This invention relates to threaded insert placing tools.

Threaded inserts are widely used to incorporate a thread into a sheet of material. A hole is drilled in the sheet of material. An insert is screwed onto a placing tool and is then placed in this hole. The placing tool is then used to compress the insert, which deforms and becomes locked onto the sheet leaving a permanently fixed threaded bush, to which any item can then be bolted.

There are two types of hand tool available to compress the inserts. The first is a lever type, which consists of a threaded portion which screws into the insert, a former to hold the insert and a lever arrangement to pull the screw and thus compress the insert. Tools of this type leave a uniform finish on the front end of the insert, but the effort required for the compression is considerable, especially for larger inserts such as those greater than 6mm in diameter. This type of tool is also very cumbersome in confined spaces because of the long handles required for leverage.

The second type of hand tool available to compress the inserts is a so-called screw-type. With these, the insert is compressed by a screwing action using its own thread for compression. This type can usually cope with larger inserts of eg up to 8mm in diameter. However, with such a tool the finish is generally poor, since to prevent rotation of the insert during compression the tool includes a sharply serrated abutment surface which engages the front face of the insert in use leaving it severely pitted. Further problems can arise from the insert not being properly centred with respect to the tool during compression.

It is an object of the present invention to provide an improved screw-type threaded insert placing tool.

Viewed from one aspect the present invention provides a screw-type insert placing tool, comprising a drive screw for threaded engagement with an insert and an abutment part for engaging the front end of the insert against which the insert is compressed when the tool is in use, wherein the abutment part includes a circular recess, the peripheral edge of which radially engages the rim of the insert during compression to prevent rotation of the insert.

Such an arrangement provides several advantages over previous screw-type insert placing tools. In particular the tool will provide an improved finish on the threaded insert. Since rotation of the insert is restrained by radial engagement between the rim of the insert and the edge of the recess the use of sharp serrations which severely pit the front face of the recess may be avoided. In accordance with the invention, the base of the recess may therefore be substantially flat, although in a preferred embodiment the base includes slight serrations to assist initial engagement with the insert. These serrations need not substantially pit the surface, as in the prior art, as the edge of the recess performs the substantial part of the gripping as the rim spreads radially into firm engagement with the edge of the recess. A further advantage of the recess is that it limits the amount of material of the insert pulled through an opening in sheet material during engagement by the insert by limiting radial spreading, thus avoiding leaving insufficient foldable material behind the opening for firm mounting of the insert to be achieved. The diameter of the recess is preferably slightly larger than the outside diameter of the rim of the insert. This allows for tolerances on the insert

size, and also limits the radial spread of the rim during compression. Because of the small permitted spread, the insert is substantially centred whilst being fixed to a sheet of material. Also preferably, the abutment part having the recess is interchangeable so that recesses, and therefore inserts of different sizes, can be accommodated. This part could be nut- shaped and adapted for engagement in a complementary recess in a body part of the tool, but is preferably a cup-shaped cap releaseably mounted on a body part of the tool. However, a simplified version of the tool more suitable for the DIY market may have only a single recess size for standard inserts supplied with the tool. Preferably, the drive screw rotates with respect to the body of the tool on bearings, thus avoiding unnecessary torque required to overcome friction. Further preferably, these bearings are contained in one unit, and may comprise roller-bearings. The tool could be automated, but the invention is particularly applicable to a manual tool. In this case, the drive screw is preferably rotatably mounted in a tubular body part, handles, hand-grips, or means for fixing hand-grips being provided for effecting relative rotation. Preferably, bearings are arranged between the screw and body part. As discussed above this has the advantage .of reduced torque as compared with hand tools in which eg washers have been arranged between the relatively rotatable parts. This itself represents new departure from known tools of this type.

Accordingly, viewed from a second aspect the invention provides a hand held threaded insert placing tool with a drive screw rotatably mounted in and projecting outwardly from a tubular body part, hand¬ grips being coupled or adapted to be coupled respectively to the drive screw and body part, bearing means being

arranged between the drive screw and body part to provide low friction relative rotational movement therebetween in use.

In a preferred embodiment the bearing means is retained in the tubular body part by means of a tubular sleeve which is removably mounted in the body part and the front of which abuts the bearing means, a radially projecting hand grip being threadedly engaged in a radial aperture in the body part, and a threaded part of the hand grip co-operating internally with the sleeve to maintain it in place in the assembled tool, so that removal or loosening of the hand grip facilitates removal of the sleeve and bearing means. Further preferably, the bearing means are contained in one unit, and may comprise roller-bearings.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows the insert placing tool in longitudinal section;

Fig. la shows the cap from the underside; and Figs. 2a, b, c show the method of operation of the tool.

The insert placing tool comprises a spindle 1, a casing 2, a drive screw 3, a serrated cap 4, bearings 5, thrust-washers 6, a connector 7, a sleeve 8, a Delrin bush 9, handle 10, bush lever 11, lever handle 12 which has a threaded end 13 which fits into a correspondingly threaded hole 14 in the casing 2. This lever handle 12 maintains the sleeve 8 in position. The serrated cap 4 is held onto the casing 2 by ball and spring 15. The handle 10 and bush 11 are held into the spindle 1 by a rollpin 16. The connector 7 is similarly held onto the spindle with a rollpin 17 and the serrated cap is prevented from rotating during use with the rollpin 18. There is also provided a socket 19 in the top of the handle

10. This is so that a square drive 20 and tommy bar 21 may be used if extra leverage is required.

In figure la is a detailed drawing of the cap 4. A locating slot 26, which fixes the cap 4 to the body 2 to prevent rotation of the cap when the tool is in use, is shown.

The method of operation of the tool is described in the following paragraph and with reference to figures la and 2a, b and c. The threaded insert 23 is screwed loosely onto the drive screw. This assembly is then placed in a drilled hole in the sheet of material 25 as shown in fig. 2a. The drive screw is then tightened. As the drive screw is tightened the slight radial serrations 24 on the cap grip the rim 22 in the initial stages. It is to be understood that these serrations are of considerably less depth than those in the prior art, their purpose being only to initiate the gripping. The rim 22 of the insert starts to splay outwards, until it has engaged with the edge of the recess 4a (Figure 2b) . The diameter of the recess is preferably .125mm to .250mm larger than inserts of diameter 6mm or less, and .250mm to ,5mm larger than inserts of over this size. The recess further prevents an excess amount of foldable material from being pulled through to the upper side of the metal sheet. The recess then acts as a grip for the insert, preventing it from turning with respect to the metal sheet. As the tool is tightened further, the foldable material underneath the sheet splays out and grips the metal sheet (Figure 2c) .

The bearing 5 and thrust washers 6 are a further improvement over the prior art. Because of the bearing, the main part of the torque applied to the tool is used only to deform the insert rather than to overcome friction between parts of the tool.