Dog/Clamp Pressure How Much is Enough?

[Trent]

Putting a few final touches on the home built rig. I have a hand winch that applies pressure for holding logs. Can someone tell me about how much pressure is enough? Currently have about 600#, but can double or triple with pullies if needed. It's an 18 HP band mill, and will cut up to about 30" logs.    Thanks.   

[Fla._Deadheader]

In my experience, I studied all the mills I could get photo access to. WM has a hydraulic 2 plane clamp. I modeled after that. One feature I did add, was, I welded teats on the face of the clamp head, so it would "bite" a little under pressure. It holds very well for keeping the cant tight to the bed and helps keep the log from rolling with the blade cutting.

  My newest project will have the same feature. I use a 1" threaded bar to run the clamp in-out. It puts enough pressure to really curve the 1"shaft and 1"dummy reinforcement bar, with a 1/5 HP 12V motor and gearing.

  Hard to tell with a winch.

[mike_van]

I don't know what #pound's are needed, you just need enough to keep the log from moving. When you get a log loaded, try to wiggle it, if it moves, you need more. Odd shaped or off center ones need more than nice round ones.  I'm able to split a 4x4 on my mill with no clamp. A sharp blade & reasonable feed speed has very little "pull".  Some things like this, you need to use it for a while to see whats going to work or not.

[Tom]

I like the "it depends" kind of answer best.

You sure dont want the log to wiggle, twist or roll, but most of us with hydraulics are guilty of applying too much pressure and throwing the mill out of kilter. 

It depends on which way the blade runs.  If your blade is moving through the log, toward the dogs and away from the clamp, it doesn't take as much pressure.

If the blade is running away from the dogs and toward the clamp, it takes a lot of pressure. It's especially critical at the beginning and end of the log when the pressure of the blade tries to rotate the log around the single axis in the middle (the clamp)

It also depends on the size of the log.  Smaller logs require more clamping pressure than larger logs.

It also depends on how you use the clamp.  Most experienced sawyers with hydraulics will use the clamp as a log turner or cant turner.  This uses a pretty good bit of force, but is more dependent on a good volume of oil flow to obtain speed.

If you have too little, you can't reach in the other pocket and get some more.  But, if you have too much, you don't have to use it all.   I vote for the too much.

This reminds me of a story.

A friend of mine was reading the newspaper in his living room one evening when his daughters ran into the house saying "the car is wrecked, the car is wrecked".

He jumped up and ran outside to find that the car had rolled backwards out of the driveway, across the street and had come to rest in the neighbors front yard.  Nothing was hurt and he was sorely relieved.   Sorely...  That's Bible talk.  :D

Well, he retrieved the car and immediately went to the kitchen to confront his wife.

"Linda, you have to put the emergency brake on when you park the car in the driveway.  We've been over this before.  We are on a hill and the car can get loose."

"I did set the brake", she said.

Frustrated, he said, "Well you must not have set it very good, I just got through bringing the car back from the neighbors house across the street.  You have to pull the handle all of the way up."

"Well I only pull it half-way".

"You have to pull it all of the way"

"But, it's just a little hill."