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Working on a Wohlhaupter UPA4 Boring and Facing Head and have some questions


Feb 8, 2021
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.



  • Overhauling A Wohlhaupter UPA-4.pdf
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These guys have or can make any spring you can dream of. I have a Deckel FP1 with MT4 arbor. I have been Jonesing for a Wohlhaupter Boring and Facing Head since I have had it. Let me know if you have any extras.
These guys have or can make any spring you can dream of. I have a Deckel FP1 with MT4 arbor. I have been Jonesing for a Wohlhaupter Boring and Facing Head since I have had it. Let me know if you have any extras.
Thanks for the link. Always good to have that kind of resource handy.

This UPA4 has an integrated Beaver shank/arbor that is 1-1/2" in diameter. I had hoped that it was removeable, but it's not. To be honest, I'm not sure what I'm going to do with it yet. I just bought it because the price was good and no-one else bid.
I also have a question about lubrication. The rebuild document and another youtube video I found discuss applying liberal amounts of grease to the parts in the feed control collar as well as the gear/drive mechanisms that mate the coarse and fine adjustment screws and the automated feed. At the same time, there are at least 3 oiling ports on the boring head. Should this boring head be lubricated with both grease and oil, or was it originally designed to be lubricated only by oil?
Here is a link to the manual. That will give a definitive answer to the question about lubrication.

I have a nice writeup by Greg Dennis, dated 2014, with the title "OVERHAULING A WOHLHAUPTER UPA-4BORING & FACING HEAD". It is a 13 page PDF file. Have you got a copy? If not, is there someplace on the PM site where I can upload it for everyone?
Thanks ballen! I actually have the manual in the link and didn't read it closely enough to see that lubrication is discussed on Page 2 of the text. I looked at it more closely and one port is for grease and the other two are for oil. Thanks for making me look again right under my nose! I sometimes miss the obvious.

Regarding the Overhauling a Wohlhaupter UPA-4, that's exactly the document I uploaded in my first post in this thread. It's extremely helpful and, as I discussed above, the way he mounts the springs and retaining ring make total sense, but doesn't seem to work in my setup. It puts too much preload on the springs and, therefore, the feed control pins can't easily be pushed in or extracted. I sent an email to Wohlhaupter and will report back. Thanks for sharing these documents and the support.

PS - There is a manuals and brochures section of PM, which may be a suitable place to upload the document. I have not actually looked there yet.
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The Operating Manual calls for lubricating the boring head with a Lithium Saponified Grease. I wasn't quite sure what that was and, while looking through my various tubes and tubs of grease, I found one that is a Lithium Complex Grease. What's the difference I asked myself. Could I use a Lithium Complex Grease instead of a Lithium Saponified Grease? The short answer seems to be YES. Here is an article about these two greases. Evidently, the Complex Grease does everything the Saponified Grease does, but a little better. The Complex grease didn't come into wide use until the 1980's and even though the date on the Operating Manual appears as 12.96 (December 1996), I'm going to guess that it is simply an update to a much older document, given that 1)the US Patent for these boring heads is 1968, and 2) the document is written with a typewriter. I know by 1996 I was using a computer and a word processing program to create and print documents.

So, I'm going to try using the Lithium Complex Grease I already have in my shop. If anyone would like to provide input as to whether this is right or wrong, please feel free to do so.
I think that lithium complex grease will work fine.
If I recall correctly, some points need grease, and some points need oil, If that's right, be sure not to mix them up!
Downloaded and saved for future use Bruce, thanks!

(though, my next boring head will definitely be a D'Andrea rather than a larger UPA)

I think that lithium complex grease will work fine.
If I recall correctly, some points need grease, and some points need oil, If that's right, be sure not to mix them up!
I agree. I've followed the various lubrication paths through the unit. I think there's only three on my unit. There is one in the feed control collar (the part with all the buttons for advancing the feed in the UPA4, 5, 6) . This takes lubricant around the upper part of the boring head and also drops it into the auto-feed mechanism inside the bottom of the arbor. On my unit there are two more, one on either side of the unit, at the elevation close to the gib setting screws. These passages go to 1) the elongated drum gear (or drum nut) that mates to both the long screw as well as the auto-feed mechanism gear, and 2) the ways. The manual seems to indicate that these both should be lubricated with grease, even though that puts grease on the ways.

The manual says to apply grease to the nipple, and then points to the multiple nipples, as mentioned above. It also says "Oil the dovetail guides with quality lubricating oil." So perhaps the whole things gets grease except for the dovetail guides. Upon rereading the aforementioned UPA4 document by Greg Dennis, he only applied oil to the dovetails and gib and grease to everything else. He mentions that the feed control collar felt a little warm after operating at 450 RPM for a few minutes, so he removed it, and replaced the grease with oil where the feed control collar interacted with, and rotated around, the arbor shaft.
I'm on the path to reassembly. The download in my first post has been very helpful at solving my issues. I did not ever hear back from Herr Thomas Pauli at Wohlhaupter in Germany, but that's OK. I really appreciate ballen's offering the address.

I ended up replacing the 12 springs from the feed control collar with ones from McMaster Carr that were 0.50" long instead of the longer 0.65" springs I found upon disassembly, which were clearly either too long or too strong. The push buttons now have a very nice movement.

Today, I finished the feed control collar and started assembling the screw/slide and the internal gears that allow for automated facing. Thankfully, I hadn't lost any ball bearings or springs.
It's all back together minus a few details. One of the M8-1.25 x 15 dog point shcs's for clamping in cutting tools is missing. Would you believe they're not easy to find? There are plenty of dog point set screws and some dog point hex screws, and McMaster even has Inch shcs's but no metric. I'm probably just going to get some regular shcs's and turn a dog point on the end with my lathe.

I may also replace the small vertical pin that keeps the large circlip from turning against the spacer ring. When removing the circlip at the beginning of this adventure, it popped off of my circlip pliers, smacked the pin, and broke it right out of the spacer. I think some people leave it out because it's a nuisance. I tend to like originality and completeness.

Besides the springs, I also replaced the gib adjustment screws. They were originally M5x0.8 flathead set screws and the heads were a bit chewed up, so I got some socket head set screws of the same size as a replacement. One of the locking nuts was also missing on the same set of screws, but they had an odd size. Instead of being 8mm from flat to flat, they were 9mm. Also not easy to find, so I replaced all three with standard half nuts that are 8mm from flat to flat.

Here's a few shots of it next to a spray paint can for scale, and next to my UPA6 S7. The UPA4 seems quite large until you sit it next to the 6 S7, which is a real beast. I think you could use it to cut a hole to China, as we say here in the US. I haven't torn into it yet, but I will.