There's only one issue with buying timing pulleys. It appears most of the stock sizes are limited to 60T. So I'd need a 15T pulley on the drive side to get my 4:1.
And it's really all about size. To get a decent hold on the 19mm motor shaft (no threaded end hole) and to stay within my max 160mm driven pulley size I'm stuck with a max of 40mm. Take away 19mm shaft plus 3mm key above the shaft and I have 18mm/2 or 9mm worth of pulley body to work with. A 40mm pulley has a circumference of 125.6mm. Let's set it at 125 and use a 5mm pitch belt. That's a 25T pulley. That means I need 100 teeth on the driven. Again not a stock value. So I think like Andy I'll have to make myself a cutter for the tooth profile I end up using. I could buy a 25T and bore it to 19mm and broach the keyway. I have the tools on hand for that since the Mill Spindle drive shaft is 19mm. But even 60T pulleys start pushing $100 so really it's time to make my own. And since I want to change to toothed pulley for the spindle drive it's a good excuse. Just need the size that can handle 2HP and 3000 RPM. So many choices... John > -----Original Message----- > From: Chris Albertson [mailto:[email protected]] > Sent: December-26-20 12:13 PM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Making L Type Timing pulleys. > > I must have missed the designed size. Yes there is a minimum size. You > need to have a minimum number of teeth engaged. So even if you have a 13T > pulley, if it is very close to a larger pully it would not have enough > teeth on the belt. > > You CAN design a system that works if you move to different tooth size and > shape. The specs on modern belts are better then the older L and MXL > belts so you might be able to fit hat you want into the same space as the > original. You do a recalculation from scratch. > > As to how to make the pulleys. Just buy them. But for testing you can 3D > print timing gear pulleys. I make mine by printing a plastic ring with > the teeth and then epoxying the ring to a steel pulley hub. Fully printed > pulleys don't work well but the hybrids are nearly perfect and really easy > to make > > To make a plastic ring, download the CAD file for the pulley from the > vendors web site. I use SPD/SI and get the .step file. Then use yu CAD > system to bore a huge hole (like 20mm or 30mm) in the pulley model. Print > that. Then as the printer is working turn a 20mm or 30mm hub on your > lathe and drill and tap for set screws. What makes this a quick job is > that they provide CAD files or every pulley so you don't need to know how > to layout the teeth. > > > > On Sat, Dec 26, 2020 at 11:57 AM andy pugh <[email protected]> wrote: > > > On Sat, 26 Dec 2020 at 19:34, John Dammeyer <[email protected]> > > wrote: > > > > > Making a new lower pulley with 9 teeth is out of the question. It's too > > small for only 9T and definitely won't fit on the 19mm motor shaft. And > > that's the kicker. At almost 3/4" the pulley that goes onto it has to be > > large enough to have a decent grip with set screws onto a 6mm key. > > > > I seem to recall that it is recommended to not go below 12T anyway. > > > > I don't know much about L and XL belts, all my machines have used T5. > > T5 is available in widths from 8mm to 25mm. > > https://www.bearingboys.co.uk/T5-Section-5mm-Pitch-1224-c > > > > I also have the correct hob for making custom T5 pulleys, so that is > > one reason for _me_ to use them. > > > > You could consider ignoring the keyway, especially if the motor shafts > > have a threaded hole in the end. > > > > I have several times taken inspiration from the Trantorque bushings: > > https://uk.rs-online.com/web/p/keyless-bushes/7542545/ > > However they require a huge central bore, so what I have done is > > machine the pulley bore with a taper and then pull or push in a > > sleeve. > > At various times I have used a bolt in the end of the shaft, a nut > > pulling the wedge through, or a ring of bolts to push the wedge in. > > > > Here is variation on the theme, with two tapers: > > https://bodgesoc.blogspot.com/2017/01/gears.html > > > > -- > > atp > > "A motorcycle is a bicycle with a pandemonium attachment and is > > designed for the especial use of mechanical geniuses, daredevils and > > lunatics." > > � George Fitch, Atlanta Constitution Newspaper, 1912 > > > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > -- > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
