Aluminum segments

[hebertjo]

I was using some 1/32 inch aluminum as segments in my latest pen and when I was drilling the blanks they separated where the aluminum was CA'ed to the adjacent segment. Any one else experience this and have some tips? I sand each segment and wipe them clean with rubbing alcohol before gluing them together. I was thinking that the aluminum was heating up when drilled and the expansion was causing the joint failure. I finally got it to work but it took 4 repairs!

 

[UKpenmaker]

One thing that i do to help reduce breakages is once the blank is all glued up. I put some heavy duty tape on it before drilling, and then you can just turn it off. It doesn't work all of the time, but i started getting a lot more success with this method.

 

[leehljp]

Tape as suggested, or wrap in string/thread and CA it. Small string is what I use and it adds considerable strength. Turn it to get it off with your favorite chisel.

I had one that separated after I had cut down through the string and had it rounded over. I was fortunate to be able to re-align everything perfectly and re-glue it.

At this point, I used rubber bands doubled and trippled over on both ends of the same blank and turned one end down to about 2 mm from the correct size, add rubber bands to that end and turn the other end down. At this point I join my friend Mr. Patience and sand the last 2 millimeters. Takes a lot of work and time, but it works for me.

OH, I forgot to say that (above) my pen segments and separation was horizontal.

For round segments as in brass or aluminum washer shaped, I had one of those come loose only once but I saw it happening and knew what the problem was - heat. Preventing heat build up will usually allow the strength of CA or epoxy to keep its strength. Take small bites and move away, let it sit a minute or so and then do another run.

 

[IPD_Mrs]

Heat will do it as CA will fail at around 165 degrees. Also how long has it been since you sharpened your drill bit? A dull bit and not clearing the bit frequently enough will do it as well.

Mike

 

[hebertjo]

Thanks for the tips. the segment was the washer type across the blank not length wise. and my finger was getting pretty hot as I was holding it up against the fence during the drilling so I am guessing heat was the issue. The drill bit I was using has not seen a lot of action since I bought it but it is not the highest of quality either. I was thinking I could help draw some heat out of the metal by holding a wet paper towel folded over several times against the blank while drilling. I will try this on the next one and report back about it.

Thanks again!

 

[randyrls]

Thanks for the tips. the segment was the washer type across the blank not length wise. and my finger was getting pretty hot as I was holding it up against the fence during the drilling so I am guessing heat was the issue. The drill bit I was using has not seen a lot of action since I bought it but it is not the highest of quality either. I was thinking I could help draw some heat out of the metal by holding a wet paper towel folded over several times against the blank while drilling. I will try this on the next one and report back about it.

Thanks again!

I would suggest a Drill Doctor is an excellent tool for sharpening bits. The tool is excellent, but is very finicky about the setting of the bit in the holder. People have mixed experiences with the DD, but my results have been positive. The exceptions occurred when I didn't follow the directions explicitly.

 

[IPD_Mrs]

Another thing you can do while drilling is blow compressed air into the blank. It helps to cool it as well as clear the shavings. The shavings are another possibility. If they do not clear out the flute of the drill bit where are they going to go? The build up pressure on the side of the blank.

Mike

 

[Nolan]

Are you roughing up the aluminum where it glues to the wood?

 

[hebertjo]

Yes I sand it with 180 and wipe it down with rubbing alcohol before gluing. Should I be using a lower grit paper?

 

[Nolan]

Yes I sand it with 180 and wipe it down with rubbing alcohol before gluing. Should I be using a lower grit paper?

Personally I would use lower grit like 120 or so.

 

[UKpenmaker]

One other thing that i do, after the original glue up has been done (i use thick CA ) and then get some thin CA and put in on where the joins are this will flow into any little gaps that you have between the metal and wood thus making a stronger bond.

I find that i can get away with much smaller segments this way. (see photo)

 

[hebertjo]

Thanks again everyone. I will put some of these ideas to work on the next one.

 

[hebertjo]

I drilled the other half of the pen with aluminum segments and used 120 paper to rough up the surface and had mixed results. This was the lower barrel so the diameter was smaller and the bit was of better quality. One piece drill through without breaking the other one broke.. This same segment broke several times while turning on the lathe as well. Eventually I replaced it with a plastic segment. The pen in question is here:

http://www.penturners.org/forum/showthread.php?t=35385

 

[VisExp]

How long after doing the glue up are you waiting before stressing the joint? CA takes at least 24 hours to reach full strength.

 

[hebertjo]

It wasn't 24 hours but I glued up the sections one night and then drilled them the next day. Maybe 12 - 14 hours after the glue up. I noticed that the drill bit tended to deform the metal causing a dome shape that I had to punch out and file smooth before I could re-glue the segments.

Also, I will never again put a metal segment in a location where there is no brass tube. I had one very near the end of the lower pen section and this separated 3 or 4 times while turning it on the lathe. I finally gave up on it and glued in some plastic. I think when the metal has the added support and glue contact area of the brass tube it performs better.