GB2354964A - Scribing device - Google Patents

Abstract

The device comprises two clamping units capable of being positioned on and locking to a Tri-square blade and carry either a pencil, a sharp metal scriber or pivot point, or, a cutting blade for marking. The clamping units, made in a left or right hand configuration, may be used singly, or in pairs where two lines are to be scribed. In use the stock of the square is drawn along a datum edge and a line is scribed parallel to that edge. When a pair of clamps are locked to a steel rule, one carrying a pencil and one a pivot or scribing point forming a trammel; arcs may be struck on a flat surface.

Description

2354964

Tl THE TRI SCRIBE DESCRIPTION

It is usual in woodworking when making joints, especially of the mortise and tenon type, to mark out the volumes where wood or other materials (such as MDF) are to be removed or retained. The marking out process is traditionally executed using a marking gauge. This tool, which has a long history, has two parts - a wooden collar and a wooden rod. The rod passes through a hole in the collar and terminates in a sharp pin placed normal to the axis of the rod. The rod, which has a cross section designed to resist rotation, may slide in the hole and be locked in any axial position by a. locking screw.

When marking lines using this tool, the pin is displaced a desired amount from the collar and locked in position and a line is scribed down the wood by holding the collar in contact with a datum edge and drawing the gauge down the work. This tool can be difficult to use especially when a) the wood is heavily grained and b) when the pin is located at points farthest from the collar. Both a) and b) can cause an untrue line to be scribed. The collar, when held to the datum edge, must resist changes in scribing force on the pin. As the ratio of pin displacement from the collar to collar width increases to as much as 3:1 scribing a line in a steady and accurate manner becomes more difficult and a possible source of dimensional error.

The purpose of this invention is to dispense with a need for separate marking gauge, mortise gauge, panel gauge and cutting gauge and to adapt a standard Try Square to perform the same functions with greater efficiency, it being able to scribe a steadier line at a greater distance from a datum edge.

Provision is made to scribe a line with a pencil, scribing point or a disposable blade.

This invention comprises a clamp unit designed to fit on the blade of a try-square and to be secured with a locking screw. An integrally mounted block is bored to take a pencil with its own locking screw or alternatively a scribing point or a cutting blade mounting post, emulating the action to that of the historic scribing gauge. The clamp units are made in both a left and right handed form for use by left and right handed users and also for use in pairs where more than one line is to be scribed in relation to other lines.

The clamp units may also be used when locked on to, say, a steel rule where they may constitute a trammel for the laying out of arcs or curved lines or with the cutting blade, to cut circular shapes.

Embodiments will now be discussed using 8 figures:

In Fig 1 the clamp unit is shown working with a standard try square used, typically, by wood workers. Clamp units lRand 1L are made in the form of a ""U"' section shown in Figs 3,4,and 5 which slides over the Try Square Blade 3 (Fig 2) and located, relative to the I blade, in the base of the "U" section, so that it may slide along the length of the blade and may be locked at any point by Locking Screw 2. The lower or shorter arm of the "U" section has a relieving angle so that, when in use, it may rest on the work surface being 5 marked and may allow the Stock 4 of the try square (Fig 1) to be tilted in an anti- clockwise direction so bringing the pencil point or scribe or cutting blade into contact with the work surface in a controlled manner. 10 The hole in the body of the clamp unit designed to carry a pencil, scribe or blade is bored at a compound angle in the horizontal and vertical planes. This angle enables the Pencil 5 and also Scribe 6 conveniently to make contact with Work Surface 7-in Figs 1, 3 and 4, whilst, viewed from above and shown in Figs 2,5 and 6 Pencils 5 are 15 angled clockwise and anti- clockwise relative to an axis normal to the edge of the Try Square Blade 3: thus, Clamp Unit 1R has an anticlockwise angle and Clamp Unit IL has a clockwise angle. Pencil 5 and Scribe 6 of Figs 3, 4 and 6 are secured in their bores in Clamp Units 1R and IL by knurled clamping screws 10 which, working in 20 tapped holes in the clamp unit bores, impinge on their diameters so holding them fast. In the case of cutting blade mounting post 11 of Fig 4a Clamping screw 10 locates in pre-drilled recesses to give the correct blade angle.

3 This arrangement enables, in the case of Clamp Unit IR, the point of Pencil 5 to touch the face of Stock 4 (Fig 2). When used to draw a single line displaced from the face of the Stock 4 this allows values of displacement of such a line to start effectively from zero.

A second embodiment shows the clamp units working with a try square in Fig 2. In this use of the devices two clamp units 1R and 1L are shown mounted on Blade 3 of a try square in such a way as to permit the drawing of two parallel lines displaced from a datum edge of the work. It will be noted that the points of two Pencils 5 may be (0 brought together almost to touch allowing delineation of very thin sections. In another embodiment, clamp units may be used, in conjunction with a steel rule or any bar of suitable cross section and is shown in Fig 6. This arrangement may be used to strike circles or arcs. Clamp Unit 1L is fitted with a Scribe Point 6 as shown in Fig 4 S and is clamped to one end of bar 8. At the other end of bar 8 and at an appropriate distance is locked Clamp Unit 1R. When in use as a trammel mechanism a steadying hand pressure may be applied to the top of scribe 6 of Fig 6. Thus maintaining location of the scribe point during the striking of arcs and circles.

EC> In a final embodiment pencil 5 of clamp unit 1R shown in Fig 6 may be replaced by blade post and cutting bladell of Fig 4a and 4b.

This arrangement when used in a trammel bar configuration enables circular sections of material to be trepanned from a sheet of material.

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Claims (1)

1. CLAIMS Title TRI SCRIBE

   A means for scribing or drawing a line or lines specified distances from a datum edge after the manner of a marking gauge. Clamping units designed to hold a marking device like a pencil or a scribe point are rigidly attached to the blade of a try square which, when the stock there of is pressed to and slide along a datum edge will draw or scribe lines on a surface of uniform distance from the datum edge. A means where by the clamping units of claim 1 may be rigidly attached to a bar or rule of appropriate section in which a clamping unit fitted with a scribing point is clamped to the bar whilst another clamping unit fitted with a pencil is fitted to the bar set at a required distance allowing arcs or circles to be struck but where the steel rule or bar is caused to lie essentially flat or parallel to the plane of the work. A means whereby the clamping units of claim 1 may be made both in left and right handed configuration for ease of use by left and right handed users and when used in pairs, may permit the marking of two lines in close proximity. A means whereby a pencil or scribe point may be replaced by a cutting blade set in a mounting post and attached to a Try square, steel rule or bar, and may be used to mark out material on a flat surface enabling material shapes to be trepanned or formed.