Thread: Show Us the Things You Find in Logs...

I did my first mango a few months ago - the saw bogged down for a few seconds half way through a slab but then continued ok. When I flipped it over I saw that I had cut clean through a 4 inch nail. I told the owner of the tree, and he said that while he never put that nail there, it is a common belief that whacking a couple of nails into a mango improves fruiting, so he wasn't surprised. I reckon that chain hasn't held an edge well ever since.

Originally Posted by timbertalk

I did my first mango a few months ago - the saw bogged down for a few seconds half way through a slab but then continued ok. When I flipped it over I saw that I had cut clean through a 4 inch nail. I told the owner of the tree, and he said that while he never put that nail there, it is a common belief that whacking a couple of nails into a mango improves fruiting, so he wasn't surprised. I reckon that chain hasn't held an edge well ever since.

Sounds odd, it should be possible to recover the chain from something like that within about 3 touch ups.

Well that raises an interesting subject - just what does something like that do to the chain - the cutter steel I mean? That Malloof guy states that a chain cannot be returned to normal after such an event by hand sharpening alone because the steel gets 'glazed', presumably he is refering to a change in temper. Just how significant this is, and for how many millimeters the effect is, I don't know.

I have never heard the term (glazed) when refering to steel, be that mild steel or any form of harder or hardenable steel..
Pottery...yes
I wonder tho if he (mallof) is using the term to describe some hardening of the cutter right at the cutter edge? and then if u try to sharpen u only take the teeth of the file?

It could be possible...rapid heating of the cutter edge as it is hitting the nail then rapid cooling as the cutter returns to cutting wood.

I havn't observed any heating effect when I have hit a nail, I reckon rocks, gravel, dirt sort of stuff does more damage than a nail.

Mostly whenever I have hit a nail I just pick the chips out of the cutters, a quick sharpen and all good again.

Just my thoughts
Peter

The chain would have to get very hot to change the temper and this would not happen hitting a nail. It could bend a few teeth.

I agree Glen, unless the chain is dead blunt sitting there trying to grind its way through a nail it just won't get that hot. What happens when you hit a nail depends on the type of nail and how fast you hit it. A sharp chain approaching a bog standard mild steel nail at slow to moderate speed should cut straight through it, and affect a relatively small number of cutters. However, those spiral threaded or serrated hardened steel jobbies can make a mess of a chain. I've lost complete cutters on those suckers.

What I have found is the chain wont cut properly untill sharpened completely past the damaged parts of the teeth & that can be a few millimeters sometimes, so you can lose 1/3 of the life of the chain in one hit.
regards inter

In theory every cutter on a 4ft bar would hit the foreign object 10 times per second (I think), so if it doesn't cut through, it breaks/bends/overheats the cutters untill you pull out, or push through. Using a metal detector beforehand might be very worthwhile. My detector would pick up a 4 inch nail at about 6 inches away.

Originally Posted by timbertalk

In theory every cutter on a 4ft bar would hit the foreign object 10 times per second (I think), so if it doesn't cut through, it breaks/bends/overheats the cutters untill you pull out, or push through. Using a metal detector beforehand might be very worthwhile. My detector would pick up a 4 inch nail at about 6 inches away.

What type of detector is it? I have a cheapy it will pick them up 2 to 3 inches in if they are side ways end on they are much harder to find.

I mean having chunks in your timber - is a pain in the ass for the home grown cherry tree being converted into something else.....

But I am surprised that there is no "portable X-ray" scanner for the professional industries - You know the old portable TB chest X ray machine, style of mechanism, mounted about 1 meter ahead of the saw blade, with the screen in the operators booth.

A basic X ray machine or some thing similar....

Well you can buy a modified ground penetrating radar that will find metal, hollows even roots in the ground but last time I looked they were $35,000.

Originally Posted by timbertalk

In theory every cutter on a 4ft bar would hit the foreign object 10 times per second (I think), so if it doesn't cut through, it breaks/bends/overheats the cutters untill you pull out, or push through.

Theory is one thing - reality I find is different. I am always surprised at how relatively little damage occurs when real chains hit real objects. For example I have cut through many nails when milling and they never seem to affect more than 3 or 4 consecutive cutters in a major way and maybe 3 or 4 more randomly staggered cutters following thereafter are a little duller than the remainder of the chain. I cut through a 1/2" coach bolt last year and only about 12 cutters all up were affected. My guess is that these cutters were the ones that take the brunt of the hit and the rest follow in their wake so to speak.

One time I didn't quite tighten up a 3/8 tensile steel bolt on my mill and the bar gradually moved so the chain was able to slowly make contact with the bolt and it cut half way through the bolt before I noticed, hey this thing is cutting a bit slow. I guess I was lucky it did not slip big time!

I realize that these situations are different to hitting something like a really hard rock but nevertheless I am surprised that the chain damage is not greater than it is.

Using a metal detector beforehand might be very worthwhile. My detector would pick up a 4 inch nail at about 6 inches away.

The one time I did have my metal detector with me was when I went to mill a small log in a back yard. The homeowner assured me it had never been anywhere near a nail or anything metallic. I took his word for it and that was when I hit that coach bolt!

I'm with BobL on this one, it is suprising how little damage does occour when the chain hits a nail, rocks and the like are far worse
Peter

My metal detector is a Minelab GP3000 - its a serious gold searching detector, cost me $3,000 secondhand a couple of years ago. After reading this thread, I reckon I will use it on any logs I mill which come from suburbia, or near farmhouses or along fencelines. Rocks and sand will have to remain as just bad luck.