Hello All,
I'm new to this forum and not an engraver at all, but I spent some time putting something together that may be useful to some of you so I thought I'd post a note about it in case anyone is interested.
I'm a watchmaker and micro-machinist and I use a GRS Powerhone with their Dual Angle Sharpening Fixture to sharpen turning gravers for cutting by hand with a t-rest (watchmaker style) or for use with a tool post and cross-slide (machinist style). The more I learned about cutting faces, clearance, rake, etc., the more I wanted to be able to very precisely dial in the angle of the various faces of my turning gravers in conjunction with the clearance angles desired.
I had the Dual Angle Sharpening Fixture already, but trying to use its two simple adjustments (pitch and roll basically) to set a desired angle for the face and clearance gave me a fair amount of consternation. After much head scratching and dusting off the basics of trigonometry all but lost within my memory banks I was able to come up with some calculations for determining these things and put them into an Excel spreadsheet.
The spreadsheet basically asks for what "facing angle" (the angle between a perpendicular to the axis of the graver and the desired face when viewed from the top) and "clearance" (the angle between a perpendicular to the top edge of the graver and clearance face of the cutting edge) you want and then it spits out the pitch and roll settings for the dual angle sharpening fixture (don't worry there's a handy if somewhat crude illustation of the angles and terms as I'm using them in the spreadsheet as well). If there are some standardized conventions for the descriptions of these various angles, please drop me a line so I correct them in the spreadsheet and not sound so foolish/green.
Because I made all calculations based on the idea that the top edge of the graver (remember that the "top" edge of a machinist's turning graver is not at all the same as the "top" edge of a hand engraving graver if I'm not mistaken) parallel to the grinding stone is 0 degrees of pitch, I reset the degree scale on my sharpening fixture to agree with this to make it easier to use the calculator. It can be used without resetting the tool by simply doing some math plus and minus 45 degrees where appropriate.
I then also added a handy macro to "remember" any of the calculations that I thought I'd need again in the future on a different worksheet with the workbook so I could save them and print them out, etc.
If anyone wants a copy of this spreadsheet, feel free to drop me an e-mail and I'll send you copy (yes, for free). Obviously you'll have to have Excel or some kind of compatible spreadsheet program and you'll also have to macros security setting set to medium or lower to be able to use the "remember" function, but perhaps you'll find it useful. Of course, feel free to modify it or adapt it for your purposes as well.
I've also published a "snapshot" of the spreadsheet on Google as well (I couldn't figure out how to publish it and allow folks to use it online):
http://spreadsheets.google.com/pub?key=p5ow-lnTBjx9HvT6S7f6QHA
If this post is out of place or inappropriate here, please delete. Likewise, if this is old ground or better resources for similar things exist already, please let me know as well. I'd love to hear about it!
Thanks for reading!
_john davis
ei8htohms at hotmail dot com
I'm new to this forum and not an engraver at all, but I spent some time putting something together that may be useful to some of you so I thought I'd post a note about it in case anyone is interested.
I'm a watchmaker and micro-machinist and I use a GRS Powerhone with their Dual Angle Sharpening Fixture to sharpen turning gravers for cutting by hand with a t-rest (watchmaker style) or for use with a tool post and cross-slide (machinist style). The more I learned about cutting faces, clearance, rake, etc., the more I wanted to be able to very precisely dial in the angle of the various faces of my turning gravers in conjunction with the clearance angles desired.
I had the Dual Angle Sharpening Fixture already, but trying to use its two simple adjustments (pitch and roll basically) to set a desired angle for the face and clearance gave me a fair amount of consternation. After much head scratching and dusting off the basics of trigonometry all but lost within my memory banks I was able to come up with some calculations for determining these things and put them into an Excel spreadsheet.
The spreadsheet basically asks for what "facing angle" (the angle between a perpendicular to the axis of the graver and the desired face when viewed from the top) and "clearance" (the angle between a perpendicular to the top edge of the graver and clearance face of the cutting edge) you want and then it spits out the pitch and roll settings for the dual angle sharpening fixture (don't worry there's a handy if somewhat crude illustation of the angles and terms as I'm using them in the spreadsheet as well). If there are some standardized conventions for the descriptions of these various angles, please drop me a line so I correct them in the spreadsheet and not sound so foolish/green.
Because I made all calculations based on the idea that the top edge of the graver (remember that the "top" edge of a machinist's turning graver is not at all the same as the "top" edge of a hand engraving graver if I'm not mistaken) parallel to the grinding stone is 0 degrees of pitch, I reset the degree scale on my sharpening fixture to agree with this to make it easier to use the calculator. It can be used without resetting the tool by simply doing some math plus and minus 45 degrees where appropriate.
I then also added a handy macro to "remember" any of the calculations that I thought I'd need again in the future on a different worksheet with the workbook so I could save them and print them out, etc.
If anyone wants a copy of this spreadsheet, feel free to drop me an e-mail and I'll send you copy (yes, for free). Obviously you'll have to have Excel or some kind of compatible spreadsheet program and you'll also have to macros security setting set to medium or lower to be able to use the "remember" function, but perhaps you'll find it useful. Of course, feel free to modify it or adapt it for your purposes as well.
I've also published a "snapshot" of the spreadsheet on Google as well (I couldn't figure out how to publish it and allow folks to use it online):
http://spreadsheets.google.com/pub?key=p5ow-lnTBjx9HvT6S7f6QHA
If this post is out of place or inappropriate here, please delete. Likewise, if this is old ground or better resources for similar things exist already, please let me know as well. I'd love to hear about it!
Thanks for reading!
_john davis
ei8htohms at hotmail dot com
