DIY Buffing Rig - Next Steps

Discussion in 'Luthier's Corner' started by chinjazz, Aug 18, 2020.


  1. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    Good Day All,

    I recently got the bug for making my own buffing rig/machine. Signs of it started back on the mega Using water based products for instrument finishing thread, but I thought to not further litter that thread any further :)

    One of the reasons I'm investing time in this is because I've used hand drills and buffing attachments to do the work enough to realize I really like being able to look down at the wheel from the top with the piece in my hands, especially when working on a body.

    I found a circa 1950's buffing/grinder for $40 at a garage sale, and proceeded to get some great advice from @Bruce Johnson for getting link belts and 8" buffing wheels.

    I've taken to attaching it to the end of my workbench:

    Buffing Jig 2.jpeg
    Buffing Jig1.jpeg

    It actually works nicely - thankfully the old GE Motor seems like its got many more years to go on it. It's a 1/3 hp motor running at 1725, so with the pulley sizes it's dialed into a slower rpm - approx. 850.

    Anyway, arbor assembly is a heavy beast, but it's secure enough on the end here.
    The cost of pillow bearings, and arbor wheel are low so it's not a worry.

    All this got me thinking that I'm not too far off from making a stand alone buffing machine like some you see on YouTube (Highline Guitars, or I actually like this one by Kekani427 because it's less top heavy.

    Q1: Because I'm not a mechanical engineer I actually don't know if I could make one with a 3 foot bar that was 5/8" D, as opposed to 1" D?? I'll most likely get a fully threaded rod due to the cost related to having a machine shop thread the ends.

    Q2: The other factors unknown to me at this moment are if I went 1"D on the rod, will I need larger buffing wheels, and a 1 HP motor?

    Any thoughts or insights on these Q's would be very much appreciated :)

    Thanks!
     
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  2. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    A long extended spinning shaft needs to be strong, rigid, straight and well balanced. If it gets even a tiny bit bent and out of balance, it will vibrate and shake itself apart. Even at 850 rpm, if that buffer shaft gets bent 0.010", it will vibrate the whole machine enough to be very annoying to use. At 1750 or 3400 rpm, an out-of-balance buffer can break and throw parts. High speed vibration of spinning machinery can be dangerous.

    That's why buffing machines with extended shafts are typically 1" or 1 1/4" diameter. The larger diameter is more resistant to bending. How large diameter the shaft needs to be will depend on how far it extends. As a rough guide, a 5/8" dia smooth shaft is good for maybe 6" extension. A 1" dia smooth shaft is good for 12".

    Most smaller size commercial buffers with extended shafts are made to take buffing wheels with 5/8" holes. The shafts are typically 1" dia smooth steel. Then end is turned down to a straight 5/8" dia section, and 5/8 threads. Cheaper machines will use standard 5/8-11 threads. Better machines will often use 5/8 Acme threads. If the machine has shafts on both sides, the left side shaft has left hand threads and the right side shaft has right hand threads. This is so the nuts don't loosen up while the wheel is spinning.

    Don't attempt to use threaded rod for a spindle shaft. It isn't rigid enough, and most threaded rod isn't very straight or accurately machined. A spinning spindle shaft with a wheel on the end needs to be a nicely machined part.

    Your rig as you've built it so far looks fine. I'd put an 8" unsewn cotton wheel on it and you are good to go. Don't forget to add some kind of a wood or sheet metal guard over the belt and pulleys. You don't want to rub a painted body or your knuckles against that belt.

    That old arbor assembly is nicely built and strong. It looks like the shaft is 7/8" (?) going through the bearings and pulley, and is then turned down to 5/8" out at the ends. If you wanted to extend the shafts on it, you could machine up a new shaft from 7/8" stock, extending out 5"-6" on either side.
     
    Last edited: Aug 18, 2020
  3. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    Hi Bruce,

    I'm actually off to get (2) 8" unsewn cotton wheels now.

    Yes, this old arbor assembly is a tank!

    Before I attached the kit to my bench I took apart the arbor, and knocked out the rod. The ends were in fact 5/8", and as you described it as thicker at 7/8". I do like your idea of machining up a new shaft from 7/8" stock extending out further. I'll see how it feels with the 8" wheels before I go that route.

    Thanks for your time and thoughts!
     
  4. Huw Phillips

    Huw Phillips Life is like TV if the channel sucks change it Supporting Member

    Jan 4, 2019
    Hoboken
    You could get luck with a propeller shaft from a small boat the steel will be good quality and they are threaded at each end so may be of interest good luck
     
    chinjazz likes this.
  5. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    Thanks for the tip! I’ll check into that as well.
     
  6. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    I put in the two 8” buffs and took this short video clip with it operational.



    The left side provides more clearance than the right. And it got me thinking maybe what I can do is use the existing rod, and replace the Arbor housing with a 2 pillow bearings and a narrower 4” pulley.

    If I installed it on a vertical structure I could hide the belt inside. Like the above examples.

    I removed the bar again and it’s actually only 13” long, but solid.

    E50F9EC3-77BD-4D8E-BDB7-BE3737D72E28.jpeg
    I’m fairly certain I can get better clearance with this approach.
     
  7. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Another configuration would be to leave the pulley out of the center. Get a single narrow pulley with a 5/8" bore and put it on the right end of the shaft. That shifts the whole belt drive over to the right side, giving you more clearance.
     
    wraub likes this.
  8. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    Interesting thought. That would definitely give me more room on the left side buff.
    Would it be mechanically incorrect to put a 2" high pulley on the bar, and 4" pulley on the motor side?
    I'm probably suggesting huge no no's...
     
  9. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    You want to stay with around 850 rpm for the 8" buffing wheel. That is: a 1:2 ratio of the belt drive; motor:spindle. Putting a 4" pulley on the motor and a 2" pulley on the spindle would be a 2:1 ratio. The buffing wheel would spin 3450 rpm!
     
    wraub likes this.
  10. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    Oops.. I knew I was out of my league on that question.

    I definitely want to optimize as much as possible to have two buffing wheels, and obviously limited on bar space if I were to keep this bar. Back to the wood shed to ponder :)
     
  11. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Why do you need two buffing wheels? With the liquid buffing compounds, I use the same wheel for the two grades of rubbing compound that I use. I clean the wheel with a wire brush whenever it starts loading up, and whenever I switch compounds. There doesn't seem to be any problem with that.

    If you want to be really cool, machine a 5/16-24 thread on the end of the right hand arbor shaft, and thread on a keyless drill chuck. They are available as replacements for electric drills, and most of them are 5/16-24 thread. That's what I have on the main spindle shaft on my buffer machine (more on it later). So, I have a collection of buffing wheels of different diameters and materials, all set up on individual arbors with 1/4" shafts. With the keyless chuck on the buffer spindle, any of the wheels can be swapped in the chuck in seconds. Or popped into one of my electric drills that I use for buffing.
     
    Last edited: Aug 18, 2020
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  12. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    Interesting :). I've been using the 3M Super Duty rubbing compound, then moving on to Meguiars ultimate polish - as a progression/next step. Other than the 3M, what is your other grade rubbing compound?
     
  13. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    I've also been using Meguiars Ultimate. For the fine compound, I've also tried other compounds with good success. The 3M Super Duty as the coarse compound is the real magic. I don't know of any competitor.
     
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  14. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    I do like the 3M as well. So I'm curious, when buffing a body, do you use the 3M Super on the stationary buffer wheel, then switch a hand drill for the fine? I was just thinking left side for 3M, and right side for Meguiars (the rationale for two buffing wheels).
     
  15. dwizum

    dwizum

    Dec 21, 2018
    I know everyone has their own safety tolerances, but to me, that uncovered belt/pulley just screams DANGER DANGER DANGER at a high volume. I'd put a cover on it before turning the machine on again. Even just a cheap bent sheet cover, mdf, hardboard, anything to keep a stray finger or loose clothing out of the belt.
     
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  16. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    Agree, I’m actually planning on creating a different stand like the second link
    I referenced in my first post.



    The main intent on what I put together this far was to look at what inventory I had, check the link belt and get design ideas.
     
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  17. T_Bone_TL

    T_Bone_TL

    Jan 10, 2013
    SW VT
    My armorer friend (out of the game now due to body problems, but wicked high end work when...) built a buffer that reminded me of the robot dog from Dr Who (old Dr. Who - but with the body going right into the head, no neck, looking at pictures to refresh my memory.) Plywood sides that slanted in and cut to form an arm (or the dogs head) that stuck out with the arbor at the end of the arm. I think the motor was at the bottom for weight distribution (probably some sandbags as well) with a jackshaft to make the corner, which also meant the pulley on the working shaft could be quite small, with reduction/speed change taken care of at the jackshaft/corner. Since everything was tapered cutting the ply was annoying, but it made for a large base and a small working end that stayed out of his way, and a pretty rigid structure.

    I am struck by three points with your setup as is.
    1. The lack of belt guard
    2. The fact that you say you want to work looking down on the work but you have the belt in the way of the work under the wheels (consider putting the motor up under the bench, or higher above the axle if making a station)
    3. The size of the pulley even if you did get the motor up out of your way.
    By using a small pulley and moving the belt out of the way of the work you can have good access without having an overly long shaft that's prone to bending and vibration. Now that I think on it I believe I might have turned him the shaft for that buffer. I had a lab tech job where we were allowed/encouraged to use the lathes on our own time if we wanted (self education and all that) and it was the first thing I put workable left hand threads on, if I recall correctly. Rather than being mounted "on top of" the "arm" or dogs nose, it was mounted on the face of the end, with the belt runing back inside the box, again, for better access (and a belt guard that was mostly the machine structure, so free.)

    To be clear: - whether or not you also use it to "turn a corner" a jackshaft (intermediate shaft) allows you to have a fixed ratio final drive (say 1:1 on some small pulleys) while still having reduction and change of ratios (with step/cone pulleys) between the motor and the jackshaft.
     
    Last edited: Aug 19, 2020
  18. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL

    Thanks for the constructive feedback!

    I received pillow blocks and a new wheel for this smaller / limited in length bar, and was eye balling the setup and trying to envision a solution given all the variables, and I decided to scrap that plan and materials except the motor and link belt....

    I guess it was out of sheer pandemic boredom and I had a few bux to play with...

    Here’s the result of plan B as of today:



    I decided to try my hand at buffing with Menzurna compounds. Will let you all know if I like it or not.
     
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  19. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    Looks cool! Where did you buy the spindle shaft assembly?

    It looks like you have the wheels going at 850 rpm? That's about the max you want to run those big wheels. Be careful when testing. That combo with the Menzerna compound could melt through the paint quickly.
     
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  20. chinjazz

    chinjazz Supporting Member

    Sep 11, 2002
    Atlantic Beach, FL
    Thanks! It actually may be 850, not 100% sure. I don’t have a tool to check that, but my pulley calculations show it should be 700.

    I’m definitely going to test on scraps.

    I’ll post a link to the spindle shaft when I get home later. It was from McMaster.
     
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