Glen Blanchard
08-16-2018, 11:37 PM
Over the last week or so, I have made a couple of inquiries on this forum hoping to find some kind of ornamental turning device that can be placed and used on a woodturning lathe. I was intrigued by a device called the JaHo Ornamental Turning Device made by a company in Germany. (I should point out that this is not a Rose Engine.) They have an interesting YouTube demonstration of the device here (https://www.youtube.com/watch?v=3AHOfuIBP8I&list=WL&index=18&t=0s). Following some very helpful responses to my SMC inquiry, I elected to replicate the device myself as it is not all that involved.
I made some alterations from the JaHo making the device easier to use. Don Bunce offered up the notion of using a spin index to hold the spindle adapter rather than the rotary table of the JaHo. This was a great suggestion as the spin index is very easy to use and more importantly, its’ position is totally repeatable. Thanks, Don! Don also suggested using a Lee Valley adapter that would be placed in the spin index’s 5C collet and would supply the 1 ¼”x 8 tpi threaded adapter I needed to accept my chucks. The Lee Valley spindle adapter is actually designed to be used with their carving stand – a fact that had some repercussions that I only discovered later. After the initial assembly of the entire device, I took it for a test run. It quickly became obvious that I had some major runout issues – at the end of a 4” workpiece the runout was .079”! The spin index had no runout whatsoever. I isolated the runout to the Lee Valley adapter. The shank of the adapter ran true with no runout as it exited the 5C collet, so I figured it had to be the threaded portion. Closer inspection revealed that these were actually two distinct pieces of metal and it appeared that the two pieces were press fitted. This explained the runout. Had I been a bit more astute, the fact that this was designed to hold a chuck for carving work would have raised a red flag for me. It was never intended to be used in a high precision application. DUH!
So I found a machine shop about 45 minutes from the house. I drove out there with the Lee Valley spindle adapter, explained my dilemma and had them mill up a duplicate (but with the precision that I needed). 7 days later I picked it up from the machine shop. I placed it in the collet and threaded a chuck with workpiece on to it. No visible signs of runout at all when placed close to the cutter and no need to put a dial indicator to it. It was indeed the press fitted Lee Valley spindle adapter that was at fault. No disrespect for Lee Valley. I was attempting to use it in a totally different manner than intended. My error, not theirs.
Here are a couple of photos of the device for those who might be interested as well as the results of my first attempt at using it.
391684391685391686
I made some alterations from the JaHo making the device easier to use. Don Bunce offered up the notion of using a spin index to hold the spindle adapter rather than the rotary table of the JaHo. This was a great suggestion as the spin index is very easy to use and more importantly, its’ position is totally repeatable. Thanks, Don! Don also suggested using a Lee Valley adapter that would be placed in the spin index’s 5C collet and would supply the 1 ¼”x 8 tpi threaded adapter I needed to accept my chucks. The Lee Valley spindle adapter is actually designed to be used with their carving stand – a fact that had some repercussions that I only discovered later. After the initial assembly of the entire device, I took it for a test run. It quickly became obvious that I had some major runout issues – at the end of a 4” workpiece the runout was .079”! The spin index had no runout whatsoever. I isolated the runout to the Lee Valley adapter. The shank of the adapter ran true with no runout as it exited the 5C collet, so I figured it had to be the threaded portion. Closer inspection revealed that these were actually two distinct pieces of metal and it appeared that the two pieces were press fitted. This explained the runout. Had I been a bit more astute, the fact that this was designed to hold a chuck for carving work would have raised a red flag for me. It was never intended to be used in a high precision application. DUH!
So I found a machine shop about 45 minutes from the house. I drove out there with the Lee Valley spindle adapter, explained my dilemma and had them mill up a duplicate (but with the precision that I needed). 7 days later I picked it up from the machine shop. I placed it in the collet and threaded a chuck with workpiece on to it. No visible signs of runout at all when placed close to the cutter and no need to put a dial indicator to it. It was indeed the press fitted Lee Valley spindle adapter that was at fault. No disrespect for Lee Valley. I was attempting to use it in a totally different manner than intended. My error, not theirs.
Here are a couple of photos of the device for those who might be interested as well as the results of my first attempt at using it.
391684391685391686