Plywood tearing out badly.

[Newsawontheblock]

I’m doing a stack cut of 4 layers of 1/4 Baltic Birch. The bottom layer is tearing out quite badly. I am using a FD Ultra Reverse 3 Any ideas as to what I could/should change?

[Rockytime]

I have not done a lot of stack cutting but unless you are using quality BB tear out can be expected because the outside veneers are so very thin on ordinary plywood. I use a sacrificial piece of 3/16" luan underlayment.

[JimErn]

insure the blade is mounted so that reverse teeth clear the table

[Fedido]

I don’t have any experience in this, but maybe put some painters tape might help. 

[NC Scroller]

The first thing that comes to mine is this real Baltic birch or the birch plywood they sell at Lowes or Home Depot.  If the latter there is not much you can do.  Sorry to say you got what you paid for.  The second thing is you said you were using #3 FD Ultra Reverse. Is the blade installed with the crimp at the top?  

Can you post a picture of the bottom layer?

[redwine]

You stated that the bottom layer is "tearing out" badly? Is it the actual wood that is tearing out or is it just the "fuzzes" that is always to some extent, present on the bottom layer. I use the FD ultra reverse blades when I stack cut the bb ply and they will produce fusses but not as much as a regular blade. As NC Scroller stated if it is not true BB ply but the utility ply or even their cabinet  grade ply, you run the risk of the ply tearing or even breaking out! 

Erv

[Newsawontheblock]

It is true Baltic birch. Here is a photo.

[Fedido]

Thank you for the photo as it helps a lot describing your problem. I have experienced this  a lot. I now use Maple 1/2 plywood and it splinters some, just not as much. I have used basswood plywood and while more expensive, doesn’t have this problem and is a dream to work with. 

[heppnerguy]

I have never used the ultra reverse blade before so not sure if this is the problem or not. There are different grades of BB Ply also. I have purchased some where the outer layers are very thin and they tore out quite badly. I can not examine the wood you are using, so I also can not be sure if that is where your problem lies. Have you used this blade to cut only one layer and if so, have you experienced the same problem? Do you have any other blades that you can use to see if that helps or is this the only blade that  you have on hand?  Maybe if you cut less layers at a time, this may help. Experiment on some scrap wood if you have any and see if a different blade helps or less layers. Sorry I can not think of anything else to tell you on this problem without being with you

Dick

heppnerguy

[Karl S]

It also appears that your drill bit is dull or that you are forcing it through the plywood rather than let it cut it's way through Just guessing since there are splintered places where the bit came out the back side. this would give your surface ply a place to start tearing away from the other layers as you cut.

[Newsawontheblock]

27 minutes ago, Karl S said:

It also appears that your drill bit is dull or that you are forcing it through the plywood rather than let it cut it's way through Just guessing since there are splintered places where the bit came out the back side. this would give your surface ply a place to start tearing away from the other layers as you cut.

Yeah, I think that might be what is happening. Might have to redo this piece. 

[dgman]

Like Karl noted, it looks like the problem is tear out from the drill bit. As the drill bit exits the wood, it is breaking the grain on the bottom of the board.Three things to prevent or minimize this. First, make sure you use a sharp bit, second, you must use a backer board. The backer board supports the grain in the blank so it doesn’t splinter as the drill bit breaks through. Third, you must match the drill speed to the type of drill bit you are using. There are all kinds of speed charts available on line. Wood Magazine has a great one available online.

[Rockytime]

For extremely small number bits like 68 and 72 work atheir optimum with speeds like 20K and up. My go to bit is #68 ans I use a drill presswhich is not near fast enough so I just let the bit plow through and let the backer bear the brunt. The bit burnt black but still makes the hole. Those little bits are pricey and on the Dremel they are a pita to change without removing is from the router attachment. I guess I'm lazy so I take the easiest road.

[Matt B]

dgman said it, but it is good advise, so I will second it. You need a backer board when drilling. I use an old cut off 1 x 6 or something like that as a backer when drilling. Using a drill press, just set the depth to go into the backer an 1/4 in or so. Let the drill bit do the work and don't force it into the wood.

[Fab4]

Hi Steven:
I agree with Karl 100%
The problem is not the blade - the damage is done even before you start scrolling
Take care of your method of drilling and your problem is 95% solved
If you still have tear outs with a clean drill hole then add a sacrificial piece as your bottom layer as mentioned above
NOTE:
Then and only then, if you still get tear outs, after doing all of the above,
Get a new hobby, because this isn't for you.......just kidding!!! honest
You'll be alright, 
Please let us know how these suggestions worked for you
Fab4

[Newsawontheblock]

I tried cutting some more on it, and it keeps splintering Planning to recut and drill very clean holes this time! Thank you for all the help!

Edited May 12, 2020 by Newsawontheblock