Offset boring through rectangular blank

[stomp10]

Hi All

I need to bore a 1.5 inch hole through a thick hunk of 6061 on an Enco 9x20.
Stock 4 jaw chuck.
How much slop should be on the faceplate bolts? I have it as close to zero by feel without binding as I can.
Do these need to be tightened and when during setup? But if you get them too tight the adjusters wont work right.

My first attempt made a beautiful hole but the stock shifted. I think I caught that before it was too late to save the piece. I was just having too much fun in the moment. lol
The sides of the hole are square to the top at least.

I have attached some photos of first setup for critique. Its also sat like that for the last 3 years. I need to make some progress. lol The first 2 you can see the scrape marks from the jaws when it shifted. There is a circle scribed on top where the hole is supposed to be. Luckily, the hole isn't outside of that.
Sooo, what went wrong here?

 

[mmcmdl]

What do you mean by " slop " on the faceplate bolts ?

 

[stomp10]

How tight should they be? If you lock them down you wont be able to adjust the jaws.
Or how much play in the jaws when not clamped

 

[mikey]

Wait, I agree with Dave. You are not being clear. This is a 4 jaw independent chuck, right? The chuck should mount directly to the spindle so there is no faceplate involved, or are we missing something?

Or are you asking about how tight the jaw adjustment bolts should be? If so, they should be snugged pretty tight but evenly. You go around to each jaw bolt and tighten each to be similar in tightness to the others.

Keep in mind that your bore is off center so the load is off center and balance will be off as well. Therefore, you need to slow the lathe down a bit or you'll have a lot of vibration.

 

[mmcmdl]

Therefore, you need to slow the lathe down a bit or you'll have a lot of vibration.

Or , you'll walk that lathe into the room next door !

He has me confused Mike .

 

[stomp10]

Yes a 4 jaw independant.

Or are you asking about how tight the jaw adjustment bolts should be? If so, they should be snugged pretty tight but evenly. You go around to each jaw bolt and tighten each to be similar in tightness to the others.

This a better way to ask my question, thanks and thanks for that answer. I had a hard time elucidating... lol
I cut this as slow as the lathe will go but, its still too fast for my comfort level. These are the bolts that go through the top of the jaws and the faceplate of the chuck, secured by nuts on the backside. its a cheapie chuck.

I do have a 550w dc motor waiting for an install but I want to get this aging project finished first

 

[Cadillac]

I think I understand what's going on. The 4 jaw that he's using in the picture has studs that lock the jaws down after adjustment through the face of chuck. Those lock bolts need to be snug when adjusting stock. The pressure of the adjusting will cause the jaws to move away from face of chuck. Real PITA! I used the one that came with my jet lathe once and it was just like that never used again.

 

[mmcmdl]

Ahhh................never heard of a chuck like that . I would trash that thing in a heartbeat ! Sounds like an instant projectile in the making

 

[stomp10]

LOL! dang glad I asked!
So maybe its deficient tooling and not operator error this time.
Thanks for the laugh!

 

[savarin]

The stock 4 jaw that comes with the 9x20 is little short of useless.
Get a real 4 jaw as soon as possible with a backplate that fits your spindle nose.
Having said that tighten up the rear nuts until the jaws are movable but stiff.
tighten the jaw adjusters to tighten up the piece in place.
Now tighten up the rear nuts to prevent the jaws from moving.