ya think but it worked with brass

Yeah, he must really know the machine. That could easily go wrong...

If you have a 3 phase mill it will automatically reverse when you throw the power switch in the opposite direction. No need for waiting for a complete stop. If you have never tried this, you should, but I would suggest you bring the rpm down to a very low speed until you get the hang of it. Drill the hole at the correct spindle speed, put the mill in back gear, put the tap in a KEYED chuck (ball bearing type the best).....not keyless as it will self tighten sometimes to the point of cracking the chuck, make sure the vise is tight, and bring the tap to the work using the quill feed handle until it begins to self feed, keeping your hand on the power switch to instantly reverse before you run out of threads on the tap.I had high school students doing power tapping on Bridgeport’s in just a few minutes. You can do it too. And after you get the hang of it use common sense........no you should probably not tap 1 inch-8 threaded holes using this method and use a spiral point or gun type tap that pushes the chips ahead of the tap. Through holes only. No blind holes until hours of experience unless you like removing broken taps.

@@37yearsofanythingisenough39 Power tapping as you described (quite well I might add) is a pretty reliable way to tap holes if you are already set up in the mill. Leaving the chuck just slightly looser than you want it to be lets the tap do its work, but slip rather than snap if it binds. Saves a lot of arm and wrist strain, especially if you have a multiple hole pattern to do. Source: I am apprenticing in tool and die at my job and did this last week, instructed by a 40 year veteran machinist.

John Birkholz thanks John. Nice to know I can still verbally cover a technical subject to the point of understanding.

It's always a pleasure to watch someone with the heart of a teacher sharing what they've learned. "Don't ask him how he knows that..."

Michael Marks Not as pretty as the Edgetech solution, but quite a bit cheaper!

@@seanrodden6151 My coworkers put a light duty spring between the parallels, same idea as the rubber band, just pushing them out rather than pulling them back.

Texicles machinists have been using these techniques for a long time

@@MrCellardoor7 I know they have, and it's not the first time I've seen it. My comment was exaggerated for comedic effect That said, while I've seen all sorts of tricks before, I don't get to interact with real machinists much. CNC folks seem to have little use for the arcane arts of machining, and sometimes look at you like you've got lobsters crawling out of your ears when suggest such things. There are people out there, running successful shops, who don't understand the concept of grinding a HSS form tool. Literally willing to buy a whole box of carbide insert blanks and have a tool grinder make form tools with them for a one-off, 2 piece aluminum job because they don't quite grok that you can buy a $4 piece of HSS and get the same (possibly better) result Old school toolmakers exist, Tom's proof enough of that, but there are places where manufacturing takes place seemingly without their sorcerer's ways

Texicles all manufacturing takes place without sorcery, most manufacturing takes place without hand ground tools

@@MrCellardoor7 Whooooooosh...

The biggest pitfall, as I see it, is that your datum moves around when you exploit the symmetry. As long as you are keeping an eye on that, and the parts required precision supports it, it's a great technique!

So do I😁🤜🏻

Povl Besser an expert is a person who did all the mistakes in that specific field

@@hassiaschbi I like that explanation more than the bone-dry one I've been given: An expert is someone who has more than 10.000 hours worth of experience in a specific field.

I second that, 100mm would be a nice size.

Meh ... even if the length is exactly 100mm, you always end up with odd sizes of gauge blocks to be stacked together. But since my vises are only 100mm wide that would be a nice size. But you do need to engrave the length of the sine bar, preferably in metric as well as imperial sizes.

You definitely are in the right hole.

And a price for supply to the U.K. if that is possible?.

I tried looking them up for you but I got a cosine error.

Also gotta be able to trust your ability to square the part properly, if you're going to reference different corners. (Or maintain symmetry if your part has other than square corners). You can't rely on DRO to make interior features symmetrical with one reference corner, then machine the profile to the reference as well.

www.mscdirect.com/browse/tn/Measuring-Inspecting/Calibration-Layout-Machine-Setup-Tools/Layout-Setup-Tools/Sine-Bars?navid=12107956

@@ccamen - I think he wants one that Tom had lasered out, with the logo and all. It seems like a modest fundraiser, like Keith's t-slot cleaners. Something to buy that would support the channel a bit, not MSC?

"It's never happened to me and I hope it never happens again"

A center drill is most commonly referring to the drill used in lathe work, for putting a 60 degree cone in one end for a lathe tailstock center (it has that 'pilot hole' to make a reservoir for lube, a legacy feature for the Old Skool 'dead' centers that did NOT spin with the workpiece. They are used because they are cheap, rigid, and generally laying around in handfuls at a busy shop. As an example: www.grainger.com/category/machining/drilling-and-holemaking/countersinks-center-drills-spotting-drills/center-drills A spotting drill is designed specifically for spotting. Design features include a deliberately short flute length, to maintain as much resistance to deflection / flex as possible. They often have 120 included angle tips, so that when you follow up with a common 118 degree twist drill, the center of that drill contacts the work before the vulnerable outer corners of the cutting edge. Many a drill (particularly inexpensive ones) have had chunks of those corners torn off by using a little too aggressive downfeed. Real spotting drills should not be used for making holes, as you can see chip removel quickly becomes a problem. It's not much of a risk to use a center drill for the purpose of spotting, provided you take care when starting the twist drill. Don't shock load it, but make a habit of getting the the chip to an appropriate thickness (say 2 to 5 thou), as fast as you are comfortable with. That habit will greatly help you from ruining drills and parts, by minimizing 'rubbing' the cutting edge rather than taking an actual cut. Rubbing generates excessive heat, which can work harden materials like stainless and even some carbon steels, promotes welding the base material to the drill, and cause the hole to cut oversize. As an example: www.grainger.com/category/machining/drilling-and-holemaking/countersinks-center-drills-spotting-drills/spotting-drills IMO, the only good reason to use a center drill for spotting, is convenience. There are some tricks to choosing drills for spotting. When making threaded holes, if you make your 'spot' a little bit larger than the outer diameter of the thread, it can serve as the chamfer for starting a tap. You can do a similar thing if your hole needs to be countersunk (typically for a flat head fastener). Choose a spotting drill tip angle the same as the angle required by the fastener head. Spot and countersink in one operation. You may even have to 'pre-spot' with a flat bottom, center cutting end mill when you have to drill on rounded or sloping surfaces, then spot drill on the flat, perpendicular surface you just made.

Somebody else, very well explained. Now if more people would read your comment.

somebody else so a spotting drill is used on a mill and a center drill is used on a lathe?

for surface finish and accuracy, I think. Just like drilling then boring then reaming, while boring can actually give and acceptable accuracy and straightness, you still need to ream it in order to have a smooth surface. Or maybe he just want to do it in that way because that is a training project, lol.

looked this up too... www.shars.com/products/workholding/vise/precision-toolmakers-insert-vise-1 no affiliation, i dont own many tools from Shars.

I caught that too! Although I burnt to many brain cells working it out in my head over and over just to be sure.

After 45 years, I know this to be true. The true test, is how can you recover from that "learning moment"/?

Where can we grab the sine bars