Blade diving on beginning of cut?

[pri0ritize]

Hello all,

I'm finally getting around to doing a decent amount of milling. Put about 10 hours on the mill in the past few days (up to a grand total of 28!) and I'm noticing that most logs end up being 'tapered' but not exactly. The best way that I can describe it is that when I sticker and stack the 1" boards I'm making the start of the board where the blade entered the log is not quite as wide as the rest of the board. Anyone have an idea of how to combat this? If I haven't described it quite right I'll see if I can't post some pictures up tomorrow of the phenomenon I'm talking about.

Thanks!

[beenthere]

Pics will help.  8)

This a band mill?
Do you edge on the mill?  And when you say "not quite as wide", is that in thickness (not in width) ?

Have you adjusted the mill to specs? And this happens with a new (or recently sharpened) blade?
Tension settings up where they should be?  Do you start slow into the cut?  Sawing what species, and do you cut small end first?

Just some questions that come to mind, from reading other posts about what sounds like a similar problem when entering the cut on the log.

[pri0ritize]

I was referring to width but I'd wager they are slightly less thick near the ends as well. Bands are adjusted to suggested tension. Saw is a brand new LT40HD. I do start slow into the log. I'm using Woodmizer bands (.035 1.25" 10°). It could be that this only happens when the blades are getting dull. I'll pay more attention tomorrow and see if that is the issue.

[highleadtimber16]

I had this when I first started milling. There is two causes. First make sure that the ends of your cant are not lifting on both ends when you cut it this will cause it to be, Ex. a perfect 6" in the middle and 5 7/8" on each end. Second if your cant is laying flat then check your mills levelness. This also got me as I was setup on top of clay. Hope this helps!

[ladylake]

 
The way you describe it your blade is rising with the ends being a little narrow, A rising blade is real common. the biggest reason is its dull, wrong set, blade tilted up slightly . Shouldn't you be running at least .42 blades on your mill, that might help. Also maybe try some 7 or 4° blades.   Steve

[rimshot]

I believe also that the culprit is the blade.  I had that happen one day when cutting wet eastern White Cedar.  I was preparing a cant and the blade was cutting through several cuts close to the outside in the bark area.  There was a white fuzz accumulating on the tip of the blade causing the blade to act very dull.  I took time to clean up the tips and sap and was back to work in no time.

rimshot

[thecfarm]

I sure don't know what I am doing when it comes to sawing,but I go into the log the same speed as halfway through. Wide open,full throttle,on my mill.

[millstead]

check your drive belt a loose belt will allow the blade speed to slow down and let the blade rise

[Bibbyman]

check your drive belt a loose belt will allow the blade speed to slow down and let the blade rise

Ditto. 

New mill, new belt. Time to check and adjust drive belt tension.

[Happycamper]

Increase blade set a little.
                     Jim

[hunz]

This exact same thing happened to me a few months back. If it isn't just the butt logs then it is most likely a blade alignment problem(in my opinion). There are a lot of factors that can cause this as others have mentioned above. For me, it was my band wheels not being exactly perpendicular to the bed. My idler wheel was tilted up slightly causing a slight raise up when entering logs, but then the cut would straighten itself out. I'm not sure if this is your exact issue but thought it sounded similar.

[Bibbyman]

Another thing to look for is logs with dry ends.   If a log had been around over a few months the first couple of inches are very hard.

[Finn1903]

I had the same thing happen to me on white oak.  My blade already had sawn some b.f., so I changed the blade and checked the alignment, also think I slowed down a bit.  This corrected the problem.
I am not sure how fast your should enter the log and saw, but I notice when I go fast, and have knots the blade dives on me.

[pri0ritize]

Thanks for all of the help so far. When I get home from work I'll make sure to verify the belt tension and check my alignment. The logs have been down for a considerable amount of time. Some of them up to a year and a half. I'm sawing 99% Doug Fir. I've got Woodmizer blades and Cooks blades. I've also got a few Woodmaster C-Sharp blades that I'd like to try but they are 1.5" and I believe I need 1.5" roller guides for those. Is that the case?

Thanks again!

[ST Ranch]

P-O-T  - I cut a lot of Douglas fir, both green and dry on a woodmizer LT40 with .045 by 1.5  - 10° blades.  Bibbyman is correct about dry ends being harder and if the blade is getting dull it will sometimes cut offline.
Also I find that a lot of Douglas fir- especially dry belt fir [grown in the more open grassland ecosystems with Ponderosa pine] often have compression wood [uneven growth rings from one side of the tree/log to the other]. Also many trees that grow on hillsides [especially in snowy mountainous areas] can have compression wood.
I find it best to turn my cant regularly 180° when sawing [cut a couple boards and then flip the cant 180°] and then cut a few more and flip again if required. - This relieves the stress which often causes the cant to bow during sawing.

In terms of changing to 1.5 inch blades, my understanding is you do NOT need new guides, but rather you need to adjust yours back by ¼ inch to accept the wider blade.

Hope this helps and good luck.  Tom

[Tom L]

believe the manual says to retighten drive belt after 5 hrs then check it every 50 hrs

you can run 1-1/2" on the same guide rolls, I only adjust my guides back 1/8" to center the blade on the wheel and saw away.

[hunterbuild]

I was having the same problem. My blade would dive about 8th of an inch in the first two inches than cut true for the rest of the board. Because it was so little I just cut it off as the rest of the board was good. Then it started getting wavy cuts. I Finely admitted I needed to learn how to set my guides. It turned out to be easier than I thought. Good information here on that. Wow what a difference. Learn your guides, take it apart study it and put it back right. You will be amazed.     

[JustinW_NZ]

Others have already said all you need to know but just to add - I've Just been through some of this with some very hard stuff as well, and adding more set on the bands did work for me along with one guide that was a little out.
It appeared like it was not one individual thing, but two small ones meant a world of pain...

Cheers
Justin