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Offset boring through rectangular blank

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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?

IMAG0516.jpgIMAG0515.jpgIMAG0513.jpg
 

Comments

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
 
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.
 
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
 
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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.
 
Ahhh................never heard of a chuck like that . I would trash that thing in a heartbeat ! Sounds like an instant projectile in the making
 
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.
 
Hmmm, really wanted to buy a toolpost next.... :frown:

I may try your suggestion, Savarin but I dont think I'll stand in line with the cutter this time when I do.
It would be nice to have this part done.
 
Yeah , really . That thing sounds dangerous ! Out of balance and loose jaws can spell disaster especially at high rpm . Imagine cutting the OD with an interrupted cut ! :cautious: But yes , savarin summed it up above .
 
Put your dimensions on here . I most likely have the aluminum and the time . If I do it , shipping cost would do . I would rather not hear about someone being injured on the site . :cool:
 
I spend nearly an entire 40 hour week every 2 months or so turning square and rectangular parts in a lathe using a 4-jaw chuck, my employer holds all of this work so that it is done at one time after the chuck change which takes some time.
I fail to see your problem.
Chuck it, indicate the location and have at it, I often use different jaws for this work depending on the part shape and size.
 
Glad you got this sorted but let me be especially ignorant here. Your chuck has screws that lock down the jaw adjuster bolts once the part is secured? I've not seen a chuck like that before - learn something every day!
 
Aww, thanks mmcmdl. That is very kind of you.

It will be an interrupted cut almost the whole rest of the cut too.
Perhaps if I bump up the dc conversion before this, I can slow it down to a not so fatal speed.
I may feel confident enough to try it then.
 
Glad you got this sorted but let me be especially ignorant here. Your chuck has screws that lock down the jaw adjuster bolts once the part is secured? I've not seen a chuck like that before - learn something every day!
LOL! Yes it is a weird chuck!
 
I think its meant as a wood chuck, mine broke and the replacement they sent also went westward soon after but it did give me another face plate..
In my humble opinion the list of jobs to do on the 9x20 in what I think is a good order is...
1, Make a solid plinth to replace the compound, you can thread at 90' so you really only need the compound for short tapers, This mod alone boosts rigidity by a huge percentage and makes parting off a breeze.
https://www.hobby-machinist.com/threads/plinth-for-qctp-on-9-x-20-lathe.45628/
2, Get the QCTP and extra holders of choice, AXA works well with these lathes, I like the wedge type but there does not seem to be much difference in rigidity overall. Make sure the centre post is the correct size for your tool post holder. The one that comes with the lathe is a bit flimsy.
I bored out the original 4 way tool post so it would fit the 14mm shaft required for the QCTP and could be used until you get the qctp
3, A real 4 jaw chuck, dont forget a back plate unless you want to make your own.

You can set the block up in the three jaw by using the three jaws to the side, ie, two jaws on one side and one jaw on the other side and squeezing the block between them, if you lucky the hole will be where it can be bored. (its worth a look to see if it will line up)
The first couple of shots show what I mean by gripping at the sides of the jaws and how the centre would be off set if using the three jaw, you can also off set the same way with the 4 jaw.
https://www.hobby-machinist.com/threads/a-vertical-slide-for-a-9x20-lathe.49724/
also how much stickout can be accomplished with care and fine cuts.

https://www.hobby-machinist.com/threads/the-9x20-mods-thread.30050/
post 12 to see offset boring the compound slide to fit the 14mm post.

Hope this helps.
 
Huh, I'll take a look at the 3 jaw.
I have been fooling with this 4 jaw this evening.
This thing is a nightmare.
Seems like its impossible to tighten the stock and have it be square to the jaws. Stuff shifts as it draws up tight. I think you're right about it being wood chuck.
It just might work in the 3 jaw too!
Thanks for that tip!
 
Savarin, I also like your qctp mod too. I've been looking at axa tps. Seems like they do need to be raised a bit. I also like the 4 bolt design on yours too!
 
The rest of this story...

I have been productive this past month.
Got a decent 4 jaw 6" chuck off of FleaBay. Nothing fancy but it works.
The backplate threads were too short to fully engage the register on the lathe, so I made an appropriately sized spacer and superglued it to the chuck. Also used the superglue chuck method to face the other side of the spacer. First time for me doing the superglue thing. What a great solution for stuff like this. This is in my book for good now!
287493
Mounted and centered the hole, bored it and it too came out beautiful.
Also sprung for the Bostar wedgie toolpost with holders....
Have it mounted quickly on the cross slide for now, and already an improvement.
It'll do till I work out the nice mounting plate for it that is in the 4 jaw.
I want it to be really solid.
So, I appreciate everyone's input. You really helped me out.
Now I know the difference between a 4 jaw wood chuck and a 4 jaw metal chuck! And the 2 are not interchangeable.
 
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