Drilling thin plywood

[JackOfDiamonds]

I need to drill 3/8 holes in 5 mm thick plywood. No matter what I have tried, nothing works without splintering.

I think the correct answer is water jet or laser cutting. But failing that, is there any special drill bit for this? The stuff sands a lot better than it saws, so a tapered abrasive bit would seem to be the best, but I've never seen such a thing. Sanding drums are far too big. A 1/8 mill at high speed and a cnc router would work too but I don't have one. I need to drill it.

 

[rsanter]

Splinters on the front to back? Or both?

Have you done the tape trick?
Have you used a drill guide?
Have you done the sandwich trick?

 

[Dumber than lumber]

Support it from the back with wood (not plywood).
Clamp it.
A Forstner bit can be found in that size. Would advise that.

 

[66HertzClone]

I've had good luck placing a board beneath the board I'm drilling, clamped tight in place when possible. I always start with small bits and work my way up.

 

[JackOfDiamonds]

Splintering mostly on the back side. Tape trick doesn't work, but I will try clamping.

I found some tapered carbide burrs for my dremel. That might do the trick at 30,000 RPM. Precision is not required but final appearance matters.

 

[lardy1]

Back it up solid and try brad point bits. Cheaper than forstner and should work.

 

[Bogie1632]

Have you tried a drill guide block? What kind of bits are you using? A block and some sharp forstner bits should do the trick. There some tricks to getting both sides to cut smooth without blowout but I usually just measure both sides and only drill halfway then flip over.

Good luck.

V/R
Bogie

 

[LXCam]

You want a brad point drill.

 

[shoot summ]

Clamp it between 2 pieces of wood, and use a brad point bit.

 

[Ray-CA]

Drill your hole just until the bit just starts to poke out the back side. Then, flip the piece and finish the hole from the back.

Ray

 

[rlitman]

Splintering on the back is unavoidable, no matter that bit you use. The only way to not get splintering on the back is to not have a back.

So, you have two options. If you can only drill from one side, then back up the piece with another solid piece of wood, FIRMLY clamped in place that you drill into. If you can drill through both sides, locate the center by pilot drilling with a 1/16" bit (DO NOT use anything larger), and then drill in from both sides. The drilling in from one side only needs to go through the outer ply into the next layer.

As for bit, you have two choices. Brad point and forstner. I'd suggest the forstner in anything up to about 12mm thick. In deeper holes, the spiral flutes of the brad can be of assistance, but in all cases, the forstner will have a cleaner hole.

FYI, I just (last week) drilled eighteen 3/8" holes through 12mm hardwood ply in a set of kitchen cabinets using a forstner bit. For my purposes, the minimal back-side splintering was acceptable. In a few cases, I had to return with a knife, because I didn't want the splinters to run away on me.

Drill your hole just until the bit just starts to poke out the back side. Then, flip the piece and finish the hole from the back.

Ray

That's an option, but one I don't recommend. It takes your attention away from keeping the drill perpendicular, and puts your focus on waiting for that fleeting instant you get as the center peeks out before it causes damage.

 

[Spacey_G]

Have you tried a router with a template? Maybe plunge a 1/4" bit down and then run along the template to make your clean edge.

 

[MoonRise]

A "good" sharp bit, brad point or Forstner is a must to start with.

Also, a backing board FIRMLY clamped to the thin plywood is also essential.

Technique matters too. If you just muscle the bit through the plywood, you will enhance the splintering on both the front AND back faces. Slow down the feed rate and have a higher RPM on the bit and give the SHARP bit time to actually cut the wood and not just push it out of the way.

If you can stack your plywood pieces and clamp them together and drill through the stack you can maybe use the stack to back up itself except for the top piece and the bottom piece, where you will still need backing (fronting? ) pieces.

With a Dremel, there are also the small(er) diameter sanding drums and sanding bands. Don't remember what their diameter is and don't feel like going and checking for you.

OK, so I check online, and the small diameter Dremel sanding drum is the #430 1/4" diameter drum.

https://www.dremel.com/en_US/products/-/show-product/tools/430-1-4-sanding-drum

https://www.homedepot.com/p/Dremel-1-4-in-Rotary-Tool-Sanding-Drum-for-Rust-and-Rubber-430/203362600

Assortment of drums and bands, with 1/2" and 3/8" and 1/4" diameters:

https://www.amazon.com/dp/B007FER2IW/?tag=atomicindus08-20

There are also the structured carbide bits, and diamond bits for a Dremel that could be options. Again, let the bit/tool do the work and don't hog out the material with an aggressive feed rate.

What is the application? How many do you have to do?

Can you use a drill press, or only a hand held drill?

Etc.

 

[The Cobbler]

Drill your hole just until the bit just starts to poke out the back side. Then, flip the piece and finish the hole from the back.

Ray

^^^ this and use a brad bit or a forstner bit

 

[MoonRise]

Drill your hole just until the bit just starts to poke out the back side. Then, flip the piece and finish the hole from the back.

Ray

That's an option, but one I don't recommend. It takes your attention away from keeping the drill perpendicular, and puts your focus on waiting for that fleeting instant you get as the center peeks out before it causes damage.

If you can do the drilling in a drill press, you can set the depth stop on the quill travel to stop right as the brad point (on either the brad point bit or the Forstner bit) just penetrates through the back face of the plywood (still backed up by some backing!). Then flip the workpiece over and finish the hole.

You might be able to do the same technique using a depth stop on the drill bit itself on a brad point bit.

Using the 'flag of tape' on a bit probably won't be consistent or positive enough to reliably work though.

 

[Higgins]

I've done this many times. I use a GOOD sharp FORSTNER bit
> Drill a small 1/16" pilot hole
> I back up with a scrap piece of hard wood!
> Use in a drill press running at a slow speed.
> Proceed slowly !!

AL