Lathe Parting Tool Spring Type Tool Holder For QCTP

[Ralphxyz]

What rpm do you use?

Great tool, I am thinking of this as a challenge.

thanks for posting.

Ralph

[jjr2001]

Lots of great info here guys thanks for all the tips.
I can only add that I have not tried 12L14 but use a lot of hot rolled cutoff scraps
and 1018 along with some drill rod and brass and aluminum.

Additional points to keep in mind are the lathe spindle speed. I find it best to use a rather slow spindle speed.
For feed speed I like to keep it relative high. Lots of cutting oil applied with a brush. (I use thread cutting oil).
Remove the compound and replace it with a QC tool post block. That will eliminate one source of movement.
Cutoff tool height is very important and it must be sharp as a razor.
Keep the cutoff tool stick out short.
Keep the cut near the chuck.

Cheers, JR

[Toolmaker51]

What RPM is dependent on material, diameter, tooling, feed-rate, and a bit of nerve. Sharpen the bit, set the holder shy of the OD, insert the blade that center or wall of hole is reached and have at it.
If working unfamiliar combinations, I start with RPM about 50% that I'd use for turning, and feed in by hand first. If there are multiple parts to run, I use a stopwatch or count turns to calcu-guess a feed rate on chip appearance and that parting off will occur in the next minutes instead of hours. You can part too slow, just like you can attempt parting too fast.
Both cost $$$, and throw a job off-quote.

[mklotz]

If you have power crossfeed, it can provide a nice constant rate feed that's often difficult to do by hand.

I'll admit that, until you've learned to part by breaking the required number of blades, the idea of powering that tool into the work is scary. Once you work up the nerve to try it, start with aluminum, then brass, then leaded steel, then 1018. Powered feed is a blessing for stainless which work hardens quickly.

With powered cut off you have both hands free to apply lubricant (or cover your face while you cringe).

[Toolmaker51]

I use a tank and needle valve, just like Marv's http://www.homemadetools.net/forum/p...7738#post37592 That way one hand is free to operate lathe, while other doubles up in assisting the cringe.
About 50% of the time water based coolant is good. A flux brush usually works OK, but lags behind when running stainless. Dripped or brushed, I use a 2" deep tray to catch oil, to keep it out of coolant. You can reuse it basically forever. Plumbers figured that out lo-ong ago. Like everything, variations occur. You can turn a part dry just fine, but tapping or part-off are not so cooperative. It's good to be prepared for such instances.

[mklotz]

Incidentally, a dripper along the lines of my oil dripper, if filled with water, works nicely if you use a horizontally rotating sharpening stone.

[Metalmuncher]

Lots of nice and valuable advice here! I agree that one need not use parting off as a mandatory step, and I do have a horizontal bandsaw. Based on all this dialogue and some testing, the custom ground cutoff blade I had on my 7x10 works well on non-ferrous materials on the Grizzly, provided I properly lock things down so they don't move. One thing I learned today was to try instead of leaving the compound oriented parallel to the ways, turning the compound parallel to the cross slide, before making the parting cut. That makes it much harder for the tool post to raise the compound if the blade grabs, rather than allowing it to "roll" sideways. This lathe is new, and I am finding as I use it the gibs are wearing in and I have to periodically tighten them to maintain the same resistance while they move. That turned out to be part of the problem I was having.

I think if I were going to use something along the lines of the aforementioned Gibraltar Block, I would not want to be removing the compound, but instead screw it directly to the back end of the cross slide, and remove it when not in use. This way the compound is unaffected. I think if I get around to trying this spring model parting tool I would modify the design to do that, instead of hanging off the side of the tool post. I can see the advantages to the old rocker style post, since it puts the load centered directly on the compound, instead of hanging off like a sidecar, creating much more torque to try and move things. Has anyone ever made a QC tool post that centered the tools instead of mounting them on the side?

[Toolmaker51]

Most QC toolposts capture holders via wedging or cam action. Some ridiculously short in height and narrow like the KDK yet offer good accuracy, and are very popular. Others are beefier, per the Aloris pattern; proportionally taller wedge resists torque better, very typical on larger lathes. The widest alignment is probably the Swiss and Italian versions with 2 vee's at right and left side.
It depends on lathe size and available power. When I run the HLV, KDK are the go-to. Nice, compact, assorted blocks, plus 5C holder, and a KDK 6 station turret. It is second operation work, not hogging, so lightweight QC's are ideal. On the Pacemaker, incredibly powerful despite only 10HP, I wouldn't spend a dime on KDK. Tooling for it is geared to capability, only strongest will do. I select from Aloris when many steps are involved, 4 station turrets for simpler but heavier work, and Swiss when I really want to 'pour it on'. All were bought used. I had to exchange Aloris holders until each locked at nearly the same handle angle. That aids muscle memory and visual confirmation of repeatability. I want to unlock lefthanded and pull the holder, affix second holder with the right, and slap the lock left handed.
There is a QCTP that clamps on the side, pulled in by a cam-operated wedge [Kirkelie] that is decent; offering more engagement of male and female wedge.
In the end, solution is simple. If you can't experiment, buy heavier. The shortest distance between tool and wedge is going to be most rigid.

[Paul Alciatore]

I must totally agree that the first thing for any kind of work is that the tool post must be as solid as possible. Of course this is specially true for parting. The idea of a tool post that keeps the tool in line with it's own center is interesting but, having designed a QCTP myself, I do not know how that would be accomplished. The lantern style does that, but it suffers a lot in the process and leaves a lot to be desired in terms of rigidity.

I also do not like the design of the tool posts that use a dovetail to fasten the holders to the post. These dovetails, in addition to having the tool offset to the side of the post, rely on a couple of relatively small areas of contact between the post and the holder. The piston design is the worst in this regard. In either case, the total area involved is well under one square inch. And the post itself must have a mechanism inside it to provide the clamping/release action so it is hollowed out to a certain degree. All of this allows a certain amount of movement of the holder and even the post itself during heavy cuts.

I believe my design provides the most rigidity of any QCTP that I have ever seen. It uses a solid steel post where the only material that is missing from the interior is the central hole for the mounting stud. And this central mounting stud places the post itself in compression mode of stress, much like pre-stressed concrete so it actually adds to the rigidity of the post. Then the holders are held in place with a complete, 360 degree wrap-around design. When they are tightened in place, they are in intimate contact for their full height as well as for the full 360 degrees of wrap. This provides many square inches of contact area and there is little chance of the holder moving on the post.



In short, the post and holder with this large contact area between them, become much like a single, solid piece of steel. On top of this, the repeat-ability of the tool's position when changed is excellent in all directions, well under 0.001". And it really lives up to the "Quick Change" part of it's name. The tool holder can be unlocked and removed with ONE HAND in a SINGLE, FLOWING MOTION. No tools are needed to remove it. And the new holder is installed in much the same manner, again with NO TOOLS. No wrench or Allen key, just your ONE HAND. The design of the post with a generous chamfer at the top literally guides the holder onto the post. I can not see how any manually changed tool holder could be faster. In a production environment that would save valuable seconds at each tool change.

To answer the most often asked question about this tool post, YES there is a height adjustment. It is hidden in the hole on the top of the tool holder. And it does not require any locking nuts or screws, it just holds the adjustment on it's own. Another time saver: just adjust and go.

The plans for this holder are available here on this board in the Tool Plans For Sale forum. In addition to complete drawings, they discuss the construction in great detail. Oh, and the design is for an 8 to 10 inch lathe, but it should easily scale for larger or smaller machines. So if you have a 14" or 16" lathe, just multiply the numbers up and perhaps make the post a bit longer.

http://www.homemadetools.net/forum/q...st-lathe-52118

I have included a cutoff tool holder in those plans, but it is not a spring type design. It relies on the rigidity of the post and the lathe for proper cutting action. It is good, but not perfect. After reading this thread I want to try to make a version of this cutoff holder for my QCTP. If that is successful I will post the results and drawings in the discussion at the link above for all the users of my post to use.

Most QC toolposts capture holders via wedging or cam action. Some ridiculously short in height and narrow like the KDK yet offer good accuracy, and are very popular. Others are beefier, per the Aloris pattern; proportionally taller wedge resists torque better, very typical on larger lathes. The widest alignment is probably the Swiss and Italian versions with 2 vee's at right and left side.
It depends on lathe size and available power. When I run the HLV, KDK are the go-to. Nice, compact, assorted blocks, plus 5C holder, and a KDK 6 station turret. It is second operation work, not hogging, so lightweight QC's are ideal. On the Pacemaker, incredibly powerful despite only 10HP, I wouldn't spend a dime on KDK. Tooling for it is geared to capability, only strongest will do. I select from Aloris when many steps are involved, 4 station turrets for simpler but heavier work, and Swiss when I really want to 'pour it on'. All were bought used. I had to exchange Aloris holders until each locked at nearly the same handle angle. That aids muscle memory and visual confirmation of repeatability. I want to unlock lefthanded and pull the holder, affix second holder with the right, and slap the lock left handed.
There is a QCTP that clamps on the side, pulled in by a cam-operated wedge [Kirkelie] that is decent; offering more engagement of male and female wedge.
In the end, solution is simple. If you can't experiment, buy heavier. The shortest distance between tool and wedge is going to be most rigid.

[Toolmaker51]

Valid observations Paul Aliciatore. I am torn as to the wedge issue. Imports have details that make them seem second rate. A set is on lathe at work. I can feel a lessened positive action and clamping compared to ancient Aloris on my personal lathe. It is very consistent, making an easy job of presetting for the DRO.
The import's different story. I'd rate +/- maybe .002 of all it's tool holders. I don't even like the set screws, the elevation screw, nut and female hole aren't very well executed, closing the wedge feels indefinite. Import is 250 size BX, mine are 400 CA's, roughly double the mass and locking area. Import also doesn't have equal quality insert and HSS tools.
All told and IMHO no commercial set equals double vee'd style mentioned. They are not common here at all, never been in a shop using them. Bought first block and a few holders out of curiosity; using them best advertisement possible.

Your design is excellent, addresses every fault of conventional QCTP's. Had I not invested so much on holders the plans would be in my library.