Mounting heavy logs

Discussion in 'Tutorials and Tips' started by John Tisdale, May 12, 2014.

  1. John Tisdale

    John Tisdale

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    To quote Dennis Miller, the following is my opinion and I could be wrong:

    I made the following response in the newbie forum to a guy asking about steady-rests.

    Steady rests are necessary when doing large work with chucks. I do hollow-forms up to 22"-dia and have never had a problem using a Oneway faceplate and no steadyrest. If I'm doing a smaller piece of 16" dia or less, I'll use the Oneway 4" - larger and I use their 6". I do about 20-pieces per year and have never had a problem.
    I'll start with the log on a 1.5" spur drive on what is to be the top of the vessel - drilling a shallow hole with a 1.5" forstner is critical. Of course to get the piece on the lathe, a chain hoist is needed - some weigh 300-lbs or more. Crank down the tailstock and start knocking down the facets. I'll do the bottom profile and then turn the face-plate tenon. It's critical that this be flat and the same dia as the faceplate.
    Position the faceplate on the tenon, mark one hole at 12-o'clock, drill with 11/64 for #14 SS sheet-metal screw - oval heads give a little more bite for the screwdriver - insert one screw. Then determine the rest of the holes with a SELF CENTERING DRILL GUIDE (available any hardware), remove the one screw holding the faceplate, and drill all hole with the 11/64 using a depth stop. I use two different screw lengths: 1.25 for the six inner holes, 1" (points ground off) for the twelve outer. The reason for the shorter screw is that the last cut before finishing is to cut under the 6" faceplate to achieve a 4" base - as the tenon is typically 1" long, I avoid unsightly filled holes near the bottom.

    If this seems too much hassle, add one more step: after the rough has dried for up to a year, I'll put the dry and warped piece on the Kelton mandred just to true the surface for the faceplate. New holes are drilled - the tenon looks like Swiss cheese. No way can you use the old holes.

    I've never had a piece come off or even wobble. But that's because I go to great lengths to have a flat surface for the faceplate, all screw holes are centered in the faceplate holes, all screws are used - no exceptions

    The only time I'll use a steady rest and chuck is doing large, heavy (350-lb+) that are also tall (30" length). To my thinking, cantilevering out that far and then subjecting to the rigors of hollowing might be a bit much.
     
  2. hu lowery

    hu lowery

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    Nice post!

    John,

    I need a steady rest myself just because my lathe is flimsy! Reading over your post a couple of times I think I got the gist of it. One thing that I see even master turners being very casual with in video's is putting the screws in the faceplate. Seems odd in all the videos I have watched I have never seen someone even go so far as to use a center finder in a screw hole while obviously running the screws in at any angle they happen to start. I have wondered about the percentage of holding strength of the screws that is lost, especially the screws belonging to the people that advocate using the same screws over and over.

    Do I understand you correctly that you use the 1.5" spur drive as both a locating pin and driver? No reason I can think of not to, just the first I have heard of doing it like this. I have done it a few times turning punky wood but I freely admit that wasn't the plan! :eek:

    Hu
     
  3. hockenbery

    hockenbery AAW Advisor Staff Member

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    I use a face plates for my hollow forms. After getting a rough shape between centers.
    I don't mount to a flat surface. I turn a shallow cove for the mating surface of the faceplate.
    When I hold the gouge ( my straight edge) across the mounting surface I look for a 1/16" gap at the center.

    This method ensures a solid contact on the outer rim of the faceplate which is where the drive force is applied and there will be no movement of the secured face plate.
    A secondary test is before putting in screws I push opposing sides just to be sure there is no rocking.

    For me Turning a cove is easier and faster and I believe better for mounting the faceplate..
    My forms are hollowed through the face grain and the biggest I have done is "17" diameter and tallest around 12" which means 14" before the faceplate tenon comes off. Some of the blanks are over a hundred pounds. But most are in the 20-40 range hefty but not big. I don't use a steady rest. I have one that I have used for a few endgrain forms.

    I put some circles with a pencil in my cove. Center the faceplate in a circle.
    Since I'm putting screws into face grain In green wood I just run one screw in 1/3 of the way check centering of the faceplate once in a while I need to do a better centering so I pull the crew out and try again with another hole in the faceplate.
    If I have a centered faceplate a run a second screw in Opposite the first stop 1/2 way check for center and run that screw in then put in all the screws and finish driving the first.

    I never have a faceplate come loose in solid wood. Sometimes with burls and wood that is a lot spalted I will drive all the screws in 3/4 then take each one out out, put thin ca down the hole let it penetrate, and run the screw in all the way.

    Two important considerations for the faceplate tenon.
    1. The screw will make a hole ahead of itself so I leave an extra 1/4 inch depth for the srews.
    2 The tenon diameter for mounting the faceplate need to be at least an inch larger than the scree circle diameter to avoid splitting the when the screws are driven in. Once mounted in the lathe the tenon can be turned down Roma smaller diameter.

    On rare occasions I turn dry wood or cannot make a tenon a larger diameter I will drill pilot holes. A self centering drill gizmo works wonders.

    Al
     
    Last edited: May 13, 2014
  4. Dale Miner

    Dale Miner

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    The need for Steady Rests

    I think the need for a steady rest has more to do with the length of the piece than it does with the diameter.

    I've done pices up to 22" long X 15" diameter using a chuck with steady rest support. I would not try hollowing a piece that long with either chuck or faceplate mounting without steady rest support. Even if the mounting was secure, vibration from that much overhang would be more than I would be willing to fight.

    I do think that when a faceplate is properly mounted it is a more substantial mounting. When done improperly, not as substantial as a well formed and sized tenon. I've seen pieces come loose with both methods.

    Earlier someone mentioned that the steady rest needs to be at the largest diameter of the vessel. Often, the largest diameter is 1/3 the length of the vessel. I disagree. The steady rest provides the best support when the wheels are near the end opposite the headstock. When roughing and finish turning a vessel that needs steady rest support, it is fairly easy to leave a small flat for the wheels to run on, and turn the flat away using tailstock support when the work on the inside is finished.
     
  5. hockenbery

    hockenbery AAW Advisor Staff Member

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    Dale,

    Agree that the Small flat for the wheels is a must. And the close it is the the tailstock the easier to turn off.

    I think a tenon holds better on end grain up to a point. I don't turn 3 + foot tall vessels but if I were I would want them on a faceplate screwed into dowels cross mounted in the wood.

    I know a faceplate hold significantly better than tenons on face grain forms for me.
    I do occasionally turn hollow forms with a chuck especially if I don't have an extra inch of wood to sacrifice for the faceplate.
    I just have to slow the hollowing down because I can't take the large cut I can with the faceplate. The large cut begins a vibration and I back off.

    As to steady rests. One thing they allow us to do is turn the outside of the form to a narrow base and then hollow without excess vibration.
    Many of us would leave the base thick hollow down to the las few inches
    Turn the outside base then hollow.
    It takes a long time for people to imagine the form inside a block of wood.

    Al
     
    Last edited: May 13, 2014
  6. Mark Hepburn

    Mark Hepburn

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    John ,if you happen to have a video or a photo sequence would you mind sharing? I would really like to have a better understanding I'd the process, as large works are on my near horizon. I read this in your reply post and have been meaning to ask. Thanks!
     
  7. John Tisdale

    John Tisdale

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    I agree that a teeny bit concave is better than a flat - as truly flat is not a reality, it's going to be either convex or concave - convex is a guaranteed disaster.
    A screw in a drilled hole is superior to a forced screw, regardless of the point geometry - boat builders have taken this subject to the extreme.
    Truth be known, I'm not smart enough to understand what is sufficient - instead of worrying about it, everything is probably overkill. My 6" faceplate has 18-holes and so I'm always going to use 18-screws. These will be centered in each hole and each hole predrilled to the proper depth.

    Regarding the spur drive, the following is the complete mounting process and will hopefully clarify:
    - beginning with the log, with the chainsaw I'll cut small flats on what will be both top and bottom.
    - NOW THE REAL SECRET: Take a plastic garbage can lid (33-gal are about 22" dia), and drill about a 3/16 hole in the little center dimple. Put the lid on the log, get it just like you want, and then use a nail or scratch awl to hold it. Mark around the lid with chalk and, voila, you have a perfect circle with a marked center. Then chainsaw the chalk line and, for the center, I drill a hole maybe 1/2" deep with a 1.5" Forstner.
    - To do large work, you gotta have a chain-hoist - even if you have strong neighbors, you will find them strangely absent when log mounting time comes.
    - I insert my 1.5" jumbo drive into the headstock, hoist the log, and position - it's a lot more fun when the spur drive stays put in the hole in the log while you screw around getting the tailstock end just right.
    - when perfect, remove chain-hoist and chain - hopefully the log will clear the bed - if it does not, you can use an electric chainsaw provided your life insurance is paid and you've got really good health insurance and, oh yes, someone standing by with their cell pre-dialed to 911. Better to take it off, take outside and re-cut with the chainsaw.
    - I start turning at about 200-rpm on a large log - I always begin with pivot cuts at the tail-stock end. Objective one is to remove facets and dangerous points that can grab sections of one's anatomy. I then proceed as far as possible to the final profile and then cut the tenon for the faceplate. I'll usually cut about 1/2" larger diameter than the faceplate - gives me the option of repositioning the log to get the max diameter and/or include desirable features.
    - To actually secure the faceplate, put a chain or ladder-web around the piece, put it on the chain-hoist, attach the faceplate (see beginning of thread), and attach to headstock.
    - As there is no way the faceplate is perfectly centered (more so if purposefully repositioning), always use the tailstock live center for additional support.
    - I try to do the finished profile at this stage. If the diameter is such that the banjo won't clear, either get a second banjo or a toolrest with a long left side. A machinist made one for me that is 10" on the left and 6" on the right - by pulling/angling the banjo just right, I can work the headstock end without a problem.
    - then hollow, dry, do it all again, finish and, slam-bam, you got a finished piece.
    John

    I don't want to be boring. But that's not always easy.
    John Malkovich
     

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