Oversize drill bits for acrylic blanks...???

[Herb G]

I realize a lot of people back or reverse paint their acrylic blanks and/or tubes so the brass tube won't shine thru. How many of you oversize the drill bit to accommodate the thickness of the paint and/or the epoxy glue?

If so, how much larger do you go? Is 1/2 MM enough to allow for the paint or glue?
For example, a Slimline pen uses a 7 MM drill bit. Would a 7.5 MM drill bit be enough to allow for the thickness of the paint & glue, so it doesn't scrape off when inserting the tube into the blank?

Thanks for any experiences, tips, or tricks.

 

[eharri446]

I normally make pens like the Sierra and when I have to paint the tube and back paint the blanks I have not had to use a larger drill bit since they use a 27/64 but it seems that some of them have a 3/8 inch o.d. tube. That is one reason why I am switching from CA for gluing the tube in to epoxy so that it will completely fill the void around the tube.

 

[MillerTurnings]

I measure the brass tube and add .010" for paint and epoxy clearance. That seems to give me a tight enough fit but still has easy assembly. Many times, rounding up to the next standard drill bit size is too much.

 

[rd_ab_penman]

No need to reverse paint the blanks with too much paint so the tube is too tight.

Les

 

[TonyL]

Unless the blanks is 100% opaque, I paint tubes and blanks. I am not saying that it what you should do, but what I find the need to do. I do used compressed air to clear any drilling debris, but that is it. I find the epoxy acts as a lubricant and the painted tubes slide in easily into the reverse painted blank. I drill according the kit's instructions. I have not had any tubes get jammed, and I have performed this hundreds of times. I am about to perform this right now. Maybe, my holes are sloppy (too large)...don't know, but I use the drill size recommended by the kit. Maybe I can record it and send.

 

[TonyL]

Here's the video. https://www.youtube.com/watch?v=ZGAUY-d9eZ4

 

[SteveG]

Here is my direct experience:
After drilling the blank, I check the fit of the brass tube. If it is snug, the drilled hole needs more work. If there is a little "Wiggle Room", then the tube will fit after drilled hole is painted.

If the test fit was snug, I use a rat tail file, or sand paper wrapped on a transfer punch to slightly enlarge the hole. It does not take much work to get it how you want it. Do it a few times and you will know how much wiggle room is needed. Quick and easy process!

 

[randyrls]

Herb; I spray the inside of the tube with a rattle can available anywhere, in many colors. This does not change the drill bit needed. You may want to use Polyurethane (Gorilla) glue as it expands and fills any voids. If you do this, be sure to check the blank after about 15 minutes to an hour to make sure the tube doesn't move inside the blank.

PS. I do sometimes find that the drill bit needed for wood is slightly larger than the drill bit needed for plastic. The same drill bit will make a slightly smaller hole in wood vs plastic.

 

[budnder]

I test fit the tube and if it binds at all, I will go to a 1/64 bigger bit. But only if I'm back painting.

 

[Wildman]

Not sure have ever used a bigger drill bit when painting tubes but do wait for paint on tube to completely dry before gluing in tubes. I have a drill bit chart which helps decide what bit to use after measuing tubes. Like everyone else will test fit tubes before gluing up. Have both metric, standard, and wire size bit indexes. I use epoxy glue for gluing tubes. I like polyurethane glue too but stuff goes bad in the bottle on me so stopped buing it. Had too many glue failures using CA.

https://www.imperialsupplies.com/pdf/I_DrillSizeDecimalEquivalent&TapDrillChart.pdf