Need help, blanks with aluminum separating

[jholbrook81]

I want to move to more challenging turning. I found some pictures on here of pens with stripes of metal running the length of the barrel. I found this was aluminum flashing so I promptly went out and bought some, cut it, scuffed up the faces, and bonded it into two sandwich blanks using System Three epoxy with the 15 min hardener. I clamped the blanks and waited a full 24 hours.

The first blank I tried running the aluminum perpendicular to the barrel to make rings around the pen. When I drilled it it separated at every metal joint.

The lengthwise blank also separated when drilling. I sanded the surfaces that separated, re-applied epoxy, clamped it and let it sit for about 8 hours. I was able to mount the brass tube and start turning. It separated almost immediately with my roughing gouge. I tried my skew on another piece and that worked well. I got it shaped down from rough to round like that. Then I had to put a tenon on the blank so I used my parting tool, and it separated again.

Why is this coming apart on me at every step of the way? I noticed the flashing has a gold color on one side, is that adhesive or something causing my joints to fail?

Any advice you have in this area is welcome. I'm using high speed steel tools, I hone them with diamond stones before each pen and during turning if needed. I do my boring on the lathe with jaws to hold the blank. I do not use bit lubricant. I'm using my 7mm bit cause it's the smallest for now. I'm using bloodwood, sapele, and wenge in my blanks. If there are any questions about tools I'm using or my process please ask; I tried to be very thorough in my description.

 

[Krudwig]

The only thing I can think of would be the epoxy was not fully cured before drilling and you may have your lathe turning to fast when you drilled the hole and you may have tried drilling the hole to fast. Heat is the big problem with adhesives, you have to keep the heat down. I also have been using the gorilla glue I have not used epoxy but have used CA glue and found I like the Gorilla glue best. Even when you do everything right you will probably have some blanks that will separate. Remember sand the flashing but then wipe the surface with denatured alcohol to remove the dust and just keep trying.

 

[JohnGreco]

Once cured, gorilla glue is not affected by heat- I've had no problems using it. Also, maybe your drill bit wasn't sharp enough. I've only used aluminum cans which I'm sure is thinner than the flashing you used so I don't know for sure, but I would start with changing your adhesive.

 

[jholbrook81]

you may have your lathe turning to fast when you drilled the hole and you may have tried drilling the hole to fast. Heat is the big problem with adhesives, you have to keep the heat down.

That is entirely a possibility. It is an older delta homecraft lathe I inherited. I have it on the largest pulley, but even that seems fast.

Remember sand the flashing but then wipe the surface with denatured alcohol to remove the dust and just keep trying.

Good point, I was not cleaning the surface after sanding. I have some acetone, will that work just as well as denatured alcohol?

 

[jholbrook81]

Once cured, gorilla glue is not affected by heat- I've had no problems using it. Also, maybe your drill bit wasn't sharp enough. I've only used aluminum cans which I'm sure is thinner than the flashing you used so I don't know for sure, but I would start with changing your adhesive.

Maybe I'll give aluminum cans a shot. I did try gorilla glue before. I switched to epoxy mainly because I couldn't get gorilla glue in large enough quantities and I wanted a longer work time.

 

[firewhatfire]

how fast are you drilling? Aluminum will heat very fast and break the glue bond.

 

[jholbrook81]

how fast are you drilling? Aluminum will heat very fast and break the glue bond.

Not sure. I need to get a tach. I have an older lathe with pulleys; you move the belt to change speed. The motor isn't original either so I can't look it up. It definitely was hot to the touch after drilling so I wouldn't be surprised if it's too fast. I've been looking for a better drill press, maybe I'll have to wait until I get that too move on to more advanced blanks.

 

[mikespenturningz]

What kind of drills are you using? Are they super sharp? How hard are you pushing the drilling speed? Drilling is the hardest part in my estimation. Also make sure you turning tools are ultra sharp. I would not expect to get through a two barrel pen without sharpening my skew. If I have to help the skew much at all it isn't sharp enough. Same with the drills...

 

[Wood Butcher]

Here's one to try: Sand all surfaces flat of the blank and insert with 100 grit paper, use 5 minute epoxy, or long cure if you can wait for a full day, allow it to fully cure. Now get some wooden tongue depressors and use medium CA glue to glue them to all 4 sides of the blank before drilling. When that's cured, drill slowly and test for heat with your finger, a lot, if it burns you it's too hot, let it cool. If you're drilling really brittle wood, i.e. ebony or any plastic, do not drill all the way through. Works for me............usually.
WB

 

[edman2]

Another method is to wrap the blank tightly with string and soak that with thin ca before you drill. Sharp bits. Slow drilling. The string with ca will turn off when you turn it. Do the ends first and leave the middle of the blank till last. That helps hold the blank together while turning. Good luck.

 

[Jim Burr]

This works for me every time...anyone else, have no idea, but for me, no issues. I use Devcon 5 minutes clear epoxy. I use a 100g pad on a ROS. Sand the crap out of whatever metal you are using, wipe with alcohol...DNA is really expensive. Glue and apply pressure. Here's the problem...to little pressure and you end up with a wad of glue...to much and you squish it all of the joint. I never drill metal over 100 rpm...just no reason to. Heat is always the enemy! 1/8" and let it cool...repeat. Round off the corners so the impact of the gouge on the 90* corner is lessened...impact causes fracture and weakening. High speed, like 3k rpm and very light cuts. If you start to hear a "tap-tap-tap" you have a joint ready to let go. The rest you can trial and error.