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Bessey's new Auto-Adjust Toggle Clamps take this useful design to new heights. After having tried them for a few days now I wonder why toggle clamps weren't always made this way!
Click image to enlarge

Bessey Auto-Adjust Toggle Clamps

A decidedly user-friendly step up

Text, photos and video by Tom Hintz

Posted – 3-28-2011

Note: This is an exclusive first-look that you will not see anywhere else! Bessey has given NewWoodworker.com the first chance to review these new clamps!

Toggle clamps have long been a favorite of woodworkers for projects such as building jigs and fixtures. Though obviously useful traditional toggle clamps often had a frustrating side, specifically in setting up the contact foot position and its height to accommodate the thickness of wood being worked with. If the stock being clamped is not uniform in thickness the frustration factor juts upward sharply. The idea folks at Bessey along with their engineering horsepower massaged the toggle clamp concept and came up with what you see here. Easy to use is just the start. I know that something that is simple to use was often very complicated to design so it would be simple to use. Still, it makes me wonder why toggle clamps were not always made this way.

The Basics

The Bessey Auto-Adjust Toggle Clamps look relatively similar to traditional toggle clamps except that there are more parts in the mechanism below the handle. Also, all three of the Bessey Auto-Adjust Toggle Clamps styles (two horizontal, one inline) are capable of generating clamping forces from 25 to 550-lbs! Yes, the clamping force of the Bessey Auto-Adjust Toggle Clamps is adjustable and that setting is totally independent of the clamping size capacity. All three versions are currently rated for a holding capacity of 700 pounds.

The STC-HH50 is approximately 8-1/4”-long, has a 2”-opening and weighs .77-lbs. The STC-HH70 is about 8-1/4”-long, has a 2-3/4” opening and weighs in at .86-lb. The STC-IHH25 inline version is 9”-long, has a 1” opening and weighs .86-lbs. The lengths were measured with the clamps in their “applied”, handle down configuration.

All Bessey Auto-Adjust Toggle Clamps have identical mounting flanges (left) which makes swapping them out a snap. All also have this swivel contact pad (right) equipped with a removable plastic cover.
Click images to enlarge

All three versions of the Bessey Auto-Adjust Toggle Clamps have a 2-1/4” by 2-1/2” mounting flange with identical hole patterns. Each plate has four holes designed to work with ¼”-diameter (or M6) fasteners. All of the bases also have four slotted holes that can be used if the application requires fine-tuning of the clamps position. I like the idea of one mounting hole pattern because it allows the user to interchange Bessey Auto-Adjust Toggle Clamp styles on the same jig to build in more flexibility. That adaptability could reduce the number of jigs and fixtures that you need to have on hand and perhaps reduce the number of toggle clamps you need overall.

The swinging arms on the Bessey Auto-Adjust Toggle Clamps look very much like the traditional ones and they do have an adjustable contact pad. However that contact pad is on a threaded shaft with a single locking nut on top of the arm. That makes it much easier to set and to lock in place than the older ones that use nuts above and below the arm with the shaft going through loose plates top and bottom as well.

Because of the auto-adjust feature you can set the contact pad once and in many cases forget about them through the rest of that job and maybe a couple more as well.
The design of the Bessey Auto-Adjust Toggle Clamp contact pad differs from most of the older designs. The Bessey Auto-Adjust Toggle Clamps have a 7/8”-diameter round pad mounted on a swivel mount that helps it get a good grip on surfaces that might not be perfectly flat. The threaded shaft that supports the contact pad is long enough that you can adjust its length to compensate for mounting the Bessey Auto-Adjust Toggle Clamps on a pad or pedestal if need be. The removable plastic cover that comes on all of these clamps helps protect the surface of the wood being secured.
All of the Bessey Auto-Adjust Toggle Clamps have a generous 1” by 2-1/8” handle. The larger handle is more comfortable to use but combined with the overall length of the handle makes applying the higher clamping forces that the Bessey Auto-Adjust Toggle Clamps are capable of generating easier.


This spring mechanism (left) is part of how the auto-adjust feature works. The adjustable pressure screw (right) lets you dial in the amount of clamping pressure needed for the job.
Click images to enlarge

Probably the most notable feature of the Bessey Auto-Adjust Toggle Clamps is their ability to apply a given force to a range of material thicknesses without adjustments by the operator. I’d like to say that I fully understand how this self-adjusting feature works but that would not be totally true. I know that a portion of the mechanism slides rearward against an internal spring as pressure is applied and that movement is apparently what makes the auto-adjustment happen. I expect that the complete explanation of how this auto-adjuster works will involve a bunch of geometry that might frighten me a little. However it happens the auto-adjust system works.

The ease with which the Bessey Auto-Adjust Toggle Clamps handles apply pressure also suggests that the engineers have figured out the most beneficial pivot points. Those pivot points give the operator a good measure of mechanical advantage which makes applying the pressure easier. You can still feel the handle going over center but it is not the sudden lurch as so often happens with traditional toggle clamps.

Pressure Control

With a mechanism that allows the Bessey Auto-Adjust Toggle Clamps to clamp up a range of material thicknesses the last thing I expected to find was another level of adjustability. This system allows the operator to adjust the amount of pressure applied when the handle is pushed down. This pressure adjusting system has no impact on the auto-thickness adjusting which makes it a bit more mysterious.

A simple cross-bit screw (with a knurled edge) with locking nut at the hinge point is what controls the amount of pressure. I should caution you that backing this screw out increases pressure while tightening it reduces pressure. I know that seems backwards but that is how it works and I was able to find that out after only a little messing around before noticing a sticker with graphics that clearly show what happens when you turn that adjusting screw either way. I was nearly done in again by the man law that prohibits reading instructions.

In the Shop

The large handle (left) makes applying the sizeable pressure easy. The contact pads are mounted on a single spindle (right) with one locking nut on top to make adjusting them much easier.
Click images to enlarge

The Bessey Auto-Adjust Toggle Clamps work just as you would expect a toggle clamp to work only they do more than their traditional counterparts do. The hardest things to get used to could very well be not having to adjust for varying material thicknesses and being able to adjust for the amount of pressure that we want to apply. Since both of those features are independent of each other learning to use them properly takes very little practice. Getting familiar with these features takes a few minutes, just long enough to justify adding this paragraph to the review.

Adjusting the position of the contact pad is another near no-brainer. The locking nut can be turned with a 9/16” or 14 mm open-end wrench. You really don’t need to strain when tightening this nut to secure the contact pad where it is needed. The good thing is that with the range of contact pad adjustment you can fine-tune the clamping range to surround the expected dimensions, if need be. The range of thickness available with auto-adjusting feature will often make adjusting the contact pad unnecessary.

Even the pressure adjustment is easy to use (if you bother to look at the sticker right next to it) and makes it possible to clamp more delicate things without damage. If you are used to the traditional toggle clamps I think that you will find being able to vary the pressure very handy.

I suspect that learning to apply the new features in the Bessey Auto-Adjust Toggle Clamps to your style of work will happen faster than you might think. You simply have more capabilities with the Bessey Auto-Adjust Toggle Clamps so you have to find the best way to apply them in your shop. For me that learning curve was over within 30-minutes because the Bessey Auto-Adjust Toggle Clamps repeat very well. That lets you find a setting that you like, lock it in and then forget about it.

Oddly it was the auto-adjusting thickness capability that took the longest for me to accept. I kept wanting to adjust the contact pad for a new thickness of wood when the Bessey Auto-Adjust Toggle Clamps didn’t need it. I just had to un-learn old toggle clamp habits to let the Bessey Auto-Adjust Toggle Clamps do more things for me, as they were designed to do.


Video Tour

Despite everything that the Bessey Auto-Adjust Toggle Clamps can do, they are not difficult to use. They look (and are) well-built and should last a very long time with minimal care on your part. In this case “minimal care” means not running them over with your car or something.

Throughout the evaluation I used the Bessey Auto-Adjust Toggle Clamps for everything I could think of. In each case I installed them and that was all that was necessary with the exception of one time when I had to adjust the contact pad so that it would clamp a single layer of paper and a 1-1/2”-thick piece without adjusting the contact pad again. By adjusting the contact pad up or down you can more the full clamping thickness range if you are mounting the Bessey Auto-Adjust Toggle Clamps on a pedestal or another slightly elevated surface. You can see in the video how that worked.

With an expected price of around $20.00 each (all three versions) the Bessey Auto-Adjust Toggle Clamps are not as pricey as I thought they might be. With all of the quality construction and new but dependable functions I really thought that these clamps would cost $25 to $30 ea. We will have to see how the street price shakes out after the Bessey Auto-Adjust Toggle Clamps come available in late May but I think the gap between these Besseys and the more traditional toggle clamps is not going to be very significant.

If you build jigs and fixtures for your shop the Bessey Auto-Adjust Toggle Clamps should be of great interest to you. I know that I am tired of dealing with the double-nutted contact pads and limited range of the traditional toggle clamps. The Bessey Auto-Adjust Toggle Clamps are likely to become the favorites of lots of woodworkers very soon. Like Bessey isn’t used to that!

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