On Fri, 10 Dec, 2021 at 3:44 AM, John Dammeyer wrote: To: 'enhanced machine controller (emc)' Well there are standards but more and more it doesn't look like they are being followed.
Since this forum is all about CNC my request follows with the subject of power tapping. To hold the taps so they don't spin in the collets I found what are called Tap Collets in the ER20 size. The attached chart shows the sizes and the photo is of the JIS variety. The collets are slit 4 ways on each end rather than 8 so they are not nearly as flexible. Where an ER20 collet might be rated as 5mm-6mm or 6mm-7mm the tap collet is marked [M6 6.3-5] or [M8 6.3-5] If you have an ISO 6.0x1.0mm tap the shaft part will be 6.3mm and the square, which fits in the square part of the collet to prevent the tap from spinning, will be 5mm square. When my 6mm tap didn't fit in the M6 collet I complained to the supplier and got the same shrugged shoulders. However both my M4 and M5 taps fit into the M5 collet which is also wrong. So I thought I'd buy American and order an M5 and M6 for $20 each. The taps arrived with several part numbers and Made in USA laser engraved on them. The shaft measured 6.42mm and wouldn't go in. The Chinese 8mm tap with the 6.3 shaft went smoothly into the collet marked M8 (or M6). And it measured exactly 6.3mm. To get the tap in I resorted to force. I jammed 3 thin bladed flat screwdrivers into three of the slots on the collet. The US M6 tap now dropped into the now larger than 6.4mm hole and an 1/8 turn twist of the tap made it drop further into the square hole. Pull the screwdrivers and the tap was held tight. Tighten the collet and the TTS ER20 appears to turn the tap true. All this is of no importance, as demonstrated by the huge forum response of actual tap measurements, unless you have specific holders for tools that are supposed to be of a specific dimension. Then it is important. And I'm sure there are those who hold it in a drill chuck and have no problem with it spinning in the chuck. Or in a standard collet without issues. I don't seem to have that luck. Anyway. My request for measurements was to try and get an idea of how widespread tap shank and square variations are. John Like I said, there seems not to be a std at all. But w/o gripping the flats with grub screws or the custom-made tap holders, there is a possibility of slippage, so the best idea is to do as I did and order a few lengths of 3/4" brass rod. Cut it in 1.25" pieces in the lathe. Take a spare 3/4 collet and a 1/4" SC tool and cut a 1/4" deep notch in the mouth of the collet. Then I mounted an alu block with a 3.4" thru hole, slit so a clamp could squeeze its slit closed and put a clamp on it from each side so loosening the clamp on the slit side would allow the slug to be inserted w/o moving the jig, and leaving about 5/16" projecting on the right end. Then I mounted a drill chuck facing up to hold the next size up number drill sticking up hat would clear the taps shank. I also mounted my A axis clear at the left end of the table facing right. Then I found I needed another 3/4" R8 chucked in the A axis chuck and a block of maple for support under the open end, which also gave me a flat to superglue a piece of dbl-sided pcb to use for a touchoff point. Then I wrote some gcode that treated all that stuff as stations in a production line. Changing tools as needed, moving the slug from "station" to "station", with breaks to allow moving the slug, so at the end of the run I had already installed a short 4mm cap screw in the slugs side and and needed to install the 4 grub screws to grip the square butt of the tap. And I did that for around 75 taps I had that were small enough my go704 could drive them. The operation sequence was put the slug in the clamped alu jig, drill, countersink and tap the side hole for the 4mm key screw, remove the slug and install that cap screw, place the slug in the notched R8 in the spindle with the thru hole bit in the chuck on the table, drill thru the slug, then pause to move the slug to the A axis rigging, and install the bit for tapping the grub screw holes, move to the pcb and and probe for the drills TLO, then drill the 4 holes by driving the A axis in 90 degree steps, the pausing to change to the grub screw tap, probing it for TLO length, then tapping the 4 holes. Done. Take the slug out of the R8 in the A axis and install the grub screws. All in one swell foop that took about 15 to 20 minutes per slug. By the time I'd run out of taps at or below 3/8", I'd used up 4 3' sticks of brass rod and made 75 or thereabouts of them. Made a tray box about 15" square, cut 1.25" pieces out of plastic ballister sticks and glued them into the tray to store them in some semblance of order. Got boring after 3 or 4 days of that. It was while doing that, that made it pretty obvious the post wasn't exactly square. This may not exactly fit your way of doing things as your way give neater results. But my way works like me, cheap. I spent about 3 hours looking thru the first 30 pages of fleabay w/o finding a circular square. So I guess I'll try to make one on the sheldon. Take care & stay well John. Cheers, Gene _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
