Cracks in acrylic

[Harry]

I am having problems with very translucent acrylic blanks. This is the second time this has happened.


I painted the inside of the hole and used epoxy to glue in the tube. SWMBO says it adds to the look, but I'm not so sure!

Any ideas?

 

[Buckeye]

If you are talking about this area, it doesn't look like cracks to me, but the adhesive that is not even.

Peter

 

[Jimjam66]

Quite possibly heat bubbles from drilling too fast. Try drilling veeeeeeeeery sloooooowly, withdrawing the bit every 1/4 inch or so. Feel the bit with your fingertip regularly, if it's hot wipe it with a wet rag to cool it. Acrylic bubbles when it boils ...

 

[Terry]

As David says. It can also happen when you are cutting with whatever tool you use. Make sure it is sharp and try taking lighter cuts !!!!

 

[PhillH]

Noooooooo you have to drill at maximum speed with expensive drill bits. Don't you remember the thread

Please ignore this "advice". It was posted purely to amuse because I'm bored at work.

 

[Walter]

Doesn't look like cracks to me either, could be either of the previous suggestions but my gut feeling is that David's suggestion is the most likely as it looks like the inside of the hole was not smooth before the paint was applied.

Noooooooo you have to drill at maximum speed with expensive drill bits. Don't you remember the thread

No! No! No! Don't start that again!!. Where's me tin hat?

 

[Buckeye]

Doesn't look like cracks to me either, could be either of the previous suggestions but my gut feeling is that David's suggestion is the most likely as it looks like the inside of the hole was not smooth before the paint was applied.



No! No! No! Don't start that again!!. Where's me tin hat?

I think you are right, it makes sense, CA drizzled through the blank before painting should fill the voids and make it smooth again.

Peter

 

[chas_41_uk]

Quite possibly heat bubbles from drilling too fast

Thats what I thought as soon as I saw it :wink:

Try drilling veeeeeeeeery sloooooowly, withdrawing the bit every 1/4 inch or so. Feel the bit with your fingertip regularly, if it's hot wipe it with a wet rag to cool it

Follow David's advice and you can't go far wrong

 

[Harry]

Thanks for your thoughts, all. I think the most likely reason from what was said is that I was drilling too fast and not clearing swarf enough.

 

[Neil]

Not convinced on the boiling acrylic theory as it would first go thick and gooey as it melted and think that the drill would have given up the ghost before it boiled. One possible answer could be a not too sharp drill being forced through the material too quickly and/or the possibility of a metric drill being used with an imperial tube.

What pen was being made and what drill were you using?

 

[Harry]

Not convinced on the boiling acrylic theory as it would first go thick and gooey as it melted and think that the drill would have given up the ghost before it boiled. One possible answer could be a not too sharp drill being forced through the material too quickly and/or the possibility of a metric drill being used with an imperial tube.

What pen was being made and what drill were you using?

It was a streamline and I used a 7mm drill. I think I pushed the drill through too fast.

 

[Neil]

It was a streamline and I used a 7mm drill. I think I pushed the drill through too fast.

Harry,

Who knows what exactly went wrong, however, try drilling a blank next time you do a streamline in acrylic with a dewalt extreme 2 drill bit from screw fix or others. 7 mm drill bits are prone to wander and vibrate in tough materials, the extreme 2 is a great cost effective bit.