Review on Hole Back Plate - HHIP 3900 3215 by Derek Dolla

I purchased this base to mount an ER-32 collet (HHIP 3901-5032 ER-32 collet, 80mm diameter) from the same manufacturer on my two Sherline spindles. Turning and Milling. I was hoping it would fit right into the cartridge, but that's not entirely true. That's partly why I only gave it three stars. The cartridge looks like it is made of high quality stainless steel. But that back panel looks like it's made out of low-grade steel that will rust. It wasn't as blue and shiny as in the photo, but it will sparkle a bit after I cut some to put the two pieces together. Luckily the three mounting screw holes line up correctly so they both work with the M6 hex screw pack I bought. The insert at the large end of the backplate is 76.6mm in diameter, while the recess on the back of the cartridge is only 74.6mm in diameter. I have to cut the insert to fit the recess on the back of the cartridge. It would be possible to drill a larger recess in the chuck, but this would remove the material supporting the threaded holes in the chuck. But before doing this operation, I need to do some planing on the narrow end of the back plate first. The 3/4-16 spindle thread fits my machine's spindle but doesn't go all the way through the backplate. Also, they look pretty rough (with a small burr on them), but the device mounts well. Removing 5 or 6mm of metal from the small end of the backing plate brings the threads closer to the outer surface, allowing more grip for the threads on the spindle. I hope the back plate is easy to machine as all the cutting tools on my lathe are HSS. To do this facing operation, I mount the back plate on the spindle with the back and the back plate becomes my workpiece. After this process is complete I can flip and install the back plate as it attaches to the cartridge. Rotating the plate down about 1mm will reduce its diameter, allowing the cartridge to fit around it. The bolts are not intended to align, just hold the two pieces together. When the backplate is firmly in place, it serves to hold the chuck in precise position relative to the backplate and hence the lathe itself and its tools. This is the most important part of the operation and I need to check the fit between successive passes to make sure the insert doesn't get cut. If the backplate already fits on the chuck, I would give this product four stars. . If it were also made of stainless steel, then my rating would have been five stars. Let's see how the machine works. --------- Later I did all the editing operations and everything went fine. I cut off about 6mm from the small end and that exposed a 3/4-16 thread. This left a few burrs on the surface so it wobbled when installed. Luckily I didn't panic. After removing the burrs with some drilling, the wobble went away and noticeably became very stable. It should be noted that the bit has a slight taper on the large end, as does the collet I bought to fit. But I don't think the taper matters much with such a short insert with only 3mm overhang. But this is enough to firmly fix the cartridge. I made 0.01mm cuts the entire length because I was afraid of making an insert that was too small in diameter that might ruin the backplate. I checked for consistency after each run towards the end. After the last pass, the bet fell off and I was done. I know I've voided the warranty on this thing, but it's usable now. O happy day! I can finally use 3/8" and larger end mills on my milling machine, and I can mount round stock up to 20mm diameter on my lathe without resorting to a 3-jaw chuck.