GB2120163A

GB2120163A - Cross-cutting jig

Info

Publication number: GB2120163A
Application number: GB08214628A
Authority: GB
Inventors: Mcmillan James Swan
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-05-19
Filing date: 1982-05-19
Publication date: 1983-11-30

Abstract

To facilitate accurate cross-cutting of a workpiece, such as board 31, provided on a work surface 16 for the board 31 is a cross-cutting jig which comprises securing means, in the form of two right- angled brackets 11, 12 to enable the jig to be fixed relative to the work surface 16 via a board 17, and guide means in the form of two substantially L-shaped rails 21, 22 which are adjustably secured to a rod 19 extending between the brackets 11, 12 and which can be laid over the board 31, which can abut the board 17 and a stop 32 on the surface 16, to enable a saw to be guided across the board 31. To accommodate different sizes of saw the distance between the brackets 11, 12 can be adjusted by means of rod 19. <IMAGE>

Description

SPECIFICATION Cross-cutting jig This invention relates to a cross-cutting jig, that is to say an assembly for guiding a saw relative to a workpiece while the saw's blade cuts the workpiece across its width.

The most popular material which is widely available to so called 'do it yourself' enthusiasts for making items of furniture is prefinished board which comes in many types.

Such boards are usually in widths from 3 inches to 30 inches by 3 inch increments, and in lengths from 6 feet to 8 feet and of 5/8 inch thicknesss.

Thesrnain problem with working such boards is in their accurate cross-cutting i.e.

cutting them across their width as opposed to their length. Although there are many types of machine saws available for cross-cutting in practice it has been found that only radial-arm saws can cross-cut such boards quickly and accurately. Such saws are not however readily or easily available to the 'do it yourself' enthusiast due mainly to the expense of such saws.

Cheaper saws normally require the tedious and time consuming procedure of clamping the board for each cut to be made. Where a saw is not available the board has to be cut free-hand with resulting inaccuracies.

An object of the present invention is to overcome the problem as aforementioned, to do away with the need to employ expensive and complex saws and to provide a crosscutting jig by which the cross-cutting of boards of a type with which the present invention is concerned can be done accurately and quickly.

With this object in view the present invention provides a cross-cutting jig comprising# securing means for fixedly positioning the jig on or relative to a work surface for receiving a workpiece to be cut, and guide means adjustably connected to said securing means, in order that it can be positioned over the workpiece, and adapted to carry cutting means and guide the cutting means across the workpiece.

Advantageously the securing means comprises a pair of spaced-apart right-angled brackets, the foot of each bracket having slots or holes into which screws are inserted to screw the brackets firmly to the work surface.

The brackets may be secured individually to the work surface or to a board clamped to the work surface adjacent one end thereof. However in either case it is advantageous to secure the brackets adjacent one edge of the work surface or one edge of the board.

Although the brackets may be secured to the work surface or board independently of one another, a rod may extend between the end of each bracket which is immediately adjacent said one edge of the work surface or board. The upright portion of each rightangled bracket may have a slot or hole in order to receive a respective end of the rod.

The rod does not fixedly secure the two brackets to one another. Instead it may provide an axle for one end of the guide means.

Advantageously the guide means comprises a pair of substantially L-shaped guide rails, each guide rail having at one end a fixing block and at its other end a portion bent over at approximately 90 to the rest of the rail.

Each fixing block is preferably mounted on the axis, a hole being provided through the block for this purpose and a grub screw being associated with the hole so that the fixing block can be secured to the axle. The L-shape of each guide rail facilitates the sliding of the cutting means which advantageously is a saw.

The guide rails are preferably positioned between the right-angled brackets, each guide rail abuting a respective bracket. The distance between the guide rails can therefore be adjusted to accommodate different sizes of saw.

The invention will be described further, by way of example, with reference to the accompanying drawings, it being understood that the following is illustrative and not limitative of the scope of the invention.

In the drawings: Figure 1 is a perspective view of a preferred embodiment of the cross-cutting jig of the invention mounted on a work surface and carrying a saw; Figure 2 is a part-sectional side view of the jig taken along the line 2-2 of Fig. 1; Figure 3 is a view on the line 3-3 of Fig.

2; Figure 4 is a side view of the jig of the invention in its stored position where the work surface is adjacent a wall; and Figure 5 is a view corresponding to Fig. 1 but illustrating the jig adjusted to accommodate a saw of a different size.

Referring firstly to Fig. 1, the preferred cross-cutting jig illustrated therein comprises securing means in the form of a pair of rightangled brackets 11, 12. These brackets 11, 12 are made from, for example, mild steel angle and on their respective foot 13, 14 have two holes for receiving screws 15. The holes enable the brackets 11, 12 to be secured relative to a work surface 16. In the embodiment illustrated the brackets 11, 12 are actually mounted on a board 17 which is clamped to the work surface 16, adjacent one edge thereof, by means of a G-clamp 18. The board 17 has a width which corresponds to the length of the brackets 11, 12 and the brackets 11, 12 are secured thereto in a spaced-apart manner.

A rod 19, which is round in cross-section and made, for example, of mild steel, extends between the end of each bracket which is adjacent the edge of the work surface. A respective hole is provided in the upright portions 20, 21 of the brackets 1 1, 12 for receiving the ends of the rod 19 and it will be appreciated that the rod 19 is not fixedly secured to the brackets 11, 12. In fact the rod 19 serves as an axle for guide means as will now be described.

Said guide means comprises a pair of substantially L-shaped rails 22, 23 made for example of mild steel. Each guide rail 22, 23 has at one end fixing block 24 of mild steel, and at its other end has a portion bent over at approximately 90 to the remainder of the rail.

Each fixing block 24 is substantially square in cross-section, with one of its edges being rounded, and has a hole extending therethrough so that the block 24 can slideably engage the rod 19. Communicating with each said hole is a grub screw 25 which secures the blocks 24 to the rod 19 after they have engaged the rod 19. As can be seen in Fig. 1 the blocks 24 are fixed to the rod 19 in a position where they abut that face of each upright 20, 21 of the brackets 11, 12 which oppose each other.

To ensure stable fixing of the guide rails 22, 23 relative to one another that end of each rail which is bent over at 90 is provided with a rectangular shaped block 26 made of the same material as the rest of the jig. The blocks 26, which can be seen more clearly in Figs. 2 to 4, each have a pair of spaced apart holes extending through the block in a direction parallel to the base portion of the re spctive guide rail 22 or 23. Extending normal to and communicating with each said hole is a grub screw 27. There are therefore two pairs of holes which are in alignment with each other so as to enable respective rods 28 and 29 to extend between the blocks 26 and to be securely engaged in the blocks 26 by means of the grub screws 27.

It will be appreciated therefore that the fixing of the guide rails to the axle rod 19 and to the rods 28, 29 provides a jig structure of considerable rigidity which is easily able to cope with the forces arising from a saw 30 (shown in dot dash outlibe in Figs. 1 and 5) which can be slid along the guide rails 22, 23.

In both Figs. 1 and 5 the cross-cutting jig is illustrated in its assembled condition and secured to a board 17 clamped to the work surface 16 wherein a board 31 to be cut abuts a stop 32 screwed to the surface 16 by screws 33. The board 17 acts as a reference for aligning the board 31 and is therefore of the same thickness as the board 31. The weight of the saw 30 acting on the guide rails 22, 23 ensures that the board 31 is firmly clamped to the work surface 16 to prevent any movement of the board 31 when it is being cut.

Once in its assembled condition the jig can be used for cross-cutting boards to a variety of lengths simply by adjusting the distance between the saw blade and the stop 32. Furthermore the spacing between the guide rails 22, 23, or between the brackets 11, 12 is adjustable to accommodate different sizes of saw (as illustrated in Figs. 1 and 5). The rod 19 can have a sufficient length to provide for this adjustment. However, when initially setting up and assembling the jig the following procedure is adhered to.

The right-angled bracket 12 is squared to one edge of the board 17 using a set square.

This is a most important operation since the correct angle of this bracket determines the square of every saw cut made. Holding the bracket 12 in position a hole is drilled in the board 17 via one of the holes in its foot 14 and screw 15 is driven in to partly secure the bracket 12 to the board 17. Checking the square again, another hole is drilled in the board 17 using the other hole in the foot 15 and another screw 15 is driven in to secure the bracket 12 firmly to the board 17.

The rod 19 is inserted into the hole in the upright portion 21 of the bracket 12 and the guide rail 23 is engaged with the rod 19 by means of its fixing block 24 and slid up to the bracket 12 so that it abuts it. The grub screw 25 can now be tightened to secure the block 24 to the rod 19. At the other end of the guide rail 23 the rods 28 and 29 are secured to the block 26 associated with that rail 23 by means of grub screws 27.

The guide rail 22 is now engaged with the rod 19 by means of its fixing block 24 and with the rods 28, 29 which engage the block 26. The guide rail 22 is slid along the rod 19 and rods 28, 29 until the spacing between the rails 22 and 23 matches the width of the saw 30 such that the saw 30 can be easily and securely moved along the guide rails 22 and 23. When this is achieved the grub screws 25 and 27 are tightened to secure the rail 22 to the rod 19 and the rods 28 and 29 respectively.

The right-angled bracket 11 is now engaged with rod 19 and slid up the rod 19 to abut the guide rail 22. The square of the bracket 11 is measured using a set square and when this is correct the bracket 11 is firmly held down onto the board 17 and holes are drilled in the board 17 via the holes in the bracket 11. The screws 15 are now driven in to secure the bracket 11 to the board 17.

A test board (not shown) is placed against the stop 32 on the work surface 16 and after adjusting the depth of cut of the blade of the saw 30, the saw 30 is placed on the guide rails 22, 23 and a test cut made in the test boards to check that the jig is properly squared up.

Once this is done the board 31 to be cut is moved up against the stop 32 and the board 17. The guide rails 22, 23 are placed over the board 31 and the saw 30 placed on the guide rails 22, 23. The depth of cut of the blade should be adjusted so that the saw blade passes through the board and 1/8 inch into the work surface 16. Where several pieces of the same length from the board 31 are required the test cut can act as a convenient point from which to take measurements up to the position of the stop 32 on the work surface 16.

When not in use the guide rails 22, 23 of the jig can be raised up from the work surface 16 leaving the work surface 16 free for other uses. As illustrated in Fig. 4, where the work surface 16 is placed near a wall 33 the raised guide rails 22, 23 can be supported by the wall 33 so that it does not obstruct the work surface 16 when not in use but is readily available for use when required.

The invention is not confined to the precise details of the foregoing and variations may be made thereto within the scope of the invention. For example the rod 19 can have divisions or markings so that the distance between the guide rails 22, 23 and/or the brackets 11, 12 can easily be measured.

Claims

1. A cross-cutting jig comprising securing means for fixedly positioning the jig on or relative to a work surface for receiving a workpiece to be cut, and guide means adjustably connected to said securing means, in order that it can be positioned over the workpiece, and adapted to carry cutting means and guide the cutting means across the workpiece.

2. A jig as claimed in claim 1 wherein the securing means comprises a pair of spacedapart right-angled brackets, the foot of each bracket having slots or holes into which screws are inserted to screw the bracket firmly on or relative to the work surface.

3. A jig as claimed in claim 2 wherein the brackets are secured individually to the work surface adjacent one edge thereof.

4. A jig as claimed in claim 2 wherein the brackets are secured individually to a board clamped to the work surface adjacent one edge thereof.

5. A jig as claimed in claim 2, 3 or 4 wherein a rod extends between that end of each bracket immediately adjacent said one edge of the work surface or board.

6. A jig as claimed in claim 5 wherein the upright portion of each right-angled bracket has a slot or hole in order to receive a respective end of the rod.

7. A jig as claimed in claim 5 or 6 wherein the rod does not fixedly secure the two brackets to one another but provides an axle for one end of the guide means.

8. A jig as claimed in any preceding claim wherein the guide means comprises a pair of substantially L-shaped guide rails, each guide rail having at one end a fixing block and at its other end a portion bent over at approximately 90 to the rest of the rail.

9. A jig as claimed in claim 8 wherein each fixing block is mounted on the axle, a hole being provided through each block for this purpose and a grub screw being associated with the hole so that the fixing block can be secured to the axle.

10. A jig as claimed in claims 8 and 9 wherein the L-shape of each guide rail facilitates the sliding of the cutting means.

11. A jig as claimed in claims 8, 9 and 10 wherein the guide rails are positioned between the right-angled brackets, each guide rail abuting a respective bracket.

12. A jig as claimed in any one of claims 8 to 10 wherein the distance between the guide rails is adjustable to accommodate different sizes of cutting means.

13. A jig as claimed in any preceding claim wherein the cutting means is a saw.

14. A cross-cutting jig substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.