Precision Blade Dressing Tool

Hamilton Lichfield manufacture a well proven range of Precision Blade (PB) and Precision Needle Blade (PNB) tools which may be used on all straight pass and all but the most exacting profile dressing operations. These tools have been shown to provide considerable cost savings over conventional tooling such as expensive chisel tools, both in initial cost and in machine down times.

The current range of tools is shown in table 1.

Tool Composition

Two general types of tools are produced in order to cope with the variations in grinding wheel composition. These have more recently been complimented by some specialised tools for more demanding applications. The variation in bond is used to classify the blade type. (see fig 1.)

Bond Type

'W' - Tungsten bond, for use on aluminium oxide and similar wheels

'H' - Hard Metal Carbide bond, for use on silicon carbide and the more abrasive wheels.

Diamond Selection

Two types of diamond may be employed as the dressing media in these tools:

'Grit' - High quality synthetic diamond grit is used in both the 'H' and 'W' tools. The grit size is carefully selected to match the grit size of the wheel to be dressed, the grit itself being selected to be of appropriate friability and uniformity.

'Needle Diamonds' - Interlocking needle diamonds are used as an alternative to grit in 'W' type blades only. Of necessity these diamonds are somewhat more expensive but easily repay their costs when specified for larger wheel grit sizes or, where severe dressing conditions are encountered.

Dressing Concept

Both types of blade present diamond to the wheel which is contained within a well defined cross-section, of consistent width, throughout its length (see fig 2). The active width of this 'corridor' will vary from one grit size to another but is obviously smaller than the plate width quoted in table 1.

The presence of this uniform corridor enables the tools to emulate the chisel and single point tools which they may supersede and can, if correctly applied, profile all but the most complex forms. In the case of 'W' type tools the direction of dress should always be such that the diamond bearing plate is pushed into the steel backing. With both types of tool it is necessary to counteract the effects of any drag angle by having the full face width of the blade in contact with the wheel. A full flood of coolant should be directed immediately onto the blade.

Shanks

Standard blades are produced in 'nib' format which may be used with a variety of swivel type tool holders, thus allowing the blade to be set to compensate for the drag angle found on most machines. All of the usual tool holders found in the grinding shop, such as taper and headed shanks may be adapted to suit the blade tool concept (see illustration). Fixed blade tools can be supplied when required.

Ordering Standard Blades

Specifying Precision Blades can be simplified by reference to Fig. 3 which shows the relationship between grinding wheel sizes and the blade width required for economical dressing. The steps required to arrive at the tool specification are as follows:-

1. Select 'W' or 'H' type of blade for the type of wheel being dressed, ie: W - Aluminium Oxide or soft wheels H - Silicon Carbide or harder wheels.
2. Determine the blade width needed from the chart. - see Fig 3.
3. Determine the depth of impregnation (10 or 15mm) - this is a matter of choice depending upon factors like length of run, tool change time, etc.
4. Determine the grit size required for the wheel being dressed from table 1. This may also indicate the need for needle diamonds as opposed to grit.
5. Select the appropriate code from table 1 which embodies all of the above parameters.

Specialised Blade Tools

In addition to the tabulated standard tools, bespoke variants can be designed to overcome the more arduous or demanding dressing applications.

The following are some of the more common examples:

PB39HM / PB40HM

Heavy duty tools designed for dressing of items having a double sided profile which must be accurately maintained. A feature of these tools is that they are produced with a Heavy Metal (HM) backing which not only rigidly supports the active dressing blade but does not interfere with the dressing operation ie: it will not load the wheel. The two code numbers denote the most common grit sizes employed.

PB41CS / PB42CS / PB43CS

These tools are specifically manufactured to suit the newer, often high speed machines, such as Twingrips. The tools have double sided blades with a central coolant feed (see fig 4). Again the code denotes the common grit sizes employed.

PB44DF

Intended for rough dressing work on pantagraph or CNC forming devices, the tools utilise exceptionally thin controlled blades. Figure 5 illustrates a tool for the 'Diaform' attachment although 'Optidress' and tools for other copiers are also produced.

Table 1

Blade Tools

TYPE	REF NO	BLADE SIZE	PLATE	CT. WT.	DIA. SIZE	WHEEL GRIT
Blade Tool	PB1W	20x15	0.75	1.50	D501	120 - 180
Blade Tool	PB2W	20x15	0.90	1.50	D711	80 - 120
Blade Tool	PB3W	20x15	1.15	1.50	D1001	54 - 80
Blade Tool	PB4W	20x15	1.40	1.50	D1181	36 - 54
Blade Tool	PNB5W	20x15	1.80	1.20	NEEDLES	54 - 100
Blade Tool	PNB6W	20x15	2.50	1.50	NEEDLES	36 - 60
Blade Tool	PB7W	10x15	0.75	0.75	D501	120 - 180
Blade Tool	PB8W	10x15	0.90	0.75	D711	80 - 120
Blade Tool	PB9W	10x15	1.15	0.75	D1001	54 - 80
Blade Tool	PB10W	10x15	1.40	0.75	D1181	36 - 54
Blade Tool	PNB11W	10x15	1.80	0.60	NEEDLES	46 - 80
Blade Tool	PB12W	20x10	0.75	1.00	D501	120 - 180
Blade Tool	PB13W	20x10	0.90	1.00	D711	80 - 120
Blade Tool	PB14W	20x10	1.15	1.00	D1001	54 - 80
Blade Tool	PB15W	20x10	1.40	1.00	D1181	36 - 54
Blade Tool	PNB16W	20x10	1.80	0.80	NEEDLES	54 - 100
Blade Tool	PNB17W	20x10	2.50	1.00	NEEDLES	36 - 60
Blade Tool	PB18W	10x10	0.75	0.50	D501	120 - 180
Blade Tool	PB19W	10x10	0.90	0.50	D711	80 - 120
Blade Tool	PB20W	10x10	1.15	0.50	D1001	54 - 80
Blade Tool	PB21W	10x10	1.40	0.50	D1181	36 - 84
Blade Tool	PNB22W	10x10	1.80	0.36	NEEDLES	46 - 80
Blade Tool	PB23H	20x15	0.75	1.50	D501	120 - 180
Blade Tool	PB24H	20x15	0.90	1.50	D711	80 - 120
Blade Tool	PB25H	20x15	1.15	1.50	D1001	54 - 80
Blade Tool	PB26H	20x15	1.40	1.50	D1181	36 - 54
Blade Tool	PB27H	10x15	0.75	0.75	D501	120 - 180
Blade Tool	PB28H	10x15	0.90	0.75	D711	80 - 120
Blade Tool	PB29H	10x15	1.15	0.75	D1001	54 - 80
Blade Tool	PB30H	10x15	1.40	0.75	D1181	36 - 54
Blade Tool	PB31H	20x10	0.75	1.00	D501	120 - 180
Blade Tool	PB32H	20x10	0.90	1.00	D711	80 - 120
Blade Tool	PB33H	20x10	1.15	1.00	D1001	54 - 80
Blade Tool	PB34H	20x10	1.40	1.00	D1181	36 - 54
Blade Tool	PB35H	10x10	0.75	0.50	D501	120 - 180
Blade Tool	PB36H	10x10	0.90	0.50	D711	80 - 120
Blade Tool	PB37H	10x10	1.15	0.50	D1001	54 - 80
Blade Tool	PB38H	10x10	1.40	0.50	D1181	36 - 54
Special Blade	PB39HM	20x15	1.50	2.00	D1181	36 - 54
Special Blade	PB40HM	20x15	1.15	2.00	D1001	54 - 80
Special Blade	PB41CS	20x15	0.90	3.00	D711	80 - 120
Special Blade	PB42CS	20x15	1.15	3.00	D1001	54 - 80
Special Blade	PB43CS	20x15	1.40	3.00	D1181	36 - 54
Special Blade	PB44DF	10x10	0.90	0.50	D711	80 - 120