Wohlhaupter UPA4 Boring and Facing Head Operation

I've been using a Wohlhaupter UPA4 boring and facing head to bore the cylinders for my traction engines:

Among the many problems encountered was that the fine feed didn't work as I expected. The coarse feed screw, on the end of the slide as per most boring heads, worked fine. But on one of the flat faces there's a fine feed that also acts to move the slide under the influence of the facing rings, which are between the head and spindle nose in the picture. I made sure that the feed pins were disengaged, so no facing.

The fine feed worked sometimes after a number of turns, but on other occasions just didn't work. The main screw was turning, but the slide didn't move as indicated by a DTI. I don't understand how that can be. I've used the head in the past for facing, so I know it works. I have a manual downloaded from the manufacturer website, but it's fairly brief and doesn't show the internals. Anecdotally I'd say the fine feed tended to work after I'd been through the routine to disenage the facing pin settings. So I wonder if something internally is sticky or gummed up? I've seen the disassembly video on Youtube, albeit for a UPA3.

Has anybody used one of these heads, or knows what the internals look like. An exploded diagram would be helpful, but there are complaints on the net that such a diagram doesn't exist. I'm loathe to strip down the head until I'm convinced that the problem isn't operator finger trouble!

Andrew

https://passion-usinages.forumgratuit.org/t1058-tete-a-aleser-wohlhaupter-upa-1-2-3-4-5-6

Maybe less brief:

http://us.wohlhaupter.com/uploads/tx_whproducts/102166_BA_UPA4_6_engl_kl.pdf

Possibility of help:

https://sites.google.com/site/kalengineeringrepairs/about-us

Patent images:

https://www.practicalmachinist.com/vb/machinery-manuals-and-brochures/wohlhaupter-upa1-upa2-upa3-boring-head-exploded-parts-diagram-333626/

Am i right in thinking that while the UPA3 has limit stops on facing and hence either an automatic reverse or a clutch the UPA4 doesn't. Or if it does have a limit does it have a clutch that is not gripping? I thought though that you had to have the facing pins set and used a tommy bar to provide continuous facing, or gripped the control ring as needed to advance manually but would still need the pins set otherwise there is nothing to provide the pulse to advance the leadscrew.

Someone's been trying to sell a couple of UPA4s on ebay for about a year but at £700+ not much chance.

Hi Andrew, purely out of interest did you get it going? I don't have one of these but your "I wonder if something internally is sticky or gummed up" resonates with me. The manual does say that the engagement of any of the feed buttons will foul the fine feed Section IIf talks about a sharp thrust of the T wrench against the stop rod causing the buttons to be released which by my translation means they should all ping out if they are free to do so. I hate it when kit doesn't operate properly when I'm in the middle of a particularly important operation especially one you really don't want to foul up. Best of luck.

regards Martin

Andrew,

I don't have a 4 but do have a 3. Looking at all the info available the two are significantly different in operation. However there was one comment I heard or read last night after seeing your post and nosing around the web which referred to a built in design flaw that causes the internal gears to break! There was no real exact detail apart from saying one type of gear (unreliable one) is two part the better gears are single piece. Not sure if this is applicable to yours as the inference was more towards the 3. I could imagine though that if a gear has sheared the drive may be intermittent as the fracture slips and grips? There is a quite a good you tube video on operating the 4 by a French chap - unfortunately my French isn't up to the job of understanding but you may pick up a few points by watching.

Paul.

It;s been about 30 years since I had one apart, so memory might be a bit hazy about their construction.

Looking at the instructions and exploded parts photo for the NAREX MTE range of boring heads, they appear to be of a similar internal construction and so this might help:- **LINK**

Andrew,

I have a UPA4 and have never experienced any major problems.

I am not too sure whether exactly what you mean in your post. Are you having problems with the auto feed for facing cuts, or does your problem lie with getting the fine feed screw to work when you attempt to put a cut on for boring or turning? If the latter, do you find the problem manifests itself after using the coarse feed screw? The reason I ask is because it is necessary, when withdrawing the Allen key from the coarse feed socket, to pull it out about half way - you can feel where because of a spring detent inside - and then to turn the coarse feed screw until it re-engages. I suspect failure to do this might cause the symptoms you are experiencing.

Apologies if I'm teaching grandmother to suck eggs.

John

Thanks very much for the replies. The link to the patent applcation and to the Narex manual were very interesting and have been duely downloaded and saved.

I'll have to look harder on Youtube. The video I watched was dismantling the UPA3 and was in German. Annoyingly the 3 and 4 have significant differences.

The UPA4 does have a limit stop on facing although it doesn't seem to have automatic return or reverse. I know this worked in the past, but haven't used it recently.

My current thinking is as follows. The coarse feed is simply a screw and nut as per most boring heads. The fine feed (and facing) is via a worm and worm wheel on the coarse feed screw. Clearly if the worm wheel is locked to the screw then the coarse adjustment will not be able to turn the shaft against the fine feed worm. Ergo there must be a locking mechanism, or clutch, on the worm wheel. This leads to two possibilities. One, the mechanism isn't working properly or two, I'm not using the feeds properly. Although the manual isn't explicit it would make sense that you can't mix 'n' match between coarse and fine feeds. Logically one would use the coarse feed first and then engage the fine feed for final adjustments. If the coarse feed is then used again it would disengage the fine feed.

So the plan is to one, spend some time playing with the controls and see if I can get fine feed, and facing, working in a logical manner. I'd better oil the internals too. If I can't get the fine feed working consistently I'll have to take the head apart.

Andrew

Postscript: I've a nasty feeling I'm going to end up taking the head apart come what may if only to satisfy my curiosity.

Progess courtesy of the post by JDEng!

My problem was getting the fine feed to work purely for straight boring. There is no obvious detent in either the fine or coarse feed dials. However, looking in the coarse feed dial with a torch there is a hole about half way down the hexagon with something in it. So I suspect that the ball/spring that provides a detent is either broken or gummed up.

A quick test this afternoon shows that ensuring the facing pins are disengaged allows me to use the coarse and fine feeds one after the other with no slack in the fine feed. So I could do a cut with the coarse feed and then add a half thou cut with the fine feed. However if one turns the fine feed the "wrong" way even slightly it seems to disconnect. Further investigation is needed but right now supper calls and I need to cut the grass this evening.

Andrew

Andrew,

You said that you have watched a strip-down video but it was in German. Here is another (UPA-3) strip-down YouTube but with heavily accented English soundtrack if it's of any use.

By the way, I have a pdf of the UPA-3 parts list, which might come in handy for someone. PM me if you want a copy. I can't see that there will be massive differences between UPA-3 and -4 models......... But I have been known to be wrong many times before.......

John

There is.

That is why the manufacturer produces two manuals only. The first covers UPA1, 2 & 3. The second covers 4, 5, 6 & 7.

I'll shut up, then. Please disregard my previous post.

John

Andrew,

I had a quick look at mine when I got to work this morning. The coarse feed is graduated into three parts, each putting 0.080" on the diameter; total of 0.240" for one complete revolution of the dial. The fine feed puts 0.016" on the diameter in 0.0005" increments.

Inside the hexagon socket of the coarse feed there are three balls, about half way down. They are retained but loose, if that makes sense, and they are located at 120 degrees to each other in the vees between the flats. The two at the top (10 and 2 o'clock when the head is vertical) are loose but the bottom one is tight so I assume this is the one that does the locking; it locks up whenever one of the graduations is opposite the fixed line.

When the coarse feed is used it can be easily turned with the key in all the way but, when the key is pulled out half way the ball takes over and locks the dial once the next graduation is opposite the line. The fine feed dial then operates. The operation of either dial does not cause the other dial to turn although there is obviously a 15:1 ratio between them.

John.

JDEng: Thanks for the information. I've had another look at my head this evening. The graduations on the coarse and fine feed dials agree with your figures. A closer look at the internals of the coarse feed dial does indeed show three holes, not the one I originally though. However, none of them have anything sticking out, so the Allen key moves freely to full depth, and moves the dial at all positions. So it's clear that the locking mechanism on the coarse feed is not working. Moving the fine feed dial also moves the coarse feed dial which is another indicator for it not being locked.

Ho hum, I'm definitely going to be dismantling the head as otherwise it's going to annoy me!

Thanks also to the people who have PM'd me and supplied copies of the manuals and patents. A special mention is due DC31k who supplied me with a PDF giving detailed disassembly and assembly instructions for the UPA4 head. That's going to be really useful as there seem to be a number of gotchas and a myriad of small balls, pins and springs that can go flying if items are taken apart without due care. I'll be doing my disassembly on the kitchen table so there'll be more chance of finding parts that try to escape than there would be in the workshop.

Andrew

Finally got around to disassembling my UPA4:

Fairly straightforward, although it wasn't quite as the instructions detailed. I also fell at the first hurdle and had to buy a set of larger circlip pliers. Once I'd got the correct tool it took 5 seconds to remove the circlip!

It's clear that the locking mechanism for the coarse feed has parts missing. It's missing one ball, a spring and a detent. Sadly the spring and detent are not shown in the picture in the instructions. I can see how it would work, but it would be very helpful if someone could confirm that the lock only works in three places, spaced by 120°, and corresponding to the positions of the three balls. It's simple enough to get a replacement (4mm) ball but I'll need to make the detent and possibly the spring. I also need to replace a missing 4mm dowel pin.

Andrew

Doing such disassembly in one of the transparent / semi transparent plastic tubs or storage boxes is frequently an effective way of keeping the "bits that go ping" corralled. For smaller stuff one of the big family freezer ice cream tubs works fairly well. For larger things its probably worth dropping a fiver or two at the local "cheap useful stuff" shop for one of the attic storage boxes. Even if you have to cut it down for arm access so it can no longer be used as intended its still better than having an unobtanium component whose appearance you are unsure of disappear into one of the workshop gremlin nests. Even completely clearing and dismantling my old workshop didn't unearth a couple or three such losses over 20 years or so of active use.

With a large storage box I find it best to sit it on a hop-up and sit down at the job so as to reach what I'm working on down in the depths. My back doesn't really approve!

One day my big box might get a vice mounted on a suitably chunky wood block jammed into one end.

Clive

A bold move - a bit like taking a clock apart. Perhaps you could take some good photos of each of your sheets of paper sectons of the innards above for the record as you have demonstrated nobody else has ever done that on the internet.

Andrew,

The coarse feed on mine locks in three places, each at 120 degrees. The detent appears to be at the bottom and the ball in this position is spring loaded, with the other two balls being loose when the key has been removed.

Regards,

John.

John, thanks for the confirmation. Here are the parts:

You are correct that the detent and spring are housed in the hole in the block at top right. Note the block is missing a 4mm dowel. At least the serial number on it agrees with that on the main body.

I don't think the 4mm balls are spring loaded directly. When the Allen key is fully home (as above) the ball is slightly proud of its hole. I think there must be a tophat shaped detent in the hole in the block. When the ball is proud of the hole the detent can't engage with anything. As the Allen key is withdrawn the ball drops to the bottom of its hole and when the screw is in the correct place the detent can drop into the 4mm hole, thus locking the screw. The hole in the block is quite short so the spring is going to be short, given that the detent needs to be long enough to stop it canting over.

Andrew