I have the 602 lathe.
I bought the Grizzly T10166 QCTP and a Grizzly 1/2" keyless chuck when I bought the lathe. For me, the ability to easily adjust tool height was an important feature. The QCTP set is compatible with AXA tooling and I bought additional tool holders from Shars as they seemed better made than the Grizzly tool holders and were actually less expensive. The QCTP has performed well for me. If I were buying a new QCTP, I would get the wedge style rather than the piston style. Not that I have had problems with the piston style but the wedge style is reported to have better repeatability.
A collet chuck is a good addition as it permits reasonably low TIR work without having to resort to dialing in the four jaw. It also provides for better grip on parts, especcially thin wall and less chance of marring the finish of the part.
I bought a 5C collet chuck for the lathe, largely because I already had a 5C collet set. Had I not had the collets, I probably would have gone with an ER32 or ER40 chuck as they had a larger grip range and would require fewer collets to cover the entire working range. A 5C collet set would increment by a least 1/32" and preferably by 1/64".
For tooling, I already had a good selection of brazed carbide and HHS tool bits. I regrind my worn tool bits which makes for very economixal operation. For carbide, I use a $100 HF diamond disk. I recently added carbide insert tooling.
The first major upgrade that I made was to make a six bolt hold down for the compound. It is detailed elsewhere on this forum and has been copied and is available commercially. It greatly adds to the rigidity of the compound. I also made a carriage stop and a spindle stop. Both are detailed elsewhere on this forum.
The largest and most complicated modification was adding a reversing tumbler. Aside from adding the capability of left hand threading, it permits easily disengaging the lower gear train which saves wear and tear on the gears and lead screw. I made a new threading dial as the OEM dial was poorly made and didn't register properly. A detailed posting was done on the site.
I added a three axis DRO to the lathe (x, z, and tailstock) based on the TouchDRO by Yuryi. At the very least, adding an iGaging DRO to the tailstock makes for accurate movements when using the tailstock. A detailed posting was done on the site.
