Blade Gone Bad??

dusty · Post by **dusty** » Thu Sep 17, 2009 12:32 pm

I have a particular saw blade that I use for all general saw work that I do. It is a Shopsmith Combination Blade and it has given me extremely good service until this morning.

I passed this lamination through the rip saw to size it for a project and this is what I got.

Any ideas what has just happened to my blade?

[ATTACH]5996[/ATTACH]

The cut is perfectly square but, as you can see, unusually rough.

beeg · Post by **beeg** » Thu Sep 17, 2009 1:07 pm

What is the thickness? Is the blade sharp? LOOKS like maybe a tooth's set is out of line.

jmoore65 · Post by **jmoore65** » Thu Sep 17, 2009 3:01 pm

I've a couple of questions to make sure I'm oriented correctly.

Is this the fence side of the board?

Is the right side of the board the leading edge of the cut?

dusty · Post by **dusty** » Thu Sep 17, 2009 3:19 pm

Beeg, the works I have done the last couple days were nothing like this. Now the blade is not new nor is newly sharpened. The stock is a lamination of two 3/4" boards.

JMoore, the waste came off the left side of the blade. In other works, this board was to the right of the blade between the blade and the fence. The board is being fed from right to left.

The blade was set for a depth of cut significantly greater than necessary.

greitz · Post by **greitz** » Thu Sep 17, 2009 4:22 pm

Dusty- the marks look to be a little less than 1/4" apart- is that correct? If so, I don't see how that could be made by a single bad tooth. If the blade is rotating at roughly 60 revolutions per second (3600 rpm), there's no way you could be feeding the wood through the blade that fast.

It reminds me of the mill marks made with a bandsaw if you're resawing with a non-variable tooth blade. I think I remember Nick telling us that a non-variable tooth blade can set up some sort of harmonic vibration which causes those mill marks.

If it is some sort of harmonic vibration, are the set screw and arbor nut both locked down tight? Does the wood have some sort of twist which might cause it to vibrate at a certain frequency as you're cutting it? Were the carriage, headstock, and quill locks tight?

Gary

dusty · Post by **dusty** » Thu Sep 17, 2009 4:51 pm

greitz wrote:Dusty- the marks look to be a little less than 1/4" apart- is that correct? If so, I don't see how that could be made by a single bad tooth. If the blade is rotating at roughly 60 revolutions per second (3600 rpm), there's no way you could be feeding the wood through the blade that fast.

It reminds me of the mill marks made with a bandsaw if you're resawing with a non-variable tooth blade. I think I remember Nick telling us that a non-variable tooth blade can set up some sort of harmonic vibration which causes those mill marks.

If it is some sort of harmonic vibration, are the set screw and arbor nut both locked down tight? Does the wood have some sort of twist which might cause it to vibrate at a certain frequency as you're cutting it? Were the carriage, headstock, and quill locks tight?

Gary

You ask some good questions that I can not answer right now because I have changed the set up to do other work. I will have to go back to the TS Mode and do some more ripping.

I'm wondering, because of your comments, if maybe I was set at a slower speed than appropriate. It's hard for me to imagine doing that without noticing but these days anything is possible.

EVERYONE WHO READS THIS, please take notice. As you get older things can happen that make you less safe in the shop. BE AWARE.

Thanks for your comments. I'll be back with other observations.

JPG · Post by **JPG** » Thu Sep 17, 2009 6:09 pm

SOMETHING is wandering (oscillating) towards and away from the fence. This could be a warped blade(it now wobbles!) or is loose on the arbor(not likely if NOT slipping also) or the arbor is loose on the shaft(I really do NOT want to mention a bent arbor shaft!:eek: ).

As Beeg mentioned, a tooth set, but also add the effects of a tooth bouncing off the glue or being deflected by the board(tooth acts like a sled rather than a sharp cutting edge).

Ed in Tampa · Post by **Ed in Tampa** » Thu Sep 17, 2009 6:09 pm

Dusty those marks look just like the marks I got when I bought a new saw blade. I took it back with a sample plus a sample cut using my old Shopsmith blade. The manager took one look and gave me my money back.

That said I have seen those marks caused by a table not square to blade and fence not square to the blade. I think they are actually caused by the back side of blade rubbing on the wood as the teeth pass over it.

keakap · Post by **keakap** » Thu Sep 17, 2009 9:44 pm

dusty wrote: As you get older things can happen that make you less safe in the shop. BE AWARE.

I dunno-- I feel the same, but my machines are getting older...

charlese · Post by **charlese** » Thu Sep 17, 2009 10:33 pm

dusty wrote:I have a particular saw blade that I use for all general saw work that I do. It is a Shopsmith Combination Blade and it has given me extremely good service until this morning.

I passed this lamination through the rip saw to size it for a project and this is what I got.

Any ideas what has just happened to my blade?

The cut is perfectly square but, as you can see, unusually rough.

Hi Dusty! I'll throw in my hunch as to what happened with this cut.

After enlarging your photo to 350% It looks like there are also some lighter saw marks from the front of the blade. This tells me your table/rip fence is reasonably in line with the blade.

This does not look like wood to me. Is it a press board product?

The above post by Gary (greitz) makes a lot of sense to me! Especially because your blade was set so high. I would bet you had almost 2" of blade sticking out of the top of the cut. (or 3½" from the table) This maximum exposure of the blade would emphasize the effects of vibrations as compared to using only the top 1½" of the blade was higher than the table.

I feel also it is necessary to mention, such exposure of the blade is not safe!!.

Blade speed and blade height could be a couple of major factors causing those saw blade marks.

Please let us know if changing the blade speed and height helps with this issue. I would recommend speed "O".

(sent to you from Eureka, MO)