If it was me I would have went with common 1 HP 4 or 6 pole (~1050 - 1725) RPM three phase AC motors powered by off the shelf VFD units instead of high speed router motors.

Thanks for pointing that out, I was already giving serious consideration to that alternative at this point.

To me the fact you have to use special speed control to make the routers run slow enough (and well under their rated power band) says you picked the wrong motors for the job to begin with

Yes, I realized that as well at the time. But I was already stuck with the motors I had chosen and just had to make them work the way I wanted them to.

The advantage of using routers instead of common induction motors is that they're lighter, and are easier to remove and reinstall for maintenance purposes, plus they're single phase. The disadvantage, as you've pointed out already, is that their rpm range is not the proper one, and have carbon brushes that have to be replaced every few months.

 

I wouldn't put too much concern/justification over the weight issue being I and my brother have several assorted routers and I can assure you that the bigger commercial grade one of his on his CNC router weighs as much or more than any common 48Y or 56C face type 1 HP single phase motor does.

Even more so when you factor in that a good 1 HP TEFC 1725 RPM single phase motor sells for under $150 whereas any commercial grade router like the one you may be using is pushing $350+ and the specialty bits you want to have made for it are going to cost near that or more each as well.

Maybe you have 1000's of dollars laying around to waist on making a less than properly designed system sort of hopefully more functional but for me if I could buy a pair of common electric motors for less than the cost of single custom drill bit and have a properly built and working design that will be reliable in long term use I can't see where doing a redesign of the system can't be cost and time justified.

On a related note,
Back some years ago my brother made a big CNC 3 axis router system (~ 36" x 48" table with 12" Z axis travel) he asked me a bunch of questions on what I thought was the proper way to do it, but didn't like anyone of them being they all required him to either accept this goals were not realistic or that to meet them his design would have to be substantially reworked. What he wanted was sub 1/10,000" resolution on the three axis since his choice stepper motors and lead screws would give him that and to be built as cheap as possible out of as cheap of material as possible on top of it.

The reality he got was that those stepper motors and screws gave him a crazy slow travel speed (3 - 4 minute end to end or side to side) plus the fact he built the whole thing out of aluminum conduit, wood and other lightweight high flex material it had crazy amounts flex slop at the tool to the point it was for most part useless.
Sure (in theory) it could do sub 1/10,000" steps (but in reality )it had a +- .250"+ slop value when running. He fought it for about a year before I picked up a bunch of heavy structural aluminum X and H bar stock from a scrap yard buddy of mine and he then remade the whole machine and with far more realistic tolerances in mind. .0025" step and +- .010" running tolerances proved to way more than adequate for wood work plus given it was structurally at least 10x stronger and heavier made it pretty durable too!

I don't know how much money he spent on trying to make the first design work but I suspect that he probably could have built the second one 2 - 3 times over for what he spent in time and money trying to make the first one work 'sort of well most of the time'.

 

After much searching, I found a commercial bit that I could adapt to my process. Of course it's about 3 mm shorter than I wanted it to be, but it's also less than 1/3 the price of my local manufacturer.

Now if I could only find a 6" long 21/64" carbide drill bit.... At this point, I don't care if it has a 1/2" shank or not, I can always make an adapter for it.

 

I've finally found two good and affordable sources for the drill bits I've been looking for. I'd post them here, but I don't know if that would violate the TOS of this site. Anyone interested, feel free to PM me.

 

I've finally found two good and affordable sources for the drill bits I've been looking for. I'd post them here, but I don't know if that would violate the TOS of this site. Anyone interested, feel free to PM me.

What's the biggest penalty you'll face? "Hay, that looks like spam, don't do that". Please post. I'm interested.

 

What's the biggest penalty you'll face? "Hay, that looks like spam, don't do that". Please post. I'm interested.

Woe unto you, Gopher, if one of the mods raps my knuckles in public and tarnishes my unimpeachable reputation!!!!...

Having said that, my best options were:

From www.rtscut.com: 0.3281'' DIA (21/64"). SOLID CARBIDE DRILL 6.0'' OAL, 4.50'' FLUTE LENGTH, 2 FLUTES RHS-RHC 0.500'' DIA. SHANK X 1.35'' LENGTH, $163.00 USD. each, NET.
And from www.travers.com: http://www.travers.com/super-tool-c...ll-point-angle-118176-size-2332/p/24-010-044/ (11/16" carbide-tipped drill bit $96.30 USD each)

I cheated on the 11/16" bit because it's not solid carbide, but carbide-tipped. But it should work just as well, since it'll be used to drill wood, and not metal. Otherwise, that bit would've cost me something in the neighborhood of $320.00 dlls

And btw, Traver's website has that bit mis-titled. It reads as 23/32" but it's actually 11/16", as it's mentioned in its detailed description. I called them personally and checked.

 

I tend to think passing information about sources of supply is not against the TOS.

Trying to gin up business is against the TOS.

Back in the day, of bulletin boards and dial-up modems, the admins didn't like people advertising their products, however, a simple link with no explanation was allowed. The theory being, if someone wanted to research it more they could. The owner could not "advertise" any details.

A question was asked and a source was found. That, to me, is not advertising.

 

@ cmartinez, Before starting up you router with your new carbide drill, the 21/64 one you might be wise to check out the bearings in that router. If it has been wobbling for some time they may be shot. While your new carbide bit may be stiffer, it is also more brittle and it is not as tolerant of whipping around as a HSS bit. And the wobbling would make me think the bearings are suspect, not a drill problem on its own. Hate to see an expensive drill break on start up.

 

Hate to see an expensive drill break on start up.

So would I. But the router is brand new, and I've modified its speed controller to make it run at 2,500 rpm's, which is low enough for the bit not to vibrate and break. Again, the wobbling only happens when using HSS, and this is because it's a long bit. In standard length bits the wobbling is barely noticeable.

 

I don't understand the wobble, a 6" bit is not really a long bit, I've got some home made extension drills up to 18" long 1/4" diameter and they don't wobble.

 

I don't understand the wobble, a 6" bit is not really a long bit, I've got some home made extension drills up to 18" long 1/4" diameter and they don't wobble.

It's not that I actually see them wobble ... it's that they leave oval holes... and of course I assume that they wobble...
But could something else be the cause of their oval shape?

 

But could something else be the cause of their oval shape?

Some smaller drills will follow the "grain" of the wood. The "summer" wood, the lighter colored wood that grew in the summer is usually harder than the "winter" wood or dark colored stuff. So it will push the drill sideways. That's the reason that a spur or brad point drill cuts a rounder hole, the spur being thinner slices the grain and doesn't move sideways.