View Full Version : internal grinding - mounted points

09-09-2014, 11:37 PM
grinding internal bore and angle for collet holder. I have a nice toolpost grinder. Any comments on a grinding point for RC36 4140? Cylindrical bore is 20 mm and about 30 mm deep. I was thinking 5/8" would be about right OD. AlOx abrasive maybe 50-60 grit? Mounted points are pretty vague. I'm used to actual grinding wheels that are explicit in their bond, abrasive, grit, etc. Internal wheels of that specificity seem to only be available special order. I will be using an 8 mm collet to hold the shank in the toolpost grinder spindle. Would you use an 1/8" or 1/4" shank? (1/8" is through-bore, 1/4" would be a cut off, shortened shank) Thoughts? Many thanks in advance! :)

09-10-2014, 11:23 AM
Norton mounted points are specific.


I wouldn't use any shank diameter except the collet size plus or minus .001"


09-10-2014, 12:23 PM
I wouldn't use any shank diameter except the collet size plus or minus .001"
To clarify, the collet is an 8 mm shank type ( B8/WW (http://i771.photobucket.com/albums/xx357/Arrak_Thumrs/Schaublin%20items/DSCN4600.jpg) ). Both 1/8" and 1/4" bores are available for use with the grinding spindle.

09-10-2014, 01:30 PM
The 1/4" shank will be a lot more rigid. Grinding tends to have a lot of vibrations so you need the stiffness.

Mark Rand
09-10-2014, 04:01 PM
Have you got dust extraction available, either through the bore or from the open end? If not, you're going to get a lot of dust/grit being re-ground/entrained with that large a wheel in the bore.

09-10-2014, 04:11 PM
randm - flood coolant, but not high pressure in any sense. Through-bore hole. For some reason I had 75% wheel diameter to bore in my head. I can't say from where or why. You'd advise closer to 50% (3/8" - 1/2" wheel) maybe?

Mark Rand
09-11-2014, 01:59 PM
With something flushing the crud away, there shouldn't be any problem. I was just worried by the thought of that size wheel in the bore with no dust extraction/coolant. :)