(01-04-2018, 08:32 AM)f350ca Wrote: Its an interesting idea, just because its not done YET doesn't mean it wouldn't work. Could you make a core of sand or carbon or what ever that would break out after.

(01-04-2018, 09:27 PM)randyc Wrote:

(01-04-2018, 03:50 AM)Pete O Wrote: ......I've come up with an idea to use the head off my drill press to turn and feed a shaft with a boring tool on the other end, might just be crazy enough to work...

I LOVE crazy ideas, even if they have 50% chance of working !  As a guy on YouTube, whose name I have now forgotten, said "Every day is a school day in the machine shop".

Will you use an outboard bearing for the drill press ?  Hope that you photograph and post the setup, Pete, even if it doesn't perform as well as you'd like.  Even partial successes (NOT implying that your idea will be anything but successful) are very useful as a learning tool !!!

Cheers !

Here's a verbal sketch of what I have in mind: A length of I-beam welded across the two loader arms, parallel to where the bores will be; Pillow-block bearings mounted to the I-beam, between the loader arms, so that the bearing I.D. is on the bore axis; A length of shaft that goes through the bearings, one end carries the HSS tool bit, the other end protrudes through the other (rough finished) hole and has 3 flats machined on it to be driven by a drill chuck; the drill-press head mounted outboard of the frame so that the drill press spindle is on the bore axis and that end of the boring shaft is driven by the drill press chuck, feed being via the quill. The shaft has holes drilled across it at appropriate points to position a HSS toolbit for each bore location, the toolbit being adjusted manually between cuts. In an ideal world, a J-head takes the place of the drill-press head and I stand back and smile while the power feed does all the work .

(01-05-2018, 01:20 AM)SteveG Wrote: In a previous life, we used to replace the hard bronze bushings that attach the engines to the wing pylons on B747's.
The bushes were fitted using liquid nitrogen to shrink them then the machinists would line bore them in place.
My memory is a bit sketchy as its been 20+ years, but I don't recall the tooling being complex, and was just driven using large right angle pneumatic drill (slow speed and small head for access reasons). I don't recall any mechanical feed mechanism.

Since you're not looking at a high precision application, I don't see why you couldn't get away with making up a long boring bar with a HSS cutter, and mounting 2 guide blocks - one on the outside face of each bearing and simply driving it slowly with an electric drill.

I think the feed needs to be via a quill feed or similar, a 'grab' with a drill powerful enough to drive the cutter at a 30mm radius would probably result in wrist fractures.


If you make the boring bar so its longer than the whole setup by sufficient length that you can get the cutter to the space in between the faces to adjust for the next cut, and also have a second cutter hole in the bar in the appropriate place to let you bore the other bush without disturbing the setup I think the result should be plenty good enough.
I might be able to help you out with some bronze if you don't already have some. What size are the bushes?

We're definitely on the same page Steve, although I'm picturing the bearings mounted to a length of I-beam and slightly inboard from the arms; that way I can re-use the same setup to bore the cleats on the bucket (or quick-attach frame). Nothing actually measured yet, but I think the bushes will need to be about 2" o.d. by the time I have made the existing flogged-out holes round again, and about 1 1/4" i.d. for the pins. I would look favourably upon any offers of bronze!!

Edit: re-reading you post, I think you were referring to line boring the steel pivot arms themselves. I was referring to line boring bronze bushes.
An option might be to bore the arms independently, fit bushes and then line bore them. As long as you make sure the bushes don't turn in operation the outcome should be the same.

There's a steel insert welded into the end of each arm, with badly flogged-out bores. I'll either be reboring the existing holes to accept bushes (in which case I'll line-bore the existing holes, insert bushes and then line-bore the bushes) or I will cut the inserts off and make new ones, in which case I'll pre-bore the steel inserts before welding them to the arms, then line-bore the bushes.

Steve