Knee Raising Crank Handles - BP Type Mills

[petertha]

It isn't hard to get precise positioning with the crank handle. When getting close to the required depth I reposition the handle so the weight is on the downside of the turn (from 1:00 o clock to 4:00 o clock). Then gently apply pressure to the top of the handle while watching the dial. It doesn't take much effort to get the precise graduation.

Thanks, that is the technique I am gravitating to. I do already have power feed on the lift axis. Its not that my lifting forces are that high (yet), but it certainly takes the monotony of spinning it up & down a longer displacement like to accommodate tool changes. My comment/question was more about the finesse bit of last couple thou & hitting the mark, either by dial or DRO. I'm just getting used to the workflow of this new machine & have been taking the handle on/off mostly to get it out of the way. So even re-engaging the hub teeth & with the handle cantilevered, seemed like potential to move it off its mark. I think make gravity your friend & keep the handle pointing mostly downward is smarter. I'll figure it out. Thanks for the useful comments.

 

[BGHansen]

Not adding anything here, but seems like someone with one of the 1/2" cordless drill driver adapters could put a torque wrench on the knee adapter and measure the torque required to move the table. Estimate double the torque assuming a load on the table equal to the weight of the table and knee. That'd tell us definitely what would work for an alternative to the typical crank.

One thing that got my jaw to drop was the first time I saw the drop links on the 2007 Cadillac CTS produced at the Lansing Grand River plant in Lansing, MI. The drop links go from the stabilizer bar to the control arms. They had ball joints on either end, but the link itself was made from glass filled nylon. The warranty for fractures was the same as the previous steel cans/rod version.

Bruce

 

[pstemari]

To try to hit my number, I find it works better for me to lower the knee a bit too far, and then hit my number while raising the knee, not when dropping it, which does not work well for me and my machine at all.

Yeah, for reasons similar to why climb milling can just problems. When you push up, the forces are balanced and there's no slop. When you lower the knee, you're moving the support down, introducing slop, and trusting gravity to push the table down and take the slop back out. It's entirely possible for it to stick a bit and then fall down to the support.

You always get more precise positioning when two forces are acting in opposite directions, vs two forces pushing in the same direction, with the slop changing sides whenever one force pushes a bit harder than the other.

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[RockingJ]

The longer length aids in finer adjustments. The heavy mass also helps when making fine adjustments, a small tap doesn’t move the handle very far, where a much lighter handle would be moving much further.

At least that is my take on it!


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