I don't know your ultimate goal, but 1/4" chrome rod in nylon or
Delrin would last a long time and be fairly easy to work. I would
use it as a mountable block rather than as a bushing.

--
______________________________
Keep the whole world singing . . . .
DanG (remove the sevens)




"Bob La Londe" wrote in message
...
I am working on an idea that involves a guide rod (3 actually)
sliding back and forth in a "bushing" with some degree of
accuracy. Actually the guide rod would be in two different
bushings about 2.75 inches apart. Side load would be very light,
but there would be some. (less than inch pounds in most cases)
During the course of use the guide rod might have to move 40-50
times, and have continuous movement from .001 to .009 for a 20
minute job. Some small amount of side play would be tolerable but
experimentation is required to determine how much. Greater for
some jobs. The idea is that the bushing can be pressed out and
replaced periodically as needed.

1. If you were to do this ideally what would you use for the
bushing and the guide rod?

2. If the ideal materials where not available what would you
use that is commonly available?

3. What would you use that is commonly available and cheap?

Due to space limitations I am looking at a guide rod diameter of
approximately .25, but I could redesign for up to .375. Extra
mass could have a negative impact on the intended direction of
travel, but mass could be removed elsewhere.

I am working on an idea that involves a guide rod (3 actually) sliding back
and forth in a "bushing" with some degree of accuracy. Actually the guide
rod would be in two different bushings about 2.75 inches apart. Side load
would be very light, but there would be some. (less than inch pounds in
most cases) During the course of use the guide rod might have to move 40-50
times, and have continuous movement from .001 to .009 for a 20 minute job.
Some small amount of side play would be tolerable but experimentation is
required to determine how much. Greater for some jobs. The idea is that
the bushing can be pressed out and replaced periodically as needed.

1. If you were to do this ideally what would you use for the bushing and
the guide rod?

2. If the ideal materials where not available what would you use that is
commonly available?

3. What would you use that is commonly available and cheap?

Due to space limitations I am looking at a guide rod diameter of
approximately .25, but I could redesign for up to .375. Extra mass could
have a negative impact on the intended direction of travel, but mass could
be removed elsewhere.

"Bob La Londe" wrote in message
...
I am working on an idea that involves a guide rod (3 actually) sliding
back and forth in a "bushing" with some degree of accuracy. Actually the
guide rod would be in two different bushings about 2.75 inches apart.
Side load would be very light, but there would be some. (less than inch
pounds in most cases) During the course of use the guide rod might have
to move 40-50 times, and have continuous movement from .001 to .009 for a
20 minute job. Some small amount of side play would be tolerable but
experimentation is required to determine how much. Greater for some jobs.
The idea is that the bushing can be pressed out and replaced periodically
as needed.

1. If you were to do this ideally what would you use for the bushing
and the guide rod?

2. If the ideal materials where not available what would you use that
is commonly available?

3. What would you use that is commonly available and cheap?

Due to space limitations I am looking at a guide rod diameter of
approximately .25, but I could redesign for up to .375. Extra mass could
have a negative impact on the intended direction of travel, but mass could
be removed elsewhere.


I was thinking of something like this for the bushing. The guide rod will
be fixed and not rotate in the bushing. Just slide back and forth. The
guide rod will be vertical. Side load (minimal) will be in any and all
directions at one time or another.

http://tinyurl.com/yjub9ak

And something like this for the guide rod.

http://tinyurl.com/yzhmvlm

"DanG" wrote in message
...
I don't know your ultimate goal, but 1/4" chrome rod in nylon or Delrin
would last a long time and be fairly easy to work. I would use it as a
mountable block rather than as a bushing.

It could be done as a mountable block although space is limited. There are
some issues in my mind regarding accuracy (or is that precision) of
replacement parts, but I suppose if I looked at it with block mounting in
mind I could figure that out.

"Bob La Londe" wrote in message
...
"Bob La Londe" wrote in message
...
I am working on an idea that involves a guide rod (3 actually) sliding
back and forth in a "bushing" with some degree of accuracy. Actually the
guide rod would be in two different bushings about 2.75 inches apart.
Side load would be very light, but there would be some. (less than inch
pounds in most cases) During the course of use the guide rod might have
to move 40-50 times, and have continuous movement from .001 to .009 for a
20 minute job. Some small amount of side play would be tolerable but
experimentation is required to determine how much. Greater for some
jobs. The idea is that the bushing can be pressed out and replaced
periodically as needed.

1. If you were to do this ideally what would you use for the bushing
and the guide rod?

2. If the ideal materials where not available what would you use that
is commonly available?

3. What would you use that is commonly available and cheap?

Due to space limitations I am looking at a guide rod diameter of
approximately .25, but I could redesign for up to .375. Extra mass
could have a negative impact on the intended direction of travel, but
mass could be removed elsewhere.


I was thinking of something like this for the bushing. The guide rod will
be fixed and not rotate in the bushing. Just slide back and forth. The
guide rod will be vertical. Side load (minimal) will be in any and all
directions at one time or another.

http://tinyurl.com/yjub9ak

And something like this for the guide rod.

http://tinyurl.com/yzhmvlm

I would add that the over tool body would be aluminum (for weight) and the
guide rod would be fixed into the carriage or moving part of the tool
directly either by a press fit or possible with green Loctite bushing and
sleeve locker. This would make a stainless alloy for the guide rod
desirable.

"Bob La Londe" wrote in message
...
"Bob La Londe" wrote in message
...
I am working on an idea that involves a guide rod (3 actually) sliding
back and forth in a "bushing" with some degree of accuracy. Actually the
guide rod would be in two different bushings about 2.75 inches apart.
Side load would be very light, but there would be some. (less than inch
pounds in most cases) During the course of use the guide rod might have
to move 40-50 times, and have continuous movement from .001 to .009 for a
20 minute job. Some small amount of side play would be tolerable but
experimentation is required to determine how much. Greater for some
jobs. The idea is that the bushing can be pressed out and replaced
periodically as needed.

1. If you were to do this ideally what would you use for the bushing
and the guide rod?

2. If the ideal materials where not available what would you use that
is commonly available?

3. What would you use that is commonly available and cheap?

Due to space limitations I am looking at a guide rod diameter of
approximately .25, but I could redesign for up to .375. Extra mass
could have a negative impact on the intended direction of travel, but
mass could be removed elsewhere.


I was thinking of something like this for the bushing. The guide rod will
be fixed and not rotate in the bushing. Just slide back and forth. The
guide rod will be vertical. Side load (minimal) will be in any and all
directions at one time or another.

http://tinyurl.com/yjub9ak

And something like this for the guide rod.

http://tinyurl.com/yzhmvlm




Sintered bushings will last a long time. You can buy shafts that fit the
bushings from the same bearing supply place, at least in the old days.

Are linear bearings overkill? I see they are $15 each in Mcmastercarr.
http://www.mcmaster.com/#6489k61/=4az5du
6489K61
Self-Aligning Linear Ball Bearing Closed, 1/4" Inside Diameter
In stock at $14.60 Each

Or cruise eBay, I've seen small ones for a fraction of this
price.

Karl

On Sat, 31 Oct 2009 10:50:31 -0700, "Bob La Londe"
wrote:

"Bob La Londe" wrote in message
...
I am working on an idea that involves a guide rod (3 actually) sliding
back and forth in a "bushing" with some degree of accuracy. Actually the
guide rod would be in two different bushings about 2.75 inches apart.
Side load would be very light, but there would be some. (less than inch
pounds in most cases) During the course of use the guide rod might have
to move 40-50 times, and have continuous movement from .001 to .009 for a
20 minute job. Some small amount of side play would be tolerable but
experimentation is required to determine how much. Greater for some jobs.
The idea is that the bushing can be pressed out and replaced periodically
as needed.

1. If you were to do this ideally what would you use for the bushing
and the guide rod?

2. If the ideal materials where not available what would you use that
is commonly available?

3. What would you use that is commonly available and cheap?

Due to space limitations I am looking at a guide rod diameter of
approximately .25, but I could redesign for up to .375. Extra mass could
have a negative impact on the intended direction of travel, but mass could
be removed elsewhere.


I was thinking of something like this for the bushing. The guide rod will
be fixed and not rotate in the bushing. Just slide back and forth. The
guide rod will be vertical. Side load (minimal) will be in any and all
directions at one time or another.

http://tinyurl.com/yjub9ak

The housing bore determines the ID of bronze bushings that are pressed
in place. It's best to plan on reaming after installation if the ID
and alignment is at all fussy. The manufacturers' catalogs have info
on tolerances and how to predict the installed ID.

The dimensions on that page are only the nominal size -- the actual
part will measure oversize by a few thousandths on both the ID and OD
before being pressed into place.

For slow speeds and intermittent use, Thomson shaft (hardened linear
bearing shaft) running in drill jig bushings can be very accurate. The
tolerances on drill bushings are much tighter than bronze bushings,
but proper alignment is more critical.

I've used bronze bushings in a split adjustable housing that allowed
adjusting bearing clearance, similar to some drill press quills, with
good results.

--
Ned Simmons

Karl Townsend" wrote in message
anews.com...
Are linear bearings overkill? I see they are $15 each in Mcmastercarr.
http://www.mcmaster.com/#6489k61/=4az5du
6489K61
Self-Aligning Linear Ball Bearing Closed, 1/4" Inside Diameter
In stock at $14.60 Each

After playing with a slip fit tool that does this same job (in a different
manner) I may not have any choice but go with a super free linear bearing.
With a spring light enough to do the job I do not get positive enough snap
back. I would hope to be able to go with just gravity pressure in my most
extreme application.