Boring question for the machineists

[fivetenben]

Im hoping some of you machinists out there could save me some phone calls. Refering to the drawing below, I need to open up the 4.7in (top)bore to ~4.9 and keep it coaxial with the 4.7244 bore at the bottom. The bore on top locates a D300 and the bottom one holds an output shaft bearing. The upper piece is mild steel, lower is cast aluminium. The two pieces are located together with two 12mm pins. I also need the uppermost surface milled just make sure its parallel to the bottom.

Would I be better off buying some cheepo tooling (flycutter and a coax indicator?) and doing it on a mill/drill I can borrow, or taking it to a job shop? How much should I expect to pay? Seems pretty simple to me, but I have limited experiance.

Thanks

Ben

[PTSchram]

Depends upon your accuracy requirements. If you farm it out, you can blame somebody else when they fawk it up.

As for how much you will have to pay, the setup to bore the hole accurately might be kinda pricy. If you do decide to go with the mill/drill setup, I think I might be inclined to use a good boring head to enlarge the hole and the fly cutter/face mill to true up the outside surfaces. While I prefer to bore such holes on a lathe, the eccentric makes me uncomfortable (freaks me out watching such pieces turn on a chuck/faceplate).

D'Oh, now that I look at it again, you might be able to do the whole job on a lathe if you can get it setup concentric.

Mill/drills are notorious for lack of repeatability. Once you get the setup done, lock everything down and don't move anything but the quill.

Peace,
PT

[MAD MAC]

have someone do it for you on a boring mill very simple to do should not cost you any more than 1 shop hour charge

[fivetenben]

Thanks for the help guys. Sounds like ill be able to get it done for less than buying the tooling. Cheapest import boring head Ive seen in the MSC cat is around $75, and Id still need a coax indicator (or is there another way to find center?).

What kind of position tolerances to factory tranny-to-tcase adapters have?

Ben

[d.d.machine]

just about any small machine shop can turn it out for you for $50 to $75
Just tell them to pick up the lower bore for there center point,,, as long as there head is square to the table and they take there time .002 should be easy to hold.....

[MC]

I second what Duffy says...thats a no brainer. A simple criterion boring head will do the job

[fivetenben]

Thats good new, thanks again.


Ben