ckoehler wrote:
On Dec 17, 11:12 pm, Chris wrote:
ol3_m3 wrote:
On Dec 17, 5:51 pm, Chris wrote:
ol3_m3 wrote:
Need to enlarge the bore on a pc of bronze stock fron 1/2" to 3/4" the
length of the material is a bit over 12". any suggestions on where I
can find drill bits and reamer with extra long shanks? any tips on
keeping the hole concentric to the OD?
thanks
OM
first question, is the bore of the stock finished or just the rough
cored hole from extrusion?
second what type of finish do you require and size tolerance on the
finished bore?
very hard to keep a bored hole straight and true for that length
without dedicated gun drills or such
if you have access to a lathe , i would consider mounting a boring bar
between centers and boring with the stock mounted on the cross slide.
or alternately using same type of bar mounted in the tool post and
passing through a bushint in the headstock 9 making a sort of line
boring rig in the lathe.
i placed a roller bearing in a spindle through hole once and used a 6T
borring bar to bore a 32" long bore, held .001 for the length.
of course the bar was 3" diameter and i wa boring a 4" hole out to 4.125
need close tolerances, will be a sliding fit on the shaft it is to
fit over, is the stand for a precision grinder I am trying to build.
strongly suggest you look at other methods for this part, 12 inches of
sliding / rotating contact ?

might want to look at thompson shafting, and a sleeve with either
bearings or pressed in bushings

you can get to bores on either end of a lon gpiece in line with little
fuss , just takes patience with a good .0001 indicator

the other thing to do is make both bushings od , and rough bore the id,
bore each end of the shaft to a good press fit to the od of the bushing

use a mandrel long enough to go through each bushing and after using
some lapping compound to get them running true with each other , turn
the od of the shaft concentric with the shaft between centers

still only going to get it withing .001 or .002 of play no matter how
hard you try.

is that good enough for your grinder?

might look at moglice too, form in place bearing material

http://www.moglice.com- Hide quoted text -

- Show quoted text -

Pick up a cheap gundrill @ MSC.


and get a high pressure coolant set up and some starter bushings too