- Joined
- Jul 29, 2014
- Messages
- 2,737
I got this Kunming clone of a Deckel SO grinder, and it's very well done. It's pure Chinese, People Republic of China stuff. I notice that compared to some clones, this model has the drive belt and motor completely enclosed in the unit, and the belt is at the opposite end of the spindle from the wheel. That makes it pretty compact and keeps grit far away from the belt.
I watched a bunch of good YouTube videos and figured out how to do things like 4 facet grinds on drill bits, and how to make say, a 0.030 radius end on a carbide tool. The precision and flexibility of control is really impressive (and fun).
But the set of 7 collets that it comes with, and seem to be the standard equipment set for these tools are all for round bits. I would like to make lathe tools with a lot of 5/16" square HSS blanks I have. So I looked for square collets...available, but real Deckel collets seem to be in the $350 each region, though I did find some for maybe $35 or so. It's a hobby, so taking a day or so to make one seemed feasible.
I found a drawing with some of the dimensions, and got the rest from direct measurements on my set. The most interesting feature is that the thread is not a typical V thread, but is a "buttress" thread, designed for applications where the force is predominately from one direction. And of course, it's metric. I measured it to be 20mm with a 2mm pitch.
Machinery's handbook shows buttress threads as having a 45 degree included angle instead of the 60 degree for a V thread. And one of the faces of the threadform is basically perpendicular to the axis of the shank. I thought about grinding a lathe tool for this but I have a vertical insert holder, with triangular vertical inserts, so in just a few seconds I ground off 15 degrees or so from one side of one of the insert tips. Then I set the tool post so that the unground face was normal to the spindle axis. This worked basically perfectly, so standard procedure from now on will be to first consider stock inserts, if not that, grind some insert to fit, if not that then make an HSS tool.
In any event, it was a successful project. Steps included setting the compound to 17.5 degrees and verifying against an existing collet, drilling and broaching with a 5/16" square broach, changing the gears around for 2mm pitch (for the first time, brought up some new issues and subgoals), slitting the collet at the four corners of the broached hole, and turning the metric buttress thread (first time for metric threads, too).
This square collet with the grinder is going to make some operations very easy, like O ring grooves, trepanning, etc,
I watched a bunch of good YouTube videos and figured out how to do things like 4 facet grinds on drill bits, and how to make say, a 0.030 radius end on a carbide tool. The precision and flexibility of control is really impressive (and fun).
But the set of 7 collets that it comes with, and seem to be the standard equipment set for these tools are all for round bits. I would like to make lathe tools with a lot of 5/16" square HSS blanks I have. So I looked for square collets...available, but real Deckel collets seem to be in the $350 each region, though I did find some for maybe $35 or so. It's a hobby, so taking a day or so to make one seemed feasible.
I found a drawing with some of the dimensions, and got the rest from direct measurements on my set. The most interesting feature is that the thread is not a typical V thread, but is a "buttress" thread, designed for applications where the force is predominately from one direction. And of course, it's metric. I measured it to be 20mm with a 2mm pitch.
Machinery's handbook shows buttress threads as having a 45 degree included angle instead of the 60 degree for a V thread. And one of the faces of the threadform is basically perpendicular to the axis of the shank. I thought about grinding a lathe tool for this but I have a vertical insert holder, with triangular vertical inserts, so in just a few seconds I ground off 15 degrees or so from one side of one of the insert tips. Then I set the tool post so that the unground face was normal to the spindle axis. This worked basically perfectly, so standard procedure from now on will be to first consider stock inserts, if not that, grind some insert to fit, if not that then make an HSS tool.
In any event, it was a successful project. Steps included setting the compound to 17.5 degrees and verifying against an existing collet, drilling and broaching with a 5/16" square broach, changing the gears around for 2mm pitch (for the first time, brought up some new issues and subgoals), slitting the collet at the four corners of the broached hole, and turning the metric buttress thread (first time for metric threads, too).
This square collet with the grinder is going to make some operations very easy, like O ring grooves, trepanning, etc,