Reviving Old Clamps

Mark Palma describes the techniques for cleaning and repairing old tools.

Let’s start with the confession, I subscribe to the theorem ‘You cannot have too many clamps’. So I am a sucker for any opportunity to add more clamps to my meagre collection. W hen my father-in-law passed away I grabbed a box of clamps (or two) out of his workshop and brought them home. He worked his tools hard and they were well worn when they arrived and in need of some restoration. In this article, I’ll look at some strategies to clean up clamps and get them ready for years of future service.

High-quality clamps are expensive and many of the high-quality brands have closed their doors. Now, most clamps on the market are inexpensive replicas made in China. They function, but are not the same as the originals that they are modelled after. In the box I found some old Jorgensen deep-reach clamps (Model 4506), as well as two very strong Jorgensen 106 ‘C’ clamps with a 150mm reach and made of good old-fashioned cast iron. A search on eBay surprised me to see that even in poor condition they were selling for over $45 (£35) each!

Inspect or damage and missing parts

Not every clamp is worth saving, nor can all they be saved. Make a careful visual inspection of any clamp before you undertake any effort to revive them. Cracks in castings, missing parts, bent parts and loose rivets are a sign of trouble. Most of these symptoms are fatal. On the other end of the spectrum globs of glue, surface rust, and dirt and grime are things that can be addressed and resolved. Take the time to pick your battles and only work on clamps that can be repaired.

Gather your supplies and choose your strategy

There are two different strategies for removing rust: mechanical or chemical removal techniques. Each has its advantages and disadvantages. Chemical removal products range from household vinegar, to proprietary chemicals, to chemicals that ‘convert’ rust into another form of oxide that forms a protective layer on the metal. Safety measures vary, but by and large you need to wear protective equipment which can resist chemical spills (generally a higher level of protection compared to the general PPE we use in our shops). Some of these materials are toxic, and require special handling and disposal. Read the instructions carefully and heed their warnings!

Mechanical rust removal involves either wire brushes, abrasive pads, steel wool, silicon carbide abrasives or some other technique to scrub the rust from the metal. Wear eye protection and consider a dust mask too as you may be making metal dust if you use powered wire wheels or abrasive discs. After you remove the rust, bare metal will start oxidising (rusting) again unless you protect the metal surface. I use a combination of light machine oil and paste wax to protect bare metal. Paste wax has an additional benefit in that glue doesn’t stick well to it and glue spills usually pop off of waxed clamps. Plastic bits respond well to some washing up using soap, warm water and a little vinegar. If you are really ambitious, some spray paint, wood stain and wood finish will allow you to really dress up your clamps.

Jorgensen 4506 clamps

In the box I found four of these obsolete clamps. They are heavy, well constructed and with a 125mm deep-reach design are invaluable for adding clamping pressure in areas where other clamps cannot reach. These clamps have a 544kg working limit. The main beam is 8mm thick and 35mm wide. If you want a frame of reference, that makes the main beam about four times the size of a standard F-style clamp.

The metal portion of the clamp was cleaned up with a green abrasive pad and oil. An abrasive pad for small rotary tools and a wire brush for that same tool cleaned up the rust in the threads. The orange paint was in serviceable condition. The handle was sanded with 180-grit abrasive, stained and then coated with polyurethane. If you ever have sliding clamps like these or the F-style described. later, remove the rivet, slide off the sliding jaw and remove the two or three metal plates and spring within the sliding jaw. The plates need to move freely and independently from each other. Take them apart, clean them up and oil the spring. Look for damage or deformation of the spring and bend it back to shape as needed.

Pony spring clamps

On the other extreme of the clamping world are spring clamps. They have light load limits, are inexpensive to purchase and the difference between high-and low-quality versions is harder to spot. These brand name clamps have great springs that provide smooth and consistent tension throughout their range of motion. However, they are plated sheet metal and rust will pit the surface. These clamps did have both cushioned grips and tips, which is a nice feature.

The plastic pieces were removed using a heat gun, then they needed to be cleaned. Some warm water, vinegar and a few drops of dish soap was the cleaning solution used. A white non-abrasive scrubbing pad, the type used for pots and pans, cut through the grime, dried spray paint and glue on the plastic pieces. A cotton bud was used to dig debris out of the inside pockets of each piece, then they were left to soak for several hours.

To clean the metal parts of the clamps, first they were put in rust remover overnight to soak off as much rust as possible. Then, following instructions on the rust remover, the metal was rinsed off in water. The steel was scrubbed with an abrasive disc on a rotary tool. These discs work really well, but be prepared to use a couple on each clamp. I buy them in bags of 40 to 50. After removing the surface rust a light coat of oil was put on everything including each coil of the spring. Work the clamp in and out to get the oil between the spring coils. Lastly, the plastic pieces were reinstalled. They slid right on without any heat.

C clamps

C clamps are a workhorse in a shop. They can clamp metal, wood or other materials. Old C clamps were made of iron that was stress relieved. This allowed them to be dropped on the floor without breaking. Their screws were well machined Acme thread that worked regardless of the goo on the threads or the tension they were under. Modern C clamps, however, are made of poor-quality metal and the threads are poorly formed. The cross bar on the end of the screw is usually fairly thin and they often bend when turned and the ends of the crossbars are crimped and can cut you.

In the box were two large cast-iron Jorgensen 106 C clamps with 150mm of capacity and a sturdy stout Acme screw with a large swivel cap. They have over 1,088kg of clamping force and are brutes. Also in the box were three small 75mm clamps from Unbreakable, which seemed to have a nickel plating.

To clean up the cast-iron clamps I used a green abrasive pad and oil. I oiled the cast iron and then scrubbed aggressively with the abrasive pad. Wear gloves as this is a messy process. You are really driving the oil into the pores of the iron as you scrub. The same process of cleaning up the screw with a rotary tool and abrasive disc was used here. On the small C clamps, an abrasive disc made fast work of the rust and grime on the clamp.

I like to cook with cast iron and it takes years to develop a hard oil finish on the pan. I decided to try the same approach on the big cast-iron clamps. I oiled them well with a healthy coating of gun oil and then took them outside and put them in my shop toaster oven. Do not do this in the house or in any appliance you cook food in as you can poison someone. Beyond the health danger you can start a fire with this step.

I set the toaster oven to 93°C and baked the clamps for 20 minutes. Then I let them cool down outside in the oven. The oven smoked and smelled so do this step outside. The oil seemed to be drawn into the cast iron and the finish that was achieved was phenomenal! The small C clamps were oiled and wiped dry. Dispose of oily rags carefully so that they do not spontaneously combust. I have a wood stove in my shop and use it to incinerate my rags.

F-style clamps

F-style clamps are the little brother to the large 4506 clamps discussed above. They are available in many lengths. They are fast to adjust due to the combination of the sliding jaw and the screw thread attached to the handle. They can exert 225kg of clamping force. If they have a problem, it is that they can be over tightened. Many F-style clamps are damaged and the relatively lightweight bar will deflect when tightened, particularly as the length of the bar increases.

You can actually watch the bar deflect as you tighten the clamp. This isn’t a problem with clamps 300mm long or less but 460mm and 600mm clamps are actually unable to achieve the same clamping force as shorter lengths. The small grooves on the front edge of the bar can fill with glue and make the clamps ineffective. Fortunately, they are relatively inexpensive if they fail or break.

The process for reviving these clamps was similar to the processes used before. These clamps had the optional plastic tips, which were removed and scrubbed like the plastic on the spring clamps. The process of refurbishing the clamps was exactly the same as that used on the 4506 clamps above. Then the process took a turn. As these clamps had 460mm bars on them about 255mm of the bar was cut off with a hacksaw. Then the sawn end was filed smooth and the cut end of the bar eased with the file so that there were no sharp edges.

On older style clamps from the factory a rivet is located at the end. This rivet is a safety feature to prevent the sliding jaw from falling off the end and landing on your foot. So, I drilled a hole in the end of the bar and inserted a rivet. Using a ball peen hammer I peened the end of the rivet so that the shortened bar would be as safe as the original clamp.

Handscrews

Handscrews are a versatile style of clamp that holds tight, can hold uneven surfaces and grip tightly. These 300mm Jorgensen and screws were made of hard maple. We are woodworkers so cleaning up these clamps should fall squarely in our wheelhouse. I used 180-grit stearate-coated abrasives and a block of wood to sand down the wood surfaces. The handles were sanded down as well. A small wire wheel fitted in the rotary tool did a great job of taking the rust out of the threads of the screw threads. Then they were oiled with light oil and the excess wiped off.

The wood was then wiped with a tack cloth and a light maple stain was applied. After that had dried, a coat of oil and wax finish was applied to all the wood surfaces.

Conclusion

So was it worth the effort? Everyone values their time a little differently, but I will walk you through my analysis. The Jorgensen 4506 clamps were a great find and the four of them are probably worth over $200 (£155) all cleaned up. The two large cast C clamps are maybe worth $60–90 (£45–70). So these more expensive clamps are worth saving if you find them at a yard or boot sale, or in a garage.

Inexpensive spring clamps are just $1–2 (£0.8–1.5) each, new versions of the clamps cleaned up in this article sell for $9 (£7) each. The box yielded six of these. I am not sure if the F-style clamps are the best return on the time taken to refurbish. They took almost as much time as the big 4506. clamps, and you can purchase new clamps for $8 (£6) each. Further, the difference in performance between the cheap version and the higher quality model isn’t that large. The teeth on the front of these clamps wear over time and they are lower quality no matter who manufactured them.

The handscrew clamps are relatively inexpensive to buy. A new 300mm clamp is around $17 (£13). That is a large version of the clamp. A 200mm clamp sells for around $10 (£8) new. So, you can decide if they are worth your time to refurbish. I spent about 30–45 minutes on each clamp. Overall, it was a fun and rewarding project. I will think of my father-in-law whenever I use one of these clamps.

Further reading

PHOTOGRAPHS BY MARK PALMA