Abstract:
A device and a method of using the device for construction of baffles that may be used in suppressors or solvent traps for firearms out of metal cups sold as engine block freeze plugs. The device has a bottom die, a top die and an alignment cylinder. The metal cup is transformed into a baffle by placing the metal cup on the bottom die, placing the bottom die inside the alignment cylinder, placing the top die inside the alignment cylinder, and applying compressive forces to the bottom die and top die. A hole may be drilled in the center of the baffle by placing a drill bit into a top die center hole completely penetrating through the top die and coaxial thereto, and drilling through the baffle, the drill bit passing into a bottom die center hole penetrating at least partially into the bottom die and coaxial thereto.

Description:
FIELD OF THE INVENTION 
     The present invention relates to suppressors and solvent traps for firearms. More particularly, the present invention relates to a construction of baffles that may be used in suppressors or solvent traps. 
     BACKGROUND 
     A suppressor or a sound suppressor is a device that may be attached to the barrel of a firearm which reduces the amount of noise and visible muzzle flash generated when firing. While suppressors are desirable for stealth purposes, they are also desirable for mitigating noise pollution and lowering the risks of hearing loss. 
     Suppressors are typically constructed of a metal cylinder body with internal mechanisms that reduce the sound of firing by slowing the escaping propellant gas. The most common internal mechanisms are baffles. Baffles are typically circular metal dividers which separate the cylinder body into expansion chambers. A suppressor typically has multiple baffles. Each baffle has a hole in its center to permit the passage of the bullet. The hole is usually slightly larger than the bullet caliber to minimize the risk of the bullet hitting the baffle. Spacers typically separate the baffles and keep them aligned at a specified distance from each other inside the suppressor. 
     Suppressors are regulated by firearm legislation in most countries. While some countries allow civilian use of suppressors, other governments have opted to ban them from civilian use. In the United States, possession of suppressors is legal in most states, but regulations make purchasing them difficult. Regulations for making one&#39;s own suppressor are easier to comply with, and many people do make their own. The baffles are the key parts of the suppressor and individual baffles are treated as suppressors themselves. Hence one cannot buy suppressor baffles ready to be assembled into a suppressor or contract out the work of making them with any less regulatory difficulty than purchasing an entire suppressor. 
     Many designs for making a suppressor are available and if one has access to a fully equipped machine shop, particularly lathe tools, making one&#39;s own suppressor is not too difficult. However, many people do not have easy access to a fully equipped machine shop. Some suppressor designs are devised for people who have access to a limited set of tools. 
     Some popular suppressor designs that require minimal tools modify engine block freeze plugs to make the baffles. Engine block freeze plugs (or core plugs) are thin metal cups (see  FIGS. 2 a  and 2 b   ) used to plug holes left in the engine blocks of water-cooled internal combustion engines as part of the manufacturing process. Holes are put into the casting of an engine block to support internal sand forms, and to facilitate the removal of the sand after the casting has cooled. It is also thought that core plugs will pop out and protect the engine block from cracking in the event that the coolant water in the engine block freezes and expands. Hence core plugs are popularly called frost plugs, freeze plugs, or engine block expansion plugs. Freeze plugs are inexpensive, readily available through auto parts stores, and are not subject to firearms regulations. 
     To make baffles for a suppressor, freeze plugs are typically reformed from a cup that is “U” shaped in cross-section to a cup that has a conical depression in the middle with an “M” shaped cross-section. In some design methods, the conical depression is formed by drilling a hole in the center of the unmodified freeze plug, then putting it into a vise along with an object, such as a ball bearing, that has an increasing cross-section diameter that ultimately is somewhat larger in cross-section diameter than the center hole. The vise is then tightened and the freeze plug reformed into an “M” baffle. A socket from a wrench set can be used to hold the freeze plug during the compression in the vise. However, this method is not all that reliable. The center hole expands about 50% during the process, with a good deal of variation between each baffle made this way. It is highly desirable to have the center hole only slightly larger than the bullet. So this means that the finished baffles must be measured to ensure desired tolerances for the size of the center hole are met. Typically many do not and must be discarded. Alternatively, one can undersize the initial drilling of the center hole, then re-drill the center hole after the vise reforming. However, this is hard to do without a drill press using only a hand-held drill and still keep the center of the center hole in the center of the baffle. The finished baffles must be measured to ensure desired tolerances for the location of the center hole are met. Again, many typically will not and must be discarded. 
     What is needed is a simple and reliable method for making baffles from engine block freeze plugs using only simple hand tools and not high precision machine shop tools. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described by way of exemplary embodiments, but not limitations, illustrated in the accompanying drawings in which like references denote similar elements, and in which: 
       The accompanying drawings, which are incorporated into and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the detailed description, serve to explain the principles and implementations of the invention. 
         FIG. 1  shows a perspective view of an exemplary embodiment of a baffle forming device. 
         FIG. 2 a    shows a perspective top view of a freeze plug with which the baffle forming device is configured to work. 
         FIG. 2 b    shows a perspective bottom view of the same freeze plug. 
         FIG. 3  shows sectional side views of the four components of the baffle forming device and the freeze plug. 
         FIG. 4  shows a sectional side view of the bottom die being inserted into the bottom die holder. 
         FIG. 5  shows a sectional side view of the freeze plug being place on top of the bottom die. 
         FIG. 6  shows a sectional side view of the assembled baffle forming device holding the freeze plug prior to compression. 
         FIG. 7  shows a sectional side view of the assembled baffle forming device holding the freeze plug after compression. 
         FIG. 8  shows a sectional side view of the assembled baffle forming device holding the freeze plug during drilling. 
         FIG. 9  shows a sectional side view of the bottom die holder and the bottom die holding the baffle. 
         FIG. 10  shows a side view of the bottom die bolted to the baffle with a bolt and secured with a bolt. 
         FIG. 11  shows a side view of a user inserting the bottom die post into a drill chuck. 
         FIG. 12  shows a side view of the process of filing down the baffle side wall. 
         FIG. 13  shows a sectional side view of the finished baffle. 
         FIG. 14  shows a top perspective view of the finished baffle. 
     
    
    
     DETAILED DESCRIPTION 
     Before beginning a detailed description of the subject invention, mention of the following is in order. When appropriate, like reference materials and characters are used to designate identical, corresponding, or similar components in different figures. The figures associated with this disclosure typically are not drawn with dimensional accuracy to scale, i.e., such drawings have been drafted with a focus on clarity of viewing and understanding rather than dimensional accuracy. 
     In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the developer&#39;s specific goals, such as compliance with application and business related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure. 
     Use of directional terms such as “upper,” “lower,” “above,” “below”, “in front of,” “behind,” etc. are intended to describe the positions and/or orientations of various components of the invention relative to one another as shown in the various Figures and are not intended to impose limitations on any position and/or orientation of any embodiment of the invention relative to any reference point external to the reference. 
     Those skilled in the art will recognize that numerous modifications and changes may be made to the exemplary embodiment(s) without departing from the scope of the claimed invention. It will, of course, be understood that modifications of the invention, in its various aspects, will be apparent to those skilled in the art, some being apparent only after study, others being matters of routine mechanical, chemical and electronic design. No single feature, function or property of the exemplary embodiment(s) is essential. Other embodiments are possible, their specific designs depending upon the particular application. As such, the scope of the invention should not be limited by the particular embodiments herein described but should be defined only by the appended claims and equivalents thereof. 
     The Exemplary Embodiment 
     Structure 
       FIG. 1  shows a perspective view of an exemplary embodiment of baffle forming device  100 . The baffle forming device  100  has a bottom die  101 , a bottom die holder  102 , a top die  103 , and an alignment cylinder  104 .  FIG. 2 a    shows a perspective top view of a freeze plug  106  with which the baffle forming device  100  is configured to work.  FIG. 2 b    shows a perspective bottom view of the same freeze plug  106 .  FIG. 3  shows sectional side views of the four components of the baffle forming device  100  and the freeze plug  106 . These four components of the baffle forming device  100  can be used to form the freeze plug  106  into an M-type baffle to be used in a suppressor. To make a baffle, the freeze plug  106  is placed on top of the bottom die  101  and the bottom die  101  is placed in the bottom die holder  102 . The alignment cylinder  104  is placed over this assembly and the top die  103  is placed into the top of the alignment cylinder  104  (see  FIG. 6 ). The assembled baffle forming device  100  and freeze plug  106  is then placed in a vice and compressed (see  FIG. 7 ). Freeze plugs come in a variety of sizes, so a particular embodiment of the baffle forming device  100  will be dimensioned to accommodate a particular dimensioned freeze plug. 
     The Bottom Die 
     The bottom die  101  comprises a bottom die body  110  and a bottom die post  112 , with the bottom die body  110  coupled to, and on top of, a bottom die post  112 . The bottom die body  110  and the bottom die post  112  are both cylindrical and coaxial, with the bottom die body  110  having a larger diameter than the bottom die post  112 . The bottom die post  112  is configured for mating with the bottom die holder  102 . The bottom die post  112  is configured to be inserted into the chuck of a typical hand-held drill. As such, the diameter of the bottom die post  112  in the exemplary embodiment is about one half inch. In other embodiments, the bottom die post  112  may have a diameter with a different value. 
     The bottom die body  110  comprises a bottom die base  122  and a bottom die block  114 , with the bottom die block  114  coupled to, and on top of, the bottom die base  122 . The bottom die block  114  and the bottom die base  122  are both cylindrical and coaxial, with the bottom die base  122  having a slightly larger diameter than the bottom die block  114 . The difference between the diameters of the bottom die block  114  and the bottom die base  122  forms a block notch  118 . The bottom die block  114  is configured to hold the freeze plug  106 . The bottom die block  114  has a diameter no wider than the inside diameter of the freeze plug  106  that it is designed to work with and a height at least the height of that freeze plug  106 . The bottom die base  122  has a diameter about the same diameter as the outside diameter of the freeze plug  106 , but less than the inside diameter of the alignment cylinder  104 . 
     The bottom die body  110  has a conical cavity  116  coaxial thereto, with its base open to the top. The sides of the conical cavity  116  and its base form a cavity angle  124 . The cavity angle  124  will determine the angle of the finished baffle. In the exemplary embodiment, the cavity angle  124  is about 40 degrees, but other embodiments may have different values for the cavity angle  124 . In the exemplary embodiment, the conical cavity  116  is no deeper than the height of the freeze plug  106  and does not extend past the bottom die block  114  into the bottom die base  122 . However, in other embodiments, the conical cavity  116  may be deeper than the height of the freeze plug  106  and extend into the bottom die base  122 . 
     The bottom die  101  has a bottom die center hole  120  that is coaxial thereto. The bottom die center hole  120  joins the bottom of the conical cavity  116  and extends at least some distance into the bottom die base  122 . The bottom die center hole  120  allows for drilling of a center hole in the freeze plug  106 . In the exemplary embodiment, the bottom die center hole  120  extends all the way through the bottom of the bottom die post  112 . This allows the freeze plug  106  to be attached to the bottom die  101  with a bolt after compression and drilling in preparation for grinding and filing. However, in other embodiments, the bottom die center hole  120  does not extend all the way through the bottom of the bottom die  101 . 
     In the exemplary embodiment, the bottom die  101  is machined out of a monolithic piece of steel, but in other embodiments, may be made out of other suitable materials and the bottom die block  114 , the bottom die base  122 , and the bottom die post  112  may be formed separately, by machining, casting or other process, then joined by welding or some other suitable fastening mechanism. 
     The Bottom Die Holder 
     The bottom die holder  102  comprises a holder block  126  and a holder base  128 . The holder block  126  and holder base  128  are both cylindrical and coaxial, with the holder base  128  having a slightly larger diameter than the holder block  126 . The difference between the diameters of the holder block  126  and the holder base  128  forms a holder notch  130 . The holder block  126  has a diameter that is no wider than the inside diameter of the alignment cylinder  104 , allowing the holder block  126  to fit inside the alignment cylinder  104 . The holder base  128  has a diameter at least as large as the outside diameter of the alignment cylinder  104 , which prevents the holder base  128  from entering the alignment cylinder  104  and prevents the alignment cylinder  104  from sliding over and past the holder base  128 . 
     The bottom die holder  102  is configured to hold the bottom die  101 . To facilitate this, the bottom die holder  102  has a holder center hole  132  that is coaxial thereto. The bottom die holder  102  is configured to have the bottom die post  112  inserted into the holder center hole  132 . The holder center hole  132  is as least as deep as the bottom die post  112  is long, so that the bottom die base  122  contacts the holder block  126 , which will allow force to be uniformly transmitted through the bottom die holder  102  and bottom die  101  to the freeze plug  106 . In the exemplary embodiment, the holder center hole  132  has a depth that is the same as the bottom die post  112  to allow force to be transmitted through the bottom die post  112  to the bottom die base  122  as well as through the holder block  126 . However, in other embodiments, the holder center hole  132  may be deeper than the bottom die post  112 , so that the bottom die post  112  does not transmit force, keeping it from being damaged during the compression process. 
     In the exemplary embodiment, the bottom die holder  102  is machined out of a monolithic piece of steel. In other embodiments, the bottom die holder  102  may be made out of other suitable materials and the holder block  126  and the holder base  128  may be formed separately, by machining, casting or other process, then joined by welding or some other suitable fastening mechanism. In yet other embodiments, the bottom die  101  and bottom die holder  102  are permanently joined together, made either from a monolithic piece or made separately and then joined by welding or some other suitable fastening mechanism. 
     The Top Die 
     The top die  103  comprises a top die base  134  and a top die block  136 . The top die base  134  is cylindrical and has a diameter that is no larger than the inside diameter of the alignment cylinder  104 , which allows the top die  103  to be inserted into the alignment cylinder  104 . In the exemplary embodiment, the top die base  134  has a diameter that is only slightly less than the inside diameter of the alignment cylinder  104 . The top die block  136  is shaped as a truncated cone with the base of the cone against the top of the top die base  134 . and this value will determine the angle of the finished baffle. In the exemplary embodiment, the top die angle  138  is about 40 degrees, but other embodiments may have different values for the top die angle  138 . 
     The top die  103  has a top die center hole  140  that is coaxial thereto. The top die center hole  140  allows for drilling of a center hole in the freeze plug  106 . The top die center hole  140  extends all the way through the top die  103 . However, in other embodiments the top die  103  does not have a top die center hole  140 . 
     In the exemplary embodiment, the top die  103  is machined out of a monolithic piece of steel. In other embodiments, the top die  103  may be made out of other suitable materials and the top die base  134  and top die block  136  may be formed separately, by machining, casting or other process, then joined by welding or some other suitable fastening mechanism. 
     The Alignment Cylinder 
     The alignment cylinder  104  is a hollow cylinder with an alignment cylinder inner wall  144  around an alignment cavity  142  open on both cylinder ends. The alignment cylinder  104  is configured to allow the bottom die  101  holding the freeze plug  106  to be inserted into the alignment cavity  142  from one end and the top die  103  from the other end. The alignment cylinder inner wall  144  aligns the top die  103  and the bottom die  101  during the compression process. The alignment cylinder inner wall  144  also prevents the freeze plug side walls  146  from bowing outward during the compression process. 
     In the exemplary embodiment, the alignment cylinder  104  is an extruded piece of steel. In other embodiments, the alignment cylinder  104  may be made out of other suitable materials and may be formed by machining, casting or other process. 
     The Exemplary Embodiment 
     Operation 
       FIGS. 4-13  show steps of a method to make a baffle from a freeze plug  106  using the exemplary embodiment of the baffle forming device  100 .  FIG. 4  shows a sectional side view of the bottom die  101  being inserted into the bottom die holder  102 .  FIG. 5  shows a sectional side view of the freeze plug  106  being place on top of the bottom die  101 . 
       FIG. 6  shows a sectional side view of the assembled baffle forming device  100  holding the freeze plug  106  prior to compression. The bottom die holder  102  and the bottom die  101  with the freeze plug  106  have been inserted into the alignment cylinder  104 . The freeze plug  106  still has its original “U” shape. The top die  103  has been inverted with the top die block  136  facing downwards towards the freeze plug  106  and bottom die  101  and inserted into the alignment cylinder  104 . The assembled baffle forming device  100  is then compressed in a vise (not shown) or similar compression providing device. The vise applies compression to the top die  103  and the bottom die holder  102 , which transmits the force of compression to the bottom die  101 . The freeze plug center wall  148  is deformed and forced down into the conical cavity  116  of the bottom die  101 . 
       FIG. 7  shows a sectional side view of the assembled baffle forming device  100  holding the freeze plug  106  after compression. The freeze plug  106  now has been formed into an “M” shape in cross-section. The top die  103  has penetrated deeper into the alignment cylinder  104  and has stopped when the conical cavity  116  has been completely filled with the freeze plug  106  and the top die  103 . 
       FIG. 8  shows a sectional side view of the assembled baffle forming device  100  holding the freeze plug  106  during drilling. A drill bit  150  has been inserted into the top die center hole  140 , has cut through the freeze plug  106  (now a baffle  152 ) creating a baffle center hole  154 , and penetrated beyond into the bottom die center hole  120 . The drill bit  150  is then withdrawn and the top die  103  and alignment cylinder  104  removed. 
       FIG. 9  shows a sectional side view of the bottom die holder  102  and the bottom die  101  holding the baffle  152 . The top die  103  and alignment cylinder  104  have been removed. The baffle  152  has its final shape, but its outside diameter may have expanded slightly during the compression process. This may be corrected by filing or grinding off some of the baffle side wall  156 . 
       FIG. 10  shows a side view of the bottom die  101  bolted to the baffle  152  with a bolt  158  and secured with a nut  160 . The bolt  158  will keep the bottom die  101  and baffle  152  together during the grinding/filing process. 
       FIG. 11  shows a side view of a user  164  inserting the bottom die post  112  into a drill chuck  162 . The drill chuck  162  may be part of a drill press or may be part of a hand drill either held in the user&#39;s  164  other hand or in a vise.  FIG. 12  shows a side view of the processes of filing down the baffle side wall  156 . The drill is run, spinning the bottom die  101  and baffle  152  assembly. A hand file  166  can be held against the baffle side wall  156  to file it down to the proper size.  FIG. 13  shows a sectional side view of the finished baffle  152 .  FIG. 14  shows a top perspective view of the finished baffle  152 .