What uses 6 1/4" pitch rails?

Nothing listed in my 1979 Cat. Custom Track Service Handbook....jumps from 6-1/8 in to 6-3/4 in.

Check here: http://www.crawlerheaven.com/wearlimits.htm
Looks like Case is the only exactly 6-1/4 in. pitch.

OM is correct. Case is the only manufacturer that uses 6.25" pitch undercarriage. The next closest is JD, who use a 6.29" pitch. If you give me the make of dragline, I can tell you what it takes exactly.
What has me a little puzzled here, is that most draglines are pretty sizeable machines, and use heavy undercarriage .. but the size you're talking, is only between D3 and D4 size undercarriage. This sounds more like a small excavator undercarriage.

If you can measure the pitch its very unlikely that they were off a dragline unless it a fairly modern one,all the draglines I have come across would be fitted with dead tracks,ie the pads pinned together and no chain.
AJ

Hi, AJ.
Some crane manufacturers, Link Belt probably being chief among them, started putting crawler tractor style tracks on the undercarraiges of some of their cranes many years ago and calling them pipeliner bases or something similar. I first saw this set-up on a Link Belt LS78 track mounted crane in Sydney, Australia, in 1977. The track chain, rollers and shoes were standard Cat D8 wide shoes with full grousers. I used that crane as a dragline, amongst other things. The machine had originally been used on pipeline work not far out of Sydney. The pipeliner bases were used to give them more mobility in hilly terrain as pipeliners are not known for making user-friendly access roads in rough country.

I note that Leibherr also has an option for crawler tractor style tracks on its track-mounted cranes. There are at least 4 x 120 tonners working in Brisbane at the moment with this style of undercarriage and triple-grouser track shoes, all-same excavators.

I have not heard of any of the earlier manufacturers of the smaller cranes and draglines using this sort of base.