Cylinder grinding questions

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Mre4
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Cylinder grinding questions

Hi,

I have a couple of questions about the finer points of cylinder grinding, forgive me if they have been asked before. 

Firstly, what's the best was to make sure a cylinder is ground parallel if it's ground in the mower? One option I've come across is to measure the distance between the centre shaft of the reel and the shaft that the stone spins on, but I don't know how to do that accurately. 
 

Secondly, I understand it to be the case that on Bernhard grinders putting the stone on a few thou for just a few runs once a cylinder is sharp creates a little relief on the blades; how does it do this? 
 

Thanks,

Mre4. 

wristpin
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To avoid grinding in or

To avoid grinding in or correcting a taper on a cylinder is, as you suspect, a function of the geometry and adjustment of a particular make of grinding machine . I occasionally check my vintage BRL with a dial test indicator ( clock gauge) to ensure that the datum scale on the adjustable head stock is correct.  I have no experience with a Bernard / Atterton and Ellis Dual but presume that there is a similar provision. Why not talk to their service department?

It is standard practice when spin grinding to finish the session with a couple of heavy cuts to create some “ false relief”.

hortimech
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The Bernard Dual has gauges

The Bernard Dual has gauges in the stone shaft adjusters, these were not fitted to the early machines but can be retrofitted. Originally the machines came with a simple depth gauge.

Any cylinder that has been spun ground should not be left to spin out (a common mistake), the last few passes should be 'hard' on, this removes metal from the rear of the blade and gives a pretty good relief angle.

Mre4
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Thanks for your replies. 

Thanks for your replies. 

The machine I'm using has dials on the adjusters. Assuming, these are correctly set up, wouldn't it still be necessary for some kind of measurement between the centre of the cylinder and the stone shaft when grinding cylinders in-frame? I'm concerned that I can't rely on the cylinder and the front and rear rollers being parallel with each other precisely enough to be able to use the dial read-outs to ensure an untapered cylinder. 
 

Thanks, 

mre4. 

hortimech
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It is my understanding that

It is my understanding that the gauges were really only fitted because Toro asked for them when they introduced the Greensmower SPA units. The SPA units were very good, but depended on being ground correctly and then set up correctly. The latter was something that pretty much defeated most greenkeepers, until a video and training was introduced.

Most machines do not required the precision that the SPA units did (these units were ground in frame, without the rollers and using special brackets), so if you drop the front roller to the lowest cut and clamp the machine into the grinder, you should be able to find the high end of the cylinder and then set the gauges level and grind the cylinder parallel.

Mre4
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Thanks again for your

Thanks again for your response. Interesting about the SPA units, I haven't encountered them before. 
 

I tried setting a unit to its lowest possible cut to ensure the front roller was level but unfortunately then the stone couldn't move low enough to provide light contact with the cylinder. I guess I could adjust the spacers on the back roller but that's probably unnecessary work. Instead, I used a feeler gauge to check for a gap under either side of the rear roller whilst applying pressure to the front roller whilst the unit was on the flat surface of the grinder, which I assume will be flat enough for this purpose. Given that the dials on the grinder are within .001" of each other, can I be confident that this method will allow me to grind any taper out of the cylinder? 
 

Thanks again, 

mre4. 

hortimech
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I feel you may be over

I feel you may be over thinking this, have you ever really used this grinder and who taught you to use it ? You mention 'light contact' between stone and the cylinder, you only want this whilst manually setting up the grinder, once you start grinding, you want a constant, fairly hard contact, you never let the cylinder spin out at the end of the grinding process. I think you might just run away if I was to show you how to grind a cylinder.

All cutting cylinders wear tapered in use, so you need to grind this taper out, but unless you are dealing with something like the Toro Greensmower SPA units (in case you haven't realised it, SPA stands for Single Point of Adjustment), you do not need to be fanatical about it. Ensure that the front roller is adjusted level at both sides, easy if it is single point of adjustment, bit harder if you need to adjust both sides (I am taking it here that you are doing in-situ grinding and do not have the loose cylinder attachments). Adjust the front roller to give you sufficient clearance between stone and cylinder to allow set up of the grind, then go from there.

All of this would be easier to show you, but you live too far away.

 

Mre4
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It wouldn't be a surprise if

It wouldn't be a surprise if I was overthinking it.

 

I was first taught to grind without sufficient contact and waiting for the stone to spark out, however I was subsequently shown by someone at Bernhard (I've forgotten his name) to use the machine properly - decent contact, not allowing it to spark out etc. 
 

I am grinding in situ - I do have the loose cylinder attachments but I'd rather save time and not have to disassemble the units if possible. 
 

With DPA units what's the best way to make sure that the front roller is level? 
 

 

hortimech
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Put the mower on the machine,

Put the mower on the machine, On machines like 20" Atcos where you set the cut by adjusting the bottom blade to the cylinder, the next bit is easy, just measure from the top of the cylinder shaft to the top of the grinder bed, these should be the same (as near as possible), if not, adjust the front roller until they are. Bit more difficult if you set the cut by adjusting the cylinder down to the bottom blade, you have to set the cylinder down to a central position (to put some tension on the springs) and get the cylinder as level as you can in the frame, then set the front roller as above.

Good job you do have the loose grinding attachments, without them you will not be able to grind Ransomes Auto-Certes/Marquis machines, well not without stripping them down, refurbish components, rebuild without the bottom blade, grind cylinder, strip down again, fit bottom blade to block and reface, rebuild again and set cut, phew, what a lot of work.

Mre4
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Luckily I'm working on units

Luckily I'm working on units on which the bed knife adjusts to the cylinder, so I have the easiest out of the options. I'll give it a go and see how I get on.

Thank you for your help.