Something thin to put between two pieces of 1/8" thick 1 1/2" wide
aluminum flat bar that are bolted together. A bearing that will
allow the two pieces of aluminum flat bar to be held firmly together
but move (the only way possible) against the spacer between them
with as little friction as possible.

Would that be nylon? Delrin? What is it called? At the moment, my
best guess is "thrust bearing". Even though the only thrust pushing
the pieces together is the bolt that holds them together. I'm
looking at McMaster.

Is there something not officially labeled as such that works well
for that purpose? I have some spray Teflon silicone lubricant from
Lowe's.

Thanks.

John Doe wrote:
Something thin to put between two pieces of 1/8" thick 1 1/2" wide
aluminum flat bar that are bolted together. A bearing that will
allow the two pieces of aluminum flat bar to be held firmly together.
but move (the only way possible) against the spacer between them
with as little friction as possible.

Would that be nylon? Delrin? What is it called? At the moment, my
best guess is "thrust bearing". Even though the only thrust pushing
the pieces together is the bolt that holds them together. I'm
looking at McMaster.

It would be a linear thrust bearing as far
as I can see. Without getting crazy expensive
I'd use nylon or teflon. I know M-C has some
nice thin teflon sheet that you could just
cut out and lay in. If you have more than
a small amount of force, most plastic will
tend to squash down and extrude out. I think
teflon will be better than nylon in that regard

Is there something not officially labeled as such that works well
for that purpose? I have some spray Teflon silicone lubricant from
Lowe's.

Thanks.

Jim Stewart wrote:
John Doe wrote:
Something thin to put between two pieces of 1/8" thick 1 1/2" wide
aluminum flat bar that are bolted together. A bearing that will
allow the two pieces of aluminum flat bar to be held firmly together.
but move (the only way possible) against the spacer between them
with as little friction as possible.

Would that be nylon? Delrin? What is it called? At the moment, my
best guess is "thrust bearing". Even though the only thrust pushing
the pieces together is the bolt that holds them together. I'm
looking at McMaster.

It would be a linear thrust bearing as far
as I can see. Without getting crazy expensive
I'd use nylon or teflon. I know M-C has some
nice thin teflon sheet that you could just
cut out and lay in. If you have more than
a small amount of force, most plastic will
tend to squash down and extrude out. I think
teflon will be better than nylon in that regard

teflon flows much more than nylon. Polyethylene or one of the higher
density ones might be good to try.

Cydrome Leader wrote:

Jim Stewart wrote:

....

It would be a linear thrust bearing as far as I can see.

Sounds like it. I'm talking about material maybe similar to what
they use for reducing friction in folding lawn chairs. But not
separating two tubes, separating two aluminum flat bars.

snipped stuff read and understood, thanks

On Oct 8, 6:29*pm, John Doe wrote:
Something thin to put between two pieces of 1/8" thick 1 1/2" wide
aluminum flat bar that are bolted together. A bearing that will
allow the two pieces of aluminum flat bar to be held firmly together
but move (the only way possible) against the spacer between them
with as little friction as possible.
...
Thanks.

How tight is the bolt, and what keeps it from loosening?

Jim Wilkins wrote:

see the original post

How tight is the bolt, and what keeps it from loosening?

I don't know the specific torque but it will be little, shearing
pressure between the two aluminum flat bar pieces might be in the tens
of pounds or maybe greater, as they pivot against each other.

I don't have a riveter. Anything that holds the two aluminum flat bar
pieces together with a pivot point in the center will do. Some sort of
clamp-on nuts might work, like a cotter key but maybe disposable and
without having to drill tiny holes through the rod.

At the moment, I'm trying to deal with slipperiness (and later
weatherproofing) of the bearing.

On Wed, 08 Oct 2008 22:29:27 GMT, John Doe
wrote:


Something thin to put between two pieces of 1/8" thick 1 1/2" wide
aluminum flat bar that are bolted together. A bearing that will
allow the two pieces of aluminum flat bar to be held firmly together
but move (the only way possible) against the spacer between them
with as little friction as possible.

http://www.igus.com/iglide.asp

--
Ned Simmons

On Oct 8, 5:29*pm, John Doe wrote:
Something thin to put between two pieces of 1/8" thick 1 1/2" wide
aluminum flat bar that are bolted together. A bearing that will
allow the two pieces of aluminum flat bar to be held firmly together
but move (the only way possible) against the spacer between them
with as little friction as possible.

Would that be nylon? Delrin? What is it called? At the moment, my
best guess is "thrust bearing". Even though the only thrust pushing
the pieces together is the bolt that holds them together. I'm
looking at McMaster.

Is there something not officially labeled as such that works well
for that purpose? I have some spray Teflon silicone lubricant from
Lowe's.

Thanks.

Look into some UHMW tape. UHMW is the same plastic used for ski bases,
lining hopper cars, etc.
The tape is sticky, and makes an excellent bearing for what you are
doing. Once you get a roll of it, you will have a few many other uses
for it.

Another possibility ( question?) is anodizing the parts, to make the
surface hard enough to slide. Would that work?

Ther are also Ceramic spray coatings that can be applied to aluminum,
and reduce friction.
I used to get pistons ceramic coated for racing. Google it.


Thirdly, some words on riveting.. If you use a riveted joint, a heavy
hit will bulge the rivet all the way through. Light hits will peen
over the ends, leaving the center loose.

On Oct 8, 3:29*pm, John Doe wrote:
Something thin to put between two pieces of 1/8" thick 1 1/2" wide
aluminum flat bar that are bolted together. A bearing that will
allow the two pieces of aluminum flat bar to be held firmly together
but move (the only way possible) against the spacer between them
with as little friction as possible.
[slipperiness and weatherproofing are important]

Bearings work best with hard-against-soft (this provides for
embedding of grit into the soft side), so plastic washers
are a suitable solution. Delrin and some polyacetal plastics
are intended for long life as bearing material, should be available
in washer form. Brass (a washer, or even just a disc cut from
shim material) will also work, might be better if the aluminum
surfaces are hard (anodized). Even stainless steel might
be OK, if the aluminum is not anodized (the aluminum is the
soft side, then).

The 'bolt' will rub the sides of the hole, and some loosening of
a nut can occur, so various tricks are common in this kind of
pivot. Easiest, is to fill the hole with a shoulder bolt, and
glue the nut in place. Shoulder bolts are expensive, though.
Second easiest is to fill the hole with a (slightly short) tube
and use nut/bolt through the tube to keep the joint together.
Washers (and maybe Belleville springs) are important,
use them freely. One side of the bolt could take a lockwasher,
the other then has to have slippage (like, use a brass washer/
steel washer/lockwasher/nut).

I'm a big fan of riveting, but good rivets are hard to find, like
cheap shoulder bolts. It's probably easy to order thousands,
but try to find one the right size when you need it...

Jim Stewart wrote:

It would be a linear thrust bearing as far
as I can see. Without getting crazy expensive
I'd use nylon or teflon. I know M-C has some
nice thin teflon sheet that you could just
cut out and lay in.

I'm planning to order this McMaster item, either 1/32" or 1/16". And
maybe some HDPE since it's dirt cheap.

Part Number: 8569K25
$6.25 per Ft.
Fluoropolymer Material
Virgin Electrical Grade Teflon® PTFE
Thickness
1/32"
Performance Characteristic
Weather Resistant, Very Low Friction
Tensile Strength
1500 to 3000 psi
Impact Strength
3 ft.-lbs./in.

A sampler pack:


Part Number: 8636K11
$3.06 Each
Fluoropolymer Material
Glass-Filled PTFE sheet
Thickness
1/32"
Performance Characteristic
Weather Resistant, Very Low Friction
Tensile Strength
2500 psi
Impact Strength
2.2 ft.-lbs./in.
Hardness
Rockwell R: 58

Part Number: 2636T22
$3.33 per Ft.
Material
Acetal
Acetal Material
PTFE-Filled Delrin (Delrin AF sheet)
Thickness
.031"
Width
2"
Tensile Strength
Good
Impact Strength
Poor
Hardness
Rockwell R: 118

Part Number: 8619K61
$2.60 Each
Polyethylene Material
High-Density Polyethylene (HDPE) sheet
Sheets, Bars, Strips, and Cubes Type
Square Sheet
Thickness
1/32"
Performance Characteristic
Wash-Down Applications
Tensile Strength
Poor
Impact Strength
Good
Hardness
Shore D: 62-69

Part Number: 7701T62
$0.78 per Ft.
Polyethylene Material
Polyethylene (UHMW) sheet
Backing
Plain Back
Finish
Smooth
Sheets, Bars, Strips, and Cubes Type
Rectangular Strip
Thickness
.032"
Performance Characteristic
High Impact Strength
Tensile Strength
Poor
Impact Strength
Excellent
Hardness
Shore D: 62-68

John Doe wrote:
Jim Stewart wrote:

It would be a linear thrust bearing as far
as I can see. Without getting crazy expensive
I'd use nylon or teflon. I know M-C has some
nice thin teflon sheet that you could just
cut out and lay in.

I'm planning to order this McMaster item, either 1/32" or 1/16". And
maybe some HDPE since it's dirt cheap.

Part Number: 8569K25
$6.25 per Ft.
Fluoropolymer Material
Virgin Electrical Grade Teflon® PTFE
Thickness
1/32"
Performance Characteristic
Weather Resistant, Very Low Friction
Tensile Strength
1500 to 3000 psi
Impact Strength
3 ft.-lbs./in.

Yup, exactly what I was talking about.

Jim Stewart wrote:

John Doe wrote:

Fluoropolymer Material
Virgin Electrical Grade Teflon® PTFE

Yup, exactly what I was talking about.

Oops, I'll get it next order.

(8636K11) GLASS-FILLED PTFE SHEET

Like fabric, resembles stiff leather without the shag. Doesn't feel
slick to me.

(2636T22) PTFE FILLED DELRIN STRIP

Flexible but hard, mirrorlike on one side, shiny on the other side.

(8619K61) POLYETHYLENE (HDPE) SHEET

Somewhat shiny and flexible like the plastic used for a modern school
folder.

(McMaster part numbers)