Author Topic: Mini-Lathe Chuck Upgrade Query  (Read 905 times)

Offline ShopShoe

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Mini-Lathe Chuck Upgrade Query
« on: July 23, 2018, 02:31:54 PM »
I've been working on another round of upgrades and tunings to my 7x Mini-Lathe (which I hope to summarize in a post when I get to a "stopping place.")

I have worked around to the "stock" 3-inch, 3-jaw chuck, which has runout over 0.007. I have other chucks and use 4-jaw chucks or ER collets when I need to, but the stock configuration doesn't waste power spinning a larger-than-designed-for mass or provide as much knuckle-busting potential.

I have considered just buying another "as furnished" 3-inch from LMS or grizzly at about $80.00, or getting something that might be better. "Pay the money and take a chance"????

I am also aware of Chuck Fellows's modification of a stock chuck for "set-true" setup.

Some searching leads to a Bison product:

https://www.kbctools.com/default.aspx?page=item+detail&itemcode=7-810-0300&catlist=9794&parent=2809.

I know, the price of that chuck is about the price of the entire lathe.

I'm only thinking right now, but perhaps someone has done this. Does the Bison bolt on to the stock flange, or would I have to make an adapter plate?  If someone has done this, did the final result provide the expected precision?

Ultimately, I want a new lathe, but circumstances dictate I work with what I have. I am also facing some more life events which will suck up more shop time and make it even longer between accomplishments. My main goal is getting to a place where I can use the shop time I can get to make things without so many things that require workarounds and compensations.

ShopShoe

Offline bent

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Re: Mini-Lathe Chuck Upgrade Query
« Reply #1 on: July 23, 2018, 10:19:35 PM »
7 thou runout?  Wow.  Does the stock chuck have that much slop on the spindle nose?  Have you tried putting the jaws in different slots?

Offline zeeprogrammer

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Re: Mini-Lathe Chuck Upgrade Query
« Reply #2 on: July 23, 2018, 10:35:04 PM »
I can't help but this raises a couple of questions for me...

1) Can mounting a chuck make a difference in run-out. (I have no idea.) That is, if you number the holes and the chuck posts that go through them...does it matter if you use a different combination each time? I ask because I noticed on my lathe (not a mini) a couple of marks that seem to indicate what orientation the chuck should be mounted.

2) You mention Chuck Fellow's modification...can you provide a link?

Thanks

Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Offline 10KPete

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Re: Mini-Lathe Chuck Upgrade Query
« Reply #3 on: July 23, 2018, 10:41:15 PM »
Absolutely use the alignment marks put on at the factory. Then dial in the chuck, with a nice pin in the jaws and note any run out. Then move the chuck around to the next bolt alignment and measure that run out, etc.

You've now mapped the mounting and can see which position is best.

Pete
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SB 10K lathe, Benchmaster mill. And stuff.

Offline john mills

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Re: Mini-Lathe Chuck Upgrade Query
« Reply #4 on: July 24, 2018, 01:02:10 AM »
have a good look at the faces that position the chuck the flat facet clamps against  the spigot or taper if they have been bumped or dirt has been there it can leave a bump that will make the chuck run out make sure these faces are clean a small speck of swag is enough.
some times it is can helot completely dismantle the chuck and clean ,dirt can get behind the scroll  and will put it out.

Offline ShopShoe

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Re: Mini-Lathe Chuck Upgrade Query
« Reply #5 on: July 24, 2018, 01:52:53 PM »
Thank You bent, zee, 10K Pete and John Mills.

I have tried all these suggestions over time and have disassembled and cleaned the chuck from time to time. When I got this lathe, it was close to this bad, but 0.007 is the latest measurement.  I have always just used stock oversized from what I want to make, then marked it for orientation with a mark I put on the spindle. Once something is turned down, runout of the chuck at the jaws is diminished.  Using one of my other chucks or collets is another approach and works well.

The spindle checks out OK at the MT3 center bore, the chuck registration OD, and the outer mounting flange OD. In addition, one of the Mods I have done is to replace the spindle bearings (The measurement is before that and no change afterwords, so it is most likely the chuck.)

The chuck under discussion here is wearing out: There is noticeable wear on the jaws where they engage the scroll, and the scroll has noticeable wear. I will most likely replace it, but I am considering the best path to take at this time. I am getting good at 4-jaw adjustment, but sometimes I just want to turn something and move on with another part of something I am doing.

The Chuck Fellows thread is at "The Other Place:"

https://www.homemodelenginemachinist.com/threads/starting-mini-lathe-mods.8306/

Start at post No. 36 (April 19, 2010).

(BTW, the lathe arrived without the usual huge amount of shipping grease that usually comes from overseas, just a light coat of oil, so I have always suspected someone bought it, tried it, and returned it before it was sold to me, but I acquired it as a "starter" lathe on sale for less than $350.00 sometime before 2008: I did not think I would still be using it all these years later.)

ShopShoe

Offline zeeprogrammer

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Re: Mini-Lathe Chuck Upgrade Query
« Reply #6 on: July 24, 2018, 02:46:45 PM »
Thanks for the link. That brought back some memories.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline Allen Smithee

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Re: Mini-Lathe Chuck Upgrade Query
« Reply #7 on: July 24, 2018, 11:59:43 PM »
I don't know the particular setup, but would it be possible to make an adjustable adaptor plate using the same principle as (say) the hemingway one?

AS
Quidquid latine dictum sit altum sonatur

Offline ShopShoe

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Re: Mini-Lathe Chuck Upgrade Query
« Reply #8 on: July 25, 2018, 02:04:58 PM »
Allen,

Thank You for the link. One of the problems with the Mini-Lathe is the way the mounting flange on the spindle is very close to the Headstock, so it is hard to get to any mounting for the back of the chuck. Those who have these machines know the "Pain in the ***" that changing chucks involves. But your solution starts the gears turning...

I don't know what I'll ultimately do, but I'm planning a post on all I've done to this lathe once I reach a point where I'll stop for awhile. Be patient, I just can't seem to get enough shop time to work very fast, which also means that I don't make so many midnight decisions as I did when I was decades younger and that I later wondered "Why in the heck did I do THAT?"

'Till later,

ShopShoe