In face of various posts, discussions and inquiries that arose throughout this year regarding warped spacebars, decline in quality and misconceptions around this topic, I decided to make some tests and discuss about what should be expected when it comes to spacebar keycaps included in custom kits, based on my experience of 7 years doing hobbyist work in this regard.
Given that the majority of keycap sets are sold based on 3D renders or studio pictures, customers and newcomers are being lead to believe that legends, colors and keycap shapes & forms will be delivered perfectly as seen on screen. This expectation has been echoed (and reinforced) by discussions elevating manufacturer reputations and overall high quality of the products they deliver. However, this doesn’t (or at least shouldn’t) induce the community to think and expect that the final products being delivered can, or should be absolutely perfect. Perfection in the hobbyist market of keycaps is unrealistic.
First and foremost, briefly speaking, keycaps are generally made out of ABS or PBT plastic resins which are injected in viscous (liquid) state inside metal molds. After conformation takes place, the keycaps will cool down and assume their final form. During the phase of cooling down, thanks to the molecular behavior of plastic and overall temperature/pression/humidity conditions of the environment, keycaps will warp to some degree. There is no perfect plastic keycap, to some degree all keycaps are warped. It can, however, be visible or not, constitute a defect or not.
Moving forward, regarding spacebars. The bottom spacebar plane (Figure 1) is independent from the face in which the keycap stems are attached (Figure 3). However, based on manipulation and observation of several keycaps/spacebars, I concluded that it is safe to assume that if the plane highlighted on Figure 1 is warped, the top spacebar face (Figure 2) and the inner spacebar face (Figure 3) will be warped as well. This leads me to conclude that when a spacebar presents warp on its outside faces, the body warps somewhat in progressive (or regressive) fashion until it reaches a mean point.
An important observation, based on tests and measurements I conducted, is that the dimensions of the stems remain constant regardless if a spacebar presents visible warp or not. There is practically no variation in dimension there. But positioning of the stems, however, will change to some degree and that’s the problematic phenomenon (Figure 4). In other words, the absolute coordinates of the stem in space will change, which can compromise functionality of the spacebar, since the stems must seamlessly travel inside the housing of the stabilizers. If the positioning of the stems is altered, this can’t be guaranteed. A 1% warp will cause a little over 0.1 mm stem drift.
The most accurate way to observe and evaluate space bar warping is by:
1) Resting the spacebar on a flat surface as shown on Figure 4 (without pressing corners) and observing a convexity (with the spacebar on normal orientation as seen on Figure 5) or a concavity taking place, (with the spacebar resting upside down on a flat surface, Figure 6);
2) Proceed to mount the keycap on a keyboard and observe its functionality. This is probably the most important and objective step, which will lead to a conclusion and solution (when necessary).
When corners are pressed against a surface – or spacebars are compressed against each other – the geometric curvature is visibly amplified, yes, which doesn’t automatically mean that the space bar is out of spec, or defective. It simply means that the space bar is not a mathematically flat object.
An aesthetically imperfect spacebar does not automatically mean it is defective, or out of spec. All keycaps are subjected to warp at some degree. This is practically an inevitable physical phenomenon, and largely subjected to chance and randomness. This is why some people will receive seemingly perfect spacebars and others will receive warped ones, even though they are from the same manufacturing batch.
Across different manufacturers, there is no publicly disclosed information on what the exact threshold is – (concavity/convexity/distance from spacebar to flat surface) in order to determine what constitutes a defective spacebar. But it is safe to assume that flat spacebars are within spec and the vast majority of spacebars which present some degree of concavity/convexity, are also within spec, based on what various manufacturers have communicated and delivered so far throughout the years.
As I write this, the only way for a customer to confirm a defect with his/her own hands is to ignore the physical appearance of the spacebar and focus on observing the depress and return behavior once mounted. If uncommon resistance is observed, or if the spacebar gets stuck, or if the spacebar pops out (or doesn’t even sit on stabilizers in the first place) the spacebar is defective without a doubt. In this case, the vendor (and subsequently the manufacturer) should be contacted to discuss replacements.
Do not expect spacebars to be perfectly flat as:
1) This is an unrealistic expectation at the current state of the hobbyist/keycap industry;
2) A warped spacebar does not automatically mean it is defective or out of spec;
3) There is no correlation between the price of a keycap set and the likelihood/straightness of spacebars.
I have seen $120 sets with straight, warped and defective spacebars. And I also have seen $40 kits with warped, defective and straight as an arrow spacebars. The same applies to keycap sets manufactured 40 years ago.
Mount the spacebars and observe the behavior, if something is out of place contact the vendor so he/she can arrange a solution within the manufacturer.