![]() Generally, the deeper the embedment of a concrete anchor, the better the pullout/holding values will be. While these special rebar bits work well, they are fairly expensive and add extra work when placing anchors. There is special rebar cutting bits that can be used when rebar is located in areas where the anchor must be placed. The rebar may get in the way when trying to place a concrete anchor deeply or it may cause problems when drilling a hole. This will create an unsupported edge which will reduce the holding values of the concrete anchors.Ĭoncrete reinforced with rebar may cause problems. It is important to avoid having the working end of the concrete anchor too close to the bottom of the concrete. It makes sense then that the larger the diameter- the larger the minimum embedment. As a rule of thumb, the smaller the diameter- the shorter the minimum embedment will also be. There is a minimum embedment with all concrete anchors which is determined by the diameter of the anchor being used. Standard concrete is less than 7,000 psi and high strength concrete is measured between 7,000 and 14,500 psi. For example, concrete that is designated as 3,000 psi concrete is concrete that is able to carry a compression stress of 3,000 psi after 28 days. The measurement is calculated by pouring concrete in a cylinder and then measuring the force needed to break the concrete after it is hardened. The compression strength of concrete is measured in psi, or pounds per square inch. ![]() What is the compression strength of concrete? A specific concrete anchor or fastener may not work in all applications. However, the reason there are a variety of concrete fasteners is that a variety of concrete also exists. Most other concrete fasteners will successfully work in concrete regardless of age. Tapcon® screw may not work in extremely old concrete because the lead threads deteriorate and prevent the screw from being inserted the minimum of one inch. In some cases, concrete also becomes more abrasive as it ages. The older the concrete, the harder it gets and therefore the more difficult to drill into. Green concrete, which is less than 28 days old, should not be drilled or anchored into. The truth is that only concrete sidewalks and mixers exist! People wrongly call sidewalks "cement" and point out "cement trucks" and "cement mixers". The hydration hardens the concrete for years, which means that concrete gets stronger as it ages. The cement and water harden and bind the aggregates into a solid mass over time through a process called hydration. Portland cement is not a brand name but rather a generic term for the type of cement used in most concrete. Concrete is a mixture of water, aggregates (i.e. The words "concrete" and "cement" are often erroneously used as interchangeable terms. What is the difference between cement and concrete? Just some thoughts on a frustrating job.Purchase Anchors What is the base material? I would use one of those hand tapper-cranker- thingies, if I had one. The quality of tap REALLY does matter, but so does approach and common sense and 'feel' for the job at hand. It hardens and changes the quality of the metal, and if it throws the tap off line, BOING, yur dun! Most noticable in small tap sizes I have had much better results, using my drill press, or Mill-drill and pulling the belts by hand to tap pipe and plate in stainless. A tap has a tendancy to tear stainless, and IMHO that is where the problems begin. I use my favorite bacon grease on a flux brush, and dont spare any. I dont bother to hand tap stainless anymore, I use the drill press and vice, I use the feed lever to encourage starting STRAIGHT, and a pin in the chuck key holes to feed in, and reverse, STRAIGHT. Stainless has always been a problem for me to tap, as its working qualities make it gummy to start with and then work harden to trap a tap. ![]() You didnt say how you are work holding here, so I'll guess, and maybe help anyway. ![]()
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