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

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.

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

Thought I'd finally bring this thread to a conclusion. I recently got around to making the small 'tophat' detent for the coarse feed. I made some careful measurements, with a depth micrometer, of the depth of the housing to the shaft and the depth of the housing to the ball fully home. That enabled me to design the 'tophat' and then make one in silver steel. I bought the compression spring rather than make one. Once the parts were fitted the coarse/fine feed works exactly as advertised above.

This weekend I've been boring the HP liners for my traction engine cylinders:

Now that the boring head works properly it's a joy to use. Easy to rough out using the coarse feed and then swap to the fine feed for finishing. The feeds are spot on; for one liner I put on 4½ thou (on diameter) according to the fine feed knob divisions, and as far as I can tell with an internal micrometer the diameter increased by 4½ thou.

The bores measure round and are parallel, measured at each end, to within 2-3 tenths, and the bores on the two liners are the same to within 2-3 tenths. The bores are 4-5 tenths undersize to allow for honing.

One happy bunny here! Now celebrating with a glass of wine. It's just so nice to be able to use quality kit that does what it says on the tin.

Andrew

NB: Thanks to SoD for the link to the program for generating fractions that he posted recently in another thread.