Thread: Line boring on the mill

I did this over 30 years ago but had access to a HBM which made life easier.

I would use a big boring head if you have one as this gives you easy tool adjustment. You might not have the reach & rigidity to do both the front & back holes though in which case, there are a few issues.

A HBM has a rotating table so I spun my HS casting 180 deg to do the back bore. I made up a dummy spindle to use in aligning the bores. On a mill, you could mount a RT if you have a big enough one.

If you're thinking of line boring using the mill overarm bracket to support the outer end of your modified arbor, then of course a boring head won't work and you'll have to make some form of accurate tool setting gauge to measure cutter extension. I'd be a bit surprised if a horizontal mill had enough Y travel to manage to do both front & back bores in a single setup but if so, it'd be a better way to go for concentricity I think.

PDW

Originally Posted by Ueee

Hi all,
Has anyone ever set up their horizontal mill for line boring?

I'm trying to think of the best way to bore a new bronze sleeve to size once it has been pressed into the Mars's old main bearing. I cannot see any way of doing it in the lathe out of the headstock and guarantee that it remains centered and axial. The head is too tall to bore clamped to the Antrac's cross slide.

I was thinking of taking my old slightly bent 1" arbor and drilling it for a tool bit. A pinned on collar and i can clamp the bearing in place with the retaining nut. If the arbor is too short i will have to turn a new one to put in an ER40 collet and fit the bearing on.

I have enough Y to do it, but i will also need to mount a DTI on the bar to ensure the head is aligned properly.

I will skim the rear bearing bore at the same time, if i take only a thou or 2 the adjustment in the bearing will take it up. If not i'll have to press the old sleeve out and replace it....

Any thoughts would be appreciated.

Cheers,
Ewan

Ew,

Should the bearing in bold read cutter ? Have you looked at this thread? https://www.woodworkforums.com/f65/us...ml#post1261599

Bob.

Originally Posted by Anorak Bob

Ew,

Should the bearing in bold read cutter ? Have you looked at this thread? https://www.woodworkforums.com/f65/us...ml#post1261599

Bob.

Bearing for the overarm support Bob. I cannot fit the head on the Antrac to bore it between centers, i don't have enough center height.

PDW, i have just enough Y to do it, it is only a small head. I could use the Wholhaupter but i only have a pissy 6" RT so that won't work.

If you were to run out of Y though why not put 2 cutters in? They will still cut in alignment won't they? They do in my head, since they both share there paints of rotation.

Ew

Ew, the arbors on both my mills run in bronze bushed overarm ends, hence the dull question. The link was to show you how cutter depth could be managed and measured, I know you can't line bore this on your lathe. As Peter suggests, what about your boring head? Your Wohl would possess sufficient rigidity I'd have thought.

Bob.

Sorry Bob, i was a little unclear, when I say bearing I mean the steel center that rides in the bronze bearing in the overarm support.

With the whol I can only see that I will either have to turn the headstock around or put the headstock in line with the x axis, rotate the head to bore on bearing and then flip it round the other way to do the other bearing. I still think line boring will keep things more axial.
As for adjustment of the cutting tool, I had thought of putting an adjustment grub screw in and just use a mic over the bar and toolbit.

Ew

Originally Posted by Ueee

PDW, i have just enough Y to do it, it is only a small head. I could use the Wholhaupter but i only have a pissy 6" RT so that won't work.

If you were to run out of Y though why not put 2 cutters in? They will still cut in alignment won't they? They do in my head, since they both share there paints of rotation.

Ew

I didn't think of using 2 cutters, that's all. The only times I've had to do line boring, I've had enough travel to do it with a single cutter. No reason at all I can see why it wouldn't work fine with 2 though I'd probably do one bore to completion then move the cutter to the 2nd spot in the boring bar and do the 2nd bore rather than trying to get clever and set 2 tools up to cut the bores simultaneously......

With that mill you can easily handle a 10" RT which is getting bloody heavy but none too big for some jobs. Gives you good 4th axis capability though. I'm thinking of making a 12" sacrificial plate up for my RT. I'd actually like a smaller one for the pissy jobs.

PDW

Originally Posted by Ueee

With the whol I can only see that I will either have to turn the headstock around or put the headstock in line with the x axis, rotate the head to bore on bearing and then flip it round the other way to do the other bearing. I still think line boring will keep things more axial.
As for adjustment of the cutting tool, I had thought of putting an adjustment grub screw in and just use a mic over the bar and toolbit.

Ew

Agree WRT the boring head setup. PITA without a RT or similar to swing the job 180 to do the 2nd bore. It'd work but I think using an arbor as a line boring bar is better since you have the travel.

Better way to set the tool bit is to make up a J shaped bracket that is a neat fit around the boring bar and a mike head set opposite the tool bit on the J crossbar so you have good repeatable measurements. Have a clearance hole in the back side of the J allowing access to the grub screw so you can push out to measurement. PITA for a one-off but a handy tool to have if you anticipate doing more line boring in the future.

Coffee break over, time to get back to wood butchery on the boat interior.....

PDW

Would you blokes have sufficient faith in your rotary table to swing it 180 degrees and bore again?

Lining it up using a dial with a dummy spindle or even the real spindle i would, but not off the graduations or even the dividing plates i would not. Its a moot point for me but i would be interested to see what everyone else thinks.

I like the idea of the J measuring tool, sounds good. Pete F has also given me some ideas for another possibility, of boring it in place and mounting a boring bar on the lathes saddle. I have to do some more reading before i fully understand how this method will work.

Ew

How about line boring on the LeBlond? You could locate the saddle up near the tailstock end where there may be less wear and support a long between centres bar with a fixed steady ( if you have one ).

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Pete the Wraith's method has me intrigued. What is rotating?

BT

Doing it on the LeBlond would be my first choice....except she is completely in pieces.

Here is a link to some details of doing it on the lathe bed. Fitting bronze sleeves - 9" headstock.

I could not do it this way as my head sits on flats and not on the flat/v T/S ways. I still think the mill will be best, i have adjustments for twist, i may just need to scrape the vertical alignment a bit.....down the rabbit hole we go! The T/S already needs to come up so scraping the head doesn't bother me....much! Once the Taylor Hobson Arrives (and i make a base for it) I'll be able to get a really good idea of just how bad the ways are.


Ew

Originally Posted by Ueee

Lining it up using a dial with a dummy spindle or even the real spindle i would, but not off the graduations or even the dividing plates i would not. Its a moot point for me but i would be interested to see what everyone else thinks.

No way I'd trust the grads on my RT - I'd do the same, use a dummy shaft or the real one to realign. I wouldn't even trust my RT to maintain the same *plane* since I've never checked it.....

When I did this on a HBM, I *knew* the table rotated exactly 180 deg and locked in position. We checked that first.

Dave Gingery's book on building your own lathe (and the mill) describes how to bore a HS in situ using a powered boring bar and moving the HS along the ways. Given you have a pretty good mill, I think I'd do it the way you're thinking now. The boring bar is supported on both ends if you've room for the arbor support outboard and that's going to be a lot stiffer than the other method.

FWIW I re-bored the TS ram in situ on the lathe using a boring bar in the HS supported outboard by a custom fixed steady. The bar ran through the centre of the TS and I attached the TS to the lathe saddle to push it along the ways. Had to make a new oversize ram when I finished but the bore was straight, parallel and spot on centre height.

All brings back bad memories of figuring out why I couldn't do good work and too ignorant to know if the problem was the machine or operator. It was both of course. Now I only (generally) get to blame the operator. Some things don't change.

PDW

If the rear bearing is all right, can you make up a boring bar/ shaft that will use the rear as a guide for the end of the shaft and just bore the front? You may have to make up a dummy spindle section to get the guidance spot on but if that is the right size I can't see why it's not possible. If you can make up a sliding/ rotating bearing for the front that can be held in a temporary housing you might even be able to power it with an electric drill.

Extra resources for the mix. I'm on the trail of a Tree boring head. The thing that the Tree did that no other boring head I've heard of did was that it was self feeding. As a result if you could set up a spindle on your lathe bed, it may be possible to use something like that to bore without having to have a functioning travel/ traversing system.
(the other thing that it makes possible is boring tapers - as per the recent thread on boring a propeller).

Michael

So Ew, back to the mill. How are you going to ensure that the headstock's "original" spindle centreline is maintained? How do you accommodate for the wear?

I hadn't considered planar accuracy when I mentioned the rotary table and thinking about how the Asian stuff is made to a price, my Vertex could easily be out of whack. It ain't a Moore.

BT