Squaring plate without a 4 jaw chuck or a mill

savarin

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I just happened to be knocking up a couple of small "V" sliders for my Foucault tester and thought the method of squaring some off cuts of plate for projects may be of interest to some of the beginners.
No mill? no 4 jaw chuck? stock too large for the chuck?
No worries, it can be done.
All bar the last photo were done in the three jaw chuck.
I placed the off cut of aluminium plate across the jaws and tightened them against each other, 2 jaws on one side and one jaw on the other and took a facing cut, no real attempt to align anything just got it eyeballed roughly square.
sqp1.jpg
Flipped it in the 3 jaw but this time I used the chuck face as a register and faced the second side hopefully parallel with the first, which turned out to be the case.
sqp2.jpg
Next flipped it 90 degrees so the narrow end is clamped in the jaws and used a square to ensure the sides were at 90 degrees to the chuck face. This square is a homemade one from a chunk of 3/8th steel hot rolled plate and every corner is square and its heavy.
sqp3.jpg
Faced off the end and flipped it again, this time the previous flat side can use the chuck face as a register to face of the last end.
Upon measuring with the mic it is parallel in all directions and all 12 corners are square at 90 degrees.
Then I cut it in half with a hacksaw, drilled a 3mm hole in each part and bolted them together.
Back into the chuck and faced off the cut faces
sqp43.jpg
Producing 2 small squares of the same size.
sqp5.jpg
How large can we go with this method?
edging-the-plate.jpg
Admittedly its in the 4 jaw chuck but I'm using the same method.
Thats a lot of stick out but small cuts and not too fast and all is well.
I have done hot rolled steel plate 19x150x80 in the three jaw like this with no problems as well.
 
1547738804233.png
That looks scary to me. At the very least, I would put a center drill hole in it and use a tailstock center to hold the part against the chuck jaws and restrain against lateral sliding. If it comes out of the chuck it could be really hard on your lathe, your shop, and/or your body.
 
"How large can we go with this method?"

That all depends on how much risk you are willing to take, whether your Last Will and Testament is up to date and your wife is clearly the beneficiary of your life insurance. ;)

Seriously, Bob's advice is very sound, IMO
 
I know where your coming from and I was very dubious when I first tried this but it went remarkable easy and fast with no fuss.
I did ensure the piece was very firmly held.
The largest lump I did with a very large stickout I used a centre.
sqp6.jpg
All 6 sides were squared using this method.
But even I didnt have the guts to try this much unsupported stickout.
 
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