What exactly is a 3mm dimple as required by rope cutter instructions?

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Mike k

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Sorry if this is a daft question but the instruction on a R and D rope cutter require a 3mm dimple to be drilled on the shaft to take the grub screw to hold the cutter on the shaft. R and D supply everything to do the job but as the bit will create a proper dimple i.e deeper in the middle and shallower at the sides - does anyone know where the 3mm should be i.e in the middle of the hollow or at the edges of the dimple( meaning a deeper than 3mm cut). I have put a call into to R and D but its weekend and I would like to do it on Monday so any views would be welcome. Many thanks in advance
Mike
 
The grub screw will normally have a pointed end, but it looks like the set screw provided with the R&D cutter has a plain end. There's mention in the instructions of putting the set screw into the cutter so that it protrudes 1mm on the inside, then offering it up to the shaft and locating the set screw in the dimple. So I'd imagine you need to dimple the shaft sufficiently that the set screw will go at least 1mm into the dimple.
 
Since the R&D illustration shows a dog-point set screw, I'd say that you need to drill into the shaft to a total depth of 3mm to produce a hole with short parallel sides produced by the full drill dia. ie 6.8mm, that the dog-point can fit into, the bottom of course will be conical
 
Thanks for your quick replies, from the instructions the 1mm grub screw protrusion is just so you can locate the first half on the shaft then the other before tightening the main bolts up and then you tighten the grub screw all the way home.
BUT if I make a 3mm mark on the bit when it touches the shaft and drill to that, then the 3mm will be the depth of the middle of the cone not the short sides unless of course the spherical shaft evens that out. Still a bit uncertain but maybe overthinking it.

.
 
Looking at the picture in the link that VicS provided.
The hole or dimple that you drill will serve as a housing for the tip of the grubscrew in the picture. The aim is to produce a hole into which the tip of the screw will fit snugly and completely. The shape of the bottom - cone or whatever - is immaterial; it is the sides of the tip that will be preventing the disk from rotating freely.
 
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PuffTheMagicDragon said:
Looking at the picture in the link that VicS provided.
The hole or dimple that you drill will serve as a housing for the tip of the grubscrew in the picture. The aim is to produce a hole into which the tip of the screw will fit snugly and completely. The shape of the bottom - cone or whatever - is immaterial.
Click to expand...

and that's my question - is 'completely' 3mm at the base of the cone or 3mm on the sides- want to get it right to keep the cutter on for a long time.
 
Mike k said:
and that's my question - is 'completely' 3mm at the base of the cone or 3mm on the sides- want to get it right to keep the cutter on for a long time.
Click to expand...

While you were writing I was editing the last sentence, hoping to make things clearer.
It now reads: "The shape of the bottom - cone or whatever - is immaterial; it is the sides of the tip that will be preventing the disk from rotating freely."

Does that answer your question?
 
PuffTheMagicDragon said:
While you were writing I was editing the last sentence, hoping to make things clearer.
It now reads: "The shape of the bottom - cone or whatever - is immaterial; it is the sides of the tip that will be preventing the disk from rotating freely."

Does that answer your question?
Click to expand...

thanks but not really, its the depth of the sides ( which will be shallower than the bottom of the cone) that I need to know so I can drill it to the correct depth.If I drill say 3mm then it will be less at the sides
 
Mike k said:
thanks but not really, its the depth of the sides ( which will be shallower than the bottom of the cone) that I need to know so I can drill it to the correct depth.If I drill say 3mm then it will be less at the sides
Click to expand...

It doesn't really make any difference in the real world. The application is not to close engineering tolerances; it's just to prevent one component from rotating around another. You're worrying too much! ;)
 
Mike k said:
thanks but not really, its the depth of the sides ( which will be shallower than the bottom of the cone) that I need to know so I can drill it to the correct depth.If I drill say 3mm then it will be less at the sides
Click to expand...

If its a standard drill point (59 °) and you only drill the point in by 3mm the square sides will be only approx 1mm deep measured at the deepest , even less at 90° to the axis of the shaft ( I dont know the diameter of the shaft so you can do the maths yourself)

(x = 3.4/tan59 where x is the dpth of the drill point)

Obviously then drill 3mm + the depth of the drill point ....... 2mm for a standard drill bit, but it is not going to be critical +/- fraction of a mm
 
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VicS said:
If its a standard drill point (59 °) and you only drill the point in by 3mm the square sides will be only approx 1mm deep measured at the deepest , even less at 90° to the axis of the shaft ( I dont know the diameter of the shaft so you can do the maths yourself)

(x = 3.4/tan59 where x is the dpth of the drill point)

Obviously then drill 3mm + the depth of the drill point ....... 2mm for a standard drill bit, but it is not going to be critical +/- fraction of a mm
Click to expand...

thanks Vic most helpful
 
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