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Technical Shrinking discs - 7" vs 4.5" which is better and why

Discussion in 'The Hokey Ass Message Board' started by hillbilly, May 23, 2020.

  1. I did the search thing, I have better luck putting my query followed by HAMB in Google than I do using the search on here (no fault but my own, limited e-techie skillz)...I find old posts and don't want to raise one from the dead, so here goes.

    I've tried in vain to find a suitable saucepan lid with the curve to it, in my hillbilly town there aren't ANY stainless lids with the pots/pans in the stores, just I settled for a $13 3 qt sauce pan from Antichrist*Mart...cut the bottom off, drilled out the center, stuck it on my buffer/polisher/bondo hog sander only to find it didn't get things hot enough to do anything whatsoever. This former pan bottom is about 1/8" thick...might be dissipating heat too quickly, or not enough RPMs with the sander, or both?

    Here's the question part: for you guys/gals that LOVE shrinking discs, which do you prefer? The 7" ones or the 4.5" ones?

    My hillfolk understanding of physics is just enough to make me think the surface area of the smaller diameter would be more effective/efficient due to less surface area meaning less heat dissipation would equal better heat; whereas, the larger one would have the ability to use inertia and centrifugal force and all that good stuff to the extent it might just be better than the smaller one?

    Folks around here still swear by either using a torch to heat shrink stuff or just caving and paving with plastic filler...not my idea of proper metal work.

    Hoping to draw on the vast knowledge and experience on the H.A.M.B.

    I know I'm full of questions lately, I've been on a hiatus since the times when I was on the HAMB daily, working on old cars, driving cross country to shows, etc etc...had a stroke a few years back and there's just a lot of stuff I no longer remember how to do. My apologies if anyone thinks I'm a nuisance...well, kind of...I still have bits of the "if you don't like me then (censored) you" attitude, but I'm pondering the afterlife and kinda wanna keep in good standing with the man a kinder gentler hillbilly is what you folks get.
    loudbang and '51 Norm like this.
  2. 51box
    Joined: Aug 31, 2005
    Posts: 943

    from MA

    I’m no expert but I use a 7” shrinking disc on a HF buffer with adjustable speed and it works very well and fast.
    loudbang and hillbilly like this.
  3. Dino 64
    Joined: Jul 13, 2012
    Posts: 1,902

    Dino 64
    from Virginia

    Larger diameter for large slightly curved, like a door skin. Smaller one for tight areas with less clearance.
    I have the smaller diameter one and it works fine.
    After experimenting, I found the following steps worked well.
    Spray bottle of water and small amount of dishwashing liquid. Spray the area then slowly run the disc back and forth for maybe 5 to 10 seconds.
    Spray then wipe down with a rag. Let the area cool and repeat as needed. Block sand to find high spots, dolly those down in between to check your progress. Keep things clean or you’ll get crap on the disc.
    I use a grinder at full speed, gently putting small amount of pressure.
    Works for me, good luck;)
  4. Budget36
    Joined: Nov 29, 2014
    Posts: 4,826


    How about (to the OP) a pic of what you're using?

    I asked a similar question years ago about shrinking discs, almost think they need to be cut to get a bit if bite, to generate the heat. I'll see if I can find the thread.
    loudbang and hillbilly like this.

  5. Budget36
    Joined: Nov 29, 2014
    Posts: 4,826


  6. rockable
    Joined: Dec 21, 2009
    Posts: 3,121


    The larger disc is more forgiving when it comes to finding the high spots. Use the smaller disc when space does not allow the use of the larger. That is my mode of operation.
    alanp561, Dino 64, Just Gary and 4 others like this.
  7. fresh hops
    Joined: Oct 19, 2019
    Posts: 51

    fresh hops

    I agree with rockable, I only use the small one in areas the larger one wont fit.
    loudbang and hillbilly like this.
  8. duncan
    Joined: Aug 23, 2006
    Posts: 1,131


    Large disc, surface speed is higher = faster cycle times.
    loudbang and hillbilly like this.
  9. Jethro
    Joined: Mar 5, 2001
    Posts: 1,530


    I've used the small disc on stainless trim and things like headlight buckets
    hillbilly and loudbang like this.
  10. DIYGUY
    Joined: Sep 8, 2015
    Posts: 890

    from West, TX

    You may not have enough rpm using your buffer/ polisher . That’s what I’m using and on high (variable) it just barely works close to the edge on my 7 in disc. Needs a little more power.
    Dino 64, hillbilly and loudbang like this.
  11. acme30
    Joined: Jun 13, 2011
    Posts: 175

    from Australia

    Yes spot on in my book I use both and wouldn't be without either. I don't think you can say one is better than the other because it depends on the panel you are using it on more than the disc.
    hillbilly and rockable like this.
    Joined: Jul 20, 2006
    Posts: 2,423


    I have a 4.5 inch, I borrowed a 7 inch years ago and I honestly can’t see any difference of how they perform
    hillbilly likes this.

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