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

Video - April 3, 2023

I recently purchased twelve* different brands of parallel clamps in hopes of reviewing them all. Unfortunately, I failed in my mission to come up with a fair and balanced set of parameters for testing. I did, however, uncover some interesting truths about parallel clamps that I think you need to know. So if you’re in the market for parallel clamps, you should be aware of these things as a parallel clamp setup is a substantial 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!

I noticed that many clamp reviewers will test the squareness of the clamp head to the bar and rely on it as a metric for overall build quality. They assume that an out-of-square head is a problem. I’ve even seen some companies using the squareness of their clamping heads as a selling point. The reality is that having a toed-in head is actually desirable. The parallel clamp was originally designed by Bessey in 1980 and the heads were deliberately toed-in. And they’re still manufactured that way today. Simply put, the toe-in helps the clamp achieve a parallel state while under pressure .

Of the twelve brands we have on hand, half of them feature square heads. You might be wondering, should those clamps be avoided? I don’t necessarily think so, but ultimately it’s up to you. You may have specific reasons for preferring your clamps be square in their resting state. Personally, I prefer the toe-in as it makes the most sense to me. 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 and should instead be viewed as an intentional 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.

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. Others 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 – https://amzn.to/40V4nz7
Jorgensen – https://amzn.to/3U7zbuv
Bora – https://amzn.to/40DtIy2
JET – https://amzn.to/40U5oHO
Rockler Parallel Clamps
EHOMA – https://amzn.to/3K5brT6
Irwin – https://amzn.to/3m47wxW
Dewalt – https://amzn.to/40UH5JV
Harbor Freight (Bremen)
Peachtree – https://amzn.to/3MlhLIK
Woodpecker (Semble)
Yost – https://amzn.to/3mbrPJI
Bessey I-Beam Clamps – https://amzn.to/3nCi8o5
Rockler Mini Deluxe Panel Clamps

Discussion

Derek Roff April 3, 2023 3:28 pm

This is a superb discussion of parallel clamps, panel clamping, clamping forces, and flatness. All your videos are great, but this one stands out for me as outstanding in analyzing and explaining the relevant and irrelevant factors of a complex topic in a very clear, organized, and engaging way. Thanks.

Reply
Jonathan Crone April 3, 2023 3:30 pm

One thing on my part as I’ve gotten older and grumpier, I’m having a harder time to turn the handles on my regular Bessey clamps.
I did the ‘hockey tape’ trick and that helped a bit, but I’ve ended up keeping a couple of the so-called I-beam clamps to do an initial clamp and then throw my regular bessey clamps on to finish the job because I find the handles on the I-beam easier to turn.
Looks stupid but it works

Reply
- Marc Spagnuolo April 3, 2023 10:32 pm
  
  There are quite a few brands now, including Bessey, that are making clamps that allow for easier handle turning. Current Besseys have a socket in the handle for an allen wrench and a few others have handles that bend to 90 degrees. And I’ve seen a few folks modding their old clamps by driving a bolt into the end of the handle, allow them to use a socket wrench to tighten them down.
  
  Reply
AHD April 3, 2023 3:43 pm

You can always put a shim between the panel and the bars of the parallel clamp, and then remove the shim after you tighten a bit. That way the bow in the bar of the tightened clamp won’t be pressing on the panel. And I think the toe-in of the clamp head will align under pressure without inducing a bow in the panel.

Reply
Charles April 3, 2023 3:50 pm

As someone who has owned and used several sets of parallel clamps over the years Jorgensen ones have held up by far the best. At least the wooden handled ones…All the brands work great at first but after a year or two and the accumulation of some glue both Bessey’s and Irwin’s have become close to useless. For a big panel glue up pipe claps are pretty great.

Reply
Claude Stewart April 3, 2023 4:00 pm

That was definitely an eye opener. Thanks marc.

Reply
John April 3, 2023 5:25 pm

Hey Man, Always love your videos. Comment on Pharrell Clamps.
I have both Jet and Jorgenson versions. I find the Jorgenson much easier to move, or adjust to the size you want. It seems I have to fight the Jet to move the adjustable side. The tightening side on the Jet is harder to grab and use than the Jorgenson.
I love your tip on the Bessy heavy duty bar clamp.

Reply
Allan Grant April 3, 2023 5:27 pm

I sold my parallel clamps a couple of years ago. They weren’t the best made and had a lot of problems. Depending on the individual project I’m working on, I use pipe clamps and/or bar clamps, some of which I bought 40+ years ago and deflect like crazy. I also use cauls on almost every glue up to favor the flatness in the finished product. I have very few issues with bowed panels. Good video as usual, Marc.

Reply
Jeffrey Murray April 3, 2023 6:14 pm

Before I purchase a product I most generally look at the reviews, starting with the lowest rating. Just like you said I find scathing reviews from people that obviously don’t know how to use the product. Sometimes there are the majority of reviews that are 3 stars or less and if I start reading about twisting cracking from many people, I will shy away from that particular product.

Reply
Robert Cox April 3, 2023 7:51 pm

In all the years that I was a carpenter the clamps you are talking about were referred to as bar clamps.

Parallel clamps are two separate blocks of wood connected with two separate screw arms so they are fully adjustable to obtain full contact. They are made by Jorgensen

Reply
- Marc Spagnuolo April 3, 2023 10:28 pm
  
  I know terminology can be variable by region and over time so maybe that accounts for the differences. But today, a parallel clamp is exactly what you saw in the video. A bar clamp is more like the Bessey I-Beam alternative I showed. And the wooden clamp you reference is called a hand screw clamp.
  
  Reply
Vince Bacanskas April 4, 2023 12:02 pm

Marc- what you are inferring from observation is absolutely correct and being a retired engineer, I can tell you that it can be proven scientifically as well. There are thin film strain gages that you could put at three levels on the clamp face (bottom, middle, top) for simplicity and measure the differential pressure across both the faces. You could place them on the surface of the face. You could then apply pressure to the clamp while measuring what actually occurs in tightening and loosening the clamp. It will also tell you what you normal pressure applied could be, as well as your “He Man” pressure. Probably a simple experiment that someone at UofM could help you out with. With some computer assisted data acquisition, you could generate graphs of deflection vs applied force. I have the engineer disease pretty bad!

Reply
Danny Hellyar April 5, 2023 9:38 am

I’ve been using both Bessey and Jet Parallel clamps for close to twenty years now and here’s my experience using them . There are both well built and apply more than adequate pressure. I like both for different reasons . When preparing for a glue up the Jet clamp heads stay in the position you place them better than the Besseys which is nice when your not clamping on the level . I also found the Jets tend to leave clamp marks on the edges of the stock your clamping, which requires either some sanding or grain raising to repair. The Besseys don’t leave those marks under any amount of pressure so I’m assuming they don’t deflect as much. Also the Besseys heads move along the bar more easily and smoothly than the Jets which is less frustrating. Sometimes in a glue up extra pressure is needed so it’s nice to have the extra lbs of pressure produced by the Bessey. When I was using Besseys clamps to glue and clamp faceframes onto cabinet fronts my hands were getting very tired and wished they had some way of tightening the clamps without wearing out my hands I made a suggestion to them to put socket holes on their handles or handles that swivel side ways for easier or alternative ways to allege the constant twisting of the hand . To my surprise they did change their handle design to accommodate both changes I suggested soon afterward. Overall I prefer the Besseys over the Jets.

Reply
Ed Burtenshaw April 6, 2023 12:58 pm

For gluing up larger panels I use two maple cauls, with a slight curve on one side placed against the panel. I made the cauls from patterns, and have them in 24, 36, and 48 inches. I only need two clamps, one at each end of the panel, to create pressure along the entire length of both sides.

Reply
Ed Jones April 11, 2023 12:55 pm

Interesting science, Marc.
Over a decade of occasional watching as time permits, this review of yours drew me out of the
shadows. Haha. A really value-added topic, so I’m glad I peeked.

Maybe, “high relevance” for any preferred clamp brand types of clamps (Parallel*, Bar or Sash), happens to be the dreaded task of removing dried glue. Cleaning clamps has to be among the more overlooked and dubious woodworking maintainability tasks. Clamping performance fails to work successfully without periodic proper cleaning and dry lube to these sizeable financial investments.

Reply

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

1. The heads on a parallel clamp should not necessarily be square!

2. All parallel clamp bars deflect under pressure.

3. Maybe parallel clamps aren’t the best solution for clamping panels?

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

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