DubbleTrubble
Aluminum
- Joined
- Feb 8, 2021
- Location
- Hollyweird CA
Edit - I have a bad tendency to be overly verbose when trying to explain things, so I have bolded my primary questions so you can skip through all the background if you like.
Hey Folks - I picked up several Wohlhaupter Boring and Facing Heads at a machine shop auction last year and I'm finally getting around to cleaning them up. Besides the UPA 4, I also purchased a UPA6 S7. Both of these are way too big for my Delta-Rockwell 21-100, but a boy can dream. Actually, I'm planning to eventually get a Deckel, Maho or similar. But I digress.
I'm currently working on the UPA4. I found the attached, wonderful, rebuild documentation that was shared on an Australian Woodworking Forum 10 years ago in the spirit of helping others, so I'm sure the original poster would encourage sharing it with you. Having this document helped me find a lost spring hiding in a greasy bore in the inner bowels of the unit and also helped me figure out how to remove the fine feed screw. I'm still challenged on the feed control collar by the installation of the 12 springs and retaining ring which control the movement of the feed control pins. In the attached, see Assembly Steps 1-7, and specifically Step 6.
When I disassembled the unit, I found these springs filling the entirety of their bores, without protruding from the top, and measuring ~0.610" +\-0.015" long. I can only find inch sized springs at McMaster in this size range, so I'm going to quote in inches here. A retaining ring was installed around the outside of the springs, holding the springs in place by pressing them inwards, preventing them from moving in the bore. However, the retaining ring is only long enough to fully cover 11 of the 12 springs. which seemed strange. These springs push on a pad and a ball bearing which fit into notches on the feed control pins so that when you push on the pins to activate the automatic feed, it moves with a satisfying click into place as the ball bearing shifts from one slot to the next. However, not all of the pins had the satisfying click.
I put this assembly back together in the same way I found it and was trying to figure out how to apply uniform spring force to each of the feed control pins to achieve the satisfying click. Step 6 of the attached indicates that the springs are actually to be pushed into their bore until they are seated below the retaining ring, rather than having the retaining pin wrap around them. This makes all the sense in the world and it allows the retaining ring to close more and cover all of the bores for all of the springs, rather than only contact 11 out of 12. However, when I tried this, the increased force from the pre-loaded spring was too much, and it was nearly impossible to push in and retract the feed control pin. I removed the retaining ring and experimented with preload on the springs to see what worked best. It turned out that about 0.075" of preload gives that satisfying click, however being seated under the retaining pin created 0.235" of preload (too much).
I'm wondering whether the original springs in my unit were replaced with longer ones at some point in time. If this were the case, then I would acquire or cut some shorter springs that could be seated under the retaining ring with enough preload to create the desired movement of the feed control pins. The problem with this theory is that the springs in the document look to be the same length as the ones in my unit. Perhaps the springs were replaced by ones with a larger diameter wire, making them have a higher spring rate?
Can anyone weigh in on my feed control collar issue, specifically how should the springs and retaining ring be installed? I'll also be looking for an answer in my UPA6 S7, but due to somewhat limited bench space, I'd prefer not open it up until I've finished with the UPA4.
Thanks
Hey Folks - I picked up several Wohlhaupter Boring and Facing Heads at a machine shop auction last year and I'm finally getting around to cleaning them up. Besides the UPA 4, I also purchased a UPA6 S7. Both of these are way too big for my Delta-Rockwell 21-100, but a boy can dream. Actually, I'm planning to eventually get a Deckel, Maho or similar. But I digress.
I'm currently working on the UPA4. I found the attached, wonderful, rebuild documentation that was shared on an Australian Woodworking Forum 10 years ago in the spirit of helping others, so I'm sure the original poster would encourage sharing it with you. Having this document helped me find a lost spring hiding in a greasy bore in the inner bowels of the unit and also helped me figure out how to remove the fine feed screw. I'm still challenged on the feed control collar by the installation of the 12 springs and retaining ring which control the movement of the feed control pins. In the attached, see Assembly Steps 1-7, and specifically Step 6.
When I disassembled the unit, I found these springs filling the entirety of their bores, without protruding from the top, and measuring ~0.610" +\-0.015" long. I can only find inch sized springs at McMaster in this size range, so I'm going to quote in inches here. A retaining ring was installed around the outside of the springs, holding the springs in place by pressing them inwards, preventing them from moving in the bore. However, the retaining ring is only long enough to fully cover 11 of the 12 springs. which seemed strange. These springs push on a pad and a ball bearing which fit into notches on the feed control pins so that when you push on the pins to activate the automatic feed, it moves with a satisfying click into place as the ball bearing shifts from one slot to the next. However, not all of the pins had the satisfying click.
I put this assembly back together in the same way I found it and was trying to figure out how to apply uniform spring force to each of the feed control pins to achieve the satisfying click. Step 6 of the attached indicates that the springs are actually to be pushed into their bore until they are seated below the retaining ring, rather than having the retaining pin wrap around them. This makes all the sense in the world and it allows the retaining ring to close more and cover all of the bores for all of the springs, rather than only contact 11 out of 12. However, when I tried this, the increased force from the pre-loaded spring was too much, and it was nearly impossible to push in and retract the feed control pin. I removed the retaining ring and experimented with preload on the springs to see what worked best. It turned out that about 0.075" of preload gives that satisfying click, however being seated under the retaining pin created 0.235" of preload (too much).
I'm wondering whether the original springs in my unit were replaced with longer ones at some point in time. If this were the case, then I would acquire or cut some shorter springs that could be seated under the retaining ring with enough preload to create the desired movement of the feed control pins. The problem with this theory is that the springs in the document look to be the same length as the ones in my unit. Perhaps the springs were replaced by ones with a larger diameter wire, making them have a higher spring rate?
Can anyone weigh in on my feed control collar issue, specifically how should the springs and retaining ring be installed? I'll also be looking for an answer in my UPA6 S7, but due to somewhat limited bench space, I'd prefer not open it up until I've finished with the UPA4.
Thanks
Last edited:
