DIY Swing blade vs Twin blade sawmill

[nastcat]

Been collecting parts to build a small sawmill for a while. I had settled on the swing mill design now thinking a twin blade mill would be better. Wondering what other members think about these two styles.

[Ron Wenrich]

I believe it would depend how big of motor you're planning on using.  The double cut has twice as many blades, so it needs more power. 

[woodyone.john]

and with more power and 2 blades youve got a serious wood cutting machine if you do it right.Then you need a big loader and a------------and so on.cheers john

[bandmiller2]

For adaptability and general milling your much better off with a single swing saw. Twin saws lends itself better in the resaw mode. My opinion. Frank C.

[dgdrls]

First and most important I "tip-my-hat" to you D.I.Y. sawmill builders.

There are many versions of both systems out there.

Overall I think a swing blade system can be built more portable
and overall lighter in weight than a twin blade simply due to power
and structure requirements.  The closest Twin blade to a Swing I know of is the Rimu, but you're "limited" by the lower blade dimension

Either works well, what do you anticipate for logs and sawing, stationary or portable??

Best
DGDrls

[nastcat]

Actually I have been thinking to use about 20" blades. My thoughts are to use two 20 plus hp engines. One horizonal and one vertical shaft. this would allow a greater flexibility. I would also like to be able to move the vertical blade completely out of the way for slabbing. The thought is that it would not be portable.

[backwoods sawyer]

Take a close look at the mighty might the one I ran had a 42" main saw and 32" edger saw each had its own motor. for slabling mill down to top of slab shave the last bit to get a clean surface and flip only one slab per log If you want two you have to split with chainsaw and shave a flat surface, then flip. The big advantage is everything is mounted solid set and forget.

[Ron Wenrich]

Your depth of cut on a 20" blade is only going to be about 8" when you take into consideration the room needed for your shaft and collar.  Mobile Dimension also makes a twin saw mill.  These mills run on a single beam.

Swing mills are designed differently from a single beam dimension mill.  They run on a 4 post system and use a track.  I suppose you could build a twin saw 4 post mill.  If you're planning on using 2 motors, then you could swap out the bottom saw with a slabbing attachment.  If you remove the vertical blade, then there is no need to move anything else. 

[nastcat]

A four post system is the way I was thinking of building mine. I do find the single beam design very interesting. When a slabbing attachment is talked about, is that a chainsaw driven attachment used for taking off a large slab. On youtube there is a video of a dimensional mill that han a third blade that you could saw out a couple of 2x4s in one pass if you wanted.
http://www.youtube.com/watch?v=RJt7wmy_Oeg
backwoods sawyer, What kind of engine did you have on that mill you ran? I like the idea of using bigger blades but then you need bigger engines and so on and so forth. What would some of the membership recommend for blade size and then engines to drive them and why.

[GeneWengert-WoodDoc]

I have seen more accidents (operator injuries) with the two circular blade mills than with a single blade.  One of the more common types is called a Skragg mill...kinda like an overgrown table saw.

Note that two blades (or even more) are used to resaw a cant into lumber.  The machine is called a bull edger.

One risk with two circular blades, even at 20", is that one blade decides to cut a path that is not parallel to the other blade (due to grain deviation, knots, or heating of one of the saws, etc.).  This will most certainly cause an immediate stoppage of the blades (and maybe bend the blades or the shaft), plus the cant is now wedged in and it will take a lot of effort to extract the cant from the machine.

In case it isn't clear, I do not like this two circular saw equipment very much.

[backwoods sawyer]

The 42 main saw was ran by a 75hp three phase and the 36 edger saw was ran by a 50hp. This mill is a shop built over sized replica of the mighty mite and was ran two shifts a day and can mill a 14"x16"x40' in one pass. The way it is set up you can angle the main beam from corner to corner and top to bottom at the same time giving you maximum ability to cut to the grain of the log and will mill up to an 8' diameter log 40' long, but it takes two cats to set a log that size. I looked at a smaller mighty mite I believe it could cut 8x10 or 10x12x16'. Where the mobile dimension are really limited to dimensional lumber.

Gene I agree a simple guard that folds down when not in the cut would greatly improve the safety, I simply swung the saws out of the way to do all measurements, as we were either cutting FHC beams for timber frame or CVG from old growth.   Never had an issue with sticking it in a beam but did see some deviation from time to time. Both shifts ran the same edger saw but we each had our own main saws, as well as spares in the shop. Both saws had a continues flow of water to keep them cool, we done a lot of shaving a log down to improve grade and did have an edger saw develop large cracks.

Another thing to consider is build a seperate slaber and just park it at the far end of the beam.



 


 


 


 


 


 

[Ron Wenrich]

The Mighty Mite uses a VW engine.  I believe its 67 hp.  I was around only one of them, and they had major problems with it.  Some of it was due to saw maintenance, some due to design.  These machines were designed to cut mainly softwoods.  I didn't like the way they performed in the oak.  Maximum material they cut was a 12x12.

I don't think they had too much problem with hanging the saws.  But, they would launch boards and cants to the front of the mill.  It was always away from the sawyer.  But, launching any material is a dangerous situation. 

I've sawed millions of feet on a circle mill with a vertical edger.  Its basically the same setup, except you put your log through the edger before it hits the main saw.   The headsaw is the only one that has guides.  Saws hang for various reasons, no matter if its a single blade or multiple blades.  I always felt the design on dimension mills would be better if the horizontal saw was advanced ahead of the vertical saw.  The biggest problem is when a piece falls on top of the horizontal saw.  That will launch material.

Skragg mills are a different setup than a dimension mill. 

[longtime lurker]

There are a lot of questions that need to be answered before you choose a sawmill design to build, such as expected log size, production volume required, will the mill be going to the logs or will logs be taken to the mill,  and product mix - ie are you looking to produce boards and the odd beam, or are you breaking logs down in front of a resaw.

I've spent considerable time looking at the products on the market in the last two years and come up with a few conclusions.

Swingblade mills:
There are basicly 4 manufacturers of any significance, being Lucas Mills, Peterson, Turbosawmill, and D&L Doublecut.
All build a lightweight machine that can be taken to the log. All are extremely good at producing accurately sawn boards in the hands of a skilled operator often at surprisingly high production rates. All can handle large logs beyond the diameter range of portable bandmills, and often beyond the range of a lot of fixed (carriage) circle and band mills too. All can allow for deeper cuts to be taken with less horsepower because of the abilities to take multiple bites in a single plane.
Peterson and Turbosaw both build larger semi stationary models that can be roaded, but achieve increased production through the use of a degree of automation. They have variable speed feeding, hydraulic up and down etc.
D&L do a version that is trailer mounted similar to a portable band with log loaders, turners etc.

Cons with them are that they don't like little logs. I've used one often enough to know that the issue there is not the mill designs per se, but rather the inability to clamp and roll the log during sawing to counteract stress. D&L would appear to be aware of this because they're providing a solution to the problem with the trailer package option.
Also despite the manufacturers claims about "production" there are no serious production machines in them, even the automatics (Turbosaw and Peterson) lack the HP required to get anything approaching reasonable levels although levels achieved per man/day are a lot higher then that achieved on the totally manual versions. I suspect that this is the result of a background where lightweight is seen as better. I for one would be seriously interested in a design with enough stiffness to remain accurate when fed at production speeds, and enough HP to achieve production speeds.

I like them... quite versatile, and there are more then 1 traditional fixed mills in Australia that have one tucked away in the back of the yard for dealing with oversize logs.


Twin Blades:
There are two basic twinblade configurations: North American as represented by D&L doublecut, MightyMite, Mobile Dimension, and Duncan; and New Zealand as represented by Mahoe and Rimu.

The north American designs all have the vertical blade leading and the horizontal trailing. As Ron mentioned this leads to problems as the cut piece can either pinch down onto the blade, or get spat forward by the blade at the finish of each cut.
The NZ designs have the horizontal blade leading and don't have this issue which is a far superior configuration.

D&L, Mobile Dimension, Mahoe and Rimu all build a decent enough product but don't have enough horsepower for quick cutting with both blades at capacity (ie beams). They are however capable of producing a whole lot of standard size dimension lumber quite quickly.  As with the swingmills, smaller logs present difficulties due to needing to be held and turned to reduce stress however the manufacturers all have a fixed deck or trailer package available to deal with this.
I like the D&L for its trailer, but the best mill of this lot in my opinion (and not by a little bit) is the Mahoe.

Mighty Mite also does a regular sized mill compared to its competitors, but it also has a larger variant. That big unit runs a 120HP diesel, which is enough to drive both blades in full depth cuts at production speed. They are a transportable rather then a portable option, but can reduce a whole lot of logs into boards, cants or sawdust in quick time.

Duncan Iron Works builds the most badass kid on the block. It's a monster of a saw running a 50HP three phase to each blade and another to run hydraulics for feed and sizing. It is transportable - but think tractor trailer not a pickup. Duncan will build infeed and outfeed systems and dogging and turning mechanisms to order so it is truly capable of handling logs from 8 inches to 8 feet in diameter. It does have that horizontal blade trailing issue though, and the power bill at the end of a month might be scary. Production mills always have scary power bills IMHO.

[longtime lurker]

Conclusions I reached (got called away before I could finish)

Best man carry mill into jungle on shoulder, carry wood out on shoulder - D&L ecosaw in original format, or Turbosawmill Warrior if you want even lighter.
Regular portable - Lucas 1030. (I have one to back up the fixed mill, I'm somewhat biased)
Best standard dimension (eg 6 x 2) producer - Mahoe
Best as primary breakdown saw - Mighty Mite D1212WT or Duncan Beam Saw

Best mix of ideas: take one D&L style trailer then bolt a Mahoe to it, or a Duncan or 1212W Mite on a float/lowboy if you want primary breakdown. I really like the design of the larger Turbosaw particularly with the push button setworks but even if it were beefed up further it would not produce like a twinsaw can. It can however make a wider cant... out to 24 x 12 which might to some be more attractive then straight up volume. Me I figure I can get one cant that size per log anyway if I can effectively roll and dog it, and my main priority is production.

Look at all of them, then think about what you want to achieve in your build. All of them have differences, and it really is a case of different manufacturers having one thing better then the next guy. Take the best ideas from each and you would build something that's a class leading hybrid.

[nastcat]

First, I would like to thank everyone for their ideas. I am leaning towards a stationary or at least semi-stationary mill. I would like to be able to saw about any size log I come across but, I would mostly be looking at logs 32" diameter on down. Not looking to make production with it, just don't want to take all day to saw up a log. Gene the mill I am contemplating has two blades one horizontal and one vertical. They are perpendicular to each other. I can see where the horizontal should lead so the sawn lumber doesn't drop on the blade. Not looking to resaw mostly want to turn logs into lumber. Would like to be capable of producing a 2x12. so maybe I should be looking at a 32" verical blade and 24" horizontal blade

[Ron Wenrich]

To me, this is about the slickest setup that I've seen.  Maybe you could incorporate some of the ideas here while using a different type of head. 

http://www.youtube.com/watch?v=VcwFwkfTpmE

The operation is run by hydraulics.  The limiting factor here is the size of log it can handle.  Sometimes you can't saw every log you come across.  If you're not having a steady diet of really big logs, then I don't know if I would go the route of designing a mill to cut them. 

[longtime lurker]

I love that Davco... watched the clip about 100 times in the last few years... Put a gangsaw out the back and away we gooooooooo.
Only problems I can see with it is the price... otherwise I'd be all over it like white on rice.

[5quarter]

Sawing with that machine is like printing money...wow.