4 Jaw Chuck for Mini Lathe

[RMS]

If you look here, starting at reply #37, you can see some mods I made to my 3-jaw chuck which lets me adjust it for TIR, much like a 4 jaw chuck. I've also found that once I set it to zero TIR with a 1/2" bar chucked up, the TIR doesn't change much at different diameters... maybe a maximum of .0015" out to 3/4". Haven't checked any further.

http://www.homemodelenginemachinist.com/index.php?topic=9016.15

I find that I am using my mini lathe more and more for small, precision work and my modified 3-jaw chuck stays on the lathe all the time. I would highly recommend this mod for anyone wanting precision, repeatable holding of round stock for turning and boring. It's mitigated my need for an er collet chuck on the mini lathe.

Chuck

Hey Chuck,

Nice job on your mini lathe mods and attachments, that thing is all set up nice. Kinda similar to what I have, and its all I have to work with right now so I am limited to both skill and machine power. Next step is the 4J and then a milling attachment. Then I hope a mini mill in the next year.

Rob

 

[jct842]

Unless some one here knows for sure, I am going to call Chris at Little Machine Shop and pose a question before ordering a new 4 jaw.

What I want to know is on a 7X12 cummins lathe which will hold a larger piece, a 4 jaw 4" or a 4 jaw 5"?

I know there is going to be a point where the jaws on the 5" are going to hit the ways. If both were equal or close to capacity I will probably spend the extra $10 and get the 5" to get the weight. that larger chuck has to be smoother running. I suppose one could grind a little off the end of the jaws but when mounting a odd shaped piece that may be counter productive. I do have a 4 jaw 3" and I feel that was a waste of money because I am going to go bigger. I use the 4 jaw a lot and have found it is no big deal to set some thing up true with it. John

 

[cfellows]

Unless some one here knows for sure, I am going to call Chris at Little Machine Shop and pose a question before ordering a new 4 jaw.

What I want to know is on a 7X12 cummins lathe which will hold a larger piece, a 4 jaw 4" or a 4 jaw 5"?

I know there is going to be a point where the jaws on the 5" are going to hit the ways. If both were equal or close to capacity I will probably spend the extra $10 and get the 5" to get the weight. that larger chuck has to be smoother running. I suppose one could grind a little off the end of the jaws but when mounting a odd shaped piece that may be counter productive. I do have a 4 jaw 3" and I feel that was a waste of money because I am going to go bigger. I use the 4 jaw a lot and have found it is no big deal to set some thing up true with it. John

May not be important to you, but another thing to consider is how small a piece can be gripped in the jaws. Usually, a smaller chuck will grip smaller stock than a larger one.

 

[Ken I]

Rob,
cfellows is spot on about the minimum diameter you can chuck being important.

As for setting one up....

For round stock - eyeball the amount the jaws stick out (or in - or whatever reference) - I often look down one set off jaws to eyeball the ones at right angles look more or less the same.

Then bring in a tool and rotate - eyeball the gap and adjust - you generally don't want to go straight to a dial gauge - way too much movement.

Finally let the tool scrape and keep adjusting away from it until it more or less scrapes all round.
At about this point stop backing off the "away" jaw and simply tighten the "high" jaw.

There's no point in being fully clocked up and the chuck isn't tight.

As I said earlier this is good enough if you are going to turn the O.D. in any case.

Obviously don't go scraping a tool against a finished surface.

Now introduce your dial gauge for the final "tweaking".

If you intend to turn eccentrics, it is advisable to clock the work true to center prior to offsetting - then offset only using one opposing set of jaws - this way you know you only have your offset in a single plane. This is important when you need a reference plane to the offset. (Obviously you can only push over about half the width of the flat on the jaws then those jaws will start to slack off - the best you can do here is to tighten them equally as you go.)

I normally remove my 4 jaw with the work still in it and mount the chuck in my mill vice - normally clamping on one of the jaws - hey presto you can now mill a flat or drill a reference hole for an exact future reference to the offset.

You'll soon get the hang of it.

Regards,
Ken

 

[RMS]

Unless some one here knows for sure, I am going to call Chris at Little Machine Shop and pose a question before ordering a new 4 jaw.

What I want to know is on a 7X12 cummins lathe which will hold a larger piece, a 4 jaw 4" or a 4 jaw 5"?

I know there is going to be a point where the jaws on the 5" are going to hit the ways. If both were equal or close to capacity I will probably spend the extra $10 and get the 5" to get the weight. that larger chuck has to be smoother running. I suppose one could grind a little off the end of the jaws but when mounting a odd shaped piece that may be counter productive. I do have a 4 jaw 3" and I feel that was a waste of money because I am going to go bigger. I use the 4 jaw a lot and have found it is no big deal to set some thing up true with it. John

Hi John,

Let me know if you talk with them over at LMS. Interesting is your point about the weight being a positive factor.

 

[Tin Falcon]

There is nothing tricky at all about using a Four jaw independent chuck. It does require a bit of practice and a dial indicator. In the beginning it may seem a bit fussy. Forrest Addy Who is a very experienced machinist and published in the Home Shop Machinist recommends that newbies only use a 4J independent excursively for a year. This will teach proficiency. The old Craftsman Dunlap lathes used to come exclusively with a 4 jaw independent chuck. Unbolt the chuck and back plate is now the face plate. If you wanted a 3 jaw self centering chuck that was an option. If I could only own 1 chuck for the lathe it would be a 4 jaw independent. You can do almost anything with it a 3 j self center will do and then some. Indicating a part in does not need to take a lot of time. I worked in a shop where all parts were indicated in to within a couple of tenths (Ten thousands of an inch) There is no reason not to leave the 4 jaw on most of the time if you so choose . The 3jaw is just easier. but the 4 jaw will teach patience and give all the accuracy you dial in.
Like I have said before this is easy stuff any five year old can do it with ten years experience. ;D
Tin

 

[RMS]

Rob,
cfellows is spot on about the minimum diameter you can chuck being important.

As for setting one up....

For round stock - eyeball the amount the jaws stick out (or in - or whatever reference) - I often look down one set off jaws to eyeball the ones at right angles look more or less the same.

Then bring in a tool and rotate - eyeball the gap and adjust - you generally don't want to go straight to a dial gauge - way too much movement.

Finally let the tool scrape and keep adjusting away from it until it more or less scrapes all round.
At about this point stop backing off the "away" jaw and simply tighten the "high" jaw.

There's no point in being fully clocked up and the chuck isn't tight.

As I said earlier this is good enough if you are going to turn the O.D. in any case.

Obviously don't go scraping a tool against a finished surface.

Now introduce your dial gauge for the final "tweaking".

If you intend to turn eccentrics, it is advisable to clock the work true to center prior to offsetting - then offset only using one opposing set of jaws - this way you know you only have your offset in a single plane. This is important when you need a reference plane to the offset. (Obviously you can only push over about half the width of the flat on the jaws then those jaws will start to slack off - the best you can do here is to tighten them equally as you go.)

I normally remove my 4 jaw with the work still in it and mount the chuck in my mill vice - normally clamping on one of the jaws - hey presto you can now mill a flat or drill a reference hole for an exact future reference to the offset.

You'll soon get the hang of it.

Regards,
Ken

Hey Ken,

I got you on "MOST" of that obviously I need the hands on but, basically I need to rough it close using an easy to spot alignment reference point, then use the dial indicator. My wife is going to buy me this 4-Jaw chuck for Christmas, and I am hoping to get it a bit early ;D

Thanks,
Rob

 

[RMS]

To all,

5" vs 4" 4J?

I Just read another interesting post that the extra mass of the 5" chuck on a mini lathe helps (as John said bellow). This post said the extra mass helped to eliminate the sensitive overload shut off circuit by acting as a flywheel giving some extra momentum with its weight factor. I find this interesting because a few days ago I was turning some aluminum and a few times I went just a tad to quick into the work and this shut off circuit kicked in, kinda annoying since this happened a few times.

Now mind you that I do not wish to thwart any overload protection cause that can be a good thing and prevent damage to gears, but if the 5" can act as a flywheel and help give just a little muscle then its another positive vote to go with the mass of a 5" vs a 4", or maybe its a mute point and the 4" will surface, just some food for thought I guess, but its kinda swaying my purchase to go with the 5" now.

Rob

 

[jct842]

Chris from LMS returned my call this afternoon. His take on 4 verses 5" is performance is about the same but the 5" takes longer to start and stop. I am thinking if I should need to go the little bit bigger I can always use a face plate. The part that bothers me is not the start up but taking longer to stop could be a negative saftey factor. anyway I got by for 89.95 for chuck and adapter. I also got the mounting studs and a mt3 dead center. I thought I had one but cant find it.

I found that I can make a flywheel any size right up to 7" using flat bar stock and first mounting it up to the face plate to machine the hub and rim gripping surface. then put it in a chuck to finish the other side. That was one of my concerns with getting a larger chuck. I should have got the 4" in place of the 4 jaw 3" right off the bat.

I am as always impressed with LMS. Chris has always taken the time to explain anything I need help on. John

 

[Andrew_D]

Wow, a lot of posts here since I was on...

Yes, I ordered my 5" 3-jaw, 4-jaw and backplate from LMS. I can't remember how much more/less the 5" will turn over the 4". I figured that going up to 4" wasn't a big jump, so why not go to the 5"?

I will warn you...when the 5" arrives and you see it, you are going to think..."What have I done?"...There is a HUGE difference in size between a 3" and a 5"!!! Still worth it I think. (Also a difference in weight...don't let your hand become trapped between the chuck and the ways!)

As mentioned, give the spindle a spin by hand to check for clearance before turning it on...we don't want to have to read a story about smashed up ways, carriage, etc. ;D

I don't know about the 5" starting slower, stopping longer, etc as I have swapped out the controls and motor for a treadmill motor (2 Chinese Horses...not sure how many US horses it is!!!)

Andrew

 

[Ken I]

The large inertial mass does not affect the power (needed or delivered) but the extra inertia may give you a split second more stored energy to back out of an injudicious cut.

The downside is there is more energy for the "BANG" when it does all go to hell in a handbasket.

Regards,
Ken

 

[RMS]

Wow, a lot of posts here since I was on...

Yes, I ordered my 5" 3-jaw, 4-jaw and backplate from LMS. I can't remember how much more/less the 5" will turn over the 4". I figured that going up to 4" wasn't a big jump, so why not go to the 5"?

I will warn you...when the 5" arrives and you see it, you are going to think..."What have I done?"...There is a HUGE difference in size between a 3" and a 5"!!! Still worth it I think. (Also a difference in weight...don't let your hand become trapped between the chuck and the ways!)

As mentioned, give the spindle a spin by hand to check for clearance before turning it on...we don't want to have to read a story about smashed up ways, carriage, etc. ;D

I don't know about the 5" starting slower, stopping longer, etc as I have swapped out the controls and motor for a treadmill motor (2 Chinese Horses...not sure how many US horses it is!!!)

Andrew

Man.......now I am looking at my fingers and thinking maybe 4" would be a safer bet? ;D

Those treadmill motors on your lathe in combination with a 5" chuck sounds like you have one nice mini lathe!

Thanks for the ideas!!

I will post some pics once I get it set up.

 

[Andrew_D]

Man.......now I am looking at my fingers and thinking maybe 4" would be a safer bet? ;D

Those treadmill motors on your lathe in combination with a 5" chuck sounds like you have one nice mini lathe!

Thanks for the ideas!!

I will post some pics once I get it set up.

It is a HUGE improvement over the stock lathe.

I don't use it too much since getting my 20"x48" WWII-era McDougall, but it is still handy for the odd job.

I'm thinking of giving it a make-over to tighten everything up, install tapered gibs, re-do the tailstock (something is binding there - bent ram? bent leadscrew? damaged casting? ....not sure), maybe extend the bed, lengthen the cross-slide so I can turn the max swing over the cross-slide.

Andrew

 

[RMS]

Hey Guys!

My wife got me my new chuck for Christmas! Went with the 4" Here is a couple pics compared to the original 3"-3J. I felt like testing out my new dial indicator also, there is a .001" run out; Does this sound about right?


Rob

 

[Tin Falcon]

do not worry about 1 thousands of run out you can set those jaws any where you need.
I would be happy with that little run out on a 3 jaw.
Tin

 

[jct842]

you should be well satisfied with your 4". the only thing that .001 run out could possibly do is effect balance, since it is four jaw you center on the work not the chuck. I don't think I even tried to check my new 4" for run out. I am getting ready to make a material order including some gray iron disks to make flywheels out of. I don't think I will have any trouble making about any thing I want now. John

 

[Andrew_D]

You mention 0.001" run-out, but you are measuring on the circumference of the chuck. It's nice that the chuck body is so close, but shouldn't you be measuring on a piece of stock held in the jaws???

Andrew

 

[RMS]

You mention 0.001" run-out, but you are measuring on the circumference of the chuck. It's nice that the chuck body is so close, but shouldn't you be measuring on a piece of stock held in the jaws???

Andrew

Hi Andrew,

Yeah that maybe a good idea to rule out any defects in the production of this chuck! This test was only done for fun, and to see how accurate it all went together; Chuck, adapter plate, to spindle. I am still setting up my work area right now and have not started any projects yet, but soon!

Thanks,
Rob

 

[steamer]

.001 runout is fine for a 3 jaw...let alone a 4 jaw.

It will serve you well.

Dave