# Four jaw chuck usage



## Bernd (Apr 14, 2008)

Have you ever noticed how doing a simple job can turn into a major project. Working on the Wobbler from Elmer's book I finally got to the point of boring out the cylinder. I'm using my Sherline lathe to do the job. I mounted the four jaw chuck, lined up the part and proceed to drill out the hole. When I got the hole big enough I was going to bore it out with a tiny carbide boring bar. The problem is I don't have any way to hold the boring bar in the Sherline. Time to make a holder. I used a piece or 1.25" square aluminum piece the same length as the Sherline tool holder. So, on to the Grizzly 9 X 20 lathe to make the part. Below are a couple of pictures of how I made the tool post holder to hold a boring bar that has 3/8" mounting dia.







This pic shows the 4 jaw that comes with the Grizzly. Not a very useful tool on something small. The chuck is also very awkward to work with.






This pic shows how I get around the problem by using a smaller chuck. The four jaw chuck came from a wood lathe I dragged home on day. I made a stub arbor to mount in the three jaw. Works great for small jobs.






Lining up where the hole is going for the mounting screw. The wiggler bar is one from the pages of The Bedside Reader by Guy Lautard.






I didn't take any pics of drilling out the hole to 3/8" for the bar to go into here. So a quick description of what I did. I used the 3 jaw Sherline chuck to center drill and then progressively drill larger holes in the tool post until I got to the 3/8" drill. Then drilled two holes and tapped 10-24 to clamp the boring bar with. Oh, I also made sure that the tool post was mounted square to the lathe axis.

It's nice to have three lathes. My third is a 10 X 24(?) Logan. Now it's on to finishing the cylinder. While boring out the cylinder I was thinking what John (Bogstandard) said in his book. Make things to fit. Since I'm not set up yet to measure small holes sizes such as what is being used on this engine I will use a plug gage ( a piece of 3/8" drill rod) to get my bore close and then make the piston to fit. 

See John, I did learn something from reading your posts. 

Bernd


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## Bogstandard (Apr 14, 2008)

Bernd,

Wonderful use of the bits you have knocking about the shop.

A perfect example of lateral thinking.

A job well done.

John


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## Bernd (Apr 14, 2008)

Thanks John.


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## rake60 (Apr 14, 2008)

Great tip Bernd.

I have that Grizzly 9 X 20 Lathe myself.
I hated that cheesy 4 jaw chuck. It never did work to my needs.
It really didn't work well after I "dropped" in on a horizontal plane
about 20 feet in the basement. Luckily the concrete wall stopped it
before it do any harm to anything useful. 

I've been looking at a small 4 jaw chuck for some time now.
The backing plate, the registering of the fit, the drilling of the 
mounting holes...

For the past 30 years I've seen 4 jaw chucks mounted in a 3 jaw 
on a lathe. Why I never thought of it at home is another one of those
head banging moments!  :-\

Rick


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## Cedge (Apr 14, 2008)

Bernd
Now that's a darned handy little trick. The smaller 7x## mini lathes are a pain to take the chuck on and off due to the small access available for getting at the mounting studs. I use 5 inch, 3 jaw chuck on the little machine so it's just not something I want to tackle every time I need a 4 jaw set up. 

I've got a 3 inch and a 5 inch 4 jaw chuck currently growing rust that will now have to come out of the cabinet and go to work. Just in time too... I've got a crank shaft to make real soon. Thanks for sharing the idea. Your timing was perfect.

Steve
taking an obligatory head bang too


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## Hexbasher (Apr 15, 2008)

this was a fun job i did at work a year ago


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## Bernd (Apr 15, 2008)

tattooed_machinist  said:
			
		

> (pic)
> this was a fun job i did at work a year ago



Now that looks down right scary. 

Bernd


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## Bernd (Apr 15, 2008)

Thanks Rick and Steve.

That little 4 jaw does have a back plate on it. But being lazy I just made a stub arbor with a, IIRC, 1" X 8 thread. The only draw back is the over hang. Not very rigid but works great for small stuff.

Bernd


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## Hexbasher (Apr 15, 2008)

Bernd  said:
			
		

> Now that looks down right scary.
> 
> Bernd



bomber

i took the time to balance it i bolted the step blocks in the front (with spacers inside them) and safety bolts if they were to some loose...

and afew chucks of round stock (drilled through) and bolted on the inside


i ran that at 800 rpm no problem without a vibe...

i kept the 0.0005 runout tol between concentrics...3a thread and 2 0.0005 tol dias on one side for bearings and a 0.001 tol dia and oil grooves on the other shaft

peice of cake..

the hard part was then adding a steady rest to the mix to ream a 6 inch long 1/8 hole through one of the shafts

i did the setup on our POS mill at the shop


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