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View Full Version : Trueing a 3 jaw chuck, 他"bore?



slughammer
12-05-2005, 06:45 PM
I have one of the chaiwonese multipurpose machines and the chuck has developed enough runout to be noticeable. Dial indicator showed it to be .006 TIR.

Now when you think about ideas on how to true the chuck up, just remember, the thru hole on the chuck is only about 他", so I'm working in a pretty small space to get to the back set of teeth.

The jaws each have 6 teeth; I was planning on clamping a piece of round stock at the last tooth and then machining the first 5 teeth with a boring bar. Question is, how do I get in and work the last tooth?

David R
12-05-2005, 07:18 PM
:) Get a 4 jaw :)

A 3 jaw is for quick jobs that don't need to be perfect. If you want perfection, go with a 4 jaw and take the time to get it dead nuts.

slughammer
12-05-2005, 07:55 PM
:) Get a 4 jaw :)

A 3 jaw is for quick jobs that don't need to be perfect. If you want perfection, go with a 4 jaw and take the time to get it dead nuts.

I still like my quick jobs to NOT have runout that is visible by eye!

The purchase of a 4 jaw chuck will most likely come with an assesory pack including a 13 x 40 machine to attach it to! Don't want to throw money at current machine.

KCSO
12-05-2005, 09:16 PM
Before I did anything I would strip the chuck and give it a thourough cleaning. Then I would reassemble and test with a test bar. Most of the small machines advertise runout between 3 and 7 thou so you are not out by that much. Just cleaning my old South Bend took it from about 8 to 3 and for me 3 is about as good as a three jaw will do. Your saying it "Has Developed" leads me to thing that a blot of mustard or a bit of undigested piece of beef might be all the problem.

I will check my Home Shop Machinests and see if I can find truing a chuck.

slughammer
12-05-2005, 09:57 PM
Your saying it "Has Developed" leads me to thing that a blot of mustard or a bit of undigested piece of beef might be all the problem.
I will check my Home Shop Machinests and see if I can find truing a chuck.

I had it apart several times to clean. I think the damage developed from drilling a piece and getting it stuck on the bit and spinning the part in the chuck.

Frank46
12-06-2005, 02:12 AM
slughammer, seems to me that you figure that maybe just the jaws had been damaged
when the piece of stock started rotating in the chuck jaws. One fix that I have heard of was to use either a tool post grinder or dremel tool to sort of resurface the chuck jaws grasping surface. What you could do is check www.villagepress.com website. They publish two machinists bi monthly magazines and I do seem to remember (crs syndrome) that they ran such an article some years ago. Hope this helps. Frank

slughammer
12-06-2005, 02:46 PM
The jaws each have 6 teeth; I was planning on clamping a piece of round stock at the last tooth and then machining the first 5 teeth with a boring bar. Question is, how do I get in and work the last tooth?

OK, I went in a machined the first 5 teeth. Checking runout showed it to be .001. For the last tooth I was looking at several different ways and ended up just letting the centrifical force keep them out and taking very small passes with a sharp tool. The tool didn't chip and the results are good.

I finished off by indicating on a piece of round for the .001 runout and then whacking the chuck with a brass hammer. Several whacks did nothing, then the last one did the job. Now the 0-1" .001 grad indicator is barely moveing, I'd have to put the .0001 indicator up to see more.

I think I'll call it good.

StarMetal
12-06-2005, 02:50 PM
I see how the your nickname for the forum come about. I'm glad you're not working on my Ferrari hahahahahahaha

Joe

slughammer
12-06-2005, 04:26 PM
I see how the your nickname for the forum come about. I'm glad you're not working on my Ferrari hahahahahahaha

Joe

Actually I'm sad to say the hammer whacking was not my idea, it was suggested by one of our machinist here on the board. As was explained to me, most chucks are assembled to a backing plate with four screws that can be loosened and the chuck body tapped around to run true. On my machine, the machineing of the jaws was necessary though; with the boogered jaws, mine had a run out that resembled a cork screw.

Now that I have the jaws straightened up, I'll keep an eye on the runout and just tap it back into place when necessary.

Have you checked the runout on your machine?

StarMetal
12-06-2005, 05:20 PM
My chuck runs at about .00005, can't ask for better then that. My chuck is held on by three bolts and the back of the chuck has a recess in it with a tapered edge and the spindle plate had the male counter part. There shouldn't be any moving around with my set up, perhaps yours is different since you said you have four bolts.

Joe

KCSO
12-06-2005, 06:07 PM
The whacking comes from an article in the Home Shop Machinist and the circumstances are these.
#1 your chuck is held to the backing plate with 3 or 4 bolts
#2 the backing plate is not a press fit
#3 You TAP the chuck with a brass hammer with the bolts not completely tight and test till it run's true.

If your 3 jaw is set up this way it can and will shift under a real heavy load, but it can also be re adjusted easily. All my light duty chucks are set up this way. I usually test the chuck before any important job.

What are you making that requires a three jaw to run under 1 thou?

slughammer
12-06-2005, 06:47 PM
What are you making that requires a three jaw to run under 1 thou?


Nose Punches!

Bret4207
12-09-2005, 01:09 PM
My ancient little 6" Atlas had a severe case of goofy jaws stemming from trying to hang onto something more appropriate for a 12" lathe. In laymans terms, I abused it. I found that I could chuck a new chainsaw file in my good Jacobs tail post chuck and run the 3 jaw chuck down onto the file slowly. It took the nicks and burrs out. True, I lost a little of the jaw, but Little Machine Shop has a nice chuck for the Atlas I one day hope to aquire.

Catshooter
12-10-2005, 11:15 PM
Starmetal,

You have a chuck (3 jaw?) that has a TIR of 5 one hundred thousanths?

That's, rather, uh, tight.


Cat

StarMetal
12-10-2005, 11:27 PM
Yeah it was, my jaws were slightly off though and I trued those. You can ask Buckshot I had trouble setting my lathe up. If you turned down a shaft say 10 inches long, it would be larger at one end then the other, by quite a bit. With Buckshots help I got that straighten out, but in the process of finding the problem I surely checked the chuck spindle without the chuck on it, and then checked the chuck when mounted. Me and Buckshot were both surprised. Later on Buckshot told me he heard that some of those chucks were made in Japan. I was telling him all along the quality of my chuck especially the hardness of the metal it's made from. Overall I'm pretty please with my mini-lathe, but when I first got it Buckshot would tell you how upset I was with it. Buckshot has alot of patience with folks to help them.

Joe
Edit: No no, I reread that it reads .0005 on my dial indicator....sorry so that would be 5 ten thousandths..God! 5 hundred thousandths would you even see the needle move?

Catshooter
12-12-2005, 09:58 PM
Yea, a half a thou sounds a little better. No, you wouldn't see the needle move, at least no needle I've got.

If I recall, when Starrett makes their gauge blocks they hold them true to 5 millionths. Millionths ! That's workmanship.


Cat

StarMetal
12-12-2005, 10:35 PM
That makes me wonder what kind of tool measures the tool that measures that 5 millionths.

Joe

Buckshot
12-13-2005, 03:58 AM
...........I just got done mounting a 4" 3 jaw chuck to a 5C pad. The chuck was the one that came with the Harbor Fright lathe-mill combo I bought back in 1998. The machine was actually pretty trashy with power nothing. No thread cutting & no power feed. However it was a gigantic leap forward from the 3/8" VSR drill clamped in the benchvise :D

I had a 3" 4 jaw chuck factory setup on a 5C mount, and I have found it usefull to hold stuff that my X 32nds 5C collection wouldn't handle. Tearing down the 5C collet setup to replace with a chuck was kind of an unnecessary pain if that 4" 3 jaw could be utilized. I didn't really have high hopes for it although it hadn't seemed too bad.

On the old setup it was held to a threaded backing plate via 3 M8 sockethead screws. ENCO had 5C pads on sale so I bought a 1"x4" for $18. I put it in the collet adapter and then drilled and bored a 3/4" hole though it, then faced it down to 1/2" thickness. I took the 3 jaw apart to clean it up, as it was a scrungy, gunky mess all full of petrified oil and chips.

I was very amazed at the level of workmanship displayed in this chuck. There are no markings at all to be found. I don't know if it is Chinese, Jap, Korean, or made in Peru. The scroll was cleanly milled and all cuts and slots showed very nice work. The teeth on the scroll and pinion were done as finely as you'd like to see. If this was a Chinese product and they still make chucks of this quality (or better, these 7 years later) I'd sure not hesitate to buy one.

Originally my plan was to make it a halfassed "Adjust-Tru" like KSCO was talking about, where the male spigot into the back reccess of the chuck is a couple thou smaller. Using it is as he described. Back off the mounting bolts and then tap it to have the chuck body move a bit on the back plate. Then tighten up the bolts.

First though I wanted to see just how accurate the chuck was going to be. I cut the backplate spigot to a (as close as I could tell) .0002" press fit. Yesterday I stuck it in the spindle nose and then chucked up an 11" piece of hard chromed 3/4" rod salvaged from the front struts of an '86 Chev Celebrity we used to own.

I haven't put a DI on it yet, but with about 9" sticking out, I'm danged if with the Mk-I, Mod-I eyeball detector if I can see any wobble :D. At this point I'm of 2 minds about pulling the chuck off the backing plate and taking a couple thou off the spigot, so as to have the adjustability. On one hand it IS a 3 jaw and with the adjustability feature how much closer can I get it to run then what it appears to be now? And secondly the fit is so nice now, why monkey with it.

I'll put a DI on it tomorrow and if at a 9" extension it's holding a couple thou, at the jaws it would be even better, and that would be good enough.

..............Buckshot

slughammer
12-13-2005, 04:03 PM
The chuck was the one that came with the Harbor Fright lathe-mill combo I bought back in 1998. The machine was actually pretty trashy with power nothing. No thread cutting & no power feed.
Buckshot

LOL :-)

That is the twin brother to the one I just performed surgery on. Bought mine in 97 IIRC.

Any idea what that thread would be for the backing plate? (I wouldn't mind having a 4 jaw occasionally).

Buckshot
12-14-2005, 02:36 AM
............Slughammer, "LOL That is the twin brother to the one I just performed surgery on. Bought mine in 97 IIRC. Any idea what that thread would be for the backing plate? (I wouldn't mind having a 4 jaw occasionally).

No I sure don't. For sure it's metric. You can order spare parts from the Harbor Frieght home office, so you could order the backing plate seperately, buy a plain back 4 jaw and put them together

http://www.fototime.com/B098A4398940041/standard.jpg

Here's the 3 jaw attached to the turned down 5C pad.

http://www.fototime.com/399BE768073A69B/standard.jpg

The little 3" 4 jaw next to the 4" 3 jaw. The 3 jaw came out nice. I'm jazzed :D

................Buckshot