|OXA (wedge)||Sherline (piston-wedge)||
TS Engineering (?type?)
No longer avalable
|OXA hardware||Riser detail||Holder detail||TS Engineerring detail 2||TS Engineerring detail 4||TS Engineerring detail 4|
Dovetail Forces Ilistrated
|Dovetail Forces Illistrated|
This is intended to be a short description or mini-review of the styles of QCTPs that I have.
From left to right they are the OXA Aloris-type "wedge", the Sherline piston-wedge, the TS Engineering whatever-you-call-it and the A2Z piston-type.
Note that the "A2Z" pictured may an older A2Z, as newer ones are no longer black, or a different TS Engineering model - I've had it a long, long time and it's exact pedigree is uncertain. Still, it is a fair representation of the style, if not the currently shipping A2Z prodiuct.
Note also that my explerience may be colored by the fact that I use a 13" Crosslide (Sherline part number 4088X) which is 1/4" thicker than original 6" table making most tool posts the wrong height for my lathe. Also I usually have the headstock riser block in pace, in part to compensate for the higher table. As a result tool posts are generally mounted to my own riser block that clamps to the lathe using 4 T-nuts and isn't nearly as fragile when it comes to clamping the actual tool post down.
The OXA Aloris-type "wedge" QCTP
Pros: Hardend, ground steel construction for precission, duability and stiffness. An actual "quick change" lever. Solid clamping entire length of tool holder travel on the post. Cost is on part with lesser aluminum/piston products.
Cons: It's steel, so I can rust... For Sherline's there's no mounting hardware and no extra "groove" for adding extra clamping, often needed with on Sherlines. Being hardened, there's no way to add a groove short of grinding.
Aloris is a name brand, a very expensive name brand, famous for their "wedge" style QCTPs. There are many knock-offs, of which this is one. All Aloris and other knock-offs that I am aware of are too big to fix Sherline or the popular 7x lathes. This one, however, is only 60% of the smallest (AXA) Aloris-type and fits well, size-wise. Mounting is easy enough for the 7X lathers, Mounting on Sherlines is another matter left as an excercise for the buyer.
Please note that I bought my OXA through ebay, not littlemahinchineshop.com. That's not because I have a problem with LMS (wonderful company), but because at the time I didn't know LMS sold them AND because they came with hardware for mounting it to a Sherline (so I didn't look to hard to find 'em without). See the "OXA hardware" picture above.
Generic OXA features that apply to any lathe are: hardened and ground steel body and holders plus the "wedge" style holding mechanism. Neither steel or hardening are a must at this size or for hobbyist but it's still nice. The "wedge" is the best of the best, hence the Aloris price, fame and copies. It engages the full insides of the dovetails, pressing the tool holder into the flats on the tool post evenly at all tool heights . More over when releasing the "wedge" preasure is completely removed from all surfaces so tool holders don't "stick".
Sherline-specific features: Mine came standard bolt (8MM I think) with its head machined to match the Sherline T-slots. This is pretty nice. And way better than anything that would would use the standard Sherline T-nuts. It does, however, privide a way to destroy the T-slots, so care must be used when tightening. Much has been made of relieving the underside of tool posts for the Sherline. Alas this OXA isn't relieved on the bottom (nor are any non-Sherline tool posts I have seen) but it is hardened steel so there's no changing that. Instead mine came with a disk relieved on both sides to place between the toolpost and the table. The combination seems to work well EXCEPT that I use the 1/4" thicker 13" Crosslide (Sherline part number 4088X) making the provided spacer the wrong thickness.
The Sherline "piston-wedge" QCTP
Pros: Hardend, ground steel construction for precission, duability and stiffness. piston-wedge locking mechanism similar to regular weged, contacting dovetails and flats. Designed for Sherline, with a clamping groove and a round body for extra clamping at any angle. Many exotic tool holders (ceramic, etc)
Cons: High cost of QCTP and additional tool holders. It's steel, so I can rust. No "quick change" lever, instead hex keys required. Clamping rage limited to only part of tool post dovetails.
I bought this QCTP at a deep discount off ebay when the aluminum QCTPs were more expensive than they tend to be now. I've only gotten limited use out of it simply because the tool holders are cost prohibitive. I wonder about the holding power as the tool holders move off center from the piston-wedge but I've had no problems. The only negative things I can say are that there's no "quick change" lever and it's crazy expensive.
The TS Engineering QCTP
Pros: Dual mounting holes provide dual Sherline/7x use and (with additional hardware) extra ridgid mounting at one (right, turning/facing) angle. Anodized aluminum construction: doesn't rust. Clamping for full dovetail travel. Clamping is on dovetails AND flats.
Cons: No longer avaialable. Only one dovetail. Well made but not exacly "precise" in design. Aluminum less durable/ridgid than steel. Off-center mounting.
I bought this one, again, cheap off ebay. Mostly for the tool holders, as I recall, which would hold half inch tools when most tool holders for Sherline sized posts were 3/8ths. (Half inch is seems to be the going rate these days.) But it's not a bad little worker. Clearly its off-center monting holes are even worse for letting the tool post rotate then the central hole in most QCTPs. And it's less-than-precise slip-fit repeatability isn't quite CNC worthy (front-to-back), though its height adjustment is quite repeatable and it's more than servicable manual use. Despite appearnces you don't just tighten it with the knurled knob. The knob is press onto a secket head cap screw and you use a allen wrench to finish tightening.
The A2Z "piston" QCTP
Pros: Low cost. Anodized aluminum construction doesn't rust. Has "quick change" lever. Available with Sherline mounting hardware. New versions have extra clamping goove (I've heard but not seen).
Cons: Aluminum is less stiff/durable than steel. Pistons don't "withdraw." Clamping range limited to piston location. Piston clamps against dovetails but NOT the tool post flats.
I've got a couple of theses, one for my Sherline and one for my 7x. I bought them before the OXAs were available. I've got zillions of tool holders. Well it seems like zillions of 'em. The more the merrier. Can't have too many. One plus these have over the OXA is that you can modify the aluminum tool holders or fabricate your own. I have done both. (You could make tool holders for the OXA out of aluminum, but anodized or hardened and ground steel? Possible but not likely.) They're very servicable and effective. They've served me well for years. I expect to use the OXA more and more as my OXA tool holder collection grows. But I doubt the OXA will ever completely replace my A2Z simply because of the custom tool holders I've made.
The real drawback here is the piston. First it doesn't actually "withdraw" meaning you sometimes have to press it in and out of the way to mount or remove a tool holder, a minor nusance. Second, it pushes the holder outward into the dovetails, which is effective, but that's AWAY from the toolpost so the flats of the tool holder and the tool post never touch, leaving a gap. The tool holder never gets any traction or rigidity from the flats, just the dove tails. This is especially probematic if you're using a large shank tool (requiring a lower position) or non-standard heights of the tool post - as with the 1/4" thicker 13" Crosslide (Sherline part number 4088X), which is thcker than the standard one. And third, as the tool holder moves off center of the piston, especially toward the top of the tool holder, there is a tendency for the unsupported bottom of the tool holder to flex and/or rock into the gap described above. Also I have had some tool holders require a shim (see the photo) before the too-short piston would hold it in place. That, however, could be because of different manufacturing runs, mixing different manufacturers, etc.
The pistons and lack of contact on the flats isn't a deal breaker, espeically on Sherline sized lathes. Though it does create rigiditiy issues with larger tools used in larger work envlopes. Which, of course, many (rightly) argue you shouldn't be doing with Sherline sized lathes in the first place.