Re: extrusion of Linear Bearing pillow block question...

If I were a cagey ol' retired fellar like Smoke here, an I had a
wealth of knowledge in such thigs as casting and machining, I might
cast up a bunch of these blocks n sell em.I'd probably sell them
rough cast for the guys who wanted (and could)machine their own and
Id jig up to efficiently machine them for those who prefer to buy
them ready to put bearings into. A guy might really create the system
of choice for this hobby. Could be the Mariss of linear motion. Hmm
what to call them. gecko & frog are taken, snake doesn't exactly
conjer up visions of precision straigtness. Maybe "DRAGON BEARINGS".
But then , Im not a cagey ol retired fellar.
Thanks,
Dale

--- In CAD_CAM_EDM_DRO@y..., "Smoke" <smoke@t...> wrote:
> Since you ask....
>
> First I wouldn't use an extrusion. Castings can be made a LOT
> cheaper....unless your doing them by the thousands. For $10 bucks
worth of
> propane, I could make a lot of castings all at one time from scrap
aluminum.
> These would have the flanges cast in place as well as a cored hole
for the
> bearing. If I didn't want the hole cast in place, I could cast
long bars
> and saw them to desired lengths. If I were to cast them using lost
wax
> process, I'd cast long bars with a cored hole for the bearings.
>
> I'd machine them in three steps on the mill using quick change
tooling.
> First I'd set the casting upright for machining the end (face
milling), the
> bottom mounting surface (side milling) and the bore. The bore
would be
> drilled and reamed. This method insures the bore will be parallel
to the
> mounting surface as well as square to the end of the part.
>
> The part would then be turned over for machining the opposite end.
Then the
> part is rotated bottom end up for drilling the mounting holes.
>
> If I had to do hundreds of parts I'd do it a bit different. I'd
build a
> fixture that would allow me to do all the machining in one setup.
With some
> forethought, the fixture could be build to hold more than one part
for
> machining in multiples.
>
> I would not use a press fit! I'd use the bore tolerances
recommended by
> Thompson in their catalogs. If necessary, I'd buy a reamer sized
to these
> tolerances. I'd use clips on the ends to hold the bearings in
place.
> That's what the grooves on the ends of the bearings are for. If the
> bearings do not have these grooves, I'd ream the bearing hole to a
depth
> that would leave a retaining wall on one end. Then I'd tap a hole
on the
> other end for mounting a retaining clip.
>
> Some years (lots of them) ago when I was first learning to use a
lathe, I
> made a special aluminum bushing for some roller skate wheels. I
bored the
> hole a tiny bit too big. So I experimented with something then
available
> called Loctite Bearing Mount (no longer available). I put in a few
drops,
> slid the bearing in and heated it with a match. After heating I
couldn't
> get the bearing out even using a 3 pound ball peen hammer and a BIG
punch!
>
> You don't really need stock bedding compound for holding the
bearings in
> place. There are lots of epoxies (five minute epoxy comes to mind)
available
> at the local hardware store that will work just as well. All you
need to
> remove the bearing when using those is a little bit of heat.
Naturally,
> you'd need to be careful not to get any epoxy inside the bearing,
so don't
> use very much if you go that route.
>
> If the bore is a "crummy fit" (oversize), don't bother trying to
fix it by
> using epoxy. Epoxy is not a good substitute for good workmanship!
Chances
> are the bearing will not achieve proper alignment. Throw the
defective part
> out and make one correctly.
>
> Set screws of the dog point variety will work, if the bearing OD is
provided
> with a hole, slot or groove for the purpose. You just need to be
very
> careful not to run the screw in too tight. After adjusting the
screw it
> should be locked in place with another screw or a jam nut. I'd
prefer not
> to use set screws as they are not "idiot proof" enough.
>
> Smoke
>
>
> > Hi Lloyd:
> > Setscrews are a bad idea on bearings.
> > The one-sides pressure will misalign them at best, and distort
them at
> > worst.
> > Circlips are the way to go if you can't achieve a press fit
within an
> > ACCURATELY round bore.
> > A way for crummy holes ( but not TOO sloppy) is Loctite, (and a
hammer
> when
> > you need to service them!)
> > Another really good way for lightly stressed applications is a
bedding
> > compound; Moglice or gunstock bedding compound spring to mind.
> > Ron Ginger or Smoke should be able to expand on this theme
further.
> > Ron, Smoke...The floor is yours!!!
> > Cheers