What adhesive is best to repair vintage calculator metal sheet on plastic?

[robve]

Perhaps someone on this forum can help me out with this.

I have a Sharp EL-805 in excellent condition despite its age (1973), except that the front part of the aluminum metal sheet has delaminated from the plastic cover (it still sticks on the back.) The adhesive is 50 years old, so it is not entirely surprising this might happen. See closeup picture (pardon the dust.)

   

What adhesive should I use to fix this? As pictured, there is not much space between the metal and plastic to work with, unless bending the sheet up from the plastic (the thought makes me cringe.) An adhesive that applies thinly and doesn't dry too fast should work. Double sided tape is probably too thick and may make the sheet stick up some. It doesn't need to be a strong bond to hold the sheet metal in place, recessed in and on the plastic frame.

Or should I just leave this vintage calculator as it is? I worry that the metal sheet cover may get caught on something, like the leather case, and gets bend. Fixing a bend aluminum sheet might be hard to hide the bend.

Something as simple as the adhesive of a glue stick might work. It is not damaging to the materials and not as permanent. Or is that a bad idea?

- Rob

[Jeff_Birt]

I have used 3M 137 double sided tape for sticking things like emblems and rubber feet on. It is thin and has worked really well for me.

https://www.amazon.com/Scotch-Double-Sid...B005573S48

[rprosperi]

If tape is not ideal, due to thickness or perhaps for something that is only partly unstuck, E6800 industrial adhesive works quite well too.

https://www.amazon.com/gp/product/B004JX3C2C

[striegel]

Try a little bit of rubber cement. You'll probably want to apply just a tiny amount with a toothpick then spread it around as well as you can under the metal.

The good thing about rubber cement is that if you squeeze out some excess onto the face, it can be rolled up with your fingertip when it dries.

[robve]

Thanks for all the suggestions.

(06-09-2023 03:03 AM)Jeff_Birt Wrote:  I have used 3M 137 double sided tape for sticking things like emblems and rubber feet on.

The double sided tape is indeed very thin with 3.5 mil (0.09 mm) and should work well on clean and flat surfaces. However, there is still a little bit of old hardened glue residue in the middle that is quite difficult to remove. It looks like the surfaces are not as clean and even for double sided tape to work best.

As for other adhesives like E6800, I have a tube, but application is often messy. Maybe I'm clumsy with this, but it's hard to avoid glue trails/strings/spots on places I don't want glued.

(06-09-2023 01:41 PM)striegel Wrote:  Try a little bit of rubber cement.

I will give that a try. It should even it out when thinly spread, so that bit of old glue residue should not be a problem. As a bonus, rubber cement can be repositioned and excess can be easily removed.

- Rob

[robve]

For the record, if anyone is interested, I used double-sided tape. That worked very well. The thin sheet metal cover fits snugly and flush with the plastic. Because the tape cannot be repositioned (you'll have to separate the parts and take it off), it takes a bit of patience and practice to position the two parts once and for all.

Rubber cement doesn't dry between non-porous materials like metal and plastic. I gave up after letting it set for 48 hours. It's easy to remove when dry.

Thanks again for the tips!

- Rob

[LEDfan]

I had a similar issue, and a friend suggested masking and using a spray glue. Didn’t last and resorted to double sided tape. Still holding up for now. Glad your calculator is sorted.