-
Welcome back Guest! Did you know you can mentor other members here at H-M? If not, please check out our Relaunch of Hobby Machinist Mentoring Program!
Can't tighten down my quick change tool post due to Grizzly's poor design
- Thread starter stioc
- Start date
- Joined
- Feb 17, 2013
- Messages
- 4,406
Stioc - If you find that the tool post still wants to rotate a bit, it may be because the area just around the mounting bolt is slightly domed. The cure for this is to chuck up the tool post, get out your old 4-way to hold the cutting tool, and cut a shallow relief (maybe .010") around the center hole and out to about ¼" away from the edge of the QCTP. This will place the friction (between the compound and the QCTP) at maximum radius.
I finally got a chance to do some turning. Everything tightened down well I set it to 1000 RPM, chucked up a small piece of alum. I first took a .010" cut, then upped it to .020" then I went for it at .054" with the auto feed engaged at .004" feed rate. Wow, even with a well used insert it ate it up and the finish was pretty good too! Not sure I would want to try any deeper though, may be with better inserts.
In any case it's like a new lathe! I want to try steel but don't have any decent low carbon stock on hand.
In any case it's like a new lathe! I want to try steel but don't have any decent low carbon stock on hand.
- Joined
- Dec 20, 2012
- Messages
- 9,422
That's much closer to what you would expect from your lathe, stioc. Have you considered trying an SCLCR tool with an AK insert? I suspect that would perform even better. HSS might be even better yet ... something to think about.
Thanks! I like it. However, since I already recently purchased three new SCLC boring bars and ten CCMT21.51 inserts I'd like to find three holders i.e. left/right turning and a straight threading holder. Know of any good deals on those?
Also, with the CCMT bits it seems one can only make use out of two sides as opposed to the TCMTs where you can use three sides of them.
Lastly, what makes the CCMT work better than the TCMT inserts on a smaller lathe? comparing the CCMT and TCMT the latter seems bigger in size.
Sorry, too many questions...I know.
EDIT: I'll take this discussion over to the other thread about the 12x36 lathe's insert selection.
- Joined
- Dec 20, 2012
- Messages
- 9,422
Yeah, that other thread is probably the better place for this discussion. However, let me address your question re the CCMT vs TCMT question. There is absolutely nothing wrong with the TCMT inserts. They are common, cheap and easy to find and they work. Heck, I own a set of tools from way back that uses them so I know they work well. And yes, you get three usable tips.
The key difference between the triangular and diamond inserts is in the geometry of the tool holder. The SCLCX tool holder has a 5 degree clearance angle at the front and top edges. This allows a single tool to both face and turn, whereas you need several tools to do this with a triangular insert. This geometry also allows the end cutting edge of the diamond shaped insert to participate in the cut and this affects the finish that geometry produces. A triangular insert cuts only with one cutting edge so they do not finish as well unless you use a big nose radius. For me, that bigger nose radius requires much deeper finishing cuts or it chatters. A CCMT/CCGT insert produces a better finish with a smaller nose radius and takes a much finer finishing cut.
To summarize, both work but the more modern geometry does it better with fewer tool holders and insert nose radii required. In a hobby shop, a good insert lasts for a long time. The fact that I have only two tips vs three is of no concern to me.
The key difference between the triangular and diamond inserts is in the geometry of the tool holder. The SCLCX tool holder has a 5 degree clearance angle at the front and top edges. This allows a single tool to both face and turn, whereas you need several tools to do this with a triangular insert. This geometry also allows the end cutting edge of the diamond shaped insert to participate in the cut and this affects the finish that geometry produces. A triangular insert cuts only with one cutting edge so they do not finish as well unless you use a big nose radius. For me, that bigger nose radius requires much deeper finishing cuts or it chatters. A CCMT/CCGT insert produces a better finish with a smaller nose radius and takes a much finer finishing cut.
To summarize, both work but the more modern geometry does it better with fewer tool holders and insert nose radii required. In a hobby shop, a good insert lasts for a long time. The fact that I have only two tips vs three is of no concern to me.