Fix a Broken Plastic Chair

Background

A plastic chair; my neighbor's, sufficiently strong was broken by unbalanced force and it was discarded for use at their home and given to the security who was trying to patch it with electrical tape and some stray wire. I saw this and requested that I fix the chair for him.

Assessment of damage

Three full cracks had developed where the left handle met the front-left leg- one running down, one running up into the handle, and one going just a bit to the right of the seating area. No visible chipping was observed and thus I assumed a proper adhesion and stitch would save it from further damage and make it reliable enough to use.

Plan

Use a sufficiently flexible 2-part epoxy-based adhesive to fill the cracks and stitch parts together with a strong thread.

Note: due to local restrictions, not the best of materials were procured and had to do with whatever was lying around the house. Also, apologies that not all the steps were captured visually as I remembered about the 'Fix It Challenge' only midway through fixing.

1. 2-part epoxy adhesive (better if it's more on the flexible side- I used Araldite klear with a little bit extra hardner) and a flat plate and a stick to mix and apply. Some tissues would home handy to clean up.

2. Strong nylon thread matching the chair's color of max 1.5mm dia (I used a single strand of the twisted pair network cable as it matched the brown color of the chair- not the best of options, but that's all I had) and tools to prep it (in my case- a wire stripper was all that was needed).

3. Hand drill and 1mm drill bit (for the stitch holes- adjust drill bit size according to the available stitching thread- smaller the better)

The preparation involves making the holes for the thread/wire to pass and cleaning the inside of the crack to rid it of any debris.

1. Planning and drilling the first set of holes

• Aim to leave at least a 2mm gap between the edge of the crack and the outer of the hole, and more if you feel the material isn't thick/strong enough and that the thread might just rip through the material.
• If beauty is of importance- mark the holes in advance using a contrasting marker/paint to make sure they are equidistant.
• Visualize the pattern that you wish to see in the chair after the stitch and plan the holes accordingly.

2. Drilling the holes on the other side

• The gap between the hole and the crack and also between holes is as on the first side.
• The second side can have holes either in line with the first side (option 1), or slightly vertically offset (option 2)- based on your plan.
• Whether you choose option 1 or 2 or any other fancy stitch, please remember the goal- to exert a force perpendicular to the crack at every point possible.

1. Clearing off shavings from the drilling

Gently scrub off the drilled shavings. Smoothen any surfaced plastic due to the drilling.

2. Cleaning the surface that is going to get glued.

The drilling might've generated some plastic dust (yes, wearing a mask is a good idea).

If you have sufficient time, wash with soapy water the drilled areas and the cracked surface (thoroughly). Drying it thoroughly is also very important.

If short on time, wipe the drilled area and the area to be glued with a tissue or clean cloth. The goal is to ensure that there is no shavings/dirt/oil between the surfaces that get glued.

1. Mixing the glue

Use any non-absorbent material to mix the epoxy.

Mix only so much that you can apply in 2-3 minutes (you might end up needing a bit more because of some accidental mess- so underestimation helps.) If you assume that there are tricky places and it'll take you some time to cover the entire surface, do not feel ashamed to split the mixing and glue application into batches- ensure that these are independent parts that you'll be sticking.

2. Applying the glue

Be quick and apply a thin layer of glue on either of the surfaces. Once you've applied the glue, keep the portions pressed together in the right alignment- very important (practice without glue, if necessary).

You may not be able to clamp if the surfaces aren't even, in which case be prepared to be the human clamp for 10-15minutes- this much amount of time usually cover the initial curing period.

3. Cleaning up excess glue

If there is an extra pair of hands available, wipe off the excess glue that seeped from the cracks.DON'T do the mistake of letting go off the glued portions before it has sufficiently cured.

Note: Note down the time since the application of the glue if the curing time is more than 30minutes or so, so as to well rest the chair before handing it over after the stitching.

Read instructions in the epoxy's pack to better understand how long it will take to set to better decide on #1 and #2.

If the epoxy isn't of the flexible kind, adding a little bit more harder will make the cured glue slightly more rubbery- though it'll cure faster.

If some abandoned network cable is all that you have, below are some tips to easily extract a single strand.

1. Remove the black sheath

The easiest way is to use the fiber thread within the cable. Strip a few inches of the black sheath to expose the inner wires, identify the fibrous thread, and with a firm grip on the cable, pull the fibrous thread perpendicular to the cable- the sheathing just tears open.

2. Separate a single wire from the twisted pair

If you wish to use both the strands after separating, be patient and untwist it turn by turn. But if you wish to sacrifice one within a pair, hold the strand that you wish to preserve and just slide out the other one as you are cleaning some dirt from the wire axially- this is exponentially less time consuming than the patient method :)

A single strand from a network cable can thus be extracted.

1. Decide the start point and start the stitch

Start from a side that is towards an end and has some space in the back that isn't well exposed so as to keep the splicing hidden from plain sight.

Based on the thread/wire, the starting and ending knot might need improvisation- I just had them twisted and it was sufficiently secured. Nylon thread users might need to melt the ends for a more secure stitching experience.

2. During the stitching

Tighten every stitch as you proceed, place a finger on the tightened running line after you've tightened it to sufficient tension(nylon thread users to be extra cautious here, metalcore wire will hold the tension sufficiently without much aid). The goal is to uniformly apply just enough tension to keep the pieces well pressed together- not too much (that the 2mm plastic in between gives way or the thread/wire breaks) nor too little (that there is slack in the stitches and it moves).

Any experience in gutting badminton rackets by hand helps here :)

3. Perform the necessary number of runs

Do a single run or two runs, as per design and reinforcement need. I did two runs because I had enough wire and I wanted added strength because the shielded copper wire isn't the strongest.

4. End with a secure knot

If ending at the start point after a 2nd run, use the start end to knot/splice well to the running end. Use the epoxy or melt off the end as needed to secure the knots.

Note, if the plan for multiple runs exist- check for the dia of the thread/wire and the hole that's drilled- make sure (dia of thread/wire): (drill bit dia) is at least 1:2. I used a 0.6mm shielded wire of which the shield was flexible, and I have been able to make about 4 entries into a single hole drilled by the 1mm bit. This also says that the 1mm drill bit might be slightly bigger than 1mm.

With the end well secured, look and admire the unique design on the chair and return it back to the owner to see his beautiful smile.

Note, if the curing time for the epoxy isn't completed, wait till you handover the chair :)