View Full Version : Glass Tube Alignment Tips

George M. Perzel
09-07-2014, 7:22 PM
Hi Gang;
Here's a little gadget that simplifies the process of lining up a glass tube and/or aligning the mirrors. Typically, you would spend a lot of time pulsing the laser , adjusting a mirror, and continually repeating the process until you get things all lines up- a tedious procedure.
This is nothing more than a PVC plumbing fitting, bored on one end to fit snugly over the end of a glass laser tube, and with a disc inserted on the other end and bored for a red dot laser (found on ebay and other sources for about $4). The laser is connected to either a set of DC batteries or, in this case, to a 6 volt phone charger. Put in on the tube, turn it on, and make any adjustments to line things up.
In addition, measure the diameter of your lens holders and make up some circular 1/4 discs to fit them and glue stick some circular 1" matboard targets to them-easy to pull off and change to a new one when pulsing with the actual laser.
Best Regards,

Zlatko Kursar
09-08-2014, 2:17 AM
Very, very good idea!

Julian Ashcroft
09-08-2014, 3:41 AM
Great idea. That has inspired me to have a go at making my own version. Just placed an order on eBay for a couple of 3v red dot laser diodes. I will see if I can make the holder on the laser using plywood.

pete hagan
09-09-2014, 9:01 PM
I like the idea however how accurate is this to the plane of the laser beam?? Looking at my tube it doesn't look to be a very consistent diameter as it is a blown glass piece. I have moved my shop and not re-installed my tube yet so I'm definitely interested in this idea. Do you have any pics or experience using it to align?? Thanks!!!

George M. Perzel
09-10-2014, 6:01 AM
Not sure what you mean as gadget fits over the metal end cap which, in the case of my 80 watt RECI tube, is 1.06" diameter and about 0.5" long.
Best Regards,

John Noell
09-10-2014, 2:16 PM
Great idea! Just went to eBay and bought a red pointer LED. :)

Dan Hintz
09-10-2014, 2:45 PM
I like the idea however how accurate is this to the plane of the laser beam?

I was thinking the same thing. I cannot see anything that says the laser pointer will be coaxial with the beam coming out of the tube since they are independently adjustable.

matthew knott
09-10-2014, 4:13 PM
I was thinking the same thing. I cannot see anything that says the laser pointer will be coaxial with the beam coming out of the tube since they are independently adjustable.

The only way i can see this working is if you took a burn at a decent distance away with the laser then slipped the 'pointer device' over the tube and aligned the pointer diode to the middle of the burn, the pointer diode should be pretty close to coaxial then. It would certainly be a handy guide and let you see what adjuster moved the beam in which direction, i like it !!

Bill George
09-10-2014, 5:44 PM
Would it work in Reverse? Take out the focus lens and attach the red pointer at the bottom pointing up. Make sure the first mirror has the center aligned with the pointer and work your way back. If you ended up with the red dot centered on the tube output opening, would that work or is the beam not always square with the tube?

George M. Perzel
09-10-2014, 6:29 PM
Hark ye Naysayers;
This was not meant to align the Hubble telescope with Alpha Centaurus. It is simply a sturdy PVC plastic cylinder lathe bored on one end to fit snugly around the metal end cap of the glass tube, with an internal shoulder tofit firmly against the face of the end cap., thus assuring some degree of concentricity (?) and center alignment with the assumed path of the beam. The center point is maintained at the other end is bored to accept the red dot diode. The whole thing is about 3 inches long.
The normal placement of the laser tube has the end cap about 3/4" away from the first mirror housing. To use the gadget, the tube is slid back away from the mirror, the gadget is placed on the tube end, and the tube moved back so that the red dot diode is 3/4" away from the mirror housing- a fairly accurate replication of the actual laser beam.
In actual use, the red dot diode beam and the actual beam were very close at the final table cut point-only minor adjustment of the head mirror was required.
Best Regards,

Rich Harman
09-10-2014, 6:50 PM
I made something similar, but it was 3d printed. I also included a means to align the red dot using three thumbscrews. I have found that the beam emitting from the cheap laser diodes is not necessarily coaxial with the housing.

It was useful in troubleshooting a weird problem where three successive marks made with the gantry at the near, middle and far position would trace out an arc shape on the tape that was over the third mirror. With the red dot laser on I could move the gantry around and watch how the dot moved in relation to the last mirror. It turned out that my Y axis rails were not coplanar. I had to shim up the far end of the left rail. For regular aligning I don't bother with the red dot.