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slipper sheet

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  • slipper sheet

    I'm at the point now with my lathe project where I need to choose a sheet material to separate sliding metal parts. I will probably use some PE sheet that I have, it's etched on one side for gluing and smooth on the other, and .036 or so thick. There is enough area of contact between the flat ways and the pieces riding on it that compressibility won't interfere with rigidity. The ways are smooth enough that they shouldn't scratch up the PE 'pads'.

    There are a couple more places where a slipper sheet might make sense- the t-slot table slides, for example. The table will be resting on steel bar rails, which will be turned or faced to as good a finish as I can do, then probably coated with an anti-friction spray. These bars are angled on one edge to make the mating dovetail- I may or not include a thin spring steel shim bonded to the steel part for the cast to ride against- haven't decided that yet.

    I'm mostly making do with materials I have on hand to keep costs down, so any kind of surface hardening is going to be out of the question. If it's going to be cast on steel, I'll use the anti-friction spray I have. It works pretty well and is renewable. There shouldn't be any problem using way lube as well- which brings up another question, will way lube affect the PE sheet material ?

    The basic question revolves around metal parts in sliding contact, some being cast iron and some being hot rolled steel which will be turned, faced, and otherwise prepared. I have the aforementioned PE sheet in stock, and I have some spring steel strip that's just the right width to act as a wear strip in the dovetail areas.

    I'm almost ready to think about stress relieving on the hot rolled parts before further machining on them- wondering if that would make any sense as well. I went with hot rolled instead of cold rolled so I'd have a better chance of it not warping, and judging from the angled cut I did on the length of the pieces (shown in another thread) it behaved quite well. I'd be cycling the pieces from a hot oven to the freezer a few times, at least that's what I'm currently thinking anyway. Would I turn the scale off before doing this, or do that after- I'll definitely be facing these parts and drilling the mounting holes before the final passes on the angled edge, to ensure a fairly accurate result.

    Comments, ideas?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    In our Die Shop, we used slipper sheets all the time.
    We used 3/4" thick PE (polyethylene)
    It is unaffected by oil or most chemicals
    It also does not cause rust on ferrous parts

    1/8" or 1/4" "hardboard" ,Masonite also works good in a home shop.
    I use it for table covers on my mills, with a small wooden key to keep them
    on the table either side of the vise
    Since masonite can absorb moisture, make sure it is dry before long term storage of tools on top of it.

    Cycling between the oven and freezer sounds good but will not do a lot.

    The Value of freezing is that ferrous molecules lock up as temperatures get lower. They then stay that way until heated substantially.
    So if you had a part that never saw 50 degrees (F) and then left it outside in 40 degree weather (or inside too). the material could(?) move (ie, warp etc).
    So on stuff you don't want warpage , freeze it.
    It will not move again unless it gets below the previous "freeze" temperature.
    This is unlikely to occur in your shop and so it stays locked
    However, If you turn around and reheat it , you risk loosing the molecular lock
    This would be about 900 -1200 degrees as I understand



    • #3
      Well, I did some reading. I won't be trying to stress-relieve hot rolled in my oven any time soon. Not near enough heat. Ok, I learned something. Won't need it anyway.

      Also, learned that using PE sheet will reduce friction a significant amount, but it's biggest advantage is reducing wear on the steel. Teflon sheet would be best for lowest friction and least stick/slip- nothing new here- Evan covered it pretty well during his mill build.

      I can use PE to advantage anyway, particularly if there's no lube. It might even be better with a hand-cranked machine anyway, since it might help keep the table from moving on its own.

      As far as using the spring steel strip between dovetail parts- it will prevent wear on the steel if it's bonded to it, but because it's hard it may not be good to run the cast iron against it. I'll probably just use the cast iron/steel slide without the spring steel strip, but with either or both way lube and the anti-friction spray. I will probably use the strip between steel/steel dovetail slides. One part of the slide will be six inches long, the other about 3 inches long. I'll bond the strips to the shorter part.

      This is another project that's on the long-term list. It will be awhile before I have something to show, but I'll post pics.
      Last edited by darryl; 12-02-2009, 11:58 PM.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-