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Will anodized aluminum gall ?

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  • Will anodized aluminum gall ?

    I'm making a router template from aluminum plate. There's several parts to it that have to slide and and are clamped together with a stud and wing nut.
    for weight reasons I'd like to make all the pieces out of aluminum. But I think if both pieces are bare aluminum, they will start to gall. Would anodizing one of the pieces eliminate the galling ?
    I've tried UHMW for one piece but it too has threads in it and the threads stripped out of the plastic.

  • #2
    If the parts are hard anodized they will not gall. Regular decorative anodizing will also prevent galling but isn't durable enough to last long. Hard anodizing is a very different animal as it is at least 10 to 100 times thicker and is about the same hardness as sapphire.

    [edit] If you do your own anodizing you can put on a thick enough coating via regular anodizing to do the job. I do mine that way. It isn't as good as real hard anodizing but it is much more durable than ordinary decorative anodizing. By running the process cooled in ice water and keeping the part in the bath until the current drops to near zero you can put on a coating at least 3 to 5 times thicker than normal. That is enough to be very durable. I have tried hard anodizing with poor results. It uses very high current densities and the main problem is keeping the bath cold enough. In commercial practice large industrial chillers are used to cool the bath.
    Last edited by Evan; 06-21-2009, 01:32 AM.
    Free software for calculating bolt circles and similar: Click Here


    • #3
      A face-saving problem

      Why not try it "as is" (ex-mill) and spray it with WD-40 or similar - unless the WD-40 will stain what-ever the template is used for/on. If it galls - hand-scrape it on the galled areas - no need to be too "flash" - its just to reduce the bearing/rubbing areas while providing pockets for lubrication.

      If a liquid is a problem, try using "Dri-Lube" or a silicone.

      Are the mating/rubbing surfaces rubbing frequently or only when the template is being set up prior to using it?

      I'd be pretty sure that an auto-shop or a hardware store would have something in a can or a bottle to do the job - or be able to advise as to which manufacturers might/will have such a product.

      I'd be even more certain that many here will have good ideas and advice that will solve the problem.


      • #4
        Many woodworkers simply wax the exposed surfaces of planers, jointers and saws with something like TurtleWax (tm). The wax provides a nice slick surface and does not stain.

        You can get anodized router guides, so I imagine that anodyzing does the trick too.

        At the end of the project, there is a profound difference between spare parts and extra parts.


        • #5
          If you want to try something you just apply to the surface, Moly Slip ADF (Air Drying Film) would be a good candidate.


          • #6
            If it's something for wood, it's best to stay away from turtle wax, it has silicone in it that will transfer to the wood and make finishing difficult. It's good for cars, but not for wood.
            Better is plain old johnsons paste wax, or any other 'carnuba' types. That way if it does get to the wood it doesn't cause issues.

            possible to have mating sides plated, or to laminate a wear surface? (formica, or a thin sheet of ???)



            • #7
              I've had some luck using plastic sheet material between aluminum parts to prevent galling and provide a consistent friction for a smooth sliding action between parts. I bought some snow sliders some years ago and found it good for that purpose. It's about .030 thick and has one side rougher than the other, so I'd presume you could contact cement pieces in place.

              One 'trick' I've used to keep this plastic sheet material in place on metal parts is to countersink a threaded hole deep enough for the head of a flat head bolt plus the thickness of the plastic. With the plastic in place, carefully heat the plastic only where the bolt head will go, then dimple the plastic into the bolt hole with a stick that's ground to a 90 degree point. You can then hold the plastic in place with a bolt which ends up being recessed so it doesn't interfere with the sliding fit of the assembly.

              I don't know how well Evans hard chroming method would work since I haven't tried it, but I'm leery of anything which is aluminum on aluminum where the parts slide or rotate against each other. I've had a few unfortunate experiences with galling and ruined parts.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


              • #8
                Not hard chroming, hard anodizing. It is widely used in industry to make aluminum parts with wear resistance superior to almost anything else including hardened tool steel as long as the surface doesn't require impact resistance.

                I will post a picture a bit later of the anodized mill table on my CNC mill to show how well it works.
                Free software for calculating bolt circles and similar: Click Here


                • #9
                  how about some "rebound" pucks built into it no ones done that before

                  all the best.mark


                  • #10
                    Without an idea of what you are trying to do, it's hard to say what will happen. Do parts actually slide in use? or is it a slide adjustment?

                    if the latter, forget about galling.

                    But typically, even in aluminum, a very low speed sliding contact, with relatively light loading , will not gall if kept lubed in some way. I have several items with sliding aluminum in contact, and they don't gall if lubed.

                    I even have plain finish aluminum bolts and nuts, 3/8-16, holding an ex-military motor, and they have never galled, which surprised the daylights out of me.

                    Any sort of higher speed (like rotating) system should be inherently non-galling or trouble is sure to result.

                    I would anticipate a router template as not requiring speeds which would gall, although I think hard anodizing might improve friction. Some form of lube will, I think, entirely eliminate galling at your speeds.

                    Keep eye on ball.
                    Hashim Khan


                    • #11
                      Thanks for the replies guys.
                      The parts aren't continually in motion, they only slide to adjust the template to size and are then locked down with a stud / wing nut.
                      This thing will see a rather rough life though - I'll be handing it off to employees on a Log Home building site.
                      After giving it some more thought, I think I'll inset some steel nuts into the plastic, that should solve the thread stripping problem, I'll know it won't gall and they won't have to carry a can of lube around with them.
                      I asked about the anodizing because I thought it might be fun to play with but it sounds like its the Hard anodizing I would want and sounds like thats more difficult.


                      • #12
                        I've had hard anodizing applied to a number of production opto-mechanical parts. While it is hard and tough, it does not work well around sharp edges. I forget what the minimum radius is but you might want to make sure that all edges are rounded if you go that route.

                        You might also consider a very thin wear plastic plate between the sliding parts.



                        • #13
                          Aluminium on Aluminium won't gall with hard anodising, and is especially good in this respect if you request a 'PTFE Cold Seal' as the final step of the process, where it is dipped immediately after anodising in a solution with a PTFE dispersion.

                          These are some pictures of a fixture I made about 4 years for hobbing brass inserts into a plastic moulding. Both main sliding components (carrier & baseplate) are Aluminium, hard anodised and PTFE sealed, and the carrier also slides along ground gauge-plate retaining rails.

                          It's used about once a month and slid along underneath the head which presses the inserts in place, in 5 increments/stops over about a 10" length, then back to the start to reload the moulding. On average about 1000 moulding are done at a time, so around 6000 stop-start slides a month over 4 years.
                          No lubricant is used on it at all.

                          As you can from the pictures there is no galling or wear, even where the alumunium is running agaist the ground gauge-plate, although it does need a bit of a clean as there is some crap hanging on there.

                          BTW thats not damage or dents on the sides in the 2nd picture, they are grooves that spring loaded ball-catch detents run in.



                          • #14
                            The Taig mills have alloy beds hard anodised and they run on each other.
                            As Evan says it does work.


                            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


                            • #15
                              "Raw" aluminum tends to leave black marks on wood. Most log homes are made from easily stained softwoods that have a "high" moisture content when the building is being constructed. I don't know the actual cause of the staining (looks different from the staining iron causes), but anodizing the aluminum does prevent staining from happening.
                              Today I will gladly share my experience and advice, for there no sweeter words than "I told you so."