The Truth about Parallel Clamps and Why They’re Hard to Review

Written on 04/03/2023
Marc Spagnuolo

This post appeared first on The Wood Whisperer.

I recently purchased twelve* different brands of parallel clamps in hopes of reviewing them all. Silly me! While I failed to come up with a fair and balanced set of parameters for testing, I did uncover some interesting truths about parallel clamps that you might not be aware of. If you’re in the market for parallel clamps, you should be aware of these things as a parallel clamp setup is a sizeable investment. So here’s The Truth about Parallel Clamps and Why They’re Hard to Review.

1. The heads on a parallel clamp should not necessarily be square! This was an interesting revelation as many clamp reviews will test the squareness of the clamp head as a metric for overall build quality, assuming an out-of-square head is a negative. And some newer companies that produce parallel clamps will show that their clamp heads are perfectly square as if it’s a desirable feature. But the reality is that the parallel clamp was originally designed by Bessey in 1980 with the heads toed-in and they’re still manufactured that way today. The toe-in helps the clamp achieve a parallel state under pressure (more in this in the video). Out of the twelve brands we have on hand, about half of them featured square heads. Should those clamps be avoided? I suppose that’s between you and your clamps. You may have your reasons for preferring your clamps square in their resting state. Personally, I prefer the toe-in. So while I’m not saying a square head is necessarily a negative, I am saying that a toed-in head is definitely NOT a flaw, but instead a feature.

2. All parallel clamp bars deflect under pressure. No matter which brand you buy, the bar on a parallel clamp will deflect under pressure, raising up at the center and sloping down near the clamp heads. This ties directly into Truth #1. If the clamp heads are toed-in, the deflected bar will change the effective angle of the clamp head so that while under pressure, the two clamp heads are parallel. If the heads are not toed-in, they will start parallel and end up out of parallel under pressure should enough pressure be applied. I’ve seen numerous reviews of parallel clamps that test the amount of deflection of the bar and unless they also include some way to regulate the amount of force being applied on the clamp, the resulting measurements will be fairly meaningless.

3. Maybe parallel clamps aren’t the best solution for clamping panels? I say this last point with some apprehension because I’ve been clamping panels with parallel clamps for ages. Based on Truths #1 and #2, it’s clear that the very nature of parallel clamps is that they will cause a panel to bow when under pressure. But in most cases, this isn’t a serious problem since we don’t need to apply full pressure to close the joints and wood is often more resilient than we give it credit for. But if absolute flatness is critical for your work, you might consider a different style of clamp.

So hopefully this arms you with information that will not only help you when shopping for parallel clamps, but also help you evaluate current reviews more critically. I’m not sure I’ll ever be able to pull off a full shootout style review of parallel clamps, but I can give you one piece of advice. Regardless of the brand, pretty much EVERY parallel clamp will get the job done. Some may be better built with higher-quality materials. Some may have toed-in heads and creature comfort features that make the clamp easier or more fun to use. But in pretty much every case, the clamp will hold your work together until the glue dries, and that’s really the point, isn’t it? At least for now, my buying advice is to get the clamp that you can get on sale and then stop reading and watching reviews.

*Easy links to the 12 brands you see in the video in no particular order::

Bessey –
Jorgensen –
Bora –
Rockler Parallel Clamps
Irwin –
Dewalt –
Harbor Freight (Bremen)
Peachtree –
Woodpecker (Semble)
Yost –
Bessey I-Beam Clamps –
Rockler Mini Deluxe Panel Clamps