to start with a main body the is square with each end tapering down to a round end to match the striking surfaces of the hammer (ala Artisan Makes, on YouTube). To mount the square stock I needed the 4-jaw chuck. Thus, after owning this chuck for almost 2 years, I finally broke into the box, cleaned up the chuck (still covered in the original packing oil), and put it on the lathe. After watching more videos I thought that I had a handle on highs and lows and could make this work. I opened the jaws to about 1"opening and tightened it back down, loosely. From there it turned out really bad. One jaw eventually was out more than 1/4" from where I started. I would set one jaw to 0 on the indicator, flip to the opposing jaw and see a reading but not know if the reading was a high or a low. I couldn't follow the spinning needle because it wasn't spinning. I had to hold the indicator off the square part to keep it being damaged by the square corners. When I released the indicator stem there was a reading but It was simply a reading. I couldn't tell if it was high or low. After about 30 minutes I decided to take another route.

I planned to turn the part between centers. However, it turns out that none of my lathe dogs would hold the 1" square material. I was now thinking about switching to a round head. It then dawned on me to go to the milling machine and center drill each end of the part. Going back to the lathe I mounted it between centers, then closed each jaw of the 4-jaw chuck against the part to hold it.

I turned the taper on each end.

I took out the part, removed the 4-jaw chuck and put it back in the drawer, perhaps never to be seen again. That is, unless I need to turn another square part between centers.

I feel like a freaking idiot with my foray into using a 4-jaw chuck. Are square parts harder to center up than round parts or am I simply that idiot that I mentioned? Since I've gotten along for sometime now without a 4-jaw chuck, is it even necessary to figure this out? Anybody else out there just give up on the 4-jaw?

Thanks,
Denny

 

[GeneT45]

Square parts are no harder, actually, easier. The easiest way to start is similar to what you did: scribe and mark the 'center' , then use your tailstock to get a course alignment with the 4-jaw. With the scribed center you should be able to see exactly what you need to adjust to get closer. When you have it aligned as close as your eyes and a tailstock center can tell, *then* get your indicator and start fine tuning. Adjust opposite sides first. Rotate the chuck until one side is horizontal (by eye, no need to get too picky, yet) and see what your indicator reads. Move to the opposite side (180*) and check that reading. Then adjust. For large parts I find a 1" indicator in the tool position is easier than anything in a magnetic base, etc. Then go to work on the other two sides. Lather, rinse, repeat.

Until you're accustomed to it, dialing something in on a four jaw (like tramming a mill vise) can be a lengthy and tedious process. Once you get the hang of it you should be able to dial something in to under 0.001" TIR in a minute or two. Tenths take (about 10x) longer. It's a skill well worth developing. I did so by putting the 4-jaw on my lathe and forcing myself to use it for everything for a while. Now the only inconvenience about using a 4-jaw is that it's about 140# and my other chucks are lighter...

GsT

 

[Karl_T]

There has GOT to be a you tube on this. you need to watch it done. Easy once you see how.

https://www.youtube.com/results?search_query=center+lathe+four+jaw

From the post above, more explanation on how i use the indicator. I mount it to the carriage and move it out of the way when rotating the chuck. When in place rock it back and forth to find the max reading, then set your indicator to 0. Move indicator out of the way and rotate it 180 degrees. Find the max again. Now move part in four jaw 1/2 this amount. Recheck just these two spots. Once getting close, go to the other pair of sides.

I find it WAY easier to just do opposite sides, too hard to do all four at once.

 

[Red96]

As another relative newbie, I would recommend watching Blondihacks' (on YouTube) She has a whole series on using a lathe for beginners - and she also has a series on the basics of using a mill. Both excellent for when one is just starting out. She covers and actually explains the basic stuff that everyone else seems to just gloss over or assumes everyone is born knowing.

There is a video in the lathe series about using 4 jaw chucks.

If you like it, I'd recommend you watch the full series - and the series on mills as well. Time well invested, IMHO.

And of course post questions here too - everyone here seems to bend over backwards to help anyone that asks. It's quite a community, with all the (un)usual characters you'd expect from an online forum! Wealth of knowledge & experience waiting for the question to be asked. And, well, it's the internet, so there's a couple full of BS too. But, if you read the posts, it wont take you long to separate the wheat from the chaff, so to speak.

-Chaff
(but learning!)

 

[mac1911]

Dont give up, went through the same mess. I am not a machinist and after a bit of fumbling I was able to make a crank for a broken magnetic chuck successful on my first try.

 

[gentle_1ben]

When I took a night school machine shop class back in the '80's, all we had was 4 jaw chucks on the lathes. Well we HAD to learn to use them. He showed us a trick using his "polish dial indicator". A piece of board with an old file mounted in the center, the board is long enough to span the ways. Put the file against the work, rotate the chuck 180 degrees, look at the position of the file, move the part 1/2 the gap, repeat until there is no difference, do this on the other set of jaws. your part is centered, then dial it in with an indicator.
I had acquaintance who said he would never use a jaw chuck because it took him 4 or 5 hours to get the part centered ! I usually takes me about 5 minutes or so, unless I try to make it "better" then I start over.... I have 3 jaws for my lathes, but I rarely every use one.
Ben


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'polish dial indicator"

 

[talvare]

Once I made myself learn to be proficient at dialing in parts in a four jaw chuck that's really about the only chuck I use. I really feel that I can achieve better precision, especially when having to re-chuck a part that I've already partially machined. I haven't mounted my three jaw chuck in several years. Sometimes I will use my six jaw chuck if I'm working on a thin wall part that is too big for a collet. I made a holder for a dial indicator that just stays in one of my quick change tool holders, so setting up the dial indicator takes about 10 seconds. I highly recommend getting proficient with your four jaw chuck. I think you'll like it.
Ted

 

[mac1911]

Once I made myself learn to be proficient at dialing in parts in a four jaw chuck that's really about the only chuck I use. I really feel that I can achieve better precision, especially when having to re-chuck a part that I've already partially machined. I haven't mounted my three jaw chuck in several years. Sometimes I will use my six jaw chuck if I'm working on a thin wall part that is too big for a collet. I made a holder for a dial indicator that just stays in one of my quick change tool holders, so setting up the dial indicator takes about 10 seconds. I highly recommend getting proficient with your four jaw chuck. I think you'll like it.
Ted

Im just beginning and this is one of my next projects or purchase.

 

[Nyala]

My thanks to all for your quick response and suggestions. I posted here because I didn't want this thing to beat me but I seemed to be at a dead end.

I started watching Blondihacks videos about 2 years ago. She was very interesting but lately she seems to be on a kick of making models. I don't do models or work in miniatures. I'm not that skilled. As a result I unsubscribed from her channel. She is currently on Episode 34 of a model build. Same with Joe Pie. Too many models. I'll go back and watch her earlier videos.

Abom79 has become a walking commercial for everything from factory sized CNC machines to spray cans of cutting oil, and everything in between. I think that he has become geared for professional machinists than a hobby guy like me. Unsubscribed.

I'll continue to search around for additional help but you all have given me a start to help me conquer this thing. Thank you all for your time and efforts.

Denny

 

[GeneT45]

You might check out This Old Tony - he seems to have a pretty hobby bent, and is entertaining as well. That said, practice will make you better than watching YouTube...

GsT