Drilling/Tapping acrylic

[IUfan]

Hi, I'm trying to drill my reactor lid to take the effluent from the lid.

The fitting I have is 1/8" MNPTF.

The exact fitting is here:

http://www.usplastic.com/catalog/item.aspx?itemid=42009

I've tried to look up what drill bit size, and which taper I would need but I'm confused by MNPTF and how that effects things.

Can anyone point/link me to the drill bit and a taper that I need?

Thanks for your help

 

[mcgyvr]

Thats a "Male National Pipe Thread Fine" so you need a 1/8-27 pipe tap
That will require a 11/32 predrilled hole.

 

[Legalreefing]

What he said ^

 

[Fishmommy]

Isn't NPTF a dryseal thread?

 

[IUfan]

This tap okay:
Vermont American 20371 1/8-27 NPT High Carbon Steel Pipe Tap https://www.amazon.com/dp/B000K1LZ76/ref=cm_sw_r_awd_8.neub023HF01

This Drill bit okay:
Vermont American 12264 Black Oxide Drill Bit, 11/32-Inch by 4-3/4-Inch https://www.amazon.com/dp/B002PFNOW4/ref=cm_sw_r_awd_3aoeub1R7Z6FE

Thanks for your help guys!

 

[Gorgok]

Remember when tapping its a tapered thread. Don't just bottom the tap out, tap some ways, test with fitting to see if it seats deep enough for your liking. You can always run the tap deeper, unlike if your fitting bottoms out....

 

[salty joe]

When drilling and tapping acrylic, mineral spirits is an excellent cutting fluid.

 

[IUfan]

Thanks for tips. I'll get some mineral spirits hadn't thought of that.

When you say it's tapered? How does that effect things? Why wouldn't the thread go all the way through the hole? I think the fitting I have has a flange on it so it will reach a certain point and then stop

What if the acrylic lid is too thin and to get the fitting all the way screwed in, the thread has to go all the way through?

 

[mcgyvr]

Thanks for tips. I'll get some mineral spirits hadn't thought of that.

When you say it's tapered? How does that effect things? Why wouldn't the thread go all the way through the hole? I think the fitting I have has a flange on it so it will reach a certain point and then stop

What if the acrylic lid is too thin and to get the fitting all the way screwed in, the thread has to go all the way through?

The tap is tapered (All NPT/NPTF are).. IF you tap it all the way through there is a good chance your fitting will be too lose and leak.
So what he is saying is maybe only turn it to 50% of the total distance of the tap then check it with your fitting.. If you can't turn it or seat it properly then tap a little deeper thus enlarging the threads some.

I would NOT use Mineral Spirits as a tapping fluid.. Some of the chemical compatibility charts show it as not recommend (or not suggested) and that some softening will occur with acrylic and most definitely not with polycarbonate.
What works and what should be used are a bit different. You don't need tapping fluid at all IMO for a single thread.. It will work just fine.. I'd use water over anything else if I needed to for acrylic

 

[IUfan]

Ohhh so the tap is like V shaped (from a 2d side angle?) So the deeper I go, the wider the top is going to be? This if I go to deep for the fitting, it won't fit into the V shape of the hole?

 

[mcgyvr]

Ohhh so the tap is like V shaped (from a 2d side angle?) So the deeper I go, the wider the top is going to be? This if I go to deep for the fitting, it won't fit into the V shape of the hole?

yes basically.

 

[IUfan]

Got it! Thanks for the help guys. I would have just screwed it all the way through and been like... ***! Haha

Appreciate the help

 

[mcgyvr]

Got it! Thanks for the help guys. I would have just screwed it all the way through and been like... ***! Haha

Appreciate the help

Its a very slight taper though really but going all the way mignt not give you the "best" possible seal

 

[Ma_reefer]

Water would be the best drilling and tapping fluid for acrylic being used in a reef tank, although you shouldn't need any.Just be carefull that you start the tap square so you get nice threads

 

[salty joe]

I would NOT use Mineral Spirits as a tapping fluid.. Some of the chemical compatibility charts show it as not recommend (or not suggested) and that some softening will occur with acrylic and most definitely not with polycarbonate.
What works and what should be used are a bit different. You don't need tapping fluid at all IMO for a single thread.. It will work just fine.. I'd use water over anything else if I needed to for acrylic

Any chance you give me a link showing incompatibility with acrylic and mineral spirits? I looked at five plastic compatibility charts and not one listed mineral spirits. I did find that oil paint and kerosene both are compatible with acrylic. IIRC, gasoline too. I've used mineral spirits dozens of times for a cutting fluid with acrylic with zero issues. What I did get was cleaner, smoother, cooler cutting and nicer threads.

 

[dattack]

that's a tiny tap. probably doesn't need any lubricant unless your lid is super thick.

 

[salty joe]

I found a compatibility chart that lists mineral spirits. http://www.eplastics.com/Plastic/Plastics_Library/Chemical-Resistance-of-Plexiglass-Acrylic

According to this chart ; Some effect after 7 days of constant exposure to the reagent. Solvents may cause softening, and swelling.

Once when I got distracted, I left mineral spirits on acrylic overnight with no problem. Would I store mineral spirits in acrylic? No.

While a 1/8" NPT tap is not huge, the 1/8" part is deceiving. The tap is pushing 1/2" diameter. And yes, it could easily be tapped dry. But dipping the tap in mineral spirits will yield smoother threads. Smooth threads are less likely to leak. BTW, I found water almost useless as a cutting fluid for acrylic. It helped keep things cool if I kept the water running, but did not do much in terms of getting a smooth cut.