I am surprised at what some of you fellows are talking about here.....Anoel you have yourself listed as a machinist, yet you talk about grinding down a threaded shaft to make the coupler fit? The coupler alignment must be accurate and concentrice or else the shaft will not likely run true and at high speed it will create lot of problems.
As far as speeds go, you fellows likely realize that these small dremels and zip routers etc, all run at very high speeds, but they do not have much power (torque). You need to use a regular variable speed router, like a Hitachi or a Bosch etc. If you plan on trying to route wood at speeds of 5, 12 ipm or so, you are really out of touch with what is required. To properly route soft wood like pine, cedar etc, or even into hard woods like oak, maple etc, you need to have feed rates in the range of 50 to 60 inches per minute, or you risk burning the wood with the high speed routers. Even the variable speed units need to run at least about 15,000 rpm, so trying to slow the router down doesnt help either.
As far a stepper motors go, you need to realize that stepper have their highest torque at 0 rpm when they are stopped. The faster they run, the less torque they have, and then you run into the risk of having them loose steps if they hit anything that tends to jam them up. With the lower torque available at the high speeds, this is easy. Keep your stepper motors to a max of about 250 rpm for cutting, but you can go a bit higher for rapid speeds, if your machine is nice and free moving.
If you think you can get lots of torque out of a stepper by gearing it down (by having a small pulley on the motor and a larger one on the leadscrew) this is also false thinking because to get the speed you need on the lead screw, you need to run the stepper very fast, so it looses torque as previously mentioned. You can get away with this to a degree, but if you plan on doing that then get a BIG stepper that has lots of extra torque right out of the gate.
The BEST way to get high feed rates, with only having your stepper run slow to maximize the torque is by using a rack and pinion drive. This is what the professional units use. Just think, a pinion gear that has a pitch diameter of 1" such as a 12 dp gear - the circumference of this gear, at the pitch line is 3.14", so if this gear turns at 100 rpm, then the resultant feed rate is 314 inches per minute.....that is how you get high feed rates out of steppers. The only draw back is that the resolution is lower, at about 0.001" per step, if you use the Xylotex controller and gear the stepper 2:1 to the pinion gear, but that is fine for wood working (200 steps x 8 = 1600..........then gear it 2:1 gives you 3200 steps on the pinion. The pinion is 3.14" diameter, so 3.14/3200 = 0.00098" per step).
Get your steppers from
www.homeshopcnc.com this is likely the best and the cheapest place to deal. A very good reliable place to shop, Rick is a good guy. Dont use steppers that are under 500 oz in. you are only wasting your money and fooling yourself. These are not expensive motors, get the big ones. I use the 1780 oz in, which he has now replaced with even bigger ones, but you cant run these on a Xylotex.
Pete