Author Topic: offset holes (Read 6432 times)

daz · « **on:** November 13, 2011, 07:29:41 AM »

I have so many questions it's unbelievable, I'll try not to flood you with them all at once.
I think the answer to this one is obvious. I need to make a large hole in a piece of aluminium
(1 1/8" dia). But it is offcentre and has to be exact. I only have a 3 jaw chuck, but I also have a milling machine. Is there a way to do this on the mill (non CNC) or am I better of buying a 4 jaw chuck and using a boring bar? I might be able to get work to stump up for the chuck if I can find a way of justifying it, but if not what are your suggestions? I hope this doesn't sound really stupid
I don't think my picture came out right?

daz

Jasonb · « **Reply #1 on:** November 13, 2011, 07:58:14 AM »

To do it on the mill you would need to start with various size drills and when you don't have any larger change to a boring head, this holds a cutting tool that you can adjust the radius of so you just keep winding on a cut until it gets to the size hole you want. Something like this

A 4jaw is probably more useful than a boring head but the head will allow you to put holes into material that is too large to swing in teh lathe.

If you have a faceplate for the lathe the work can easily be clamped to that and a boring bar used.

J

daz · « **Reply #2 on:** November 13, 2011, 08:02:01 AM »

Me stupid
I should have tried google a little more. I could get a boring head for the mill, probably cheaper than buying a decent 4 jaw independant chuck? I had a late night last night and my brain isn't in gear yet

daz

Bernd · « **Reply #3 on:** November 13, 2011, 08:55:00 AM »

J,

I was just looking at the way your holding the part. Neat idea if the vise won't hold it.

@daz,

I'd use a faceplate to do the hole. Much cheaper than a boring head. This is of course if you have a faceplate for your lathe.

Bernd

Jasonb · « **Reply #4 on:** November 13, 2011, 09:49:07 AM »

Yes the left hand angle plate was clocked true and not moved but the casting could be rotated so keeping a ref face to work on all 4 sides. I could not put a bolt right through teh middle as I'm actually set up to bore a concentric hole on the bottom of the casting

Daz of the two options I'd go with a 4 jaw as you will get more use out of it.

J

kvom · « **Reply #5 on:** November 13, 2011, 09:53:43 AM »

Another possibility is using an annular cutter on the mill.

daz · « **Reply #6 on:** November 13, 2011, 11:07:21 AM »

Thanks for the replies guys, I know people say there is no such thing as a stupid question but you must get bored of answering this stuff time after time so I really appreciate it.
Bernd, unfortunately I do not have a faceplate either.

kvom, I have never even heard of one of those before, google is going to start charging me soon.
Thanks to a very generous person I now have plans for a project that will A: teach me loads about machining, B: Keep me occupied through the horrible winter months when I can't go out fly fishing, and C: Give me a useful and practical machine.
The only problem is I have never attempted anything so complex before (to you guys it won't be) and the mill and lathe I have available to me are just not set up for stuff like this, they didn't even have a set of clamps or parallels for the mill, just a vice and a couple of cutters. I have made tools, fixtures, machine parts etc but nothing to any degree of accuracy, 0.02mm is about as close as it gets for me so for the last 24 hours I have been reading over instructions and looking at the drawings to see what parts will be easy and which parts will pose some challenge.
I have come to the conclusion that you guys have some serious skill to turn out the work you do.
Hopefully once I have everything right in my head, and the right tools at my disposal, I can start a new thread in the projects section, but it could take a while.

thanks again

daz

sbwhart · « **Reply #7 on:** November 13, 2011, 12:45:44 PM »

I like the two angle plate set up Jason, that ones filed away

Stew

jim · « **Reply #8 on:** November 13, 2011, 01:08:48 PM »

you could bore it on the lathe in a three jaw. just put shim under one of the jaws, clock up the o/d untill the offset is correct

Jasonb · « **Reply #9 on:** November 13, 2011, 03:51:20 PM »

Quote from: jim on November 13, 2011, 01:08:48 PM

you could bore it on the lathe in a three jaw. just put shim under one of the jaws, clock up the o/d untill the offset is correct

Not the safest method with rectangular stock as the shimmed jaw will not be pushing against another jaw, and the centrifugal forces could throw the work out of the chuck.

Dhis method is OK for round objects like eccentric sheaves where the shimmed jaw pushes the work against the other two.

J

Bernd · « **Reply #10 on:** November 13, 2011, 05:21:53 PM »

Quote from: daz on November 13, 2011, 11:07:21 AM

Thanks for the replies guys, I know people say there is no such thing as a stupid question but you must get bored of answering this stuff time after time so I really appreciate it.
Bernd, unfortunately I do not have a faceplate either.

daz

That's what a forum is all about helping those that need the help and ask for it. Now if you kept asking the same question over and over again in the same threrad then we'd have to get serious and give you

to get your attention.

Faceplate: Sounds like it's time to put that on your list of shop tooling to make.

Bernd

Jonny · « **Reply #11 on:** November 13, 2011, 06:51:41 PM »

Daz the questions that should have been asked are material size, thickness and quantity.

4 jaw is the only real way of getting any accuracy with the positioning, though i regularly slap square in 3 jaw with packer to get offset 34mm holes.

If its only a few and the mills up to the job, sounds like you have all you need except a boring head and bar.
Thinish material can use holesaws and will be cheaper than a sub 28mm drill which is the max for an MT3 shank. So on a mill i would drill 1" dia through in one go and bore to size held in vice.

MadModder

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