Lathe Parting Tool Spring Type Tool Holder For QCTP

When it comes to parting off a 2" diameter piece of hot rolled steel my little mini lathe likes to chatter a bit. I built a parting tool spring type holder similar to the ones I have seen on the net. This one is different. It will mount up flush with the QCTP block and you will not loose any cross slide travel. It is made for the smaller tool holders like the HESS 250-00x holders and mounts up fine on the mini lathe. Using a 5/32" by 1/2" blade it cuts like butter without chatter. Just a bit of noise but it is the best parting off I have had with this lathe in the last 2 years.

So you need some steel
one block 1" x3.75" x 2"
one plate 1/8" x 2" x 1.2"
one 5/64" x 1/2" x 4.5" cutoff tool
6- 8-32 button head screws
3- 8-32 flat head screws
1- 3/8" x 7/8" spring pin
1- piece 1018 1/2" square

The outboard plate that clamps the cutoff tool works very well. I was concerned that it might allow the tool to move but it is rock solid.


Short video of the tool at work.
https://youtu.be/MdI0pUtNplQ

Cheers, JR

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Thanks jjr2001! We've added your Parting Tool Spring Type Holder to our Lathe Accessories category,
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Nice work JR
This certainly reduces the tendency for the tool to dig in and grab any backlash in feed screws.
Have you thought about achieving the same result with a rear tool post, both approaches will allow the tool to move away from the work under cutting forces. I use tipped inserts in my parting tool and have parted of 3 inch blanks with auto feed on occasions in my SB, it has plain bearings and is one of the few times I think it may help with less vibration.
Thanks for posting. Attachment 17573

Hi Dan, Thanks for the tip on the rear mounted tool for parting off. I have seen that method on the net
and it looks like a good idea. I was torn between that fix and the spring tool. Thought the spring tool
would be a bit easier to do since my cross slide is pretty small. Either way both methods have merits.

Cheers, JR

I had never bumped into this and did a search because you said JR you'd seen it else where. Looking at it I had an inkling, but I wanted to make sure. What an interesting fix. Just out of curiosity did you try it without the spring pin, just the hole? For whatever reason I can't get that it really does add "spring".

My lathe does indeed put up a chatter when trying to part off. Soon as I can figure out where I can get a chunk of steel like that this is going on the must make pile.

Thanks for the plans, parts list and pix, good job.

Hi C-Bag, I have seen similar types on eBay usually under the brand Williams, Atlas, or Armstrong.
They are from the old days when lantern tool post ruled. Tom Lipton of Oxtools has one he made
years ago and explained it like this. The pivot point is above the tool bit so the torquing force tends
to move the tool bit, when under extreme load, away from the work instead of into the work like
a normal tool setup.

In my testing I did use it without the roll pin and it was just too free and the tool bit seemed
to jump around. The parting tool I was using chattered a lot when I used it in a standard
tool holder but when I used it in the spring holder with the roll pin the chatter was gone.
I could feed in and curl off chips quite well on the 2" blank I was testing it on. I have seen
versions of this tool without the roll pin.

I suppose tool rigidity depend on the steel used. I just had a piece of hot rolled and
found that the pin does make it work better. I could see an entire build of several of these trying out
different diameter holes starting with say 1/4" and working up to find a sweet spot for the particular
setup and lathe in use. The other thing in my version is the long "key" that can be adjusted in or out
for different extensions toward the work being turned. This gives some latitude in setup and the
ability to "tune" the tool in case harmonics start to give a problem. However the main reason for the long
"key" is so the tool can be set flush with the forward face of the QCTP.

Ah, so many tools to build and so little time!

Cheers, JR

Thank you JR,
I have been wanting one of these and this is it.
Jim

Thanks JR, you rock. You went to all the places I was curious about.

Thanks guys, please post a picture of your build, I look forward to seeing them.
Cheers, JR

My .01 cent worth, discount for cash. Hot rolled steel is fine. I'd venture the web of flex hole would fracture, but the roll pin distributes the load and absorbs the flex. I like the hole and profile aren't concentric.
A back tool post offers the backlash advantage, saves toolholder space and changes, can be set close to the material to save cranking the crosslide, and chips fall out of the cut.
Just keep the gravity switch on.

Thanks for your comments on the tool Toolmaker51. I never thought about stress at that point
but now that you mentioned it I can see how it is really moving a lot to absorb the energy
from the cutting forces and now I see that the roll pin has two functions.

Cheers JR

Hi JJR2001!

This looks like a nifty solution to parting tool chatter and suddenly digging in. Will your design with the dimensions on your plans work on an AXA100 Size QCTP mounted a Grizzly G0752 10 x 22 lathe? I tried their provided parting tool holder last night, very carefully adjusting the 1/8 wide x 1/2" cutoff blade I got for it, trying dead on center, and both just slightly above or below center. I was using a 3/4" dia. length of 12L14 steel, parting about 3/4" away from the chuck jaws. Running at between 90 and 150 rpm. With cutting oil. I kept having a problem of it suddenly hogging into the piece, even though I was barely feeding in. Chipped the cutter once, so I had to re-grind the end. Also tripped the shutdown on the variable speed drive when it dove in a few times. I've parted things off on my older 7x10 mini lathe successfully, so this is frustrating. I thought maybe your tool might provide a solution. I've got the cross slide gib nice and snug, and even tried tightening the compound gib very snug making it hard to turn the handle, but it is still shocking and a bit scary how much things move when it grabs like that.

I began to wonder about maybe using a rocker tool post for parting, just to get the load centered better on the compound slide. But I'd rather stick with the AXA if I can.

Hi muncher. I think the tool will work fine on most home shop lathes. If your tool post can fit a 1/2" lathe tool bit then it should work fine.
In addition to the tool which I find invaluable I always lock down my carraige and snug up the cross slide and compound gibs. Works for me when the
standard parting tool holder just chatters and jumps all over the place.


There is another way to try to reduce or eliminate chatter when cutting off. I have seen it demonstrated on YouTube. You use a rear mounted tool post
and invert the cutoff tool so that the cutting edge is down instead of in the normal up position. Lathe is still run in the normal direction. The cutoff tool will
now be less likely to bite into the work piece. On my list of things to try one of these days.

Best of luck with your cutoffs, JR

I have seen the rear mounted parting tools, and am very interested in them. The more rigid the parting tool, the better it works, in my opinion. I actually found your thread, and this forum, googling for a rear mounted parting tool.

I was finally able to successfully part off some nylon, then aluminum last night by utilizing the same parting blade I had devised, out of desperation over these same issues, on my 7x10 mini-lathe before. It is a thin 1/2" tall blade, with the typical angled end for relief below the cut, but the top edge is ground with a "bowl" shaped relief cut of maybe 0.040" deep, just behind the cutting edge. Not sure what the radius would be, as I eyeballed it on the grinder. It sort of resembles a cut away cross section of a teaspoon, but much smaller, covering maybe 1/2" or less across the top edge toward the tail of the cutter. Or resembling the profile of one of those nice aluminum ice cream paddle scoops (where I got the idea, actually). I've recently seen a similar profile being shown in some forum threads and articles. But..... it still jammed and failed miserably on that same 12L14 steel round I mentioned before. It starts to cut OK, then suddenly digs deep and in this last attempt, snapped off the lower corner of the blade.

Have you worked with 12L14 (also called leaded steel)? It is very easy to machine as a rule. I don't know why it won't work with my parting tool.

I've had a helluva time with parting off with my 9x20. Somewhere, I think here on HMT, the tip of making a little side relief on both sides of blade was brought up. So I did that on my thicker blade and have been able to part off my steel projects. Something I'd not been able to achieve before that. Sorry, don't know what steel flavor it was.

Yes, side relief on the tool is important. Also, rigidity is essential. Lock the lathe carriage down firmly while parting.

A continuous supply of sulfurated cutting oil while parting can be very helpful with steel. I made a gravity-fed oiler...

http://www.homemadetools.net/forum/p...7738#post37592

from plumbing parts that keeps dripping oil directly into the cut while parting. Very effective and not hard to make.

Use kerosene, not oil, when parting aluminum and use nothing when parting brass.

Thanks for the tips! I'm gonna check out that drip oiler. I'm not set up for flood cooling, so I repeatedly add small amounts of coolant as I work. Having an adjustable tool to do that would be a blessing.

I really don't like smelly coolants, as my shop is in our attached garage, plus there is always the issue of getting it on clothing. Although I have the sulphated one, and access to kerosene, I currently use a very low odor coolant called Reli-On. It works equally well on pretty much all the materials I work with that need coolant. However, I do admit that ferrous materials are not my first choice most of the time. I work with aluminum, brass, nylon, and UHMW Polyethelene (the latter mostly because it is very cheap, machines very well, and is non-absorbent) whenever I can. But I will use steel when it is needed.

I really don't like cast iron. I just finished the custom back plate for the 8" 3 jaw scroll chuck I added to my 10x22 lathe. It turned out very well, but that was the dirtiest, nastiest stuff I ever machined. I used Re-Lion and a shop vac dust collector to eliminate airborn particles, but it sure is messy cleanup. Like machining graphite, I imagine. :) I couldn't get a pre-machined backplate, as Grizzly uses a 1 3/4 - 8 thread on its spindle, and all the pre-machined plates I found used a different size. So I uad to machine a threaded blank.

Sorry if I got a bit off topic here. :)

Still looking into what I want to try for a different parting tool. One I could mount optionally on the top surface of the cross slide, forgoing the compound, would take half the flex problem out of the equation. Perhaps this spring model of yours, but made to mount flat onto the cross slide top.

Cast iron is normally machined dry because it's self-lubricating - one of the reasons it's so often used for metal-on-metal sliding parts.

When turning it, lay some oil-soaked shop towels on the ways. They will trap the dust. Discard safely when done.

A "Gibralter" tool block to replace the compound has been suggested in at least one of the older magazines. It seems counter-productive though to have to remove the compound and tool holder and mount Gibralter to cut-off, then remount everything. I suppose a carriage-mounted Gibralter size base for interchangeable tool blocks is a possibility but you still lose the angular capability of the compound.

Remember, just because you CAN part off with a lathe doesn't mean you MUST part-off. This is especially true if you have the ubiquitous horizontal bandsaw. Cut a starting groove on the lathe as a blade guide for the saw and let the saw do the work.

I made something like this a while back, the only essential difference being that instead of the bolted on block to clamp in a standard tool holder I cut dovetails and fit it direct to the QC main block.

Quote:

---

Originally Posted by tonyfoale

I made something like this a while back, the only essential difference being that instead of the bolted on block to clamp in a standard tool holder I cut dovetails and fit it direct to the QC main block.

---

I emphasized Tony's comment.
Cut-off can be iffy on ANY lathe, for a host of reasons. Usually, operators logically point to clearance, cutting fluids, speeds and feeds; and each is correct.
#1 But in my book, all depend on rigidity first and foremost. None of those conditions reach acceptable percentage without it.
#2 Stepped blades must remain so, as with tapered blades. The radius tempts alteration too, yet not so easily reproduced. In a proper setup it rolls and narrows the chip in most materials other than cast. That simultaneously relieves pressure on blade, admits coolant to cutting edge, and helps eject the chip. It also helps to listen. Any sound other than cutting, indicates something amiss. Like the squeak of a dull endmill or drill, the feel of a loaded tap, or motor loading up, often precede the distinct dull tone of $$$=Oops.

Tony eliminates 1, perhaps 2 losses of rigidity by eliminating the adapter and tool holder, by mounting to QC block directly. It worsens if the connections aren't hardened - to accept and transmit deflection and near impossible zero clearance in QC block and holder.

Marv also points out an imperative. Cover the ways and wipers! Oil soaked towels at a minimum. To me, they are a little coarse oiled or not. I use newsprint, oiled so it sticks in place, or plastic food wrap with water based coolants. Cost of either is practically nothing.

What rpm do you use?

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

thanks for posting.

Ralph

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

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.

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).

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.

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

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?

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.

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.

Attachment 22426

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.

Quote:

---

Originally Posted by 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.

---

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.

Quote:

---

Originally Posted by jjr2001

There is another way to try to reduce or eliminate chatter when cutting off. I have seen it demonstrated on YouTube. You use a rear mounted tool post
and invert the cutoff tool so that the cutting edge is down instead of in the normal up position. Lathe is still run in the normal direction. The cutoff tool will
now be less likely to bite into the work piece. On my list of things to try one of these days.

Best of luck with your cutoffs, JR

---

this is a often mentioned way of running a cutoff blade,usually on lathes w screw on chucks,main idea is so chips will fall off not binding up cutting tool, but it is NOT a reccomened method IMO..1 u cant see what your doing, work and tool both blocking view,2 it puts ALL the forces on to the dovetails,instead of the flat surface on crosslide,and in smaller lathes can break off dovetails sevierly damaging carridge if not ruinning lathe!! a way to eliminate some vibration is to bolt tool holder directly to compound using the threaded plate, u make a oversize plate/toolholder ,say 1 inch thick, wide enough to cover compound area around the threaded plate,and bolt directly to threaded plate, u may want to drill and tap 2 other holes in threaded plate for tool holder to bolt to.u will then need to move compound to get your 90 degrees, not a fast way to do cutoffs ..usually when i had trouble doing a cutoff i would just back off ,move over 1/2 or 3/4 thickness of cutoff tool and take a second plunge into work,fastest way to finish a cutoff.

Here is another similar version from Winky's workshop:

https://youtu.be/p93bUqpdWMg