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23rd January 2019, 06:33 AM #16
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23rd January 2019 06:33 AM # ADSGoogle Adsense Advertisement
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24th January 2019, 09:19 PM #17Senior Member
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We tried a 19mm 2TPI blade from Henry's today. The standard guides dont have enough free travel for the guide blocks to completely clear the gullet. I will probably make up some spacer pads to glue to the inside of the block, between the face and the blade to simulate the correct setup. At the moment we are unable to track the blade far enough back to center it on the crown of the adjustable wheel, because of the guide block issue. We still got the machine to cut pretty true, but there is plenty of fettling potential still there
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29th January 2019, 11:22 PM #18Senior Member
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We have now made our own guide blocks from timber. This first set are made from Turpentine and the general consensus of the 5 members testing the machine is that they are as good, if not better than the original steel blocks. Certainly cheap, easy to produce (20min) easier to adjust and easier on the blade. I am making a 2nd set from gidgee, and will also cut a few spare Turpentine guide blocks until their durability is established. They are simply 22mm square, the rear hole is drilled at 1/4" then the corners squared off to hold the keyway slide. The bolt hole thru to the front is completed with a 5mm bit
We found that the guide carrier arms were misaligned on our unit due to the rack and pinion unit being misaligned. This prevented the blade being able to track back far enough. It was rectified by loosening 3 of the bolts on the R&P unit then lifting the outer end of the rack till the channel in the carrier block aligned correctly with the blade.
In tracking the blade we found it easiest to remove the guide blocks from the fixed end, and both the blocks and the carrier from the adjustable end. The blade is then tracked using the tilt knob. We are using Center Tracking at the moment with a 19mm 2TPI blade while we experiment. The other option we are considering is tracking the back of the gullet on the crown.
Once We have the blade tracking where we want it, we install the guide block carrier arm into the rack arm (1 allen bolt )
We then re install the guides. We do the thrust bearings first. There are 3x small shim washers under the bearings to center the bearing on the back of the blade. We removed 1 of the 3 shim washers from the adjustable end to re-align it on the blade.
Next we fit the lower guide blocks on both sides of the throat. These we fitted flush with the blade (ie lift them up till they touch, but don't deflect the blade, then tighten).
Next we fit the upper blocks on either side of the throat. These we fitted with 2 pieces of paper providing the relief from the blade. We simply drop the guides in with the papaer spacer then tighten. This should be close enough to work without too much heat or wear.
The blade certainly cut well today. We slabbed a maximum size log and checked the cut with winding sticks.
Next we will be attacking the dust control, which does not seem very effective in our current setup. I'm a little concerned about the fixed end thrust bearing which cops lots of dust.
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30th January 2019, 10:38 PM #19Senior Member
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A couple more photos to show the setup more clearly
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31st January 2019, 05:02 PM #20
Most types of this style of band mill will not cut right down to the bed. The solution, with hardwood is to rotate the log. The issue will be to hold the log exactly at 90degs for the second cut. I have not looked closely at the holding dogs for this mill. Use a cant hook for rotation. 1.5m of log is easily manageable. After the second rotation you will have a flat surface to sit on the bed for subsequent cuts.
By cutting down a third each time before rotating the log the last 50mm (or maybe more) will be the heart which is useless anyway. This technique will also assist to keep the timber straight and minimise "spring," which will be an issue particularly with small diameter logs that may contains growth stress.
With soft wood you have to pack up the log or accept you cannot recover the last bit. Be careful as 1.5m of soft wood does not have much weight. It needs to be well secured for the last cuts. While not vicious like a circular saw, the bandsaw may still want to grab the timber.
Regards
PaulBushmiller;
"Power tends to corrupt. Absolute power corrupts, absolutely!"
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1st February 2019, 08:43 PM #21
OH
Just re-read this post. If the log has growth spring try cutting and then flipping 180degs. Keep doing this. It won't totally remove the spring but may minimise the issue. I was once told that to eliminate the problem you need a twin edger so that both sides of the timber are cut at the same time, but never having used one I can't comment on the success of that machine. Also I have no experience with Paulonias so I can only guess. My comments about being careful with the last cuts are particularly pertinent with a light species such as Paulonia.
John.G may have more experience with edgers than I.
Regards
PaulBushmiller;
"Power tends to corrupt. Absolute power corrupts, absolutely!"
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2nd February 2019, 09:27 AM #22Senior Member
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The big problem with log rotation with most of our Paulownia logs is turning a 6M long 900mm diam log! Getting it onto the mill is hard enough but turning it 20 times sounds like torture! But it may just solve the log tension problem so we may have to work out how to do it mechanically.
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2nd February 2019, 12:52 PM #23
OH
I am a little surprised that a log 900mm dia would have much of an issue with growth stress. However, I have had almost nothing to do with Paulonia species (I believe there are many species actually under the name, in the same way Meranti is not a single tree and to a lesser extent Tasmanian Oak) other than failing miserably trying to grow about six of them more than twenty years ago. In this regard I am a complete charlatan. Perhaps they are extremely fast growing and this causes significant stress.
However on the subject of rotating the logs and assuming your mill set up has no hydraulics for rotation, this thread may be of interest:
A winch for loading logs
In post #6 I show a Spotted Gum log which at 6.6m and around 700 - 800mm dia would have approached three tonnes. I have to say it was a battle with limited resources and operating by myself. However, your log would probably weigh only half that and while 1.5T is a significant weight it would be a little more manageable. The rotation of the log with a 4WD winch makes life easier for both rolling onto the mill bed as well as rotating. For me the biggest issue was positioning the log alongside the mill as I had only a very ancient tractor. That was a one off milling size, but if I was milling those size logs on a consistent basis I would set up rollers or at least a series of pipes so the log could be dragged more easily.
I would look closely at a device to position the log at 90 degs to the first cut and indeed line up the log in the best position in the first instance. Also pay careful attention to the system of dogs to keep the log in position on the mill.
Regards
PaulBushmiller;
"Power tends to corrupt. Absolute power corrupts, absolutely!"
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2nd February 2019, 03:53 PM #24GOLD MEMBER
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Turpentine is a very abrasive timber when used as guides. May I suggest Forrest Red Gum or Ironbark.
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2nd February 2019, 04:31 PM #25
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2nd February 2019, 07:26 PM #26GOLD MEMBER
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Yes Chris, partly so, but even when turps has a low silica content the timber remains abrasive when placed in contact with moving metal. Forrest Red or Blue gum as it is known in QLD, was the timber of choice for windmill bearings. Ironbark was exported from Australia to Scandinavia for cladding on the bows of steel hulled ice breakers. Reason? It became smoother with abrasion rather than hair up or bruise which is what other timbers and, for that matter, steel would do. At the time, when the ship builder told me this during his initial enquiry, I was somewhat sceptical. Upon visiting Scandinavia shortly after supply I got to see how the timber was performing. The Ironbark was as smooth as glass.
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2nd February 2019, 10:23 PM #27Senior Member
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Just as a matter of interest, I have made up some Gidgee blocks out of a piece we had lying around. Any opinion/info on how Gidgee performs?
As it happens I have some correct dimension Iron Bark in my box of future knife scales and some forest Red Gum, so I will make up half a dozen blocks to test them out. Always good to have spares in the cupboard. I will see if I can locate some Blue Gum in the shed.
Thanks for the explanation
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3rd February 2019, 06:55 AM #28Senior Member
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- NSW
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I must admit that we are novices at this milling game. While I have spent time around local hardwood sawmills, these Paulownia trees are different in many respects. We are trying various techniques when we are milling. We have some logs that have been racked under cover for 4 years now so they should be "seasoned" somewhat more than the other logs we have sawn in the past. We were being a bit lazy, trying to saw the logs without rotating them but I agree, it's worth a try! Thanks for the advice.
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3rd February 2019, 07:02 AM #29Senior Member
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Regarding bandsaw guide blocks, how about Tallowwood? It seems to be "greasy", even when dry. I used it as bearing blocks for a gemstone tumbler years ago and it worked well with little wear to either the wood or the metal shafting.
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3rd February 2019, 08:22 AM #30
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