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Need help with Lathe chuck please.

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SubtleHustle

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#1
Hello guys, so I am new to machining, but have a passion for learning. This may be a total newb question, but I'll be the first to admit that I'm a newb.
I bought my first lathe a week ago, and have been learning on it every day since. I was trying to decide between a new grizzly g4000 or a 1938 SB 9"C. I went with the SB, based on the number still in operation, and the deal I received on it. Problem I am having is, the old 3 jaw chuck that came with it, seems pretty worn, and I am having a hard time keeping my work piece centered. Havr been looking in to by using a new 4 jaw 6", but cant seem to find any that would fit my 1-1/2" 8tpi spindle. Thoughts? Suggestions? Any would be greatly appreciated. Thanks in advance! I have attached a pic of the lathe, just in case it helps.
 

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Logan 400

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#2
Others will know more because I am also new to the hobby but I recently purchased a used one from Ebay. I bought an independent 6"4 jaw chuck and am very happy with it so far.
 

SubtleHustle

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#4
So is used the only option then? I would just be afraid it would be as worn as my current one.
 

4ssss

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#5
If you're really worried about run out buy a Buck adjustable chuck
 

SubtleHustle

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#6
And thanks 4ssss for the link, very good find!
 

SubtleHustle

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#7
Would a spindle adapter be reliable? Like say, a 1-1/2 to 1" adaptor?
 

Bob Korves

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macardoso

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#9
Check out Shars tool company (out of Illinois), Small Tools (Euclid, OH), JTS tool (Mentor, Ohio) or CDCO tool (Illinois). They all have chucks with 1 1/2 - 8 threads (may need a plain back + backplate). I you really want them running true, you need to spend a small fortune on a super high quality 3 jaw chuck, or learn how to use a 4 jaw independent (thats what I use 95% of the time, just takes a little time to set the part up). I see chucks 6 or 8 inch for under $150.

I just bought my 8 inch 4 jaw from Small Tools and I have been very happy with it.

Shars: http://www.shars.com/products/workholding/lathe-chucks?chuck_diameter=6&dir=asc&order=price

Small Tools Ebay page: https://www.ebay.com/itm/SAVON-8-3-...le-Mounting-/131968360105?hash=item1eb9ed5ea9

JTS: http://www.jtsmach.com/store-1/

CDCO: http://www.cdcotools.com/
 

SubtleHustle

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#10
Great info guys! Thanks so much! Yeah I have been thinking about a 4 jaw independent. From what I've read, they are the way to go. That's actually what I have been looking for online, but none had the correct threading. So...an adapter plate, anything I should be looking for, to make sure the plate/chuck are comparable? And again, I am very thankful for you guys quick responses! This is my first time joining a forum, and it is great! Just forgive me, if I am not too savvy on technology. I'm just an old guy, with a phone smarter than himself.
 

macardoso

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#11
Great info guys! Thanks so much! Yeah I have been thinking about a 4 jaw independent. From what I've read, they are the way to go. That's actually what I have been looking for online, but none had the correct threading. So...an adapter plate, anything I should be looking for, to make sure the plate/chuck are comparable? And again, I am very thankful for you guys quick responses! This is my first time joining a forum, and it is great! Just forgive me, if I am not too savvy on technology. I'm just an old guy, with a phone smarter than himself.
Any adapter plate you buy will need a skim cut to true it up on your lathe. I would buy the chuck and the backplate from the same place so you know they match. Sometimes the hole patterns will be different when purchased from different locations.

What size chuck do you want?
 

Nogoingback

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#12
As others have mentioned, you'll need an adapter plate. Aftermarket chucks sold as "plain back" or flat back chucks are used
with adapter plates. You will need to machine the adapter on the lathe to ensure that the chuck fits properly in many cases, though
some companies may supply both the chuck and back plate together. An independent 4 jaw is a great way to start since they can
be adjusted accurately, and you can chuck up square stock as well as round. It just takes a bit more time to set up than a three
jaw, though as you gain experience, you'll get better at it.

Here are a couple of vids:


 

benmychree

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#13
A 3 jaw chuck is what I normally keep on my 19" Regal, it is a Buck Adjust Tru; it is nearly 30 years old now, and runs true enough for most work without adjustment, when I need something closer, I easily adjust it to run true. I only use the 4 jaw when I need it for large diameter work, or square or irregular work. You are correct in avoiding used chucks, they would be a "pig in a poke" and likely as worn as what you have.
Buying a flat back chuck and a semi finished backplate is the way to go if you cannot find one that is pre threaded for your lathe and likely if you bought a flat back and semi finished backplate, the end result would likely run truer than a pre finished one. I'd advise, get the 3 jaw first and the 4 jaw second, likely you will find that you will use the 3 jaw much more than the 4 jaw, as most people do. Speaking for myself, I'd avoid Chinese chucks, Taiwan OK and European even better; THERE IS A DIFFERENCE!
 

SubtleHustle

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#14
Any adapter plate you buy will need a skim cut to true it up on your lathe. I would buy the chuck and the backplate from the same place so you know they match. Sometimes the hole patterns will be different when purchased from different locations.

What size chuck do you want?
Looking for a 6" 4 jaw independent
 

SubtleHustle

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#15
As others have mentioned, you'll need an adapter plate. Aftermarket chucks sold as "plain back" or flat back chucks are used
with adapter plates. You will need to machine the adapter on the lathe to ensure that the chuck fits properly in many cases, though
some companies may supply both the chuck and back plate together. An independent 4 jaw is a great way to start since they can
be adjusted accurately, and you can chuck up square stock as well as round. It just takes a bit more time to set up than a three
jaw, though as you gain experience, you'll get better at it.

Here are a couple of vids:


Thanks for the video links, I'm sure they will help!
 

macardoso

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#16
Looking for a 6" 4 jaw independent

CDCO: Part numbers 26412 + 25454
Total price: $140 (you will need to drill and tap the mounting holes)

Shars: Part number 202-5431
Total Price: $130 (Ready to mount, currently out of stock, call them, they will give you a lead time, usually quick)

Small Tools doesn't have a 6" w/ 1.5-8

JTS Machinery: PartNumbers 0604F0 + 7-871-062
Total Price: $254 (That back plate costs more than the chuck :( )
 

SubtleHustle

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#17
You're awesome Macardoso! Thanks
 

BaronJ

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#18
If you think you need a new independent four chuck, then the one you have must be in a really bad way !

I would be interested in what is wrong with it.
 

ericc

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#19
Hi BaronJ. I think he has a bad 3 jaw chuck. When I bought my SB 9, it had no chuck. Somebody gave me a 4 jaw chuck with no back plate and a broken screw (missing threads). I fixed the screw with a TIG welder, and I made a back plate blacksmith style. It took a while, but once I had the back plate, I could attach the chuck and make a plug gauge, which I measured with three wires. That will allow me to make a real back plate. It would have been a lot simpler to just buy an import chuck and back plate for 1-1/2" x 8 spindle thread. Some assembly required: you will have to cut the register to fit. The fit doesn't matter so much with a 4 jaw chuck.

By the way, is there any way that one could salvage a three jaw chuck by bodging some soft jaws.? You would have to do this for each workpiece, but it would allow one to proceed without having to buy a new chuck.
 

hman

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#20
Regarding backplates and their preparation -
All a backplate really has to fit is the OD of the chuck and the thread pattern of the spindle. When you get the backplate, you mount it on the spindle about as tightly as you would the chuck. Then machine the diameter of the raised "register" to a close sliding fit with the recess in the back of the chuck. Then a skim cut from the register outward, to get a true surface perpendicular to the spindle. This "customizes" the backplate for your lathe. Threaded backplates should not be moved between lathes.

Once the above is done, you can either use transfer screws (if the chuck's mounting holes are threaded, typical of a 3-jaw) or a close fitting center punch from the front of the chuck (if it has counterbored clearance holes on its face, typical of a 4-jaw). Drill the backplate and/or tap as appropriate.

The above is mainly for threaded-on backplates. I've not dealt with other "flavors" of mounts.
 

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#21
Hello Eric,

My error, I miss read. A four jaw has to be in really bad shape to be unusable.

In order to answer your question, yes soft jaws is one way, and I've on occasions just knocked up a set to do a particular job.

30-07-2017-006.JPG
Some 40 mm alloy bar cut into slices and drilled to suit chuck jaw. In this case 16 mm, 5 mm from the edge.
30-07-2017-007.JPG
Marked on edge prior to drilling and threading for 2 Ba screws. The holes are centered on the chuck jaw.
30-07-2017-011.JPG
Threading 2 Ba under power at 50 rpm.

I did have a picture of these fitted to the chuck jaws but can't find them at the moment.

The other method I use is to make a collet. Again I use anything convenient, alloy, brass, and plastic.

21-08-2018-013.JPG
This is a collet that I made to drill and ream a 1/4" hole in a piece of 1/2" silver steel bar.
It is just a length of nylon rod the length of the chuck jaws, drilled 1/2" and the position of jaw 1 marked, and the steel bar pushed through it.
 
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SubtleHustle

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#22
If you think you need a new independent four chuck, then the one you have must be in a really bad way !

I would be interested in what is wrong with it.
Yup, it's an old 3 jaw, that I'm having problems with. Looking to get a new, undamaged, chuck and read that 4 jaw independent ones are the most accurate. So I'm looking for one of those.
 

SubtleHustle

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#23
Thanks Hman and Eric. You all have no idea how helpful you've been. I am totally learning to machine on my own. My friends just look at me when I talk about it, which I find myself doing most of the time now. The hobby machinist is exactly what I needed. So again, thanks to all of you.
 

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#24
Hi Guys,

Adding to my previous post because things got a little weird last night. I suddenly found that the Internet connection stopped and it took a few minutes to recover and then I had to do an edit post to carry on. So I just posted as far as I got.

Right lets carry on:

DSC04.JPG
These are the pictures I was looking for. At the time I only had a toothed belt pulley to make these soft jaws with.
Small_Gear-02.JPG
Here I was precision boring a steel replacement gear for my mill in order to replace a plastic one that was defective from new and failed later whilst in use. I actually replaced all the plastic gears in the mill. It has made a terrific difference.

Now the last picture in my other post. Making a collet, plastic, aluminum or steel. It doesn't matter what material you use. I like nylon, A: because I have a lot of it, and B: you can compress it easily. Being able to squeeze the collet onto the work piece is important.

The technique is this. Cut a length of the material that you are going to use that is long enough to be gripped by the whole width of the chuck jaw and big enough in diameter to allow the work piece to pass through it with a reasonable wall thickness. In the case of the 1/2" diameter bar, that piece of nylon was 1" diameter.

Place the material that you are going to make the collet from into the three jaw and tighten the jaws. Now mark the material in some way so that you know where it goes. I use jaw 1. Now carefully center drill and then drill right through using a drill about half the diameter of the work piece, stepping up drill sizes until, in the case of nylon, and in this particular case where the material is a standard diameter, a 1/2" drill.

In nylon a 1/2" rod is a very good push fit in a 1/2" drilled hole. The plastic seems to shrink slightly. In this example, I had to take the collet out of the chuck and press the rod into it by hand. Then refit it in the chuck in exactly the same place. After I put it back I went through the center drilling and then drilling to 6 mm for reaming to 1/4" for the shaft.

If you are using a metal to make the collet the steps are the same except that you may need to bore out to suit your work, bore out just a half mm or so smaller than your work. Remove the collet and slit it lengthwise, so that you have a gap a few mm wide. Obviously avoiding where the jaws land. You may need to put relief slits between the other jaws depending upon how thick you have made the collect wall.

Once you have done this, return the collect to the lathe and bore out to final size which should be a good sliding fit. Be careful not to over tighten the jaws when boring to size because you will need to be able to tighten the chuck jaws down enough to grip your work firmly.

I hope that makes sense !
 
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