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Old September 28th 10, 11:30 PM posted to rec.woodworking
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Default Cheap Linear Bearing Solution

I'm still struggling with my X,Y tables for my H-mortiser. I've tried
full extension drawer guides and they had way too much vertical
slop. I also looked at under-mount slides today at Woodcraft and
they too had too much slop.

I am thinking about using 4 steel rods (2 per axis) and using guide
bushings. Four bushings total inserted into two separate equal
lengths of wood. The wood would support the table (two per axis).
If I lube the crap out of the steel rod do you think this would work?
Hope this makes sense.



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Old September 28th 10, 11:53 PM posted to rec.woodworking
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Default Cheap Linear Bearing Solution

On Sep 28, 5:30*pm, GarageWoodworks
wrote:
I'm still struggling with my X,Y tables for my H-mortiser. *I've tried
full extension drawer guides and they had way too much vertical
slop. * I also looked at under-mount slides today at Woodcraft and
they too had too much slop.

I am thinking about using 4 steel rods (2 per axis) and using guide
bushings. *Four bushings total inserted into two separate equal
lengths of wood. *The wood would support the table (two per axis).
If I lube the crap out of the steel rod do you think this would work?
Hope this makes sense.


Give these guys a look. A lot of their stuff is very reasonable.

http://www.technocomponents.com/
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Old September 28th 10, 11:57 PM posted to rec.woodworking
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Default Cheap Linear Bearing Solution

On 9/28/10 4:30 PM, GarageWoodworks wrote:
I'm still struggling with my X,Y tables for my H-mortiser. I've tried
full extension drawer guides and they had way too much vertical
slop. I also looked at under-mount slides today at Woodcraft and
they too had too much slop.

I am thinking about using 4 steel rods (2 per axis) and using guide
bushings. Four bushings total inserted into two separate equal
lengths of wood. The wood would support the table (two per axis).
If I lube the crap out of the steel rod do you think this would work?
Hope this makes sense.


I haven't really been following, but the rod/guide description sound a
lot like what's in the arm of my RAS. Those concave guide bearings that
would fit snug on the proper size steel rod are all over the net and
ebay for cheap.

google RADIAL ARM SAW CARRIAGE BEARINGS

--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

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Old September 29th 10, 12:21 AM posted to rec.woodworking
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Default Cheap Linear Bearing Solution

On Sep 28, 5:30*pm, GarageWoodworks
wrote:
I'm still struggling with my X,Y tables for my H-mortiser. *I've tried
full extension drawer guides and they had way too much vertical
slop. * I also looked at under-mount slides today at Woodcraft and
they too had too much slop.

I am thinking about using 4 steel rods (2 per axis) and using guide
bushings. *Four bushings total inserted into two separate equal
lengths of wood. *The wood would support the table (two per axis).
If I lube the crap out of the steel rod do you think this would work?



I have tried similar approaches and found it less than ideal.
Mind you, you are not looking for a lot of travel so you might be able
to bang the stuff around so it will work for a bit...but linear
bearings are a breed on their own. The bushings have the wrong aspect
ratio to the rods, even when using two. The slightest bit of skew and
you jam.... and you just need one of them to do that by a couple of
thou.

I quite like Mike's idea.



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Old September 29th 10, 01:55 AM posted to rec.woodworking
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Default Cheap Linear Bearing Solution

In article ,
GarageWoodworks wrote:
I'm still struggling with my X,Y tables for my H-mortiser. I've tried
full extension drawer guides and they had way too much vertical
slop. I also looked at under-mount slides today at Woodcraft and
they too had too much slop.


You might want to look at the commercial offerings from Rollon Corp.
www.rollon.com/USA/rollon.htm

I haven't purchased anything from them, but have had discussions with
sales and engineering abut some of their _big_ stuff (multi-ton loads).
I found them _most_ helpful, even when dealing with an application that
was _way_ outside the scope of what they normally deal with. And this
was research _only_ for an admitted one-off project.

Their "mono-rail" has accuracy of +/- 0.1mm in the 'normal' precision units.
+0.000/-0.04mm in the really high-precision ones. lengths for single
sections, up to roughly 4 meters.

lots of other alternatives, too, if you need something telescoping.
Catalog data includes the data to figure out how much play there will be
in your application. Assuming you can build to the precis ion of their
gear.


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Old September 29th 10, 01:57 AM posted to rec.woodworking
MGH MGH is offline
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Default Cheap Linear Bearing Solution


"GarageWoodworks" wrote in message
...
I'm still struggling with my X,Y tables for my H-mortiser. I've tried
full extension drawer guides and they had way too much vertical
slop. I also looked at under-mount slides today at Woodcraft and
they too had too much slop.

I am thinking about using 4 steel rods (2 per axis) and using guide
bushings. Four bushings total inserted into two separate equal
lengths of wood. The wood would support the table (two per axis).
If I lube the crap out of the steel rod do you think this would work?
Hope this makes sense.




About six years ago I was dealing with the same problem you are having in
making the X, Y tables. My solution was to use KV 1129 center under mount
drawer slides because I was given a couple cases of these slides. Using a
set of slides for each table gave unacceptable vertical and lateral play.
This slide has a carrier holding the ball bearing in position as the two
parts move past each other. Seeing I had so many slides I added a second
carrier to each of the drawer slide, cut the drawer slide shorter and
limited the slide travel to several inches. The result is a short travel
slide supported by ball bearing throughout most of its travel with no
lateral and vertical play.

Saw dust has not been a problem yet.

Works for me.



MGH






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Old September 29th 10, 02:02 AM posted to rec.woodworking
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Default Cheap Linear Bearing Solution

On Tue, 28 Sep 2010 14:30:16 -0700 (PDT), GarageWoodworks
wrote:

I'm still struggling with my X,Y tables for my H-mortiser. I've tried
full extension drawer guides and they had way too much vertical
slop. I also looked at under-mount slides today at Woodcraft and
they too had too much slop.


How were they mounted? Were the X guides in the closed position when
the table was up against the Z gantry? Were the Y guides just a
couple inches open when the table was centered? Most joints won't be
but 2 inches in either direction, so you should have the ball bearing
glide stiffness working -for- you. Weight of the table and part
should keep them pretty much together, too. (Support that stray end
of a long table leg, bed sideboard, or whatever, though.)


I am thinking about using 4 steel rods (2 per axis) and using guide
bushings. Four bushings total inserted into two separate equal
lengths of wood. The wood would support the table (two per axis).
If I lube the crap out of the steel rod do you think this would work?
Hope this makes sense.


If you use old-technology, go with sintered bronze bushings and grease
or oil them, not the rods.

If you use linear motion bearings, you won't have slop and they'll
have seals around them. They're not cheap, though.

CNC routers usually use 5/8", but for the shorter tables, you could
probably get by with 7/16 or 1/2".


--
You can't wait for inspiration. You have to go after it with a club.
--Jack London
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Old September 29th 10, 02:02 AM posted to rec.woodworking
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Default Cheap Linear Bearing Solution

On Sep 28, 7:57*pm, "MGH" wrote:
"GarageWoodworks" wrote in message

...

I'm still struggling with my X,Y tables for my H-mortiser. *I've tried
full extension drawer guides and they had way too much vertical
slop. * I also looked at under-mount slides today at Woodcraft and
they too had too much slop.


I am thinking about using 4 steel rods (2 per axis) and using guide
bushings. *Four bushings total inserted into two separate equal
lengths of wood. *The wood would support the table (two per axis).
If I lube the crap out of the steel rod do you think this would work?
Hope this makes sense.


About six years ago I was dealing with the same problem you are having in
making the X, Y tables. *My solution was to use KV 1129 center under mount
drawer slides because I was given a couple cases of these slides. *Using a
set of slides for each table gave unacceptable vertical and lateral play.
This slide has a carrier holding the ball bearing in position as the two
parts move past each other. Seeing I had so many slides I added a second
carrier to each of the drawer slide, cut the drawer slide shorter and
limited the slide travel to several inches. *The result is a short travel
slide supported by ball bearing throughout most of its travel with no
lateral and vertical play.

Saw dust has not been a problem yet.

Works for me.

MGH


Got any more? :^P
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Old September 29th 10, 02:23 AM posted to rec.woodworking
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Posts: 156
Default Cheap Linear Bearing Solution

On Tue, 28 Sep 2010 15:21:23 -0700 (PDT), Robatoy
wrote:

On Sep 28, 5:30*pm, GarageWoodworks
wrote:
I'm still struggling with my X,Y tables for my H-mortiser. *I've tried
full extension drawer guides and they had way too much vertical
slop. * I also looked at under-mount slides today at Woodcraft and
they too had too much slop.

I am thinking about using 4 steel rods (2 per axis) and using guide
bushings. *Four bushings total inserted into two separate equal
lengths of wood. *The wood would support the table (two per axis).
If I lube the crap out of the steel rod do you think this would work?



I have tried similar approaches and found it less than ideal.
Mind you, you are not looking for a lot of travel so you might be able
to bang the stuff around so it will work for a bit...but linear
bearings are a breed on their own. The bushings have the wrong aspect
ratio to the rods, even when using two. The slightest bit of skew and
you jam.... and you just need one of them to do that by a couple of
thou.

I quite like Mike's idea.


Instead of guide bushings, consider linear plain bearings. Ones made
from Teflon are not very expensive (3/4" for $5-10). They are long
relative to shaft diameter so they avoid the jamming problem mostly.

They don't need lube and can handle high loads as long as you are
moving them relatively slowly and can tolerate more friction than you
would get with linear ball bearings (which can be quite pricey).

For a bit more money you can get self aligning versions which are a
lot more forgiving when mounting....

As this is a key part of your cool project, you don't want something
you will be constantly cursing..

HTH,

Paul Franklin


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