Clamping odd shapes on a bandmill for QS cuts, LT40

[chainsaw_louie]

I've had some failures while attempting to clamp and hold odd shaped (crescent, quarter-round) wood , in off-from-square positions on a LT40 so as to make the cuts to produce quarter-sawn lumber . 

The problem is that the combination of:
  - the geometry of the wood shape,
  - the position/orientation of the wood held for quarter-sawing ,
  - the position of clamps and the supports
....does not make for a secure grip that will resist the sideways pull of the blade. When cutting starts , the wood wants to tip over and break free of the clamp, then its a mess !

Some possible things I thought may help are:
  - Vee shaped blocks of wood between the side supports and the log
  - cutting a notch in the log for the clamp head to get a better bite
  - cut very slowly

Any suggestions ?

[doc henderson]

for short stuff, or cookies (with the log setting up) I use a wood holder that can be sacrificial I have also put screws in the log through the jig.  just have to know the screw placement and length to avoid hitting with a blade.  there is a thread somewhere about a jig to hold angles pieces.

[doc henderson]

I love to grab a log or cant and try to move it and cannot.  You can relax a bit with a heavy log as it will have bulk to help it not move.

[Magicman]

I have found that it is more about supporting the cant rather than actually clamping it.  A sharp blade is necessary to prevent it from disrupting your setup. 


My normal is to avoid that method of QS.  I take ~6 cuts through the center,


remove them, and then make ~6 cuts through the remaining two cants.  The 4 rift sawn corners are then perfect for table legs and I am not dealing with all of the odd width boards that need edging.

I only custom saw and do not sell.  I have found that my QS customers prefer this method.

[chainsaw_louie]

I love to grab a log or cant and try to move it and cannot.  You can relax a bit with a heavy log as it will have bulk to help it not move.

I actually did just that , the grab-test but still the wood broke loose , I was a bit surprised. In hindsight , I need to pull harder next time but also pull on the end of the clamped piece where the leverage of the incoming blade is greater than in the mid section , opposite of the clamps and supports.

I thought that some sort of modification or removable, slide-on cap for the clamp head that would have teeth to penetrate and hold down the wood and counter forces pulling the wood vertically.

[doc henderson]

this is a mockup that would be 8 feet long or so.

[doc henderson]

for real odd stuff, use screws if it does not ruin your project.  I also have put a length of water hose with a slit length wise over my clamp to not damage my cant.

[chainsaw_louie]

@Doc: I see on your mill the top of your clamp is beveled back so that the contact edge is like a knife that will penetrate and hold the wood down against vertical, tip-over forces.  The WM clamp is basically flat and broad so its not providing the bite and hold-down force so much when the wood face isn't flat against it.

The jig you prototyped looks like it might work. Screw in triangular blocks should definitely work. 

@Magicman: I like the speed and efficiency of your method. I definitely agree when time is money , it doesn't make sense to mess around with the time consuming process of quarter-sawing the quarters. However if diy and the wood is precious in case of QS white oak , its pretty tempting to get all the 1x3,4,5's i can, despite the effort.

[SawyerTed]

I have twisted my clamp sideways so the corner where the flat face meets the rounded back.  It's sharper and will dig in better.  I agree the Woodmizer clamp could use some sharp points at times.  

[Magicman]

Peter Drouin welded teeth on the top of his clamp, but I doubt that you would want to poke holes in QS White Oak.

Yes, I quite frequently turn my clamp as Ted suggested above.

[chainsaw_louie]

I have twisted my clamp sideways so the corner where the flat face meets the rounded back.  It's sharper and will dig in better.  I agree the Woodmizer clamp could use some sharp points at times. 

Like this below , maybe I can weld up a slip on cap for the clamp-head  that has  a protruding sharp edge or teeth to dig in and hold down wood being cut that's positioned at an angle other than 90 degrees.

[doc henderson]

Well CL, for one thing you can reverse the "cant" in the pic so the curve is on the log back stop and the angle goes under the clamp.  you must like to draw and the pics do help explain your question.  have you watch @YellowHammer video on reverse jelly roll quarter sawing.  It is faster and you only wind up with two pieces, 1/3rd and 2/3rds of the log.

The Fastest, Best Hands Off Quarter Sawing (You've Ever Seen!)

The Secret to a Reverse Roll Quarter Sawn - The Ultimate Quarter Saw Trick

watch this one and pay attention at 15:25 he talks about sawing gentle as he does not have a grip on the log.

[beenthere]

Maybe weld some 5/8 or 3/4" nuts on the top of the clamp that a pointed 5/8 or 3/4" hex-head, long-threaded bolt could become a point to hold the block steady. When not needed, keep the bolt in the tool box. 

[SawyerTed]

I've also thought the inboard side of the manual stops could be serrated to "catch" better or maybe a bolt on set of teeth.

[doc henderson]

you can also raise up log stops and clamp and saw half, then flip it over for a good grip to do the last.

[customsawyer]

If you gun barrel your log first it has many advantages. Most important advantage is that the pith is level to the bed. This is necessary for proper quarter sawing. The second advantage is that it will give you some extra flat spots to sit on the bed of the mill. Most times they will be off by a few degrees from perfect quarter sawing, but will give you a great starting place on learning how to clamp these odd shapes.

[chainsaw_louie]

If you gun barrel your log first it has many advantages. Most important advantage is that the pith is level to the bed. This is necessary for proper quarter sawing. The second advantage is that it will give you some extra flat spots to sit on the bed of the mill. Most times they will be off by a few degrees from perfect quarter sawing, but will give you a great starting place on learning how to clamp these odd shapes.

Yes , I think that's part of my problem, ie not having perfectly faceted faces completely on all sides.  

Also putting a faceted corner/edge facing towards the clamp and getting the WM clamp's top serration *above* this outmost corner would help a lot to resist the lifting/turning torque of the blade as it pulls away from the clamps and towards the side supports. 

Thanks .

[YellowHammer]

I owned an LT40 when I started quartersawing, and I don't recommend teeth or any spikes or stuff welded to clamps because it damages your wood and also is not needed. 

In some of your drawings, it is evident that if you are clamping like that, yes the cant or quarters will move because you are not getting an aligned center of pressure between the backstops and the two plane clamp.  They need to be clamping so never provide a rotational force, or a lifting force, but should always be equal contact heights and even slightly forcing the cant down, to the deck.  Never up or back, but in and down.  Also, you can pinch the bottom apex of the quarter, you don't have to grab it that high such as in your sketches.  Grabbing a cant and shaking it won't really tell you how well it's going to hold unless you put your shaking force right where the band will contact the wood. 

You should also set your clamps so that the force of the band loads the backstops and makes the cant wedge into the sawmill and make the system more sturdy, not prone to popping up.  Again, this is usually done with a low clamp so the if the band tried to rotate the cant, the clamp being low naturally stops the rotation, not enhances it.

As I've done in many videos, one of the mistakes I see many people do on the YouTube is to overclamp and actually cause an instability, where just a little band pressure causes it to pop out.  If you cant is sitting correctly and solidly, clamping is more of getting stability for the cut vs brute force.  Think of the system as a tripod between the bed, the backstops and the clamp.  Assuming the cant weighs a decent amount, there should not be enough force of just the band cutting through the wood to make the whole tripod unstable, except until you get down to the last little bit of  wedge, and then it's a matter of having to clamp solidly.  So with small quarter wedges, I will rotate the vertical face to the backstop and put the clamp on the oblique angle. 

I show lots of these techniques in my videos.

As Customsawyerf says, you need facets both for quality quartersawing and also for cant stability. 

Yes, we all have cants pop out, but in reality, the LT40 will sure nuff get it done for quartersawing.

If you haven't done so, I would recommend getting the little wheels or roller mounted to the top the movable backstops or side supports, they do make rotating and clamping easier.   

     

[Andries]

If you're after getting as much 1/4sawn lumber as possible from a log, two important points that CustomSawyer said (worth repeating).
_ Level the pith.
_ Gun barrel the log.
The weight of the log will keep it in place while quarter sawing.
But, in case you're sawing short logs that want to squirm away from the clamp, adding another set of side supports, with wheelies, to your LT40 will help a lot. It's a mill option that will pay for itself.

Doc put up the link to YH's fine videos on the topic. See how he is careful to gun barrel a specific way. It makes all the difference in getting the most true quarter sawn from a good log.
quick edit:
[dang, don't you hate the 'can't post because the other smart aleck posted just before you?]