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Author Topic: LT40 mill problem, chattering blade in wide cuts  (Read 5969 times)

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Offline Kelvin

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LT40 mill problem, chattering blade in wide cuts
« on: February 21, 2009, 09:22:52 AM »
Howdy all,
Well i'm still working on my new used LT40.  It does something i'm not familiar with.  When i put a newly sharpened and set blade on the mill it acts like the blade is catching and snapping back against the bearing guides.  This is a '94 LT40 with standard top support only bearings, and the bearings are rebuilt.  It seems as the blade dulls a bit the catching goes away, but its certainly evident in cuts wider than 12".  I've got modest set, maybe .20 each side and 9 degree blades.  Same i used on my old woodmizer so i'm pretty sure its not the blade itself.  maybe something to do with some twist in the alignment of the two bearings?  Not enough down pressure on blade?

One big problem i'm having that may be the source of my above problem is in the support blocks on the head that travel up and down the vertical rails.  Manual says leave a gap the thickness of business card on one side.  Well when i got the mill they had about 1/4" gap on the pads, maybe 3/16".  But as i adjusted them to the manual specs the head binds at the bottom so i've had to keep opening them so the head will go up and down.  Somehow it seems that the pads are tight on the bottom and open up as they travel up.  So in order that they don't bind at the bottom they have to be pretty sloppy up above.  Feels like the two rails are bowed in the middle.  I'm not sure what i could do about this, but i've only worked on it a few hours.  I may have another go around on trying to find a secret mix between the top pads and the bottom pads tightness at different points to see if i can find some solution.  I'm wondering if this is where the "catching" might be originating?  What do you think?  Where to look?  I could see that the wide cuts with sharp teeth and wide set would twist the head in the sloppy pads a bit? 
Any help appreciated,
Thanks
kelvin

Offline Kansas

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #1 on: February 21, 2009, 04:56:59 PM »
This is a long shot, but I wonder, if the problem goes away when the blade dulls a little bit, do you think it could be too much hook angle? I'm guessing if your in michigan, the logs are probably frozen. If the blade dulls slightly on the tips, that would reduce the hook angle. Might be worth a shot to back off the hook angle a bit and see if it corrects the problem.

Offline Kelvin

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #2 on: February 21, 2009, 08:30:38 PM »
I've been sawing for a number of years with the same blade under the same conditions.  This has to be something with the way the mill is set up.  anyone have anything similar?
Thanks
kelvin

Offline Tim/South

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #3 on: February 21, 2009, 08:48:56 PM »
Could it be the angle of the blade guides?
The band me be finding a "better" alignment once the blade has begun to dull and is flexing more between the roller guides.

I am not claiming to know a lot about this, just mostly thinking out loud.

Offline Tom

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #4 on: February 21, 2009, 08:53:28 PM »
might be time to buy another blade, Kelvin. They don't last forever.  :D
extinct

Offline Lud

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #5 on: February 21, 2009, 11:21:34 PM »
Kelvin, you talked about possible bowing........mill may have been roughly used by unknowing staff??   

Have you measured?  ID to ID and OD to OD?  You could possibly make a "story stick"  to slide up and down and verify your theory.

Straight edge along the rails too.

If the rack's not square you'll have a tough time achieving consistancy. ;)
Simplicity mill, Ford 1957 Golden Jubilee 841 Powermaster, 40x60 bankbarn, left-handed

Offline BBTom

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #6 on: February 22, 2009, 07:30:48 AM »
I have the same problem (uprights bowed in at the middle) and it is a pain trying to set up the wear pads.  I got mine close enough and quit worrying about it. 

Is your belt tight enough?  Do you have less power on this mill? On wide cuts in some woods the blade will "chatter" when you do not feed fast enough to keep the teeth cutting "curls".  If your belt is loose or you don't have enough power, your feed rate is slower and the problem shows up sooner. 
2001 LT40HDD42RA with lubemizer, debarker, laser, accuset. Retired, but building a new shop and home in Missouri.

Offline Kelvin

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #7 on: February 22, 2009, 12:07:37 PM »
Good ideas guys.  I'll check some of these theories out.  I should have measured the uprights.  I'm sure they are bowed in the middle.  I do believe it does have something to do with the guide angles as well. Might be a couple of things together.  I made a homemade alignment tool and aligned the guides.  The inside guide was broken off someone how and welded back on by a 3rd grader, so i had the guide to its maximum setting to achieve what i thought was level with the deck.  That is when the snapping started, so i backed off the setting and thought i got rid of it, but it might have been that the blade dulled enough to stop by itself.  Doesn't take many bd ft.  I had thought of a feed rate problem.  I think this motor is more powerful than my gasser but might be hopeful thinking.  THey are close if anything.  Hard to tell as it doesn't bog down like the gasser would.

The bands are the same across the spectrum.  Its not just one band.  But i haven't had it long enough to establish much of a pattern yet.  I just was hoping someone had gone through something similar.  By snapping i don't mean breaking by the way, i mean chattering.  I hope that was clear.  It sounds like it "snaps" back against the bearing or something.  Could be the blade finding its own course than snapping back.  Sounds good theory to me.  I'll check things and keep trying. 

Anyone else have similar condition?  I'm always the first.  On the cutting edge!
Thanks
kelvin

Offline Lud

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #8 on: February 22, 2009, 09:29:26 PM »
When you say "snapping"  I think of "slapping" ,  i.e. looseness.   Have you checked tension? 

Let alone fluctuating tension when things are not the same distance apart.  Good Luck !
Simplicity mill, Ford 1957 Golden Jubilee 841 Powermaster, 40x60 bankbarn, left-handed

Offline LeeB

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #9 on: February 23, 2009, 10:42:12 AM »
Only time I get something like that is when I have too much set.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, JD 3032 tractor, JD 5410 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Offline Kelvin

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #10 on: February 23, 2009, 01:14:00 PM »
Yes, this is what it feels like, but i've been setting the bands the same as my other mill and its not too much.  I would say its underset for the width.  I think they suggest something like .024 for cuts wider than 12" and i'm doing .020 but my setter is pretty mangled, might be the error.
KP

Offline sparks

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #11 on: February 23, 2009, 04:03:47 PM »
Remember you are not adjusting all the pads. When you raise the head to 32" you are looking at the pad on the loading side top right. This is the only pad you set the gap on. Then you lower the head to about 7" and you are check the pad on the sawdust chute side the pad on the lower right. Here is a copy of the adjustment procedure.   Thanks all
\"America will never be destroyed from the outside. If we falter and lose our freedoms, it will be because we destroyed ourselves.\" Abraham Lincoln

Offline Kelvin

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #12 on: February 28, 2009, 05:52:13 PM »
Howdy,
Just wanted to update i solved some of the problem.  I just started sawing softer wood!  No, i'm kidding, though i haven't tried the big white oak yet.  I think i got it though.  In adjusting the mill somehow i had the inside bearing with too little down pressure.  Maybe hardly any.  I followed the instructions and deflected down 1/4" same as outside bearing.  Seems to be much better.  I guess they say you can trace most of these problems back to poor alignment.  Guess they are right.  My guide rollers might be worn into a cone shape as well.  I'm sure there is more than one thing going on.
thanks for help,
kelvin

Offline woodmills1

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #13 on: March 01, 2009, 08:26:45 PM »
can you tell if the rollers are old style

the early ones had a cover that would fall off and the ball bearings would fall out


the newer ones are closed and are much better wearing all around
James Mills,Lovely wife,collect old tools,vacuuming fool,36 bdft/hr,oak paper cutter,ebonic yooper rapper nauga seller, Blue Ox? its not fast, 2 cat family, LT70,edger, 375 bd ft/hr, we like Bob,free heat,no oil 12 years,big splitter, baked stuffed lobster, still cuttin the logs dere IAM

Offline Kelvin

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #14 on: March 02, 2009, 03:30:48 PM »
I replaced the bearings when i bought the saw.  Pressed in.  Doesn't look like they could fall out so i'm not sure if these are old style.  Pretty old.  I'm wondering if they are wore into more of a cone, but oh well.  Let sleeping dogs lie?
thanks
kelvin

Offline backwoods sawyer

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #15 on: March 03, 2009, 04:09:35 AM »
If your roller guides are tapered, change them out. It will save you a lot of grief. Even if you set the tapper to the saw they will cause friction because the front part of the roller is smaller then the back and as it turns it will have to slip on the saw rather then just turning freely. If you know someone with a metal lathe that does not mind wearing out a carbide cutter, they can turn them down for you. However, honestly they are cheaper to replace.
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Online pineywoods

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #16 on: March 03, 2009, 08:20:46 AM »
Re tapered guide rollers

Mine were tapered just a few thou. Tried to turn them back flat. Carbide lathe bit just barely scratched the surface. Used a tool post grinder to cut them back flat. Made a world of difference.
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Offline backwoods sawyer

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #17 on: March 04, 2009, 12:11:08 AM »
stone will cut them better then carbide.
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Offline customdave

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #18 on: March 04, 2009, 11:02:55 PM »
Pineywoods
    If you have a tool holder for carbide inserts, pickup a ceramic insert great for machining hard metal , sounds crazy but works! You can machine a bearing race with ceramic fine cuts & slower speeds. Have to be gentle with ceramic, I have used quite a bit on lath & milling machine in my shop.



                                     customdave
Love the smell of sawdust

Offline MartyParsons

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Re: LT40 mill problem, chattering blade in wide cuts
« Reply #19 on: March 06, 2009, 06:10:11 AM »
Just a little input. You can grind them down and that is ok. Just a note is that the roller surface is hardened on the out side and you grind the hardened surface off. I am not sure how thick the hard surface penetrates but it is something to think about. On an normal operating mill you should replace the rollers at about 1000 hours. The more the blade comes in contact with the back of the roller ( those of you who push the mill to the max. or the roller to blade spacing was not set correctly ) This hour may be a little less. If this flange is grooved ( like the roller was stoped and the blade kept rubbing in one spot) it cuts a line on the flange. When the blade catches in this grove it will make it bend and break the back of the blade. I have used a grinder and smoothed this groove out.
When servicing a mill I always look at the ridges on the roller they should all be about the same depth. It will wear on the outside first. So if you cant see the first ridge on the gullet side of the roller it's time for a new one. Next time you get a new one out of the box hold the new roller nose to nose to the old roller and you can see how much wear is on the old one.
M
A pessimist sees difficulty in every opportunity; an optimist sees opportunity in every difficulty. -Winston Churchill


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