Boring a deep hole

I'm trying to bore 2 journals in a cast iron part; the journals are 1 3/4" but badly worn; I intend to bore them oversize and sleeve using Aluminium Bronze to restore the journals to their nominal size. I have a boring head for the mill that takes a 5/8" boring bar but the problem is the lower journal is 185mm below the top surface of the casting. I want to bore both journals in 1 setup to maintain concentricity but I can't find boring bars anywhere near this length. I can make up a bar from 5/8" dia. bar, but I'm wondering if it will be too flexible. Anyone have experience using such a long boring bar of a similar diameter? Martin

Reply to
Martin Whybrow
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Martin, You don't really give enough information of what machinery you are trying to do this on. I wouldn't think for one minute that a 5/8" bar sticking out 185mm plus bore length is going to be rigid enough. Can the part go on the crosslide of the lathe and a boring bar go thru.

If on a mill what taper is the machine?

-- Regards,

John Stevenson Nottingham, England.

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Reply to
John Stevenson

John The job would be done on my Elliot Sturdimill, it has an INT 40 taper in the vertical head and I have a 2 1/2" boring head which accepts 5/8" boring bars. The part is an awkward shape (the head from a Startrite pedestal drill) but has datum pads on the lower face (presumably from when it was bored originally) which would make locating it on the mill table fairly straightforward. It's probably too large to fit on the cross slide of my ML7, but Ill check just in case. I should have been clearer, the bore length is included in the 185mm (the measurement was to the bottom end of the lower journal). Martin

Reply to
Martin Whybrow

What sort of INT 40 tooling do you have besides the boring head?

-- Regards,

John Stevenson Nottingham, England.

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Reply to
John Stevenson

FWIW.. Consider boring the upper bore and facing the housing so as to get a mounting perpendicular to the bore. Machine up a stub to suit the bore and bolt to the mill table. Clock this to the mill spindle and then mount the housing to it. bore the other hole.. As for the sleeves, I'd stay with cast iron.

Tom

Reply to
Tom

I also have DA180 and 200 collet holders, small and large Clarkson Autolock holders and ER25 collet holders, a couple of arbours for larger milling cutters and facing heads and a 2 MT adapter. Does that help? Martin

Reply to
Martin Whybrow

Seems like that would work, I'll sketch out some ideas based on your suggestion. I was originally going to sleeve with CI but couldn't locate any of large enough OD in short lengths; I chose Ally Bronze after a number of suggestions over on RCM. Martin

Reply to
Martin Whybrow

I'd forget the boring head. As john says 5/8" dia boring bar over that length would not be rigid enough.

What I would suggest is making a bar from something like 1 1/2"+ dia mild steel (something tougher of you got it) Machine one end to the dia of the largest shank your spindle tooling can take. Cross drill and ream the other end for a round toolbit and tap for a grubscrew to clamp this bit.

As you are intending to make bushes the final diameter is probably not too critical, easier to turn the bushes to suit your bored hole than the other way around ;-)

Hope this helps.

Wayne....

Reply to
Wayne Weedon

In message , Martin Whybrow writes

[snip]

Mallard Metals will supply grade 250 CI by the inch - usual disclaimer other than a satisfied customer.

Reply to
Mike H

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