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  • Aluminum vs steel

    I'm thinking particularly of a homemade follow rest and wondering how much thicker it would need to be if aluminum instead of steel. Or even if it makes sense at all.

    Thanks,

    Gary Fuchs

  • #2
    For most HSM type operations the follow rest is more of a vibration damper and Aluinum should be ok for that. If your looking to stop deflection the modulus for aluminum is aprox 1/3 that of steel. That is my opinion someone that is more knowlagble will probably be here shortly.
    Byron Boucher
    Burnet, TX

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    • #3
      Originally posted by Boucher
      For most HSM type operations the follow rest is more of a vibration damper
      I thought it was to stop deflection on a long thin piece - is that wrong?

      Gary

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      • #4
        If you are going to go the trouble of making one, you should look at dura-bar cast iron. It does not cost much more than good steel, dampens vibration, and cuts like a dream. There are a lot of good online vendors, just do a google search and find one close to you to save on shipping.

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        • #5
          You might want to throw cast iron in there as well for a full comparison.
          "Work hard. Tell everyone everything you know. Close a deal with a handshake. Have fun!"

          -- Harold "Doc" Edgerton

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          • #6
            I don't know anything about working iron but do have a little experience with aluminum. Also have a few decent size pieces on hand. Is aluminum simply not suitable in whatever size, or could I aim for say a 2 1/2" thickness?

            Thanks,

            Gary

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            • #7
              What ever you got Will Work. Some material is just better for some things than another. But if you do not have a steady rest any is better than none. We can get real technical here. But it boils down to what you got to work with. So aluminun will work.
              Every Mans Work Is A Portrait of Him Self
              http://sites.google.com/site/machinistsite/TWO-BUDDIES
              http://s178.photobucket.com/user/lan...?sort=3&page=1

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              • #8
                1.78 times or 3 times depending on the wall or the thickness. respetively Solid aluminum is probably plenty and its easier to work but I've seen many very nice steel ones whose parts were machine burned from plate and welded together. Heavy though.
                Last edited by Forrest Addy; 08-10-2009, 08:23 PM.

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                • #9
                  Is the subject a follow rest or steady rest?
                  Byron Boucher
                  Burnet, TX

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                  • #10
                    Steady on there!!!

                    Originally posted by gfphoto
                    I'm thinking particularly of a homemade follow rest and wondering how much thicker it would need to be if aluminum instead of steel. Or even if it makes sense at all.

                    Thanks,

                    Gary Fuchs
                    Gary,

                    I am firmly in agreement with Lane on this.

                    My guess is that you have access to or would prefer to machine aluminium.

                    I'd prefer that as well as cutting a master-piece out of a solid when its not necessary is akin to sculpting a statue out of stone. A lot of wasted time, effort and material unless necessary. Further that amount of cutting and chip (and especially and abrasive cast-iron surface) with cast-iron is a lot harder on your lathe than aluminium will be.

                    If strain and movement of the follower/steady is a concern then something needs looking at as regards the job and the set-up.

                    Good vibration damping - if its needed - for aluminium or anything else is readily achieved with a loosely packed bag of lead shot draped over the steady. Use several if required. Use your judgment as to how much in each bag and the number of bags to use and where to put them. You will find plenty of use for them on boring bars that "chatter" as well as parting tools (if enough space/room from/to the chuck), form-tooling (including grooving and screw-cutting). Its an "instinct" sort of thing - almost a machining version of "flying by the seat of your pants"!!

                    Barn-storming machinists? What next "machining in a "Pratt Special"??

                    Both aluminium and cast-iron a both good candidates - as is mild steel.

                    Mild steel is easily welded/fabricated in most shops - but be careful how and where you weld as the "hardening zone" either makes machining difficult of impossible. A bucket to quench the welded parts in will assist to localise or restrict the heat-affected zone/s - just take it easy - "tack and dip" is a good option.

                    Aluminium is easy to machine and fit and fasten any separate parts together.

                    The best "damper" I have is my hand as it works fine - I just "adjust" to suit.

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                    • #11
                      I've made some custom tool holders from aluminum and had no problems. I think what you have to consider is how the forces are being applied to the piece. If it's in a way such that it would be excited like a tuning fork, you'd be better off with steel or cast iron. If the cutting forces (or the side of a workpiece) bears against the long dimension of the piece, such as a downforce on a vertical post attached to the carriage, then aluminum should be fine. For the most part, I'd have to say that anytime a finger of material is going to see a side force at one end, it should be a stronger and less flexable material.

                      What I've used for tool holders sees mostly a downward force through the length of the holder, so there's little chance of any resonance being excited. Where a tool holder has to stick out horizontally, unsupported at the tool end, I wouldn't use aluminum. If it stands vertically and keeps the cutting edge of the tool close to it, it would most likely be fine.

                      As I'm envisioning it, a follow rest could easily be made to handle forces directly into the length of the material it's made from, so aluminum would be fine there. Is there a 'wear plate' of some kind planned where the workpiece would actually be rubbing against the follow rest? Ball bearings attached, perhaps?
                      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                      • #12
                        Use aluminum. If you want to give it excellent damping qualities as good or better than cast iron then laminate up two or three layers of 1/4" thick plate by screwing it together with flush socket head cap screws close spaced in tapped holes in the plate. It's more work but it will make an excellent accessory.

                        Laminating like materials of any sort greatly increases the damping factor. No matter how well fastened (other than welding) there will be a microscopic amount of relative movement between the layers when the structure flexes. This absorbs energy by the tiny scuffing action that takes place. It's also one of the reasons that airplanes don't vibrate to pieces. When you drill off an old skin from a wing you can see the marks along all the seams that were caused by the scuffing action.
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                        • #13
                          Thank you all for the very useful suggestions and comments.

                          oldtiffie wrote
                          My guess is that you have access to or would prefer to machine aluminium.
                          Yes to both. I mostly get metal from the scrap yard and most of the steel is either too small or too big but so far aluminum in varied useful sizes has been easier to come by. And my milling capability (and time) is limited so I don't even think about trying to cut down a section of steel I-Beam so I can end up with a piece 2" square, etc. Also need to spend as little as possible so most likely wouldn't consider having something welded, etc. unless I was really sure it would work and couldn't do something equivalent myself.

                          darryl wrote
                          As I'm envisioning it, a follow rest could easily be made to handle forces directly into the length of the material it's made from, so aluminum would be fine there. Is there a 'wear plate' of some kind planned where the workpiece would actually be rubbing against the follow rest? Ball bearings attached, perhaps?
                          I may still not be adjusting my steady rest correctly but have noticed that when I get it set so there's no play but still free movement pretty soon the piece heats up, expands and it starts to bind. I'm thinking for this maybe bearings would be better since they'd be turning and the contact area would have a bit of time to cool as the bearing spins. Then again, it just occurred to me that if my work is changing size enough to bind maybe I need to take shallower cuts or let it cool, or actively cool it? Or something.

                          Evan wrote
                          Use aluminum. If you want to give it excellent damping qualities as good or better than cast iron then laminate up two or three layers of 1/4" thick plate by screwing it together with flush socket head cap screws close spaced in tapped holes in the plate. It's more work but it will make an excellent accessory.
                          I like that idea a lot. Do you mean to tap all three plates, or just the last one?

                          Gary

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                          • #14
                            Fasten each plate to the one next to it rather than fastening all three at once. Use 1/2" flush 1/4-20 cap screws and countersink almost to the bottom on one plate and thread the next one to match. Use a 0.200" drill bit for the tap drill and power tap using a spiral point tap and it won't take hardly any time to make. Because you have absolutely no leeway with flush fasteners install one somewhere, then the next. Then you can go ahead and drill the rest and countersink them and they will all be aligned. Another thing about countersunk cap screws in aluminum is that they are self locking. It's possible to wind them in tight enough that you can't remove them so be careful when trial fitting.

                            In the case of three plates screw both sides to the centre plate with the centre plate having the threads. Do it right and it will not only work well it will look really cool too.

                            added: make sure you use the right countersink. You will need an 82 degree 1/2" countersink.
                            Last edited by Evan; 08-11-2009, 12:07 PM.
                            Free software for calculating bolt circles and similar: Click Here

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                            • #15
                              Thanks Evan - I'm looking forward to trying that out.

                              (OT: I couldn't open your gallery pages now but seem to recall some nice ATM projects. Any chance you'll be at Stellafane?)

                              Gary

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