Make Your Own ER11 Spindle

[bergerud]

I have a B machine which came with the QC chuck. We all know how poor some of these were. Some were out of balance, the bit wobbled, and the adapters would get stuck in the taper. I spent some time fixing the original QC and used it for the first 200 hours. One day carving cast acrylic, the rpm dropped because the cut rate was too fast and the QC allowed the adapter to be pulled out. (The centrifugal fly ring halves fail to hold the outer casing down at low rpm!) Broke my original carving bit, that was it, I removed the QC for good. While others were buying the Rock Chuck, I fashioned my own using the chuck from an air die grinder. I have been using this for the last 300 hours. It worked but the available collect sizes are limited to 3/32",1/8",3/16", and 1/4" . I could not find a 3/16" and since there is significant run out on these, I decided I needed a new chuck.

The Rock and the Carvetight really do not make any sense to me. Why have a big heavy chuck which is made to hold 1/2" shanks? Who in there right mind would use router bits that require 1/2" shanks on the end of that flex cable? If the router bit you want to use cannot be obtained with a 1/4" shank, you better think again! Just because Carvewright sells a bit set with 1/2" shanks (Yes, I have the set too) is not enough of a reason to put a slug of a chuck on the machine. (I think the 1/2" shank obsession was introduced because the set screws in the QC adapters could not hold the larger router bits if they had 1/4" shanks. The QC is gone - let the 1/2" shanks go too.) I was disappointed with the Carvetight solution. I really thought they would have fixed the QC. Better quality control, a stronger spring, less mass, and a better way to break the taper… etc. At least I thought they would have made a chuck that was compatible with the old adapters. Oh well.

On the other hand, why reinvent the wheel. There are very nice collet type chucks on other CNC machines. The ER series of collet chucks sport very small run outs and they have collet sets that cover all sizes and have no problem holding solid carbide bits. The ER11 chuck is exactly what I think the Carvewright should have come with. The only argument, I can think of, against a chuck like this is that maybe projects which require bit changes are difficult without bit adapters or collars to set the bit length. This problem, however, is caused only since the software is written to measure all the bits first and then make you switch them back later. (That’s just annoying.) Just measure the bits when they are used!! Am I wrong? In any case one can still use collars, a stop plug, or collets fixed to the bits. (Most of my projects are single bit carves anyway.)

I bought an ER11 collet chuck with a 12 mm shaft on it. Bought a big bottom bearing with a ID of 12 mm and turned the end of the shaft to 10 mm to fit the standard top bearing and clip ring. I press fit a slug into the top of the hollow shaft, drilled a hole and filed it square for the flex shaft. To make the chuck hang far enough down to be compatible with the bigger Carvewright chucks, I reluctantly had to add a 1/4" spacer under the big bearing. I now have a light chuck with very small run out which will hold any size bit up to 1/4". The lightness means less stress on the flex shaft, cut motor, and the z drive.

If you have access to a machine shop (small lathe really) and you love the Carvewright like I do, you should consider making an ER11 spindle to replace your QC. (If you really want a slug of a chuck to use those expensive bits you bought, the ER20 will take shafts up to 1/2”)