Quick and simple line boring bar

[Frank S]

For the past few days I have been rebuilding a link assembly for a hydraulic thumb mounted on a large excavator.
As luk would have it the center locations that the cylinder rod pins to pulled horribly upon the assembly cooling off despite preparations and precautions to hold the weldement in a fixture while welding.
So I decided that since the locations already had a pretty bad oval wear to them I would simply line bore the locations then machine and harden a sleeve to press in them.
Enter problem #1 no line bore rig Problem #2 no boring bar even is I had a rig.
Solve Problem #2 first find a 1.75" 48" long shaft which I simply cross drilled a .625" hole then 90° to that on the center line of hole I drilled and tapped for 3/8" 18 TPI instant line boring bar
Solve problem #1 by removing the compound from my lathe and red neck mount the 400+ lb assembly atop of the carriage

lift the assembly with the jib crane then swing it over the lathe

use chuck to center one end

use tail stock to center opposite side

The definition of a lunatic anyone who would lob a 400+ lb hunk of scrap iron on the carriage of their lathe then (Seriously) use c clamps a machinist jack and 2x6 to hold it in place while using the lathe as a line bore machine.

But hay it works However tomorrow I am going to add a couple of outboard bearings to the works by first making the mounts and a pair of bushings to fit the boring bar then I will tack weld these to the assembly that way I will be able to isolate any movement in the long bar and subsequently take deeper cuts without fear that the whole thing will be tossed out of alignment.
Post script the steady rest is only there to reduce chatter, the end of the boring bar is in the live center

[DIYer]

Thanks Frank S! We've added your Line Boring Bar to our Machining category,
as well as to your builder page: Frank S's Homemade Tools. Your receipt:

Line Boring Bar by Frank S

tags: boring bar

[DIYer]

Thanks Frank S! We've added your Lathe Boring Setup to our Lathes category,
as well as to your builder page: Frank S's Homemade Tools. Your receipt:

Lathe Boring Setup by Frank S

tags: boring

[Toolmaker51]

Hats off guys. Who noticed the shop-made steady rest too? Wood planks help isolate vibration, clamping "beds" the ends into wood [instead of a tiny point of metal-to-metal contact], the setup is shimmed for height and level on the machine's own centerline. A vertical or horizontal mill couldn't very well support both arms and running bearing, or maybe even enough quill travel.
While similar tasks have been addressed in this manner; used to be only isolated tradespersons actually practiced them. Some due to 'job security', but communication wasn't quite like now either. Also illustrates why the Lathe is King of All Machine Tools. This is how the act of preservation feeds itself. Having reliable tools help, like a full set of 12" C-clamps!

[Frank S]

Thank you TM51 little tricks like using wood as an integral part of a set up has long been a practice of mine when these type of jobs come up.
My wife and most everyone who has witnessed my hacks know them as my old Indian tricks.
Once a young man who had heard me tell of so many old Indian tricks said I wish IO could have known that old Indian you always refer to. A friend who has known me since my days in the military told him son you are looking at that old Indian, because I've known him for 40 years and the only person who I've ever seen him learn anything from was he, himself.
Most would cringe at the thought of using wood in this manor, because wood has a tendency to compress and is partially unpredictable since it can flex under strain. However when it can be placed in pure compression and is well seasoned hard planks if there is sufficient bearing surface as you stated it works very well The use of c clamps was not my first choice but the carriage on the lathe although being nice and wide over 24 inches in this case does not have "T" slots like my much older smaller Leblond. I have entertained thoughts of eventually milling "T" slots into the carriage or drilling and taping it for clamp studs The carriage arms are thick enough to support this idea but since my smaller lathe has the slots if it would have had a longer bed or had not been modified in the way it was I could have done this job on it but I wasn't even sure that I would have had enough travel also that lathe is not under a hoist plus I was not at all sure that it was fully functional since I have not had the time to restore it but yesterday while the set up was running I decided to see if I could turn the bushings on it since I will need them for sizing and cannot remove the set up until completion. To my astonishment the 100 year old Leblond 16 inch runs fine and will do what I need as is.

[Toolmaker51]

I'd hesitate to mill T-slots in carriage wings. While factory versions are seen, I'm betting there is extra width and thickness to support material removal...Now drilled/tapped/tapered pull dowels in a fixture plate I'd go for. T-slots, matrix of tapped holes and a few reamed for straight edges. Compound removed, covering cross slide. Some might cut away around the wings, weld plate above and across the notches to keep it off the ways.
I'd think a mag base drill beats pulling and setting up to mill the carriage by miles.
And your 100 year old LeBlond still produces! That is why we admire old iron. My Pratt & Whitney Jig Bore is 100 next week. Date on motor tag, I believe is 4 July 1917. Yes, more pictures to post, I know, I know.

[Frank S]

I agree about the "T" slots because the 100 year old lathe has slightly thicker wings where it's "T" slots are milled in
I dare say that not very many of today's machinist have ever used the slots on a lathe if in fact they have ever even seen one with them. I became accustomed to making fixtures for my little Southbend as a teenager of course I didn't have anyone to teach me anything about lathe work or how to use one So I didn't know any better I fugured that Southbend put them there for a reason so why not use them.

[KustomsbyKent]

Frank,
If I understand your setup correctly, you'll slide the welded link assembly on the wood skids that slides on the lathe ways? Is the wood & weldment also attached to the carriage so you can get smooth movement side to side?
Any chance you can video it when you do this? The more we can learn the better!

Thanks
Kent

[Frank S]

Kent the set up was mounted on the carriage everything was clamped tight to the carriage so all I had to do was set the cutter depth in th eboring bar then engage the feed just like in any normal machining operation with the exception the cutter did the rotating

[dwbachor]

Now that's using what you have to get the job done! Nice.