Keeping things perpendicular during assembly
June 3, 2019 2:39 PM   Subscribe

I have two pieces I need to glue together. One is a flat disk one-eighth of an inch thick with a hole in the middle. The second is a tube that's 0.1mm smaller than the hole in the disk. I will be gluing these using a compatible adhesive -- but how do I keep the tube as perpendicular as possible during the gluing? Cure time will be on the order of several minutes.

The disk will be affixed to one end of the tube. From what I've determined in testing, I am not personally capable of holding these pieces sufficiently perpendicular. These are part of a larger assembly with tight clearances generally, and gluing is necessary due to object size and clearances.

Perfect perpendicularity isn't necessary, but I do need to keep things minimized as the parts will be rotating during use, and any non-perpendicularity will result in an undesirable wobble; I must keep wobble below 1/16th of an inch or parts will start to run into each other in operation.
posted by aramaic to Technology (17 answers total)
 
Would the tube be stable standing on the not-being-glued end? And how much wider is the disk than the tube? My first thought is to stand the tube up inside something (box? pipe?) that would allow you to rest the disk on it while gluing and curing.
posted by asperity at 2:47 PM on June 3, 2019


Use a machinist block and/or a square and keep things clamped. Use two clamps and two squares perpendicular to each other so that you're stabilizing it in two or more degrees.

The longer the tube, the more accurate you will be if you measure from the end of the tube, so if it's possible, glue a long tube first, then cut it to length.
posted by suedehead at 2:55 PM on June 3, 2019 [3 favorites]


measure the circumference of the pole. cut multiple sheets of thick/heavyweight cardboard, each with a hole the same size in the middle, rectangular shape. glue like, 5-10 sheets of the cardboard to each other in a stack with the holes lining up. you might need to add more sheets.

put the pole in the flat disk. apply the glue. put a piece of wax paper over the pole to prevent the disc glue from sticking. put the stacks of the cardboard with the holes over the pole. weigh the cardboard overhang with books on each side. wait til dry.

that's how i'd do it, anyway.
posted by koroshiya at 2:56 PM on June 3, 2019


It would be helpful to know the sizes of the parts.

One way would be to build a simple fixture, (2 boards fastened at a right angle).
Set the fixture on the circle such that the tube is against the inner angle along its length. Clamp the tube to the inner corner.

Good idea about the wax paper.
posted by H21 at 2:58 PM on June 3, 2019 [2 favorites]


Yeah, if you can get us a diagram with measurements and location of the parts relative to each other that would help a lot
posted by Dmenet at 3:17 PM on June 3, 2019


Support tube in a pair of V-blocks, place a stationary reference object near the disc, and rotate the tube while the glue dries. Nudge disc until wobble is insignificant.
posted by jon1270 at 3:18 PM on June 3, 2019 [1 favorite]


It would be helpful to know the sizes of the parts

An excellent point!

There are several sizes;
-- the tubes range from 2 inches long to 6 inches long, and from 1/16 inch to 3/4 inch diameter, all being 0.1mm larger than their receiving hole in the disk (disk holes were custom made).
-- the disks are all one-inch diameter BUT some of them have a single arm protruding from them that ranges between one inch long and six inches long (draw a hyphen, then put a circle at the end -- that circle is my disk).
-- the longest tubes are also the smallest diameter, alas, so the aspect ratio gets sort of unpleasant quickly.
-- tubes and disks are all nonmagnetic (varying metals and plastics)
posted by aramaic at 3:31 PM on June 3, 2019


Find a socket set of a suitable size, choose the socket the tube fits through most snugly, fit the tube through the socket so that one end projects out the bottom of the socket an eighth an inch, apply the glue, fit the projecting part of the tube into the disk, and place the socket flat on the disk until the glue sets.
posted by jamjam at 3:40 PM on June 3, 2019


I have a fairly old Black & Decker Workmate. I'd capture the tube where there v-notch between the two halves of the top. Get the top of the tube close to the table surface and make sure it's square with a ....square or a geometry triangle. Then glue the disk on the top end of the tube. Use the trick suggested by jon1270 to get the best fit (before gluing).

The cheapest Workmate is $35, and could be useful to someone forever.

Exact suggestions aside, one overriding mandate for any little project is Get The Right Tool.
posted by SemiSalt at 3:43 PM on June 3, 2019


I would use clothespins or some other clampto make it perpendicular for those minutes,
posted by theora55 at 4:10 PM on June 3, 2019


Can you cut the tubes?

Invert the assembly: Apply glue to one end of tube. Insert in through the hole in the disk so it is ‘proud’ on one side and of greater than necessary length on the other. Clamp the short protruding end and then place the assembly on a rack or between two level supports disk up with the longer portion of tube hanging down, like a T. Adjust to perpendicular with square. In this position, there will be no moment tending to move the tube off axis; indeed, the tube will tend to hang straight down.

After the glue has set, cut flush on one side and to proper length on the other.
posted by sudogeek at 4:22 PM on June 3, 2019


Can you stick the tubes into/through a piece of styrofoam? I'm imagining: make a sort of of bridge with the styrofoam (use something to hold it up on the ends) and then stick the tubes through it at 90 degrees. The disks rest on the table, under the styrofoam bridge.
posted by needs more cowbell at 4:26 PM on June 3, 2019


If you have access to a drill press, you can insert the tubes into the chuck and place the disks on the table. Adjust the table height to match them up for gluing purposes.

For tubes larger in diameter than the chuck size you may be able to place in the chuck a rod that matches the inside diameter of the tube.
posted by tronec at 5:37 PM on June 3, 2019


Expanding on that Workmate suggestion: I'd take a small block of wood (or plastic) that's wide enough to stand perpendicularly on the disk, cut a narrow groove down one face of it (perpendicular to the bottom), and put a rubber band around it to hold the tube in that groove. Wax the bit of it that might be adhesive prone.

The groove can be the kerf of a relatively thin saw (eg: 1/32" would be perfect). The rubber band doesn't want to be any tighter than necessary to barely hold the tube, to allow for a little vertical motion.
posted by straw at 5:38 PM on June 3, 2019


About the same depending on what's handy. I'd build two sides of a box so that the corner is vertical. Trim out a notch on the bottom of the corner to accommodate the disk. Attach the tube to the inside of the corner so that it protrudes down to the surface of the table or whatever. Disk, glue, lower the box/tube into position. Depending on your precision requirements, it could just be an Amazon box with the corner cut out, or you could have a flat piece of wood with a couple other joined at 90° with the corner cut off so you have a nice flat surface and nice perpendicular walls and a notch to hold your stick vertical.
posted by zengargoyle at 7:04 AM on June 4, 2019


First of all, thank you everyone for your thoughts, they've been really helpful to me in working through this (note to the future, start projects with loose tolerances! Only use tight tolerances if you really have to!)

I think I'm going to use the drill chuck idea, or possibly a variant thereof using a self-centering three-jaw (can't find my Jacobs chuck at the moment, so I don't recall the through-bore diameter).

...however, I'm marking as "best" any answer that seemed like it would work to a reasonably high precision, either with equipment I possess, or equipment I think a more normal person could possess.
posted by aramaic at 9:12 PM on June 4, 2019 [2 favorites]


Also it's embarrassing that I didn't think of the chuck.
posted by aramaic at 9:16 PM on June 4, 2019


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