Trick to drilling the center of a round tube?

Greetings!

I'm about to mount the windshield on my RV-9A slider.

Using a #40 drill, you go through the plexiglass windshield, then the roll bar.
The trick is that you need to drill into the EXACT center of the roll bar.

Someone told me a trick to doing that but I can not now find it on the forums.

When drilling the roll bar and windscreen, how do I find the exact center?

advTHANKSance

CC

comfortcat said:

Using a #40 drill, you go through the plexiglass windshield, then the roll bar.
The trick is that you need to drill into the EXACT center of the roll bar.

Click to expand...

Can you drill the roll bar first, then the plexi using the roll bar as a drill guide?

A "V" block is typically used to get a centered hole in a piece of tubing.

What you might be referring to is this? Put masking tape on the roll bar under the glass contact area. After you lay the glass onto the roll bar the tape will show exactly where the two touch. you might need to apply a little pressure on the glass with your hand. Mark the contact point on the glass and drill. The tape will change to a darker color at the point of contact and shows a narrow line. This has worked well for me but decide for yourself. Works best with good masking tape.

Similar to Larry. I used a thin film of oil on the roll bar & canopy frame. This showed the contact point very clearly & the spot to drill. This idea came from someone on VAF.

LARCO said:

What you might be referring to is this? Put masking tape on the roll bar under the glass contact area. After you lay the glass onto the roll bar the tape will show exactly where the two touch. you might need to apply a little pressure on the glass with your hand. Mark the contact point on the glass and drill. The tape will change to a darker color at the point of contact and shows a narrow line. This has worked well for me but decide for yourself. Works best with good masking tape.

Click to expand...

Same, but it works a little better with black electrical tape.

I had no luck with the masking tape. A friend suggested carbon paper between the canopy and the roll bar but I haven't tried that yet.

I made three U shaped plastic blocks about 1-1/2" x 1-1/2" x 1/2" and cut a slot the same width as the canopy frame tubes, 7/8", 3/4" and 1/2" and blackened the ends with a wide Sharpie. If you cut the slot on the tight side, the block with clip onto the tube and not fall off. Then I clipped the block onto the tube and using a trouble light on the outside of the canopy (don't let the canopy get hot), I measured half way between the legs of the block and marked this on the canopy protective film with a fine Sharpie.

Another option is the no-hole method....