Contour bandsaws - what does that mean?

GregSY · Dec 20, 2012

I've looked at a number of bandsaws, Doall in particular, that are called 'contour' saws. Just what does that add to a saw?

This is a pic of the contour parts - I assume that means the funny curve gear looking pieces. What do they do?

Is all that stuff very beneficial or should I not worry about buying a saw with that feature?

charlie gary · Dec 20, 2012

The "funny curve gear looking pieces" is actually a tool you use to push material into the blade for cutting. It is missing a couple of handles. Here is a picture of a more current type.

Woodtek | Toolmonger

PeteM · Dec 20, 2012

Countour simply means following something other than a straight line (cut off) in the material. Countour saws are usually vertical and with blades narrow enough to navigate whatever curve is being cut. Have a vertical band saw, put a narrow blade on it, and there you go . . . Sometimes you'll see more robust guides, blades with more clearance behind the teeth, and so on.

As Charlie said, the part in the photo is just to safely push the material through the saw while following a curved line.

bryan_machine · Dec 20, 2012

What Pete said - but think of it another way - there are bandsaws, perhaps the majority numerically, that are only meant to cut the straightest possible lines, and to "cutoff" pieces of something. They are NOT contour saws. Some cutoff saws are vertical - for example a Marvel-8. It would be quite hard to cut out a circle on a marvel-8 or a doall C916 horizontal. It's done every day on a Doall 2013V3 - which is a kind of canonical example of a "contouring bandsaw".

And that plastic version of the work holder Charlie linked to has to be the Good Link of the Day.

mixdenny · Dec 20, 2012

charlie gary said:
The "funny curve gear looking pieces" is actually a tool you use to push material into the blade for cutting.

But the one on a Doall is more than a holder, it is part of the "power feed" system. A pair of chains hooks onto the holder via the short sprocket track thingies at either end, and a system of weights (I think) pulls the work into the saw blade. All you do is steer. It's been so long since I used one I forget the exact motive force, but it certainly pulls the work forward. Dennis

Milacron · Dec 20, 2012

mixdenny said:
But the one on a Doall is more than a holder, it is part of the "power feed" system. A pair of chains hooks onto the holder via the short sprocket track thingies at either end, and a system of weights (I think) pulls the work into the saw blade. All you do is steer. It's been so long since I used one I forget the exact motive force, but it certainly pulls the work forward. Dennis

On the more elaborate DoAll saws the table is hydraulic feed, a chain engages teeth in the backside of the feed assist casting, the chain also is engaged by a small sprocket mounted in an extension behind the cast iron table. There is a handwheel you can turn to rotate the sprocket and therefore control the contour with great precision and little physical effort.

In below pix of my ex DoAll 2613-3, you can see the handwheel at the right of the table.

DoAll 2613-3 was probably the finest vertical bandsaw ever made. Blade speeds
adjustable from the slowest ever needed to friction sawing speeds. The table
tilted hydraulically...even the blade post moved up/down under power.

GregSY · Dec 20, 2012

OK thanks. Another question - the Doalls seem to usually come with a foot brake. What is the value in that....is it just so you can work faster or is it meant to allow you to 'stop on a dime' when contouring to reduce the kerf at the end of a cut?

gbent · Dec 20, 2012

The term dates back to the day when a DoAll was the wire EDM of the day. In addition to that funny curve gear looking pieces there should be a piece of light duty roller chain. The chain is looped around the funny curve gear looking pieces, around either a falling weight or hydraulic piston, and a gear that lets you steer. This way you can power feed your part through the saw. The saw had to incorporate a blade welder so you could thread the broken blade through a hole in the die section and weld the blade back together.

DoAll had a book on making punches and dies from the same piece of steel. Depending on the thickness and material to be punched the book had a table to tell you how much to tilt the table to saw the punch from the die. Then you would install the band file blade and file both the punch and die to layout lines. Often, only either the punch or die would be hardened. Then both would be mounted in the die shoe, and the soft one would be sheared to the hard one. The die would then be disassembled and the necessary clearance would be filed before hardening the final piece.

Now not only do we have wire EDM to replace the saw, we have laser and plasma to do blanks that would have been done on short run dies.

on edit: Caught typing slow again. The "foot brake" is actually a falling weight for power feed on the non-hydraulic saws. The crank above the weight changes the amount of leverage the weight has on the lever.

Milacron · Dec 20, 2012

GregSY said:
Another question - the Doalls seem to usually come with a foot brake. What is the value in that....is it just so you can work faster or is it meant to allow you to 'stop on a dime' when contouring to reduce the kerf at the end of a cut?

I guess gbent has you covered on that one, but in case it's not obvious, the orange foot pedal on the 2613-3 activates the table hydraulic power feed. As I recall, step on enclosed pedal forward and table feeds at whatever rate you have set, rock pedal back and table rapids away from cut.

GregSY · Dec 20, 2012

OK thanks. I've been looking at 1612's rather than 2613's for the simple fact that the 1612 uses less floor space and I believe would handle all the cutting I need. I used to run a 2613 so I know how good they are...but that was over 20 years ago and I have forgotten a lot of details.

gas pumper · Dec 20, 2012

The pedal is the control for the chain feed. There is a handle there to move the big cast iron weight that's in the cabinet that puts tension on the chain drive. If you run with your foot on the pedal you can take some force off the chain and stop feeding by pushing down a little further.

Also in your bucket of stuff there is a ratchet feeder, it hooks onto the table filler and you squeeze the trigger to apply pressure. For light feeding.

The table filler is also in the bucket.

Regular file handles fit well on the 1/2 moon geared feeder for steering handles.

I have a couple of sets of 45* offset saw guides for my 16 saw. They come in handy for setting the blade at a 45* angle to the column for use as a cutoff saw for parts longer than 16". A good accessory to have.

Need pictures of the chain drive? LMK

Frank

Keith Krome · Dec 20, 2012

The other thing that makes it a contour band saw is the built in blade welder. This is for sawing enclosed areas. Drill a hole large enough for the blade to pass thru, then break and re-weld a blade through the hole.

Fabitfast · Dec 21, 2012

Contour cutting saw is generally used for straight and complicated/curve cuts.
Amada has contour band saw too.

steamfab · Dec 21, 2012

A vertical bandsaw does perfectly this job. This quality machine tool provides fast precise cutting because it uses a strong gear box, hydraulic down feed control, a wire chip brush, and a standard coolant pump system. I have been obsessed with bandsaw boxes lately. Keeps my hands full with the extra time for the holidays.
Merry Christmas!
-www.utilitybandsaw.com

GregSY · Dec 21, 2012

Well, I bought a 1612-2 today, made a really good deal on it. It has a 3 speed gearbox and looks a little dirty on the outside but the inside parts all lok very low wear. Now I just have to drag it home from Dallas...

John Welden · Dec 21, 2012

Milacron said:
On the more elaborate DoAll saws the table is hydraulic feed, a chain engages teeth in the backside of the feed assist casting, the chain also is engaged by a small sprocket mounted in an extension behind the cast iron table. There is a handwheel you can turn to rotate the sprocket and therefore control the contour with great precision and little physical effort.

I don't understand what the black hand wheel does?

Thanks

Milacron · Dec 21, 2012

John Welden said:
I don't understand what the black hand wheel does?

Handwheel rotates shaft, on end of shaft is a bevel gear that meshes with other bevel gear on shaft 90 degrees to that shaft. Second shaft runs to bevel gear set that turns small chain sprocket that is projecting vertically behind the cast iron table top. To use, connect one end of chain to right side of the "part pusher" or work holding jaw, wrap chain around sprocket and connect other end* of chain to left side of work hold jaw. Then, combined with table power feed, you turn handwheel as needed to move chain, which pivots the work hold jaw which pivots the part as needed for whatever contour your are cutting.

It doesn't work for everything of course...for example tight radius and constant shifting of direction. But for gentle curves it works great.

*I don't literally mean the "end" of the chain but whatever it takes so the chain is relatively tight, depending on part size. Typically there will be excess chain hanging off.

Above is a non handwheel type that uses a cable rather than chain and sprocket, but only image I could find
to give some idea of what is going on.

GregSY · Dec 22, 2012

It seems like that setup was invented by someone who never actually tried to use it. that said, I've never tried to use it either so I trust you are right when you say it works well. But....why can't a person just guide a part through by hand? I mean something like 1/4" aluminum plate. Does the saw not allow that to happen without a lot of kickback or chatter or other danger?

Milacron · Dec 22, 2012

GregSY said:
It seems like that setup was invented by someone who never actually tried to use it.

Seeing as DoAll was the top dog in that field that is a ridiculous statement.

that said, I've never tried to use it either so I trust you are right when you say it works well. But....why can't a person just guide a part through by hand? I mean something like 1/4" aluminum plate. Does the saw not allow that to happen without a lot of kickback or chatter or other danger?

Of course you can guide part thru by hand...but if you are cutting a pocket or contour in 1" thick steel plate it is way less tiresome to use the table power feed and the work jaw to do so. Apparently you can't relate to cutting anything other than 1/4" aluminum on a wood bandsaw :rolleyes5:

Bottom line is I have used the handwheel chain system to cut contours in pretty thick steel and it works great...really cool idea. Of course wire EDM made it an obsolete concept for industry (and for cruder cuts, CNC plasma), but those of us without EDM the chain/work jaw/power feed does come in handy sometimes.

As an aside, I just now looked thru the Holy Grail of contour bandsaw books, the DoAll Contour Band Machining Handbook (over 400 pages), found a photo on page 122 of the chain system.... and now realize I completely forgot on the 2613-3, there is not just one chain sprocket but three. Only the middle one is moved by the handwheel, the other two are idler sprockets that simply serve to spread out the chain in a wider pattern for better control. Re the top photo, try sawing that pushing by hand !! Re bottom photo, probably can't see it due to my crappy scanner, but the operator is cutting a pretty tight "S" pattern in that plate using the handwheel and power feed.

matt_isserstedt · Dec 22, 2012

Say you have a cart piled high with parts to be sawed which is going to take you 10 hrs of cutting time. And you have another cart for tomorrow, etc.

Say you had a 4" thick plate of A2 to saw a contour in.

The power feed (so to speak) via gravity or hydraulics would be greatly appreciated. Its not that they can't be hand-fed but you would have the shoulders of a bodybuilder and thumbs of a farmer.

I have the gravity feed system as an accessory for my Powermatic vertical saw. Its not hooked up and I've never had occasion to. For what I do simply sawing by hand is fast and precise enough and I don't have enough work or thick enough metal to get me complaining very loud

Contour bandsaws - what does that mean?

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