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Do machinists do this?

WaterH

WaterH

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So I wanted to square the ends of a large tube on the lathe. The jaws could not be opened enough. The jaws can be swapped around, but then the only can grab about a 1/2”. (The tube was more out than that) So I moved the inside bolt to the outside. Not sure if this was stroke of genius or complete stupidity.

59BF1468-B7AD-49DD-B248-ED4589A2ADC4.jpeg


Tube mounted.

3097A000-C4B0-437F-B6EE-472CE39FDE24.jpeg


It worked, but I took very small cuts.

E2BA56D0-4808-497E-9CE3-2CCB021E98BD.jpeg
 
I'm no machinist but I've done way worse.

Flipping the teeth and using both bolts would have been better but that works in a pinch. If it becomes a regular thing I'd machine different teeth to bolt to your jaws.
 
Amateur like many on here, but I wouldn't recommend doing that. With the location of the jaw on the jaw base and the location of the jaw relative to the chuck body you're there's quite a lot of bending stress on the jaw base and not much metal to support it. Also dependent on a single screw to attach the jaw. Note also that normally the shoulder between jaw and base locates and takes stress between the 2, so all the screws do is hold them together, but aren't really taking any load. Here one is taking the entire load. Further, without the shoulder there's no positive alignment between jaw and base, which probably induced a decent amount of runout.

Use the chuck the right way - yes the pipe would only be grasped by a 1/2", but that should be enough. Use the tailstock with a large diameter center for support of the outer end if needed.
 
What. No.

Flip jaws, use steady rest to do end face, and a bull center to lose the steady and turn the OD. A tail chuck would be ideal, but uncommon for most people
 
This being floppy thin wall aluminum I think he did the right thing. You can't crank it real tight so it's not like the jaws are in danger. And for the same reason you need all the contact you can get hence why using the jaws the "right" way with 1/2" contact isn't ideal. He probably doesn't have an 8"+ bull center or steady rest of whatever. Sure he could make a puck to adapt a center but that's more work. For one cut this is fine. Not like he's gonna be doing a full speed cut at the limit of the tooling with a one-off like this anyway.
 
Id go on the id before having the jaws way out like that.
 
sdmuleman said:
1. Use the chuck the right way - yes the pipe would only be grasped by a 1/2", but that should be enough.
Click to expand...

sdmuleman said:
2. Use the tailstock with a large diameter center for support of the outer end if needed.
Click to expand...

1. That was not possible. After I had one end square it would work. But both ends were out of square more than a 1/2”.

2. Don’t follow this at all. Even if I had a 6” center, how would I trim the end? Maybe you mean a steady rest, but again, I can’t grab with only a 1/2”.
 
I spent a lot of time in a machine shop when I was young I don’t see anything there that looks new. The professional machinests I have seen do crazier shit than that. The jars are designed to do that.
 
In reality, I should have installed my 4 jaw chuck. But who got time for dat. (Plus, I’m getting too old to lift it.)
 
Did you check runout before you made the first cut ?
 
WaterH said:
Not sure if this was stroke of genius or complete stupidity.
Click to expand...
Both lol.

<- Ticketed machinist.

For a quick and dirty job like that with light clamping and cuts...guess so. I am sure runout would not be ideal but if it works it works.
"Do machinists do this?" The correct answer is no but I also wouldn't want to waste my time making a set of large soft jaws just to whip out a couple of those parts either.
 
The end of the unsupported tube is the sin not the jaws.

It's thin-ish tube, you can't clamp it for shit regardless so jaw engagement is pretty irrelevant.
 
Or in actuality close to the end within an inch or close, IE a steady rest.

From the look at first pic OP's lathe does not have one as its base rides on the ways.


CarterKraft said:
The end of the unsupported tube is the sin not the jaws.

It's thin-ish tube, you can't clamp it for shit regardless so jaw engagement is pretty irrelevant.
Click to expand...
 
Last edited:
I'd have wrapped it with blue tape and bandsawed the end squarerer than 1/2", then grabbed the ID.

But that worked too.

1699040459055.jpeg
 
PAE said:
Or in actuality close to the end within an inch or close, IE a steady rest.

Drim the look at first pic OP's lathe does not have one as its base rides on the ways.
Click to expand...

Wut?
 
CarterKraft said:
The end of the unsupported tube is the sin not the jaws.

It's thin-ish tube, you can't clamp it for shit regardless so jaw engagement is pretty irrelevant.
Click to expand...

It’s at least 1/4” wall. Pretty strong.

PAE said:
Or in actuality close to the end within an inch or close, IE a steady rest.

From the look at first pic OP's lathe does not have one as its base rides on the ways.
Click to expand...

My lathe has a steady rest. It’s not on in the pic.

subybaja said:
I'd have wrapped it with blue tape and bandsawed the end squarerer than 1/2", then grabbed the ID.
Click to expand...

The end I started with was sawn off with my bandsaw. I guess I could have squared it better.
 
That much stick-out of the lower jaws is not great. And extending the bolt-on top jaws like that makes it even more not great.

Ideal way would be to flip the bolt-on jaws and grip from the inside, if they get small enough. I've also seen people stick a second smaller chuck with no backplate in the bigger chuck....use the smaller chuck to grab the ID.

For a one off, light project, it obviously worked fine.
 
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