HLV compound base banana shaped

I'm scraping the top parts of my HLV and thought I would share this. I removed the pivot ring from the compound slide base and stuck it on my plate. It rattled a bit on the ends so I stoned it for burrs and went again. Still rattled a bit so I stoned the top flat for burrs and inverted it on the plate then ran my DTI over the bottom flat surface. It was high (whist inverted) in a line right across the clamp bolt and low on the ends by 2 thou and a bit.
I scraped the base flat just roughly with the Biax and put it on the plate right way up. The ways are low in the middle and high at the ends, as is the top flat face. The compound base casting is totally banana'd. No wonder the clamp bolt was so stuck it sheared when I tried to remove it - the previous owner must have barred it up tight trying to take the rock out of the base.

Got a lot of scraping to true everything up. Good job it's not a taper gib or I'd by making a new one of those too.

Here it is with the ways and top face mapped out. Base is already scraped flat. 0 is the low point, rest is marked in +ten-thousandths.

That range of measurements...

Any idea of how it got that warped or damaged in the first place? If I had a part like that I'd be tempted to make it new from some stable material.

No idea at all. The quick-retract was very tight I put it down to old oil and needing a clean-up.

The ways look just about as perfect as a way could at 60 yrs old. no scores or scuffing. Top slide flat ways that ride on it were a little worn at the ends (as you might expect riding on high spots) but nothing out of the ordinary. I'm going to scrape it all true then check it again sometime down the line. If it's started to creep more I'll have to make a new base.

I suspect that you're dealing with peening/compression stress. Generally, the stressed part is convex, like the top of the table of a milling machine.
Scraping material off the area that could have been under stress (e.g. clamping area, not just the ways), it could help bringing everything back to normal.

Paolo

I had the exact same issue with my HLV compound base. My HLV came with the end of the compound lock cam broken off and all kinds of crud between the compound base and the cross slide. I put it up on the surface plate and got very similar measurements to yours. Years ago I scraped the bottom mostly flat as a first step and then needed to use the lathe so reassembled the compound minus the screw and used the HLV as if it had no compound. Fast forward 6 years to this spring, I took Richard King's scraping class in VT and finally got the damn thing fixed. A lot of material had to come off to get everything in the right place and a very small scraper was needed to get into the little dovetails but it came out very well. After scraping the screw alignment was way off with respect to the nut so I pushed out the alignment pins in the handwheel mount and am just using the 4 attachment bolts for now. The compound is now nice and smooth and I can finally use the threading retract feature again after all these years.

Of course the cross slide is also a mess but that's another project. And then the bed...

Despite my HLV being kind of a wreck I use it almost daily. Takes some extra effort when I need something super accurate but that doesn't happen too often. The threading is a real pleasure to use and I get great finishes most of the time. Less leaning over the work than with my 14" lathe.

I can share my order of operations for the compound rescrape if anyone is interested.

Thanks for that, I was hoping that someone would come back with this kind of answer since it confirms what Paolo surmised - the bend is from many clamping/unclamping acts rather than unstable material. I have now scraped the base with a couple of tenths dish in the hope that 1. it will stave off any further bending and 2. the greater contact area will allow me to use the swivel lock much more lightly, again reducing the bending effect.