I was very fortunate recently in that I won for a modest sum a job lot of VDI 40 tooling on eBay that included a Grippex Bar Puller.
Bar pullers are useful on a CNC lathe if doing repetitive work, in that you can automate the feed of the bar stock in the chuck between components. Advance the gripper over the bar, close it, grab the bar, release the chuck grip, pull bar out the length of the next component, close the chuck, release the gripper - all so nice and easy as it's automated

Now this gripper sadly had one of it's hard steel 'talons' missing - never mind - spares still available for the not inconsiderable cost of £99 (inc postage and VAT) for a set of three - BUT you get the fixing screws AND an Allen key, so a bargain

Biting my lip and remembering that these grippers cost £1400 new I shelled out my dosh and got the three spares.
Now I have a repetition job of 100 parts to do for a friend of a friend so time to mount it and play with some code. The gripper has a cylinder inside that can be operated by compressed air or coolant. No air service on this lathe so coolant it is. The sequence is, select the gripper, put it where you want it, turn the coolant on, do the pulling bit, then turn the coolant off again to release its grip.
Well, gripping works famously, but when the coolant is turned off it doesn't release. As the coolant is solenoid valve driven to the tool turret, coolant pressure is maintained in the line keeping the gripper firmly shut

OK a modification is called for. Another solenoid valve working in anti-phase with the feed valve dumping pressure in the line to the sump. It would have been VERY easy if I could have sourced a 24 volt DC 1/2" BSP brass valve in a normally open configuration at a sensible price, but they are rare with the proper industrial ISO plug in connectors.
Never mind, use a normally closed valve, add a couple of lines to the PLC program to add another output for this valve in anti-phase to the feed valve and the job's a good 'un

So valve and a few bits of plumbing have been ordered, and today I tweaked and tested the changes to the PLC program and now I'm just waiting for the bits to arrive .