So, just how long does it take to grind a cylinder? This is the question most frequently asked by anyone looking to purchase their own mower grinder because, as we all know in business, ‘Time is money’.

IAN ROBSON, Operations Manager for Hunter Grinders, examines the variables

ALL three major manufacturers of grinding equipment offer machines or accessories to allow the operator to both spin and relief grind to lesser or greater degrees of accuracy. Hunter Grinders Ltd combines spin and relief operations in one machine, although both methods can be used independently if desired. Ian Robson, Operations Manager for Hunter Grinders Ltd examines the variables that effect the time required to sharpen a unit and explains how, despite the grinding being only one part of the process, the method of grinding adopted can have a huge impact on the amount of time you spend in a season keeping your mowers sharp. He also examines how choosing the right grinding methods to tackle particular sharpening problems can make life a lot easier for the Workshop Manager or Head Greenkeeper.

Calculating the time required to keep a cutting unit sharp

A simple basic formula has been devised to allow you to calculate this for yourself, which is described as Value A + Value B + Value C = Total Time to sharpen each unit

Value A - Time required to remove the cutting unit from the mower and prepare it for grinding.

Value B - Time required to mount the cutting unit in the grinder, sharpen it and remove it from the the grinder.

Value C - Time required to reassemble, set up and refit the cutting unit to the mower.

For the purpose of illustration I have used typical values in the equation but you may prefer to use values for A or C based on your own experiences.

Example 1 represents a unit which has only recently gone off cut requiring only a small amount of grinding to return it to sharp again.

Using Spin Grind Mode (grinding segment is floor to floor in 10mins) Value A: 20mins Value B: 10mins Value C: 20mins

Calculation 20+10+20= 50mins

Using Spin & Relief Grind Mode (grinding segment is floor to floor in 20mins) Value A: 20mins Value B: 20mins Value C: 20mins

Calculation 20+20+20= 60mins

Example 2 represents a unit requiring more intensive sharpening due to extended usage.

Using Spin Grind Mode (grinding segment is floor to floor in 20mins) Value A: 20mins Value B: 20mins Value C: 20mins

Calculation 20+20+20= 60mins

Using Spin & Relief Grind Mode (grinding segment is floor to floor in 30mins) Value A: 20mins Value B: 30mins Value C: 20mins

Calculation 20+30+20= 70mins

Looking at these figures in isolation it would appear that there are small time advantages to be gained from spin grinding only! However, there is another extremely important value to be added to the equation which is invariably over- looked and yet has a dramatic effect on the calculation. That is, that a spin &

relief ground unit will stay sharp at least three times longer than a spin ground only unit and, indeed, some operators claim their units will stay sharp five or six times longer when the relief angle is added. On average a spin & relief ground unit will stay sharp for approximately 12 weeks compared to a spin ground unit which will only stay sharp for around 4 weeks.

Verification of this comes from mower manufacturers such as John Deere, Jacobsen and Toro who between them spend millions of pounds every year on research and development. Their published conclusions are that the extra time required to manufacture a unit with a relief angle is essential if you want your units to stay sharp, essential if you want your units to cut correctly.

If we revisit our earlier examples we can now add the missing value which radically alters the time scale required to sharpen the units. During a typical growing season a spin ground unit will need to be sharpened on average at least six times whereas the spin and relief ground units need only be sharpened twice. Incorporating this value as the number of times the unit is sharpened per season gives the following results:-

Example 1 - Spin Grind all season: Total time per unit 50mins x 6 grinds = 300mins

Example 1 - Spin & Relief Grind all season: Total time per unit 60mins x 2 grinds = 120mins

Example 2 - Spin Grind all season: Total time per unit 60 mins x 6 grinds = 360mins

Example 2 - Spin & Relief Grind all season: Total time per unit 70mins x 2 grinds = 140mins

How long does it take

TO GRIND A CYLINDER?

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