Bomb techs and military EOD techs use hand crimpers, such as the old reliable du Pont No. 8 crimper, similar to pliers, to secure safety fuse into the mouth of a non-electric detonator and tightly crimp the metal shell around the fuse. The crimper squeezes and deforms the detonator shell. Some jaw types do not make a perfect watertight seal in a single operation, and require the user to do 2 successive operations, rotating the detonator a partial turn for the second squeeze of the handle. This creates a completely secure and watertight seal.
This article is about two permanently-mounted, hand-operated bench tools used for the same purpose, and which are probably seldom seen by bombtechs.
They are bench crimpers, large, heavy-duty cast iron crimping tools.
They are primarily used:
– in explosives manufacturer’s R&D labs, to hand crimp bridgewire assemblies into experimental detonator shells, and
-in the field, by oilwell drilling companies and mining companies to crimp the mouth of non-electric (plain) detonators over an inserted safety fuse or detonating cord– creating a water-tight seal.
I have two different bench crimpers that I use to assemble bridgewire / legwire assemblies into different types of empty detonator shells, to create a “factory” -style crimp on the inert detonator training aids that my company manufactures.
Above: Older model of du Pont Superior crimper from a photo in a 1940s Blaster’s Handbook
Above: Top and side view of the du Pont Superior crimper. The knurled brass nut and sliding metal strip adjust to regulate the depth to which you can insert a detonator shell into the steel face plate at far left.
Both types shown in this article have holes in the base, to allow for securing the tools to a work bench, using screws or bolts.
Both crimpers have a long handle, to produce the leverage required to impress the multi-ring stab crimps into aluminum, copper and brass detonator shells of varying hardness.
Both crimpers have a built-in cutting blade to sever the inserted safety fuse from a coil of fuse. One uses a replaceable razor blade mounted crosswise in the bottom end of the handle.
The other has an external large steel knife edge on the handle that acts as a bypass cutter, with a mounted “anvil” on the top of the base of the tool. It has a “U”-shaped slot for placement of the fuse or detcord.
Above: Modern du Pont Crimper
Above: The pale green-painted crimper was made by E.I. du Pont de Nemours and Company (du Pont), until perhaps the 1970s or early 80s.
Shown above is the later model du Pont Superior bench crimper my company uses. Note the handle razor blade arrangement, with pathway slot and metal loop at upper left, for cutting safety fuse and detcord from a spool or roll.
Above: du Pont sold its explosives business, gunpowder business, patents and tooling to other companies such as Explosives Technologies International Inc. (ETI, Inc.), Hercules Powder Company, Atlas Powder Company and Orica Explosives.
I was unable to get any information about this tool from current employees of du Pont Chemical Corp. in Wilmington, Delaware, USA, when I tried to purchase a spare jaw set from the company.
The name plate on my crimper shows the serial number 2,875, so there are probably still many of these tools in use in industrial settings.
I did see several du Pont Superior crimpers in use at a C-I-L Explosives (Canadian Industries Limited), factory in Brownsburg, Quebec, when I toured that plant about 40 years ago. The employees were working in the R&D department, assembling and crimping various experimental types of detonators. That company no longer makes explosives or ammunition, and the tooling and patents were sold off to others, such as Orica and IVI (Industries Valcartier, Inc.) in mergers.
This bench crimping tool has a series of loose teeth with two points set at slightly different angles. The teeth have a circular ring of steel passing through a hole in each tooth, tying them together, behind the face plate. The teeth all point inward toward the center of the hole in the plate.
Steel face plate on du Pont crimper. Jaw teeth are visible in the center hole
When the crimper handle is activated by a short “throw” from left to right, the teeth all move inward toward the center opening of the faceplate, and crimp the detonator shell at and just beyond the mouth, in a double row of “stabs”.
In the above photo, the tool jaws were activated twice, with the detonator shell being moved part way in and out between each operation of the handle. One operation of the handle produces two parallel stab rings. Then, when the detonator is moved in or out, the second throw of the handle produces another two parallel sets of stab rings.
The set of jaws is readily replaceable after about 150,000 crimping operations, according to the older versions of the du Pont Blaster’s Handbook, and the manual that came with the crimper, The faceplate is removed by unscrewing the four set screws with an Allen hex key, and the ring of jaw teeth is easily removed. The teeth build up some metal debris broken away from the det shells, and the jaws must occasionally be removed for cleaning. Returning the jaws or replacing them with a new set is not straightforward, and takes some practice. You can break one or more teeth if the face plate and teeth are not carefully re-aligned and re-assembled into the cast iron housing. There is no need to describe the correct process here, but if anybody is interested, I can describe it in an e-mail with photographs.
On the right side of the tool housing, there is a forked and L-shaped metal strip, that is locked in place by a knurled brass nut. A right-angled spur on the strip protrudes into a slot on the right side of the housing; when the nut is loosened, the strip can be slid back and forth to control the depth of different length detonator shells.
This is required if you are crimping shells at the open edge of the shell mouth as well as further along, to ensure a secure watertight seal for wet blasting applications.
If you insert a short detonator and the side strip has been moved and locked too far to the rear, the jaw teeth will cause the uncrimped or crimped shell to jam inside the housing. This necessitates removal of the face plate and jaw assembly, withdrawing the jammed detonator and fuse, and re-assembling the jaws and face plate to the housing.
Many years ago, one of my new employees was operating this tool on his first few days on the job, and broke two of the teeth in the jaw assembly by creating a jam and after clearing it, improperly re-assembling the tool. The next time he operated the handle, we heard “Snap Snap”! This tool cost my company almost $3,000 at the time of purchase, about 45 years ago. Replacement jaws were not available.
Part 2 of this article will be continued in the next issue.
Author – Bruce B Koffler
Bruce B. Koffler, B. Sc., MCA, is the President of Securesearch, Inc., in Toronto, Ontario, Canada–whose company he established in 1970. He has been an IABTI Associate member since 1982. He was a law enforcement officer for an Ontario Government ministry for 16 years, and instructor/ examiner in several programs for 30 years. He is a certified trainer and frequent contributor of technical articles on explosives, small military ordnance items, IEDs, firearms and ammunition, to police, security and forensic science journals, including The Detonator. He can be contacted by e-mail at: bkoffler@securesearchinc.com or by phone at: 1-800-221-9788 or international at (416) 948-8832