Stops are neat for accurate positioning. I built a really nice Kurt Vise Stop a long time ago, and I use it all the time. I also use small Kant-Twist clamps as stops on vises, lathe bed, and all sorts of other places. They hold tight and the ones with the little brass jaws don’t mar the surface. I will not take a part out of the lathe chuck or mill vise without making sure I have a way to quickly put it right back exactly where it came out. I learned the hard way by pulling a part too soon and finding it wasn’t quite right or realizing I could do one more step and avoid a new setup.
Stops are capable of very accurate position, measured in tenths relative to the stop. The biggest challenge to absolute positioning is getting the stop in the right place, but once it is there, the rest is easy.
Today I got a note from Tormach about a different kind of Stop in the form of a new product they’re selling called “Stop-Loc”:
The Stop-Loc is a neat and very inexpensive tool that’s can be used in a variety of interesting situations:
Using Stop-Loc to set Endmill Stickout…
Setting Stock Stickout with a Stop-Loc…
While it is neat to use one to as a stop for a vise or a lathe chuck, I have other solutions that I think are better. I mentioned my vise stop, and on the lathe, I just run a tool to the right position to act as a stop. Easily programmed on a CNC, useful on a manual with DRO or carriage stop, and not needed if you have a bar puller. Nevertheless, you may find it great for stock.
What I like about it is using it to set tool stickout. Tool Stickout matters hugely in CNC for two reasons.
First, the machine needs to know the tool length offset to do its job properly. CNC’ers spend a fair amount of effort getting this right, and Tormach’s Tooling System is all about making that simple. The Stop-Loc is just another way of ensuring repeatability of the tool’s stickout in the holder. Most machinists will stick a tool in the holder without regard to stickout–whatever looks good at the time. At best they may minimize the stickout, knowing that this leads to more rigidity. Stop-Loc gives you away to start the tool out at a known stickout rather than measuring after the fact.
Here’s an easy case for it–twist drills. If you don’t have a tool changer, or need more sizes than fit, or maybe just need some one-offs and don’t want to change what’s in the changer, Stop-Loc can help. Just pick a fixed stickout for a range of drill sizes. Load the holder and use Stop-Loc to ensure the twist drill has the correct stickout. Keep that stickout in your tool tables. You’re ready to go, no muss, no fuss. This can make a big difference, especially to a hobbyist without a tool changer.
Here’s one for the pros. It turns out that tool stickout is one of a relatively few things you need to keep constant to make chatter predictable. The full list is on our Chatter page, but it is surprisingly easy to turn chatter problems into a predictable science if you can control those variables and do a little record keeping. What I mean is that if those variables are the same, then you will encounter chatter at the same spindle rpms regardless of material or cutting conditions if your cutting forces get large enough to induce the chatter. Likewise, once you have found those dangerous rpm ranges, if you avoid them, you will be minimizing chatter allowing you to run much higher material removal rates. Because of that repeatability, if you can standarize your tool stickouts and keep a record of where chatter occurs, you will be on your way to eliminating it as a challenge for your shop. G-Wizard’s Cut Knowledge Base is an excellent way to keep your records, BTW. It’s designed expressly to facilitate that activity.
If any of these uses seem helpful to your shop activities, check out Stop-Loc. It’s a deal at $13.95 from Tormach.
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Bob is responsible for the development and implementation of the popular G-Wizard CNC Software. Bob is also the founder of CNCCookbook, the largest CNC-related blog on the Internet.