The C6 comes stock with a 4 tool rotary tool post. This is sufficient for many jobs, but as I added more jobs to the schedule and the jobs became more complex, I was spending too much time changing and calibrating tools. As with my manual lathe of a similar size, I felt a quick change tool post was the answer.
A QCTP is generally mounted on the compound slide (in the place of the original tool post). However, removing the compound slide, along with the rotating mount, adds a level of rigidity to the entire assembly. Given the fact that the compound slide is seldom, if ever, used on a CNC lathe, removing it presented no long term problems.
Based upon the swing of the Syil lathe, a BXA tool post, mounted directly to the cross slide, would have been a good fit. However, considering the fact that I seldom do heavy work on my lathe, I decided to save money (both on the initial purchase and when buying tool-holders in the future) by choosing the AXA size. This also matched the size of the QCTP on my manual lathe, allowing tool holders to be interchanged between the two machines.
The use of the AXA tool post resulted in the center-line for the tools being considerably below the center-line of the lathe. The solution is the subject of this Instructable.
This Instructable is based upon my C6 Syil CNC Lathe. Be sure to double check all dimensions for your lathe before purchasing materials or cutting metal. This Instructable should be adaptable to other models of lathes, both manual and CNC.
Although machine shop operations are generally safe, the opportunity for injury and accident are ample. Use caution when working with any power tool. Wear the appropriate safety gear and follow acceptable safety practices.
Dull cutting tools are especially dangerous. Be sure all drills, mills, etc. are well sharpened.
Step 1: Bill of Materials & Tools Needed
Materials for this Instructable are generic and may be sourced from any number of vendors, resulting in a large variation in costs. By purchasing the QCTP kit on sale, I was able to complete the entire conversion for under $200.00.
QCTP - AXA size with 5 tool holders - I purchased mine from ENCO during a sale and was able to get it for $139.49 including shipping
4" long piece, 1-1/2" x 2" CRS rectangular bar stock - about $20.00 including cut charge and shipping
2 each - M8 x 1.25 x 40mm SHCS - About $2.00 from local hardware store or bolt supplier (verify size on your lathe)
Blue (medium strength) thread locker as desired
12.5mm drill bit (tap drill for M14 x 1.5 tap)
5/16" drill bit (clearance drill for M8 x 1.25 SHCS)
M14 x 1.5 tap (taper or plug - for QCTP shaft, verify size on your QCTP)
1/2" mill or 1/2" metal cutting countersink
Facing mill or fly-cutter (use largest available, <2" preferred)
Metal cutting band saw (needed only if the CRS is not delivered cut to size)
Collets & drill chucks for milling machine
Micrometer or calipers
Thread gages (metric & imperial)
Step 2: Remove Existing Tool Post & Compound Slide - Verify Thread Sizes
Most compound slide assemblies on lathes of this style are mounted with two bolts (or nuts & studs) which are loosened to rotate the compound slide assembly. Loosen these bolts enough to swing the compound slide so as to fully expose the bolts. Completely remove the bolts and the compound slide assembly should lift off.
In the event your lathe has studs and nuts retaining the compound slide assembly, it will be necessary to remove the studs.
Verify thread size
NOTE: You may want to perform this step before cutting metal or purchasing any special tooling needed for this Instructable.
The threads on the bolts (or studs) retaining the compound slide assembly should be verified at this time. The bolts on my Syil C6 lathe are M8 x 1.25.
Now is also a good time to verify the threads on the QCTP mounting post. Remove the "t-nut" from the post and measure the threads on the post. (The t-nut will not be used in this assembly.) The threads on the post on my Enco QCTP are M14 x 1.5.
Step 3: Machine the Riser Block
Before cutting metal, "dry fit" the block on the cross slide of your lathe. Be sure that the block will not interfere with anything on the cross slide (oil ports, etc.). Adjust the hole locations for any interference found.
When machining, break edges, chamfer holes, etc. as needed.
The top and bottom (2" x 4") faces should be machined for flatness and parallelism. Remove only enough stock to achieve a flat finish on each of the two faces.
Pilot drill all holes to provide acceptable tolerances on finished holes.
Notice that the positional dimensions of the pilot holes for the M8 x 1.25 SHCS are referenced from the centerline of the block. This decision was taken so as to produce a symmetrical appearance.
The positional dimensions for the M14 x 1.5 tapped hole is taken from the edges of the block. This is done to position the QCTP properly in relation to the block edges.
The diameter of the head on the M8 x 1.25 SHCS is actually 0.515". Because I do not have an end mill or countersink that would produce a reasonably sized countersink, I chose to use a 0.500" end mill for the countersink and remove a small amount of material from the diameter of the head. This saved having to purchase an end mill or countersink just for this job.
Step 4: Mount the Riser Block
Note the ground area reducing the diameter of the SHCS heads.
Step 5: Mount the Stud and QCTP
NOTE: It is advisable to use blue (medium strength) thread-locker to secure the stud.
Place the QCTP on the stud and finger tighten the nut on the stud.
Step 6: Align the QCTP to the Lathe Axis
Tighten the the nut on the QCTP securely, checking the alignment as the nut is tightened.
The alignment of the QCTP can be further verified by placing a straight, round bar stock in the chuck and verifying that the face of the remaining wedge aligns with the bar.
Step 7: Tip for Setting Cutting Tool Height
Now whenever I need to set a tool height, I merely place the surface gage on the lathe cross slide and bring the height of the tool to match the surface gage tip.