any suggestions on how to do this cut?

[giantbeat]

Hi guys

I'm trying to work out how would be best to split this plywood tube.... any suggestions that i may not have come up with?

i have split hundreds of them with a straight line, but a current task requires me to split the tube with an angled cut, the only way i can think to do it is make a sled for the table saw that secures the shell on its side & allows me to slide it through... this is a 6" x 8" tube, unfortunately i need to do it on many sizes & many depths, this being the smallest so that prevents me doing something on my bandsaw as the majority of the tubes are wayy too big.. so i think its going to be a painstaking task of jig or jigs for the table saw. .

before anyone mentions hand saw, thats not really an option as i i need to repeat the cuts multiple times & produce very exact results... and my hand saw skills are not that exact.

 

[baldkev]

Are they going to be the same angle of cut? And material wall thickness?

I think you are on the right track with a tablesaw sled, v shaped section mounted on the sled to sit the tubes in, and mitre adjustable if required

 

[giantbeat]

Are they going to be the same angle of cut? And material wall thickness?

I think you are on the right track with a tablesaw sled, v shaped section mounted on the sled to sit the tubes in, and mitre adjustable if required

Same wall thickness throughout, the angle may change, the exact angle does not matter so much .... on to sled design & thinking I go.

thanks Kev

 

[space.dandy]

From the pictures I’m concerned about the table saw approach. You’re effectively trying to intersect a spinning disc with an angled cylinder. You seem to have a fairly tight radius on the cylinder in proportion to material thickness when you consider the effective length of tablesaw blade that will be exposed to make the cut. You will get a nice thin, perpendicular kerf at the apex of the cut, but I worry that the toe and heel of the blade will act to widen and chamfer the cut as the cylinder rotates.

I don’t think I’m explaining this very well and I’m not sure my concerns are well founded, but essentially I don’t think the geometry is going to work out on a table saw.

You may be better served by using a jigsaw with a guide/sled. Its much thinner blade would be more appropriate.

 

[shed9]

I agree with space.dandy above, this is possibly not a function to be carried out on the table saw. You will release the energy of the whole cylinder towards the end of the cut which will be hard to control and likely not be consistent in kerf or safety. I'd be tempted to clamp a strip across / against the edge of the cut and guide a freehand or multitool blade against the strip. There is obviously variations on this approach with single, double or slitted guides but keep it simple and just don't overthink it too much.

 

[Sgian Dubh]

U shaped channel made of three bits of ply screwed (glued?) together with sides deep enough to match largest cylinder diameter, and the channel wide enough to angle each tube. Then some sort of arrangement to firmly hold the tube at that angle (shaped blocks, screws, etc?). Track saw type of arrangement set above the channel that guides a buzz saw in a predictably repetitive line of travel for each cut, e.g., probably parallel with the sides of the U shaped channel. Line up the cylinder in the channel so that the required line of cut matches the saw's direction of travel. Set depth of cut to accommodate curve of cylinder. I'm not sure you'd be able to repeat the cut accurately on the opposite side of the cylinder, but I think methodology along these lines might be worth exploring.

I suspect you'd need a sharp fine cut blade in the saw to minimise veneer break out as the cut is made. Slainte.

 

[Ttrees]

Seems to me a router might be the thing for best results.
I don't think it would be possible on the TS as there is too much length of the plate
to overcome the change of angle whilst it's being turned.

Tom

 

[Doug B]

I’d go the router route with a very fine cutter on a barley twist jig, obviously you’d have to work out the rotation or build your own twisting jig but I’d have thought that would be the simplest way to give accurate repeatable cuts

 

[thick_mike]

Use a handsaw. Seriously, it will be quick, accurate and safer.

Japanese pull saw would be my choice.

 

[paulrbarnard]

How about a jigsaw and a barley twist type jig?

 

[Jacob]

Clamp it somehow, mark with a chalk line, cut with a hand held circular saw?
What are these interesting looking tubes and what are you going to do with them?

 

[giantbeat]

Clamp it somehow, mark with a chalk line, cut with a hand held circular saw?
What are these interesting looking tubes and what are you going to do with them?

hi Jacob, I'm a drum maker by trade so its a drum shell, i make them from 6" - 26" diameter

the cuts are for to make a new piece of tooling/jig for my production, normally we split them straight down when we need to do this... but in this case i have another requirement which i can't detail here as it involves unique process & pending patent applications.

 

[pe2dave]

From the pictures I’m concerned about the table saw approach. You’re effectively trying to intersect a spinning disc with an angled cylinder.

You may be better served by using a jigsaw with a guide/sled. Its much thinner blade would be more appropriate.

Quite agree with this. Table saw and 'moving' wood in the round smells of missing limbs.
Slow - handsaw.
In a hurry, the jigsaw and patience.

 

[giantbeat]

dont think i was clear in my post, mentioning rotating the tube, I'm not wanting to twist the cut round the tube at all.. im wanting to do a single straight line cut without any rotation or movement once that tubes in place, hence thinking a sled with the tube fixed in place... id probably need a V block or concaved radius block that is sacrificial as the cut would have to travel through all of it.

 

[space.dandy]

Hmm. From the pictures I imagine that you'd need your saw blade fully raised to do that, and without a guard. With a well made sled its doable and probably fairly safe, but... well. Rather you than me, sunshine!

 

[Sachakins]

If its a one off, I'd go with a rigid tenon saw, or router and a flutting jig type assembly.

Could go down the Dremmel route also, might be easier than other ways.

 

[Sgian Dubh]

hi Jacob, I'm a drum maker by trade so its a drum shell, i make them from 6" - 26" diameter

I didn't realise from your first post that you were dealing with cylinders of different diameter. Based on what you've said since I wonder if the idea is that you're planning some sort of production run, or perhaps repeat semi -custom runs with drums of different diameter.

I suspect my original potential solution has the kernel of an actual solution within it. So, you could make a U shaped channel big enough to accommodate the largest diameter cylinder, but include a platform above the channel's base that can be raised to accommodate smaller diameter cylinders. The channel would also need to be wide enough to allow the cylinders to be set at an angle so that the proposed cut line could be lined up parallel with the rig's sides and centred on the rig's length between the sides.

Then it would be a case of setting up a hand held power saw (buzz saw) to cut along that centre line on some sort of support, e.g., in its simplest form, the saw mounted on a board that travels in a controlled fashion supported by the top edges of the rig's sides. You make the first cut, and then you have to rotate the cut cylinder 180º and angle it the opposite way in the rig to make the second cut. You'd also need to find a way of mounting the positioned cylinder so that it can't move both during the cutting operation, and after the cut's finished.

Apart from that, another potential problem I can see is that even with a buzz saw set to its maximum cut depth, it possible that the beginning and end of the cut may not be deep enough to completely separate the two parts in some instances. Slainte.

 

[pe2dave]

dont think i was clear in my post, mentioning rotating the tube, I'm not wanting to twist the cut round the tube at all.. im wanting to do a single straight line cut without any rotation or movement once that tubes in place, hence thinking a sled with the tube fixed in place... id probably need a V block or concaved radius block that is sacrificial as the cut would have to travel through all of it.

Surely by the time you've made a sled, fastened it down just so... you could have done it with a jigsaw? Even a fretsaw?

 

[Ttrees]

Whatever tool is used it will be a rotating cut from 11 o'clock to 1 o'clock , and since this sounds like a production,
I don't think you want a alternating bevel in the join,
would it even end up a cylinder that way?
and imagine the tablesaw would be binding/destroying the previous cut whilst you're going along.

Quite tricky and I don't have an answer better than Doug B's suggestion.
Never heard of that, cheers for that nugget.

Tom

 

[EddyCurrent]

I don't know how you make the plywood tubes but is there an opportunity in that process to make the cut before gluing the laminates ?