Enlarging hole in acrylic reactor

[spscrackhead]

I have an old nano calcium reactor that I picked up years ago. It is just the base, cylinder, lid, and uniseals. I was planning on using this as a second gassing chamber for my geo 618.
I got all the plumbing I thought I needed and turns out the uniseals are not 1/2. Is there any way I can slightly enlarge these holes to make them 1/2?

 

[spscrackhead]

Photo of existing hole and a 1/2 uniseal.

 

[spscrackhead]

Was considering a step bit. Never used one before and not sure about on acrylic, especially a cylinder.

 

[slojim]

A step bit could be a good choice, except your rounded hole is deeper than the step, so before the backside is the diameter you want, the next step will be digging in the front.

 

[slojim]

This is difficult to do well, especially without something like a drill press or building a guide for your bit from a wood block. Personally, I'd probably try to adapt to the existing hole. But acrylic cuts easy, so if you have a sharp bit, and a slow steady hand, you may succeed.

 

[vetteguy53081]

I would use a half round file and finish off with very fine sandpaper

 

[spscrackhead]

A step bit could be a good choice, except your rounded hole is deeper than the step, so before the backside is the diameter you want, the next step will be digging in the front.

Would a little rotating of the wrist work this out? Hmmm tricky.

 

[burnetb1]

Do you have access to a drill press? Drilling on a curved surface requires a pretty sturdy fixture. You can definitely do it by hand if you are super careful, but I think any major defects in the hole will lead to a leak using a uniseal.
I have not used uniseals before, so I cannot say how forgiving they are. If you have a hand drill and some free time you can make yourself a makeshift drill press to do the job.
If I were doing this personally, I would not do it by hand.