Baltic birch delamination when drilled

[Carterian429]

I'm up against a problem I haven't seen before.  I am new to scroll sawing; this is my 2nd project that I am starting.  I have a piece of 1/2" baltic birch (BB) plywood that I was using to make a horse (Steve Good design).  I'm using a backer board when drilling for the inside saw cuts, and I'm still getting delamination of the BB on the backside (exit side for the drill bit).  I'm using a 1/16" or 3/32" TiN coated drill bit, but it isn't new and I can't say for sure how sharp it is.  I'm just surprised that even using a backer board, I'm getting delamination.  I've used plywood and OSB as backer board material, and it doesn't make a difference.  The problem occurs where holes are closer together (1/4" to 5/16" separation).  Do I have to sand the back of the BB after every hole to make sure it's flat when making holes this close together?  Any thoughts or advice will be appreciated.  Thank you.

[Scrappile]

The only suggestions I can make are to speed up your drill and slow down on how fast you are feeding the bit through the wood.   And maybe try some new bits.

[Carterian429]

Thanks, I appreciate the advice.

[Wichman]

What are you using to drill the holes?

The faster the rpms the better. I have a HF cordless drill @ 900 rmp, a cordless DeWalt drill @ 2000 rpm, a drill press @3500 and a cordless Dremel @ 25,000 rmp. The cordless Dremel is my preferred method ( combined with the plunge router acessorry). 

The plunge router has another benefit, it holds the panel down as you're drilling.

You may need to clamp the panel to the backer while drilling; as you approach the bottom layer of plywood while drilling, the drill bit is lifting the drilled portion while still trying to drill through the last layer. This can also happen when drilling stacked panels. I have observed this effect while drilling two 2X4's , the drill bit hits the second board and will lift the first before the bit can start drilling the second. This is much more apparent when the drill bit is worn, so a new drill bit may be in order.

[Carterian429]

Thanks for the input, I should have said that I was using a drill press.  I'll look at the rpm, and I appreciate the thought about the top layer being pulled up as the drill goes through and starts into the backer board.  I'll try a new drill bit first, and then clamp if I need to.  

 

Scrappile and Wichman, I appreciate you replying and giving such good advice.

 

[JTTHECLOCKMAN]

A couple things. I suggest get a better quality drill bit. Next the very first hole you drilled now allows the piece and backboard to separate so  each hole will blowout. I suggest you either clamp the pieces together or use doublesided tape. Finally you need to let the drill bit do the work. Just from your photo I see you push too hard to get drill through. My opinion.

[BadBob]

18 hours ago, Wichman said:

The plunge router has another benefit, it holds the panel down as you're drilling.

An excellent point.

[BadBob]

The plywood itself may be the problem, but this isn't likely if it is truly baltic birch.

• dull or poor quality bit
• forcing the bit through the wood
• plywood not flat against the backer board
• plywood lifting off the backer board
• drill speed to low

[kmmcrafts]

Forcing the bit through the wood and drill speed kinda go hand in hand.. but there is a point where a dull bit and too fast a speed will burn through and burn up the bit even more. 

Because drilling wood is much different than drilling metal many folks will push through wood way to fast. If you see no pile of fine wood chips rising up out of the hole you're drilling too fast.. when done drilling the hole and rising the drill back up out of the wood and you get a long compressed chunk of wood either packed into the gullet of the bit or falling off the bit in one big piece you're drilling too fast.. when drilling you should see a pile of small wood chips rising up around the top of the board.. Quality bits help speed up the drilling process and help prevent this.. some types of wood will almost always pack the gullet on the bit so it's not always true what I mentioned above but is a good rule of thumb for most types of wood to watch for some small wood chips.. I think close to 100% of people drilling wood go too fast.. including myself.. but there is a speed in which we get accustomed to that is a happy middle ground of not blowing through the back like shown.. 

Drilling too fast with small bits can make your drill bit bend and also the tip of the bit will follow the path of least resistance so you can end up with a hole that is slanted.. If in the middle of the board has a soft spot in the grain the bit being forced will get pulled into the soft spot leaving you a hole that is at an angle.. when doing fine detail work you may end up drilling into the wood in a spot that is not wanted thus scrapping your project. 

[Carterian429]

Thank you to everyone who replied and shared such great insights.  I checked my drill press and found it was on the lowest speed setting (about 600 rpm!); I adjusted it to the 2nd highest (around 2100 rpm) and tried a new bit (Dewalt cobalt steel).  I used the same piece of plywood for backing, and just held the baltic birch plywood to it by hand as before.  The resulting hole was nice and crisp, with no delamination at all. 

The bits I used before (TiN coated bits that resulted in delamination), I would say, had not seen much use.  They were purchased as part of a lower priced set... I guess I got what I paid for...

It would have been better to separate variables (testing a new bit first, then testing a higher drill press speed separately), but a higher quality, new bit at a higher rpm certainly resolved the issue.

[Bill WIlson]

Thanks for the update.  So often on these kinds of forums, someone presents a problem, gets lots of suggestions, but we never hear how or if the issue was resolved.

Glad you found your answer.