Re: Linear rail & ball screw size suggestions

--- In CAD_CAM_EDM_DRO@y..., JanRwl@A... wrote:

> In a message dated 09-Apr-02 20:42:31 Central Daylight Time,

js3mc@a...

> writes:
> There are "non-round" ways to do this, too, such as the fine stuff
> made by HIWIN, THK,
> etc., but I think you are talking serious $change, there.

I normally only lurk here but I feel I need to say something about
linear bearings... I've just noticed over the past several months
that there has been some discussion about linear bearings... some
trying to build their own, others using skate wheels, etc...

The square rail linear bearing market has become very competitive
here lately... For example I sell Hiwin... If you wanted a size 20,
(comparable to the THK SR20) the blocks (recirculating units) are
$34.50 each... and the rail is $2.24 per inch... For example an 18"
rail is $40 and a 24" rail is $54... and you can get ANY length you
want up to around 6 feet, before you have to join two rails
together... They are cut to length in Chicage at the Hiwin warehouse
and shipped directly to you, it takes about 1 week.

These prices are drastically different from several years ago when a
similar rail was $4/inch and bearing blocks were $80+...
I believe that these prices have made the supported Thomson shafting
and blocks look expensive for what you get... the size 20 has a load
capacity of 1400 lbs... you would need a 1.5" diameter Thomson shaft
to get the same capacity.

Hiwin ball screws are also dropping in cost... a 1" diam ballscrew
with .200 lead, preloaded flanged ballnut, 49" OAL, (need the ends to
be machined) is $185... this is a nice screw!

If I was building a machine, I would want it stiff, I wouldn't want
the tool moving around on me... the bearings and the screw are the
heart of stiffness. I know, I know... it's only a light load, and
little forces... but someday you are going to put a 3.5 hp router
head, and up the speeds, it's only natural, as Tim Allen says "more
power". You're going to need a system that can handle it, or you're
going to rebuild the present system... what's that saying about "not
enough money to build it right but always enough to rebuid it"?

Enough said... back to lurking...

ps... if you are interested in getting some rails and/or screws
contact me OFF the list.

Mike