Blade "push down"

[woodhick]

Getting ready to cut some dry timbers and from past experience I have had trouble with wavy cuts.  I posted about this a couple days ago and thanks for the responses.  I checked my mill alignment over and my guides are only "pushing" down about 1/8".  I know woodmizer use to call for a 1/4".  My guides are the single roller type with nothing on the bottom.  I'm planning to upgrade to the bearing type with a bottom pad but time and money don't warrant that yet.  Just wandering what amount most of your mills are set on the down pressure.  Thanks.

[woodbowl]

1/4" just like WM says, however a good running blade will cut straight if the guides are flat and proper back gap even with 1/8" depending on how hard you push it. (not recomended) I suspect that you have blade problems as well. How worn are your blade guides? What size blade do you run?

[Swede]

woodhick;
I made my own guides some months ago after the old with pads over and under the blade was worn out. Donīt think 1/8 or 1/4" under bottom line makes any difference for a proper blade but set them 1/4" down because I want the possibility to make the last board 1 1/8" thick.
Using this type of guides I can use my blades way much longer before they breake. If there comes bark between the blade and the roller itīs a good idea not have a plate under the blade.................I think.

There are some other things to look at.
 
The blade needs to be sharp. Iīve forgot to strengthen a sharpened blade but didnīt get waves the first 5-6 cut! Change the blade before itīs dull! Yes, I know that hurts  but the blade works much better after sharpening if itīs not worn on the sides of teeth. Using a bad blade is just wasting of time and making yourselfe problems.

The set has to be the same both side of the blade. Touching poles and dogs  ................but also when teeth running on the wheels will destroy the setting.
Never puch the sawhead more than 7-9 Kp. ( 15-20Lbs.)  The blade need a chance to take sawdut out of the kerf.

Sawing most soft wood from the storm we had Jan. 8 I make waves every day now. The logs has been stacked beside roads and there is dirth in most of them. The time has make the wood very difficult to saw. Feels like sawing cotton waste sometimes. Have to change blade after two hours or so or the fibres is hanging around the teeth, not cut off. Frech knotty soft wood isnīt easy to saw, this is a H........!! some days.

Dry hard wood shouldnīt be a broblem.

Swede.

[Rockn H]

When I first got my mill from my dad, a friend of his had borrowed it when his circle mill went down.  Anyway we cut a couple mbf before we realized the there was no deflection in the blade.  For some reason the friend had set the guides to where they were just touching the blade.   NO problems with wavy cuts or anything.  We did reset the guides to 1/4" deflection just to make us feel better.

[Dan_Shade]

so you guys set the guides to push the blade down, and make it run against the upper roller?

[Tom]

Dan,
 
The reason for the "down pressure" is to give positive horizontal control of the blade.  Contact with the full surface of the roller is necessary to accomplish this.   When there is good, positive contact, then tuning the guide will, in turn, tune the blade.

If there is no contact, or the contact is weak, the blade is on its on and will rise or dive in the cut before effort is made to control it.  Having a 1/4 inch of vertical "down" on the blade, insures that it follows the guide's alignment.

[Dan_Shade]

hmmm, I don't think my saw made any mention of that adjustment.  I'll have to look at it, however with my manual moving arm to control the throat width, that may be easier said than done...

[Tom]

Having a moveable guide is another reason for the down pressure.  It insures that the blade is parallel to the bed and gives you a means of adjustment to make certain.

Moveable guides, whether manual or motor driven, are difficult to adjust because they have to move in a plane exactly parallel to the bed of the mill.  It's hard to keep them from running uphill or downhill as you move the guide in or out.

So-o-o , I guess down pressure plays two roles.   It insures that the blade is level fore and aft as well as side to side.

[Furby]

If I remember right, the deflection or down pressure should be set with the guide all the way out, then slide it in and check to see if it's staying level with the bunk.

[Dan_Shade]

so what do you do if it isn't?  adjust with sledge hammer?

[Fla._Deadheader]

 Smoke Wrench 

[Dan_Shade]

how much space do you guys normally run from the bottom of the band to the top of the lower roller?  also, how much space between the back of the band and the backstop bearing?

[Furby]

I don't have a lower roller, so none.
I'm about an 1/8" from the back edge of the guides.

[Tom]

Most mills have either no bottom roller or they have a thin flat plate under the blade.

A roller under the blade could keep you from cutting within an inch of the bed.   Since it is desiraable, in most cases, to leave a 1" board as the bottom board, the bottom of the blade is bare.

If you have a bottom roller, I would suggest that you get it as close to the blade as you can without it touching.