Thread: BIL Mill Upgrade

Looks great Bob.

Let us know what you come up with for the bar sag, I was going to use a ply J board (based on Aggie's design), but I would prefer something better. On the pro set-ups they pretension the bars, by using the bolted bar like yours, perhaps you can tension off the frame. I don't think that would work with mine, as I think the clamps would slip.

Cheers

Originally Posted by dai sensei

Looks great Bob.

Let us know what you come up with for the bar sag, I was going to use a ply J board (based on Aggie's design), but I would prefer something better. On the pro set-ups they pretension the bars, by using the bolted bar like yours, perhaps you can tension off the frame. I don't think that would work with mine, as I think the clamps would slip.

Cheers

Thanks Neil. I tried pretensioning the frame and picked up about 0.01" but I don't think my single 25 x 3 mm ally tube outboard leg could take the sort of sideways tensions that the dual leg steel framed mills can create to eliminate the sag. I worked out I only need a 2.5 kg upward force to remove the sag and think I can do that with a swinging underarm lever. Am seeing BIL about it tomorrow.

Hi BOB

you have to much time and recources.

Love your ideas though, i am jelous.

JAMC

Originally Posted by BobL

As hinted in some previous posts the BIL Mill is being adapted to take a bigger bar.

I have replaced the current rails with longer rails and added an additional cross rail.


I added an extension to the top lengthwise ally tube handle. Since this handle is not as critical as the rails, carrying an extension takes up less space than carrying a whole spare tube.

It was very simple to lengthen the mill and is something that could even be done on the job if the other bars, chains and rails are available. Takes about 10 minutes to switch between bar lengths.

Here is a comparison with the existing 42" bar.


As reported elsewhere the "bar sag" is significant, 0.09". In this photo I have place an old ally rail on top of the bar and the gap between the bar and the rail represents the sag.

I'm working on a BIL Mill grade antisag bar device. BIL has some wild ideas which we are working on.

I have posted a similar picture elsewhere but am adding it here for completeness.

The 60" bar is a roller nose where as BIL Mill 1 outboard clamp could only handle a solid nose. The clamp has been modified with a 1/4" tensile steel bolt thru the centre of the roller nose. The clamp has steel jaws with a slot cut in it that the head and nut of the nose bolt can slide in when adjusting the chain. When complete the clamp locks the nose bolt and bar in place. I have modified all my bars to accept this arrangement.

Cutting length is 59.5"
Weight is 33 kg with a fully fueled and oiled 076. A bit more than I thought it would be.
Not exactly a light weight but I can still lift it OK.

I'm not happy with the "dump some oil on the chain" aux oiler delivery arrangement so I'm working on that at the moment.

Bob some help and advice if you could spare some, in a previous post you've mentioned that you adapted your mill to suit a GB sproket end bar, did you say there was a hole in the bar tip that you mounted the bolt through, on an oregon bar with a sprocket end you rightly mentioned the compression on the tip would fail the spocket , there is no hole in the tip, any suggestion how I could mount my bar right at the tip to maximize cutting width without compressing the sprocket,

395xp and 42" oregon sprocket bar with oregon semi chisel milling chain.

Shayne

Hi Shayne,

A hole in the nose allows you to bolt the bar direct to the mill or a number of other designs.



In a conventional mill the bolt nose bar clamps are more like A andB.

In A, the big green bolt goes right thru the nose and with suitable spacers/washers holding the nose (sprocket) away from the clamp. This is much safer than a conventional design since the bar cannot move in the clamp and if you forget to tighten the black bolts the bar won't slip and collide with them. The black bolts are in fact redundant and I have seen mills with only the top part of the clamp and just the green bolt (ie no bottom part of the clamp or black bolts) and the green spacers .

An alternative is B: This uses the existing clamps of a conventional mill but the clamp now grips onto the nose bolt rather than direct onto the bar. This is not as safe as A:

On my mill (C I put a 1/4" green bolt through the bar nose - I then clamp onto that bolt. But I can't fix my nose hard onto the clamp since my bar nose needs to be able to slide back and forth when I adjust the chain so that is why I have slots in the clamp for the nose bolt to ride in. When I adjust the chain I have to undo the black bolt, adjust chain and retighten black bolt.

The advantage of this type of clamp is it does not expose the end of the bar so I do not need a guard.

Now about drilling the bar holes
*************************

My 42" GB hardnose & 60" GB roller nose bars came with holes in the nose.

The 42" GB sprocket nose did not and I had to drill the hole. It does not need the hole but I drilled one for practice.

I also bought a 42" GB Sprocket nose - no hole in the nose. I wanted to do this right although the nose was replaceable so if I stuffed it I would not lose everything

I already had a 24" Stihl Sprocket nose bar with a tight sprocket that I picked up out of a skip! and was given another identical bar that was a bit bent so I figure I had nothing to lose by drilling the bent one first. I used a new carbide bit (Masonry bit) that I sharpen using a green grinding wheel so it has a decent edge - I just used the same profile as the masonry bit. I used a drill press on a slow rotation (240 rpm) with plenty of coolant and a lot of pressure. It some took time and made a big burr that I removed with a HSS bit.

See as that was successful I tried the second 24" bar. Firstly I loosened it up using alternate washing of CRC, machine oil, and metho and turning the sprocket until it loosened. Then I drilled the hole. I must have pushed it a bit hard because about 2 mm into the hole the carbide bit just crumbled. I finished that hole using a second used masonry bit. Once it had just punctured thru I turned the bar over and drilled from the other side to avoid the burr. This worked well although the sprocket did retighten and I had to use the CRC/oil/metho was again, I think some swarf must have got caught in the bearing.

I then felt confident to try the new 42" GB Sprocket nose. For this I used a cobalt alloy bit, slow speed high pressure lots of lube and it got through about as fast as the carbide bit. Even though it's twice the price of a masonry bit a big advantage over the carbide is the cobalt alloy won't shatter. This worked fine.

I also used the cobalt bit to drill new chain tension holes for the 60" GB Bar since the existing holes do not give optimum chain tension range for my power head. I resharped the bit and This was quite easy and I even got a couple of curlies during the drilling. I don't think the inboard end is as hard as the nose end of most bars.

I have now drilled lots of holes for aux oilers and nose bar bolts in GB, Stihl, Oregon and other bars, The Stihls are significantly harder than all the other bars, it's easy to see this just using a centre punch.

So in summary, new or freshly sharpened cobalt bit, lots of lube/coolant, low RPM, high pressure should get you through.

Thanks a heap the other issue I'm having trouble reconciling due to lack of sleep, is a bolt throught the tip, fouling the sprocket how you get around that.

Shayne

From what I can tell the following are the internal designs of Stihl, Oregon and GB sprocket and Roller noses.



The top one is the sprocket nose while the bottom is a roller nose. The dark green sprocket teeth are oriented 90º to the way I have shown them in the diagram - I have drawn them this way for simplicity and their orientation does not change the rest of the design or my line of argument.

The grey rectangles are the roller bearings. In the centre of the sprocket or roller is a solid, hard piece of steel which is held in place by rivets or welds (dark blue in the diagrams) - there are usually 6 rivets. It's at this point you can drill a hole and put a bolt through there (as per the Orange Bolt). You can squeeze down on this centre piece all you like - it won't upset the bearings.
BUT
If you start squeezing down outside the ring of rivets you may freeze the bearings and it will be all over. You will never recover proper movement. The amount of space available varies and some people have drilled 3/8" holes there and gotten away with it. I found a 1/4" tensile steel bolt has a enough strength to do the job.

Some people use a 3/8 bolt and narrow washers or spacers to keep the nut and/or bolthead away from the bearing space. Sometimes the rivets are quite proud and the centre of the circle they prescribe is a natural location to place a round clamp in between the rivets, I wouldn't like to miss though!.

I hope that clears it up! It took a while (couple of months) for me to work all this out.

I should add that I do not know how Husky bar noses work.

Originally Posted by BobL

From what I can tell the following are the internal designs of Stihl, oregon and GB sprocket and Roller noses.



The top one is the sprocket nose while the bottom is a roller nose. The dark green sprocket teeth are oriented 90º to the way I have shown them in the diagram - I have drawn them this way for simplicity and their orientation does not change the rest of the design.

The grey rectangles are the roller bearings. In the centre of the sprocket or roller is a solid nard piece of steel which is held in place by rivets or welds (dark blue in the diagrams). It's sat this point you can drill a hole and put a bolt through there (Orange Bolt). You can squeeze down on this centre piece all you like - it won't upset the bearings.
BUT
If you start squeezing down outside the ring of rivets you will freeze the bearings and it will be all over. You will never recover proper movement. The amount of space available varies and some people have drilled 3/8" holes there and gotten away with it. I found a 1/4" tensile steel bolt has a enough strength to do the job.

Some people use a 3/8 bolt and narrow washes to keep the nut and/or bolthead away from the bearing space. Sometimes the rivets are quite proud and provided a natural place to place a round clamp in between the rivets, I wouldn't like to miss though!.

I hope that clears it up! It took a while (couple of months) for me to work all this out.

I should add that I do not know how Husky bar noses work.

Bob that is perfect I'L yet you know how I go

Not wanting to hyjack the thread, but I have just about finished a version of a rail mill with the chainsaw standing up vertically. A comment I have seen is that with all the clamping of these mills on the bar, is that the power head is really unsupported.

I have been trying to design a mount that takes the weight of the power head so that no undue stress is put on the bar at the point where the motor is bolted onto the bar.

My questions are, is this really an issue ? is the bar / mount bolts strong enough to take the vibration ? or should the power head always be supported ?

Not having seen a slab mill up real close, it appears that the motor has even less support when it's in a lay down configeration, & maybe in a vertical configeration it might be OK

In general the weight of a CS engine is not really an issue with clamping the inboard end of alaskan mills direct to the bar.

With very heavy chainsaw engines such as (Stihl 088) this may become a problem when using thin short bars, since the weight of the engine will make the bar bow upwards slightly in the middle. When the bar gets longer, from about 30 up to about 60", these forces (or more specifically "torques") cancel each other out as the bar itself wants to sag downwards.

The main problems with Inboard clamping the mill to the bar (especially without removing the dogs) is reduced cutting width and poorer balance, since the CS engine is just hanging out in the breeze.

There are already alaskan mill designs (such as mine) that bolt the inboard part of the mill direct to the bar bolts.

There is also a large Granberg mill that operates in the same way.
This is Sawchain's mill - I pretty sure it's a Granberg


The major advantage of bolting the mill direct to the bar mounting bolts, instead of the bar, is improved cutting width. Also the saw cannot twist in the mill and so the chain cannot contact the clamp bolts.

Another way is to connect the mill to the bar is to forget about clamps and drill holes in the bar and bolt the bar to the mill.

The horizontal and vertical layouts have their pluses and minuses. When slabbing I like my sawdust to exit the saw below the cut - a vertical saw sprays the sawdust all over the log you are trying to saw and can get in the way of log rails - a suitable deflector can reduced this effect. I'm still going to make a vertical mill though - a 12" one, that bolts to the bar bolts and turn slabs into lumber.

Well I said BIL was working on a different antisagging bar devices and here is prototype A - of plan 3.

The idea is to use something to stop a long CS bar from sagging as the cut is started- once the bar is half way into the cut the bar will stay level and the antisagging device can be removed. The typical thing used is a wooden or plastic hook or lever that can be removed easily. The awkwardness comes in that a fixed length hook only works for one slab thickness and one needs a variable length hook for the different slab thicknesses.

Here is the gismo.

It's basically a magnet attached to the end of a bit of allthread which is bolted to the mill cross rail.

The magnet is from an old hard drive so it is incredibly strong. I just drilled a couple of holes in the supporting steel surround and bolted it to a piece of square ally tube.


Here the magnet is lifter well above the bar and shows the biggest gap between the bar and a straight bit of ally laying on top of the bar. The gap is about 2 mm. Interestingly it's not in the middle of the bar, its closer to the nose of the bar as the bar bolts help hold the inboard section of the bar level.


Here magnet is attached and wingnuts are adjusted to remove the gap.

The magnet is strong enough to lift the bar out of shape upwards by about 10 mm!

By turning the wing nuts on the all thread the height of the magnet can be adjusted to accommodate different bar heights ie different slab widths.

Of course the proof will be in the actual cutting. A couple of refinements will be needed, one is a quick release mechanism to remove the antisag device once the bar has established the level cut.

Bob, thissag is an interesting factor that I had not considered but the more i do consider it the more questions raised.

1. Does the bar stay sagged when the saw is running or does the movement of the chain around the bar lift it back?
2. If even when running the bar sags,it would be my expectation that after cutting the first 30cm or so of log the bar would have sagged back to it's orginal unsupported arc. I would think that the bottom teeth would slowly etch out the log rather than the cut supporting the bar flat. It will be interesting to see if this is the case or not.

Mill is looking good, can't wait to see some of the big slabs you will be able to cut now

Cheers,
Mike

Originally Posted by Burnsy

Bob, thissag is an interesting factor that I had not considered but the more i do consider it the more questions raised.

1. Does the bar stay sagged when the saw is running or does the movement of the chain around the bar lift it back?
2. If even when running the bar sags,it would be my expectation that after cutting the first 30cm or so of log the bar would have sagged back to it's orginal unsupported arc. I would think that the bottom teeth would slowly etch out the log rather than the cut supporting the bar flat. It will be interesting to see if this is the case or not.

Mill is looking good, can't wait to see some of the big slabs you will be able to cut now

Cheers,
Mike

I tend to agree with Mike on the two points above and its along the same lines as why badly sharpened chains make straight chain bars cut curves. it starts out straight but slowly or fast, the bar cannot compensate for the unidrectional pull on the sharp side and the drag on the blunt side.

I think pretensioning the bar so that unsupported, it will sit as level a you wish to tolerate then factor in chain weight, and its tension, then the effect heat will have on the above, and then GRAVITY, then retension everything until you achieve the tolerances your happy with.

I Think someone elso mentioned pretensioning concrete bridge girders to attempt to cancel the gravitational effect on the mass of the beam to attempt to achieve the flatness they are affter

Thats what I'm going to try. I see if it works.

Shayne

I have no direct experience in bar sagging with long bars, I'm just going on what I learned from some very knowledgeable millers on other websites.

Firstly the bar sag remains even when the chain is running.

It's perhaps surprising but if the cut is started with the blade straight, the cut will remain straight even when the support is removed. This has been clearly demonstrated with very long bars (96") where the sag is huge! This is supposedly because the bar is supported a little bit all the way along the bar. I will however feel more comfortable about it when I try it and see this for myself. I have been told that even the bar starts out sagged it can even correct itself to some extent but how long it takes down the slab to do this varies depending on many things.

The way the bar is usually supported is using a large C-section clamp made of plywood or plastic, When the bar is about half way into the cut the clamp is removed.

To use sideways tension to reduce gaps requires very high side tensions and it never completely removes the sag. I worked out that on my setup about 300 kg of sideways tension is needed to reduce the 2 mm gap to 1 mm and 600 kg of side tension to reduce it to 0.5 mm, 1200 kg is needed to get it to 0.25 mm etc. Even though this is what is done for shorter blades I don't think tensioning a mill/bar up to this extent is a good idea especially if it is not needed. I haven't measured the sag on my 42" bar but will do so tonight.

Anyway , as I said the proof will be in the cutting.