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Independent Tool Review
by Peter Brett - January 2006
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01444 440188
E-Z LOK Thread Inserts
– Idiot-Proof?
Once, in what I regard as my debonair years, I stripped the thread of one of the spark plugs of my Honda motorcycle when I was servicing it. The £££ signs in my eyes receded a little when a friend told me about a process called helicoil that would renew the thread and save me the not inconsiderable cost of a new engine head. The helicoil repair was successful, and I drove the bike for a couple of years afterwards, and in fact I see it around sometimes, still going. From the company that brought us helicoil, Armstrong Fastening Systems, come the E-Z LOK thread inserts. In some ways a similar product, but in other ways a product with so many new applications that the products can’t really be compared.
I was a little confused at first because the thread inserts I was sent to try out were all made to fit into metal. My first instinct was to think, “Well why not just drill a hole, tap a thread and screw a bolt in.” It seemed an unnecessary addition. Well, in truth, I am sure that there are many applications where you could do just that. But should a cross threaded hole need to be rescued or repaired, the E-Z LOK insert could be the answer, just as helicoil was the cure for my Honda.
But a further look at the range of E-Z LOK products provides a lot more answers. First of all there are a range of inserts for metal, plastic and wood. Wood workers among you would, I am sure, recognize that there are a large number of applications in which you could use the facility to insert a strong screw thread into wood. Most of our kitchen cabinets these days use a similar fixing to hold them together, but the E-Z LOK range is more diverse. For example, there are inserts for hardwood with knife threads that will slice into hardwood to hold very securely. There are zinc threaded inserts for softwood that are especially coarse and again will be secure in a less dense wood. These can also be used in MDF and plywood. For industrial high volume users these particular inserts can be powerdriven into place.
For uses in plastic, there is again a different range. For example, there are some inserts that can simply be pressed home. The knurling on the barrel of the inserts holds them in place without the need for having a precise hole depth or diameter and they are easy to align, whereas thread chasing plastic may not be that easy to do accurately. The brass “Finserts” have small fins on them that actually bite into the side of the hole they are put into once the bolt or screw is put in. As you can imagine this is quite successful.
Armstrong have in fact thought of so many fixing problems and their solutions in their range that end users will probably have a good choice, whatever they need. The publicity material details the huge range of sizes in metric and imperial that are manufactured. The range of materials that the inserts are made in is good too. You can get carbon and stainless steel, brass and cast zinc alloy inserts to suit the different applications.
What I have described above sounds like it might not be the right thing for a DIY user because the range sounds too sophisticated and too complicated. But Armstrong was very keen to dispel this idea and sent me some carbon steel inserts to try myself. Armstrong says it is as easy as 1-2-3 to fit an insert, that is you drill the right size hole (they tell you what it is for the insert you buy), you use a standard tap to make the thread and then put the insert in, screwing it tight with the correct size bolt and a spanner or using a special power drive tool that grips the insert in a similar way to a screwdriver. Sounds easy? Well in fact it is easy. I tried the inserts in some 6mm thick mild steel and some 8mm thick aluminium sheet. Accuracy and care, as always, are important for a good tight fit, but fitting these inserts is by no means beyond the skills of an average DIYer. I am fortunate to have the use of an industrial quality pillar drill that helps me maintain accuracy, but even a small DIY pillar drill should be good enough. What is equally important for some users is that the insert threads are coated with a special adhesive that will bond to the side of the threads. This ensures that the insert will not work loose and can be relied upon to stay in place under pressure.
Actually, the more I used these inserts and the more I thought about them, the more applications I found for them. I will certainly be bugging Armstrong for some more samples of the knife thread inserts for hardwood and the “Finserts” because I will be able to put them to good use in my furniture making. They would be perfect for strong and accurate joints in tables and cabinets.
For users who need a particular range of inserts for metal, Armstrong Fastening Systems do prepackaged kits in carbon and stainless steel in Metric and Imperial sizes. These would be a good stock item for engineering suppliers. For the high street DIY store a range of the inserts could be a good stock item. If the staff of the store have the knowledge, and perhaps even the opportunity to try the inserts themselves they might be in a position to offer advice to the customer who comes in with a fixing problem. And once used, I am sure they will be used again. There may even be an additional market for standard taps and drills for the store concerned. I feel a kit coming on!
Independent Review by Peter Brett
Airstream Communications