Problem Ripping a Groove

[BuckeyeDennis]

Here's another thought. If the problem is harmonic motion, then it will probably go away if you change your spindle speed by 10 or 20 percent. That should be enough to get the tooth frequency away from the natural frequency of that particular blade vibrational mode.

[algale]

Here's another thought. If the problem is harmonic motion, then it will probably go away if you change your spindle speed by 10 or 20 percent. That should be enough to get the tooth frequency away from the natural frequency of that particular blade vibrational mode.

Brilliant!

[dusty]

I have absolutely no idea but I have doubts about the other suggested causes. The mystery is brought about by the fact that the unwanted cut is more like a dove tail than a groove. I'd have to see it and probably "do it".

Make sure all of the locks are secured and then verify whether this happens in other than the end grain. If you make four cuts, rotating the block 90 degrees for each, does the kerf align.

Sorry but I have more questions and no answers.

[robinson46176]

After careful study I would say that "something went wrong"...

I understand why you ask about it but I also wonder if since the kerf at the surface seems to be the right width if the piece is still OK to use as is or will the end of the cut show in the finished item?

I would think that if it were the block moving from perfect vertical that the corners of the cut would still be square and not rounded?

It would be interesting to see the same cuts in the same stock with the same blade with a pair of blade stabilizers installed.

"Maybe" the blade which is apparently sharp enough for regular work could be a bit dull to cut this particular piece of hard oak?

A lot of good thoughts across the board here (sorry for the pun) but we will probably not come to a definitive conclusion.


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[robinson46176]

On a side note please tell me that you used a salvage piece from the top of a sawhorse to make that push-block and that it didn't get all of those kerfs while being used as a push block as shown...


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[robinson46176]

On a side note please tell me that you used a salvage piece from the top of a sawhorse to make that push-block and that it didn't get all of those kerfs while being used as a push block as shown...


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[masonsailor2]

My vote is that the piece is rocking back and forth as you feed it over the blade. These types of cuts on small blocks are best done using a sled. It doesn't have to be anything exotic. Take a 6 or 8 inch wide scrap plywood and mount a board to it to allow you to clamp the piece to the sled. Then put the sled up against the fence and run it through the saw. Much more stable and infinitely safer.
Paul

[charlese]

In my mind there is only one cause of the mis manufactured grooves. It is workpiece movement as it passes through the saw. I see both movement away from a fence and failure to seat the workpiece flat on the table.

I don't support saw blade movement.

[berry]

So in reply to some of the comments.

There were 8 of these pieces and the problem occurred on 3. (Not the last 3, mixed in.) There were twice the number of shallow grooves, no problem.
Once again the blade in 1/8" Shopsmith that I purchased new with the SS in 82.
I checked the arbor, it's on tight.
The push block as you suspected from a sacrificial saw horse.
I will continue making the serving trays and use the inferior parts. I have this thing about throwing things out, just because they are not perfect.
I can clean the blade and take a picture if anyone thinks that will help.


Thanks for everyone's comments.

[reible]

If you have to use the block size shown this is how I would do it.

There is no doubt in my mind what the issue is and how to solve it if we have been given all the facts. As in my first post on the subject I would start by putting in a ZCI and then use push blocks to push into the fence and down on the table. You should be cutting 1000's of these this way without any issues.

I would how ever suggest that the block size be made larger and then cut to size after.

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Ed