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+--- Thread: [HELP] Switching To A QCTP (/thread-3781.html)
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Switching To A QCTP - Cross Slide - 12-10-2017
Hey Guys.
I would like to find out how some of you guys would tackle this project of switching my lathe over to a Quick Change Tool Post. I have been thinking about this for a while now as to what would be the best way to do it. I have an idea in my head. But I would like to see if there is better ways of doing the conversion.
For reference my lathe is a Craftex CX-701. It came with the standard Four Way Tool Post. I purchased a Piston Style Quick Change Tool Post from the same company the lathe was originally purchased from. It said will fit 12" lathe. Which is what my lathe is.
Now my compound doesn't have a T Slot for the tool post. Which is what this QCTP is really designed for. It came with a flat plate to make into a T Nut and slide into the compont slide. Mine has a stud that is pressed in from the bottom of the compound slide and has a small roll pin going threw a flange into the bottom of the compound slide to keep it from rotating. The whole stud will come out from the bottom leaving the flat surface of the compound slide with a 3/4" hole.
[attachment=15381]
What I'm trying to accomplish is to have it so I can switch back and forth from the QCTP & Four Way. I don't know if I will ever really need to switch back to the Four Way for any reason. But I would like to keep that option open if possible.
The stud for the four way is a small dia. and to short to work with the QCTP. Plus the four way has a large boss (3/4") at the base of the stud that fits into the base of the tool post itself.
[attachment=15383]
[attachment=15384]
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Where to QCTP has the same bore top to bottom. Around 1/2".
[attachment=15386]
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Do you guys have any ideas of how I should do this or if you have had to do it on your lathes, any pictures!!
My idea of how to do this was to make a insert that will press into the bottom of the compound slide. I would use the roll pin idea from the original tool post mount to keep the insert from spinning. The insert will then be threaded to match the threads on the QCTP Stud. Once threaded into the insert I should be able to use the QCTP. Then I was thinking of making a new stud for the Four Way Tool Post that is threaded on the bottom to match the insert as well. If I wanted to switch to the Four Way, it would just be a matter of switching the studs. But I'm open to any suggestion, as long as I have to tooling to pull it off.
Also. My Four Way Tool Post Stud has a weird Cut in it just above the boss at the bottom. I have watch videos where guys show the stud on their Craftex lathes, and I can't see that cut in theirs. But I also have not seen a video with my exact lathe either. Any idea as to why that cut is there?
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Thanks
Trevor
RE: Switching To A QCTP - Pete O - 12-11-2017
I switched to a QCTP a while ago Trevor and it is the best thing I have bought for the workshop- the difference when using the lathe just has to be experienced to be appreciated. I also thought I had best keep the option of using the 4-way holder but now i can't imagine what I might want to do that for- I'd just make a toolholder for whatever strange job might come up.
My lathe also has a spigot for the 4-way and no T-slot just like yours does, I machined a ring to fit over the spigot as I needed the extra height for the QCTP, if yours is the right height just sitting on the compound, I would think you're on the right track pressing out the existing stud and fitting one that is right for the new toolpost.
RE: Switching To A QCTP - Dr Stan - 12-11-2017
I can only ditto Pete's recommendations. He is right on target.
RE: Switching To A QCTP - Cross Slide - 12-11-2017
Thanks for the info Pete O. I'm planning on tackling this job over the holidays.
RE: Switching To A QCTP - Mayhem - 12-12-2017
I had to press out the existing stud and make a new one, as the original was way too big. I made a sleeve up so I could use the old 4-way holder but it has never been used!
RE: Switching To A QCTP - randyc - 12-12-2017
I may be swimming against the current with a few of my tool post opinions, which were first expressed here:
http://www.metalworkingfun.com/showthread.php?tid=3668&highlight=tool+holders
It’s worth noting that my usage may be different than most peoples’ and therefore my opinions are not useful. Nevertheless, in the interest of addressing the OP’s initial desire to accommodate both his 4-way and a QCTP system, here are a few thoughts, most are recycled from the above post.
I have two lathes (well, three if I include the only-used-once Chinese jeweler’s lathe). The small Emco Meier (which originally had a proprietary tool mounting system) is always equipped with a 4-way tool post. This little 8 inch lathe has always been extremely capable when removing a large amount of material quickly.
This is a photo showing a .250 depth of cut at .007 IPR in cold-rolled steel, to an accuracy better than .002 and with a good surface finish. That is absurdly aggressive for an 8 inch lathe but commonplace for this one. In fact the only complaint that I ever had with this machine was occasional chatter when parting. (But ten minutes work corrected even that small problem.)
[attachment=15389]
The second lathe, larger of the two is an 11 x 36 Sheldon with a Chinese knockoff QCTP and six or eight tool holders. This is the setup around 75% of the time. But I have two complaints about the QCTP system: relative lack of rigidity compared to some other types of tool holders and relative lack of versatility compared to some other types of tool holders.
I know, I know, that’s likely to stimulate a response like “Them’s fightin’ words, stranger” but let me try to talk my way out of this corner I’ve painted myself into. Let’s first note that a QCTP tool system (or a Multi-Fix) with a couple of exceptions, is probably the best choice for anyone making a number of similar parts, although a 4-way works OK for less repeatable operations.
Now, if one has no need to take heavy cuts or doesn’t do a lot of parting on a small lathe, no need to read further except for amusement/entertainment. The ten-minute-fix for the Emco-Meier mentioned above has turned out to be so useful that I’m surprised that others haven’t thought of and implemented it.
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This is also described thoroughly in the link posted above. In short, it consists of a threaded post that sits directly under the right front corner of a 4-way, supporting the cutting tool just where it needs to be supported. The cutting load is directly transmitted to the cross-slide NOT through the compound and then to the cross-slide.
[attachment=15391]
The top of the post is slotted so that it can be unthreaded from the cross slide, which has been tapped for the post. When the compound needs to be rotated or advanced further toward the work (only about 5% of the time in my case) the post is simply unscrewed and put aside.
In contrast, note how the cutting tool is positioned in a typical QCTP.
[attachment=15392]
The cutting edge is hanging out in the air, cantilevered away from the mounting post by several inches and causing the cutting load to tilt the cross-slide. Conversely the modified 4-way applies the cutting load almost straight down, not only making it more rigid but (arguably) causing less wear on the cross-slide.
For most home machinists this may be of no consequence since there’s plenty of time to take shallow DOC and more passes. However it’s definitely an advantage for parting ! Naturally, the post modification isn't real practical for QCTP toolholders since they are adjusted to various heights.
As to the lack of versatility, I find this to be a disadvantage resulting in having to remove or rotate the QCTP about 15% of the time I use the lathe which is equipped with it, a Sheldon EXL-56P. This occurs in many of the following situations:
- work is needed to be performed on the face of the tailstock end when turning between centers
- threading near the tailstock end (between centers)
- threading near the headstock ("dogleg" Armstrong holder much preferred)
- when rotating the compound for spherical turning
- when using the taper attachment and tapering near the tailstock (between centers)
- when the work is short, supported by tailstock and the working envelope is small
- other situations that unfailingly happen at the worst possible times
Again, time being of no issue for most of us, this may just be mice nuts. Also most of these disadvantages don't exist when doing typical chucking work (no tailstock center required). For some reason, about 30% of my work seems to be between centers. I guess I'm just lucky, LOL.
The 4-way tool post shares almost all of these disadvantages, obviously with the additional disadvantage of taking longer to set the cutting tool on center, although I’ve never found that to be a problem.
For example, in one of the above photos, a parting tool is shown in the 4-way installed in a shop-made holder. The holder is made so that the top of the parting tool is exactly centered on the work after sharpening – shims never required. One could argue that grinding chip breakers or positive rake would change the location of the cutting tip.
While this is true, it also has never been a problem in some thirty years of using this holder. Neutral rake accomodates mild steel, stainless, aluminum, copper-based alloys and all other materials I routinely use – plastics and wood not so well, however.
A ¼ square cutting tool is also visible which has a shop-made holder so that the cutting edge is always on center. The insert tool shown must be shimmed but only once. Inserts are replaced without removing the holder from the 4-way. There is one vacant station for whatever odd cutter is required. I don't use the 4-way for boring, there is a dedicated holder for that which can replace the 4-way in about ten seconds:
[attachment=15394]
Regarding the disadvantages of the 4-way when changing the angle is required, long ago I worked around that problem by removing the indexing feature so that the 4-way is free to rotate to any angle. Like the QCTP, it must be reset after rotating so that the parting tool is perpendicular to the work. One loses the ability to return the cutting tool to a precise location but frankly, mine never did that anyway, LOL.
A wrongfully (in my opinion) maligned tool holding system is the Armstrong/Williams system used for many decades in this country and commonly known as the “lantern” tool post. It’s disadvantages are obvious, it’s advantages are not so obvious to those who haven’t used it. Using the typical angled tool holders, it is possible to “sneak” into awkward places that would be difficult, at best, if not impossible for the QCTP and the 4-way.
[attachment=15395]
It is ideal for working with very short workpieces between centers and any operations where the working area is confined. A major disadvantage is the tool overhang, limiting the cutting load obtainable without chatter. In the above photo, the tool holder has been intentionally over-extended to emphasize the problem. An advantage all other systems (except rocker variants) lack is the ability to easily and quickly change cutting tool rake angle using the toolpost rocker.
By not using the forged toolholders and placing the cutting tool directly into the lantern, one achieves what may be (ignoring custom tool holders designed specifically for the task) the most rigid turning setup that can be configured quickly:
[attachment=15393]
OK, these are a few thoughts regarding why there are often better alternatives than a QCTP. BUT remember the proviso made earlier that these thoughts apply to small lathes, of the type most often found in a home shop. (Not the machines belonging to some of our members over which I lose sleep from envy ! These monsters seem to be oblivious to the type of tool holding system employed.)
If someone were to ask "what is the best tool-holding method" my response would be "as many as you can afford and store" LOL. There will always be one situation in which one particular setup will obviously be the best. If for some reason I couldn't own a QCTP, it would be a toss-up between a 4-way and the lantern. 4-way for convenience and lantern system for versatility.
Many things mentioned above are broad generalities and need not apply in every situation or maybe not even in most. As an example, I recently parted off a few short 3 inch diameter lengths of hot-rolled steel with a QCTP and the parting tool hanging off 1.6 inches from the holder.
This was done on the 1945 Sheldon, a fairly sloppy machine from wear, as one would infer. Every movable part not required for the operation was locked and the cross-slide gibs were tightened. I did the parting in two steps, first with a stickout of about 1 inch and a speed of around 100 RPM and the remainder of the operation with the 1.6 inch stickout at around 250 RPM.
The feed was by hand and fairly aggressive with LOTS of sulphur pipe threading oil applied. It must be noted that I wouldn’t try this often on any lathe, I’d always prefer sawing the material but circumstances didn’t permit it this time. I was very, very careful (and very, very nervous).
In summary, if the OP comes up with a neat way to accommodate both of his tool-holding systems, I think he would have a seriously versatile setup, especially with a couple of simple modifications.
The preference and selection of a tool holder should be 90% based on the expectations of usage. Which - 95% of the time will be a QCTP (I'm one of the 95%) ! And, for the most part, price should not be part of the selection process, generally speaking. Buy a few holders at a time as needed.
Probably a large part of my fondness for the old-time tool holders is because that’s what I learned with. The shop classes I attended at San Jose State College (now University of California at San Jose) were set up with new-at-the-time South Bend “heavy tens” all with Dorian toolposts.
However the old Atlas in my garage had a lantern toolpost. Later, with the permission of my boss, I made a 4-way on my own time at the shop where I worked at night. (All of his engine lathes were equipped with 4-ways and I became accustomed to using them.)
(FWIW I found all of my Armstrong/Williams tool holders on eBay but I’ve noticed that prices are going up. Holders that I bought for less than $10 are now going for near $30 + shipping cost. That may be an indication that more folks are realizing how versatile these things can be.)
RE: Switching To A QCTP - f350ca - 12-12-2017
There's no doubt the four way is a much stiffer system, due to the shortened lever arm Randy. Wish I had one for the Summit. Building a dedicated boring bar holder for it is on the short list.
On the subject of rigidity. When I was building that cylindrical square, I tried using a shear tool, my HSS one would wear due to the hardness of the work piece. So I made one by silver brazing a 1 inch square carbide insert into a steel holder. Ground it to a nice sharpe edge on a diamond wheel. Could not for the life of me get it to not chatter at the tailstock end of the 6 inch piece. Would smooth out and cut beautifully at the headstock end.
RE: Switching To A QCTP - randyc - 12-12-2017
(12-12-2017, 09:16 PM)f350ca Wrote: .................I tried using a shear tool, my HSS one would wear due to the hardness of the work piece. So I made one by silver brazing a 1 inch square carbide insert into a steel holder. Ground it to a nice sharpe edge on a diamond wheel. Could not for the life of me get it to not chatter at the tailstock end of the 6 inch piece. Would smooth out and cut beautifully at the headstock end.
Greg I've had the same kind of experiences with the shear tool. HSS gets a nice finish but over a length of only a few inches, it wears. Setting up for precise operations, compound turned to 6 degrees (5.7 ideally, LOL), everything snugged down, the shear tool can cut to a tenth.
But it takes a while for that to happen, continually sneaking up on the rough-turned diameter. I found that if I touched off with the spindle stopped, when I started turning, the shear tool was cutting maybe .001 or .002 mils deeper than the rough diameter and that was enough to take the edge off within an inch or two.
This doesn't sound like much of a big deal but as YOU know, this thing has to run at low speeds and fine feeds. Anything that prolongs the process is a PITA ! And to me, the big advantage to this tool is the ability to cut within .0002 - which can happen but apparently not for long, ha-ha.
I also tried carbide - better than HSS but still not what I'd like to see, probably because of the edge of the brazed carbide cutter that I used. When (if ?) I finish my diamond grinder, that was one of the to-do's, to sharpen the edge of a brazed carbide cutter and try the shear configuration again as you did. Given your results, however, sounds like it would be a waste of time.
I wonder if a different cutter arrangement would improve results ... Perhaps a "trailing edge" configuration rather than the "leading edge" that we all have been trying. Maybe brazing an insert on the end of a shank that trails the tool post by an inch or so instead of having the cutting edge at the front of the tool post would produce enough of a different natural resonance to eliminate the chatter ?
I have no sound physical reason to think that this would be better, LOL, just something to try. I would love for the shear tool to perform like those who love it think that it does.
I've read conflicting opinions, the ones that praise the configuration show photos and post accuracy results which I believe but I also read (a while back) a review by a fellow named Carl Darnell IIRC who pointed out the wear and subsequent inaccuracy (I should say taper I suppose) when turning lengths more than an inch or so, which has been my experience.
I hope that, if you come up with a repeatable process, that you'll post it here. You're always on top of this stuff and I suspect that if a practical solution exists, someone like you or Tom will develop it.
Cheers
PS the cylindrical square was a cool and very useful project !
RE: Switching To A QCTP - randyc - 12-12-2017
Greg, I wonder if you would have achieved better results with the shear tool by turning from the headstock toward the tailstock ?
RE: Switching To A QCTP - f350ca - 12-13-2017
I'd thought about trying the other direction but didn't feel like building another tool.
I built it with a 30 degree angle from vertical, wonder if less angle would help.
It kind of amazed me that a cutter taking maybe a thou cut could resonate a piece of steel 3 1/2 inches in dia only 6 inches long.