aluminum or steel?

[Ken Fitzgerald]

The table I am building has a 3-piece tabletop, with 2 pieces attached to a rack & pinion assembly and the 3rd piece butterflying up from underneath the table. On the top edge of the table frame, I want to put metal wear pieces with a UHMW tape on top. Is there any reason I should use 1/8" thick steel x 3/4" over 1/8" x 3/4" aluminum for the wear strip?

[Jim Becker]

Since the metal is only providing structure to hold the UHMW tape, I'd probably pick the aluminum because it's just plain easier to craft into the pieces required. If the metal was going to be the actual wear surface, I'd likely choose the steel because it's going to be more durable than the aluminum for the most part.

[Rob Sack]

If it were me, I would use stainless steel. There would be no concerns about corrosion if it gets wet. Aluminum as a wear strip will work fine until a piece of grit comes in contact with it and starts to create scratches. One of the downsides to aluminum is that once scratched, it can start "self destructing". I believe the term is galling. Other metals, including stainless steel, can be prone to galling, but with aluminum being as soft as it is, the chances are higher.

[Maurice Mcmurry]

I am having a little trouble visualizing your design but am thinking aluminum should be just fine. Strips of Formica might even do the job.

Screen Shot 2024-05-02 at 6.55.30 PM.jpg
Butterfly table leaf snip from the web

[Ken Fitzgerald]

I am having a little trouble visualizing your design but am thinking aluminum should be just fine. Strips of Formica might even do the job.

I am building a butterfly extension table. The 2 pieces of the tabletop that will extend and retract are 36" w and 33" long. They will be connected to a rack and pinion wooden assembly so if either end is pulled out, the other end will extend equally at the same time. Hidden within the now emerging gap will be a hinged butterfly extension assembly 24" long, with 2 pieces hinged that rotate up and open like a butterfly's wings. That will flatten onto the side rails and the two end pieces will then be pushed back to engage the butterfly extension. Underneath the table will be lock assemblies that once engaged will prevent the 3-piece tabletop from moving. Here's an article about a similar table but without the rack & pinion that synchronizes the extension and retraction. https://www.finewoodworking.com/proj...xpansion-table

[Richard Coers]

There is absolutely no need for wear strips. With gear slides, the wear surfaces are on the inside of the slides. There are no rack and pinion slides that I know of. They are either gear slides or equalizer slides. Maybe you are looking at some new tech?

[Jimmy Harris]

From an engineering standpoint, I can't help but feel you're adding extra complexity, and thus increasing the odds of failure, for very little benefit with the rack and pinion system. But that's up to you.

As for aluminum vs. steel, I'd say it's an aesthetic choice. Either will work fine. I'd probably lean towards stainless steel if you go the steel route. Sometimes regular steel can darken some woods if left in contact, like oak or other high tannic woods.

Don't worry about aluminum galling. It's a real possibility in certain applications, but used with UHMW, it shouldn't cause any concerns. If the aluminum was sliding against something with a higher friction coefficient, it might be a problem. But UHMW is has as extremely low friction coefficient. And really, with the UHMW, you probably don't need any metal wear strips. My workbench's wagon vise has UHMW on maple, and it hasn't shown any wear at all. UHMW usually has a lower friction coefficient and better wear resistance than Teflon, so it doesn't usually even need a lubricant. That stuff is magic!

[Mark Gibney]

Ken, I built a table using this very system, some years back. I did not use any material other than wood. Works fine.
How often will the table be opened and closed? Even if it's four to six times a month there will be next to no wear.

[Richard Coers]

My comment hasn't influenced anyone yet, so here is someone else describing how these things work. There are no wear surfaces from the top sliding against anything. https://www.dutchcrafters.com/blog/t...mooth%20motion

[Michael Burnside]

Let us know what you decide and post pictures in the project sub-forum. This table isn't my style, but I guess I'd lean to wood only and forgo any complexity. My grandpa made a table that 50+ years old and it's just bare wood...still works on holidays when we add the leaf. But if I had to choose a metal, 99 times out of 100 it would be aluminum just because it's easy to cut/work/polish, lighter and won't interact with wood depending on the steel you chose. You'd probably want to use stainless and so aluminum would be less expensive too.

[Ken Fitzgerald]

There is absolutely no need for wear strips. With gear slides, the wear surfaces are on the inside of the slides. There are no rack and pinion slides that I know of. They are either gear slides or equalizer slides. Maybe you are looking at some new tech?

Richard it's a matter of which words you and I choose to use. Here's a illustration of a rack and pinion assembly.

R&P.jpg

That sure looks like what is you are calling a gear slides or equalizer slides?

The reason for the wear strips is that I believe when extended, with the extension in use, the weight will end up being supported on the table rails so I want to insure that minimize wear on the table top when being extended and retracted.

I agree the wear should be on the inside of the slides but with weight on the table I am concerned about sag resulting in the tabletop riding on the rails of the table.

[Ken Fitzgerald]

From an engineering standpoint, I can't help but feel you're adding extra complexity, and thus increasing the odds of failure, for very little benefit with the rack and pinion system. But that's up to you.

As for aluminum vs. steel, I'd say it's an aesthetic choice. Either will work fine. I'd probably lean towards stainless steel if you go the steel route. Sometimes regular steel can darken some woods if left in contact, like oak or other high tannic woods.

Don't worry about aluminum galling. It's a real possibility in certain applications, but used with UHMW, it shouldn't cause any concerns. If the aluminum was sliding against something with a higher friction coefficient, it might be a problem. But UHMW is has as extremely low friction coefficient. And really, with the UHMW, you probably don't need any metal wear strips. My workbench's wagon vise has UHMW on maple, and it hasn't shown any wear at all. UHMW usually has a lower friction coefficient and better wear resistance than Teflon, so it doesn't usually even need a lubricant. That stuff is magic!

Jimmy, the reason for the wear strips is minimize any wear on the mechanism should there be any sag in the system. I might be making it overly complex. I can do that!

I won't tell you that I am mounting the tabletop sections (all 3) to their respective mechanisms using threaded inserts and stainless steel screws so the tabletop sections can be removed for transportation into our kitchen and the reassembled to reduce weight. I am still stronger than most men my age but I am fading. When I built a red oak entertainment center for our livingroom a few years ago, it took 3 of us to move from the shop into the house. On the hinged end of each of the butterfly sections, I am inlaying 1 1/2" x 1/8" steel bar using threaded inserts to minimize any warping in the butterfly sections.

[Richard Coers]

Richard it's a matter of which words you and I choose to use. Here's a illustration of a rack and pinion assembly.

R&P.jpg

That sure looks like what is you are calling a gear slides or equalizer slides?

The reason for the wear strips is that I believe when extended, with the extension in use, the weight will end up being supported on the table rails so I want to insure that minimize wear on the table top when being extended and retracted.

I agree the wear should be on the inside of the slides but with weight on the table I am concerned about sag resulting in the tabletop riding on the rails of the table.

Please show me the model slide you intend to use, I've never seen a rack and pinion table slide. The wear WILL be inside the slides, not should be. The slides I am talking about is in the video I've shown in another post. I'm just trying to share my experience here, I won't be adding anything more.

[Ken Fitzgerald]

Please show me the model slide you intend to use, I've never seen a rack and pinion table slide. The wear WILL be inside the slides, not should be. The slides I am talking about is in the video I've shown in another post. I'm just trying to share my experience here, I won't be adding anything more.

Richard, again, you want to call them "geared or equalizer slides" but in fact they use a form of rack and pinion as I showed in the illustration.

Here's what I am using. https://www.leevalley.com/en-us/shop...s?item=17K1510

[Maurice Mcmurry]

UHMW tape is pretty amazing. If it is stuck on good hard wood I would expect a long operational life without the need for steel or aluminum. We stuck UHMW tape to MDF and used it against the table saw top, wood, other MDF, and Lexan. It lasted for several years of daily use in a factory environment. Your table sounds like a neat project. I posted an old video of a Scottish maker displaying his butterfly leaf a while back. I can't find it just now.

This is not the one but it is good.

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