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General Forestry => Sawmills and Milling => Topic started by: newdesertfox on November 02, 2017, 06:31:54 PM

Title: LT40 aligning sawhead and bed rails
Post by: newdesertfox on November 02, 2017, 06:31:54 PM
I recently purchased and am now learning how to fully run a LT40, was too good of a deal to pass up, 350 hours and 20k lower then listing price. Anyways it cuts great and I've been cutting soft and hard woods but everything was 10' or under. I had an order come in for a 16' oak beam that I cut, but when it was finished I noted that the far side was 8x5 as it was suppose to be, but the close end was 7.75" x 4.75" which was disconcerting. Afterwards I started running longer logs to test and it always comes out the same, middle and most of the time far end are always exactly what I plugged in, but close end if its closer then the 3 middle rails its always off by exactly 1/4 an inch. If I lay a 16' plank down it touches all the rails except the last rail and board return near the operator's end and its just floating over those rails by a tiny amount. So from people with way more knowledge then myself. What is causing that and how to I fix it? its really irking me and Im guessing I need to align the saw head or bed rails but don't know so wanted to ask.
Thanks
Title: Re: LT40 aligning sawhead and bed rails
Post by: Kbeitz on November 02, 2017, 06:38:29 PM
Kinda sounds like your blade is pointed up hill. When you start you'r cut there is no tension
on you'r blade but as it pushes into the wood it raises up. Put a level on your blade if you'r mill
is level and check to see if the blade is also level.

Title: Re: LT40 aligning sawhead and bed rails
Post by: newdesertfox on November 02, 2017, 06:54:54 PM
I checked and according to the level the blade is ever so slightly off pointing down hill. All the runners are the same on the level across the whole bed but the blade reading was a tiny bit off
Title: Re: LT40 aligning sawhead and bed rails
Post by: newdesertfox on November 02, 2017, 07:06:14 PM
https://forestryforum.com/gallery/albums/userpics/46993/Sawmill_001.jpg deck
https://forestryforum.com/gallery/albums/userpics/46993/Sawmill.jpg blade
Title: Re: LT40 aligning sawhead and bed rails
Post by: terrifictimbersllc on November 02, 2017, 07:16:02 PM
This is exactly what happens when I cut long beams and don't pay attention to the main rail being straight over its 20 foot length.

Nothing wrong with the  mill, it is the setup.  It is easily fixed by sighting along the top of the round 26' rail with the head at the far end, in my case it is common to see the rail arching downwards over  1/3 or so of its length, that length being that in the front of the mill.   I  also put the head at the front, and sight it from the back, for straightness, periodically through the day, when long logs, say over 12' are going to be sawn.   Sight it from both ends. 

In my case, since I have fine adjust outriggers, I tighten up the outrigger under the sagging end, for example llifting the rail in front by raising the front outrigger a few turns.   I can feel the nut being loose and getting tight as the rail is jacked up a bit.  In your case I'll bet you'll find, with the head at the rear of the mill, when it is cutting as you say, that the front jack is just a bit loose.  If this is the same as I'm experiencing,  and you dont have the fine adjust outriggers. you'll need to put a shim or some more dirt, you figure it out, under the front foot.  The adjustment will be on the order of 1/4" or whatever you are seeing the beam is off by.

What is going on is that the mill cuts parallel to the bed, but when the bed is curved a little, it is cutting in an arc, because the main rail has a bit of a curve in it, because it is not entirely rigid under the weight of the head going back and forth, that straightness needs to come in part from it being supported firmly by all 4 jacks along its length.  You wont see this usually in 8' lumber but a 16' 5x8 is a prime case for it to start showing up in.

You also won't often easly notice it in 1x or 2x lumber, because those boards lie flat on a slightly curved mill bed, because they're flexible.

Note.  There is nothing wrong with the mill.  The adjustment I'm describing, if that's what is going on for you, is something that is a part of the daily routine in using the mill accurately to cut long lumber.   Don't be alarmed that you can flex that main rail so easily.   It is 26 feet long.  :) :) :)  Also it took me about 8 years of using my mill before I understood this.  ::) ::) ::)
Title: Re: LT40 aligning sawhead and bed rails
Post by: Coltbodi on November 02, 2017, 07:16:15 PM
Try useing a 4' level across 2 bed rails at a time and work your way down the mill like that. But my thinking is it's something more than just the bed out of level like the fella above me said. Since the head runs with the bed it will rise and fall with the bed. So that points to the blade doing something or the head falling somehow. I don't have a woodmizer so I don't know how the head up and down works to know if it's possible for it to fall a tad while moveing do the mill. Maybe try setting the blade over a bunk at one end and measure up to the blade then run the mill down to the other end and measure again, just to rule out the head doing something funny.
Title: Re: LT40 aligning sawhead and bed rails
Post by: Coltbodi on November 02, 2017, 07:22:20 PM
Quote from: terrifictimbersllc on November 02, 2017, 07:16:02 PM
This is exactly what happens when I cut long beams and don't pay attention to the main rail being straight over its 20 foot length.

Nothing wrong with the  mill, it is the setup.  It is easily fixed by sighting along the top of the round 26' rail with the head at the far end, in my case it is common to see the rail arching downwards over  1/3 or so of its length, that length being that in the front of the mill.   I  also put the head at the front, and sight it from the back, for straightness, periodically through the day, when long logs, say over 12' are going to be sawn.   Sight it from both ends. 

In my case, since I have fine adjust outriggers, I tighten up the outrigger under the sagging end, for example llifting the rail in front by raising the front outrigger a few turns.   I can feel the nut being loose and getting tight as the rail is jacked up a bit.  In your case I'll bet you'll find, with the head at the rear of the mill, when it is cutting as you say, that the front jack is just a bit loose.  If this is the same as I'm experiencing,  and you dont have the fine adjust outriggers. you'll need to put a shim or some more dirt, you figure it out, under the front foot.  The adjustment will be on the order of 1/4" or whatever you are seeing the beam is off by.

What is going on is that the mill cuts parallel to the bed, but when the bed is curved a little, it is cutting in an arc, because the main rail has a bit of a curve in it, because it is not entirely rigid under the weight of the head going back and forth, that straightness needs to come in part from it being supported firmly by all 4 jacks along its length.  You wont see this usually in 8' lumber but a 16' 5x8 is a prime case for it to start showing up in.

You also won't often easly notice it in 1x or 2x lumber, because those boards lie flat on a slightly curved mill bed, because they're flexible.

That makes sense
Title: Re: LT40 aligning sawhead and bed rails
Post by: Chuck White on November 02, 2017, 07:45:43 PM
Get a Blade Guide Alignment Tool and do an actual measurement from the deck to the bottom of the blade at each bunk!

Sawmills are not "always" level!
Title: Re: LT40 aligning sawhead and bed rails
Post by: Kbeitz on November 02, 2017, 08:31:26 PM
Use a level with a laser. Put it at one end with it on and take a tape measure and touch
it to the bed and watch where the dot is on the tape. Move down the bed and see if
it changes.
Title: Re: LT40 aligning sawhead and bed rails
Post by: newdesertfox on November 03, 2017, 03:10:32 PM
Alright sounds good, I'll check out/try all the different suggestions and report back. Any suggestions for the best blade alignment tool?
Title: Re: LT40 aligning sawhead and bed rails
Post by: WV Sawmiller on November 03, 2017, 03:38:49 PM
   I like kbeitz suggestion about the laser level but the blade alignment guide is readily available from WM and should be in everyone's sawmill tool box. Use it like Chuck suggests and as described in your WM manual.

   I don't worry a bit about level. I just want my mill straight.
Title: Re: LT40 aligning sawhead and bed rails
Post by: YellowHammer on November 03, 2017, 04:47:32 PM
Quote from: newdesertfox on November 03, 2017, 03:10:32 PM
Alright sounds good, I'll check out/try all the different suggestions and report back. Any suggestions for the best blade alignment tool?
I bought two of Woodmizer blade alignment tools, and clip them on the band at the same time, spread out as far as possible.  Setting height and angle is easier because I don't have to mount and dismount it for each side, but they are also nice to use in pairs because it's easy to see if they both are parallel to each other.  If the band guides are just a little out, you can easily see by eye if they are not lined up with each other. 
Title: Re: LT40 aligning sawhead and bed rails
Post by: WV Sawmiller on November 03, 2017, 06:20:01 PM
YH,

   Very good suggestion (especially for an RT fan :D).
Title: Re: LT40 aligning sawhead and bed rails
Post by: newdesertfox on November 03, 2017, 09:16:25 PM
Thats a great idea on the dual tools, I checked and the front and rear outriggers and they were a little loose (mill has been sitting there for about a month so guessing it sank in a little) so I shimmed the riggers and cranked everything down tight. I checked with a tape over each rail with the blade and currently Im only seeing either 0 or 1/32th of a variety between rails with most being 0 (should have checked them before doing the outriggers >.< ) one thing I did notice though was that when I taped the blade the reading of the blade would be say 3' above deck, while the front of the blade would be different by 1/32-1/16th, and I noted when I extended the blade's 'guide' (think thats what its called) all the way out the blade's height went up about between 1/32-16th of an inch up, and when I watched it visibly I could see when I retracted the guide all the way that it was pushing the front of the blade down ever so slightly wherever the guides wheel was. I did have a blade snap when I was cutting the beam, is it possible maybe snapping the blade caused the guide to be slightly moved out of alignment?  Also thanks the the indepth answer terrifictimbers, I didn't think of it sagging like that cause of how thick the steel is but it makes sense, I just assumed at first maybe there was tension in the log and it was bowing up but the frame sagging makes a lot more sense with how you put it
Title: Re: LT40 aligning sawhead and bed rails
Post by: Dave Shepard on November 03, 2017, 09:21:20 PM
You can make an LTBGAT with a rubber band and a two foot piece of 1/8"x1" aluminum bar stock.

This sounds like atypical case of not having the bed supported correctly. WM wants the weight to be on the two end jacks so the bed is flat when the head goes down the track. Really easy to do once you've done it a few times.
Title: Re: LT40 aligning sawhead and bed rails
Post by: Darrel on November 03, 2017, 11:46:05 PM
When I bought my mill used with 3,000 hrs on it, it refused to cut square, straight or flat, to make things worse, it was about 3/8" off from one end to the other on the dog board.  I shut the mill down and got out the book and went through the alignment process one step at a time and was very meticulous about it.  Now my old ugly mill makes just as purdy lumber as anybody's new one.

If none of the suggestions above solve your problem, I'd do a by the book alignment and see what happens. Takes a little time the first time through but it will be time well spent.