What is that on top of the mill's head? Drawbar or a place to mount encoder?

I climbed on the mill today and made a startling discovery.

Her's a picture taken with a cell phone.

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What this shows is a round steel plate with six holes on an outer circle, and one hole in the middle. Three of outer holes are used to hole the plate and three are not used and threaded.

The hole in the middle is plugged with a soft rubber plug. I removed it and found out that it opens a hole to the spindle.

My guess is that this is a mounting plate for an optional power drawbar, which I do not have.

Some questions come to mind

1) are power drawbars needed for this mill? It would seem that the answer should be no.

2) Are power drawbars somewhat standardized, and do I ever have a hope of finding something compatible?

3) It would seem that it would be very straightforward to install some kind of a little encoder shaft that would go into the hollow spindle, lock itself from inside, and provide information about the exact position of the spindle to the EMC controller.

If so, could I use EMC to do rigid tapping on this mill? If I have the exact spindle angular location, instead of approximate RPM, then I could make Z axis a "slave" of this position, so that, for example, Z would move 1/20 inch with every complete revolution of the spindle, so that I could cut a 20 TPI thread.

Makes sense?

i
Reply to
Ignoramus1880
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Do you have a drawbar? Or, is this a quick-switch spindle?

The problem is the spindle moves up and down! It could get real tricky to install an encoder in there and allow it to slide up and down without anything binding or shearing wires.

If you can get a quadrature encoder with index pulse attached to the spindle, then EMC2 definitely can do rigid tapping. I found a totally different way to adapt a spindle encoder to my Bridgeport, it involved fitting three gear-tooth sensors for auto transmissions inside the head to pick up the teeth of the bull gear. My mill is not a quick-switch, so I do need the drawbar, and that blocks the "top route" to the spindle.

Once the spindle encoder is set up, you just use the G33.1 command with appropriate parameters for depth and thread pitch. I have a Procunier "CNC" tapping head, and it works for tapping, but it is such a long contraption that the tip of the tap ends up nearly a foot down from the spindle nose, therefore the exact position of the hole is less precise, at least with combined drill-taps. Rigid tapping is a much cleaner setup.

Jon

Reply to
Jon Elson

Quickchange. Erickson QC-30.

I do not have a power drawbar.

I thought that it is the bottom part of the spindle that slides up and down. I can check easily, I suppose.

Awesome!

Yep, this is my concern exactly.

I will check if the top part of the spindle moves up and down, or not.

i
Reply to
Ignoramus1880

Yes, the spindle is a splined, two part thing and the hollow top of the spindle stays in place, regardless of the Z axis position (bottom part).

This means that mounting an encoder on the top is very easy, just a little machining exercise to make something that I can stick inside and make it stay connected to the spindle, with some little top piece to mount encoder wheel.

Reply to
Ignoramus1880

I'm pretty certain the underside of this part holds the top bearing for the vari-drive actually. The three threaded holes you see are for jack screws to assist in removing this place. You could use them for mounting a power drawbar if you wanted.

A power drawbar sure is nice, but not the least bit needed if you are not doing production machining with multiple tool changes. Even then, I've often found I can swap parts in the vise faster than I can change a tool...

Jon

Reply to
Jon Anderson

  1. Powered draw bars are normally simply a butterfly drill/butterfly type impact wrench inside a can, with a tapered "tooth" that when you push the handle one way..it twists the mount on the tooth and it brings the wrench down (has a socket mounted on the end of it) and pushed down on the hex on the draw bar and at the same time, presses the tighten or loosen lever on the power tool. Its very simple..much simpler than I can verbalize here. And the factory ones simply bolt down to the 3 empty holes you see up there (those holes are used to push the flange out of the top of the head..remove the mounting screws, stick em in the empty holes and use it to push down, lifting the cover out of the top of the head.
  2. If you can put something in there that you can expand and grip the inside of the spindle tightly...it would be a very good place to put a positioning encoder. Such would have very little loading on it, so perhaps a long piece of rod with a chunk of rubber tubing on it with a washer welded to the shaft, and a nut on the upper end to tighten down on the rubber tubing, expanding it on the shaft and pressing against the inside of the spindle, locking it in place. Then a simple coupler to an encoder mounted on a "tripod" that will bolt to the 3 empty holes. Very simple to do, very easy to make and impliment.

What holds your tool holders in place currently? Some sort of quick detachable tool holder?

Gunner

One could not be a successful Leftwinger without realizing that, in contrast to the popular conception supported by newspapers and mothers of Leftwingers, a goodly number of Leftwingers are not only narrow-minded and dull, but also just stupid. Gunner Asch

Reply to
Gunner Asch

Correct. Try something that will expand into the top of the spindle. Its not a "wet" area, so your choice of materials is quite wide.

Gunner

One could not be a successful Leftwinger without realizing that, in contrast to the popular conception supported by newspapers and mothers of Leftwingers, a goodly number of Leftwingers are not only narrow-minded and dull, but also just stupid. Gunner Asch

Reply to
Gunner Asch

Correct.

One could not be a successful Leftwinger without realizing that, in contrast to the popular conception supported by newspapers and mothers of Leftwingers, a goodly number of Leftwingers are not only narrow-minded and dull, but also just stupid. Gunner Asch

Reply to
Gunner Asch

Did you ever get a parts manual for this machine and digitize it? If so, got a link? It might be fun to think about how to get a feed back device in.

Jon:

How many pulses per revolution does EMC2 need to accurately rigid tap?

Wes

Reply to
Wes

OK, at least I have an idea now, thanks.

Yes, something like that should be easy and safe to do. I thought to make the plug out of brass, cut it like a collet, and expand from inside with a screw.

Quickchange collar.

i

Reply to
Ignoramus2966

a link? It

Not a parts manual. I have a maintenance manual, a series of photos that I took.

Anyway, making a lockable plug seems to be a simple undertaking. After about 1-2 hours of work I could get an encoder shaft in there, safely removable.

Rigid tapping does seem to have a lot of advantages.

Good question, but I figure it should do OK with the US Digital E5 encoders that should be easy to use. Mine are 4000 ppr, but they have others that go even higher.

Making beautiful air manifolds should be a piece of cake with rigid tapping. Total expense would be appx. $100.

i
Reply to
Ignoramus2966

a link? It

Rigid is nice. If you have rigid tapping you are also set up to thread mill. That is a very nice tool to have in your tool box.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Reply to
Wes

Great!

Enjoy, DoN.

Reply to
DoN. Nichols

I think that I can easily make something from brass or some such. Let me think.

it would be a fun and inexpensive improvement.

i
Reply to
Ignoramus2966

Not a whole lot. I have a Bridgeport 1J, and it is a REAL pain to figure any way to rig an encoder to the spindle. So, I figured I could make the bull gear the encoder wheel with some gear tooth sensors. On the 1J it is an 81-tooth gear, equivalent of an 81 pulse/rev encoder. That gives 324 quadrature counts/rev. That is plenty. So, even a 50 Cycle/rev encoder would work fine.

For a look at how I did it, see :

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The particular sensor I used is out of stock, but apparently there is another version that is identical as far as I can tell, and about the same price. Somebody is trying it now, but I'm pretty sure it will work.

Jon

Reply to
Jon Elson

I've been out of town, so I'm late to the party. Youve got exactly the same top on your mill as mine. i made an expanding collar that's only 50 thou thick to hold a timing pulley. This still allows you to change drawbar tools. Something you'll likely need to do at some point. I'd suggest a complete encoder off ebay for this. get one that you can mount on slots to tighten your little belt from the spindle pulley. Allan bradley units are about the best. one example:

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FWIW, I'd watch for a power drawbar unit on eBay. Very nice addition that you'll soon wonder how you lived without it.

karl

Reply to
Karl Townsend

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I believe Iggy has a mill with a QC spindle that does not use a drawbar.

Reply to
Pete C.

If Iggy needs an encoder..I may have a spare or two.

Ill check my Stuff

Iggy, email me a shipping address.

gunnerasch at hotmail dot com

Gunner

One could not be a successful Leftwinger without realizing that, in contrast to the popular conception supported by newspapers and mothers of Leftwingers, a goodly number of Leftwingers are not only narrow-minded and dull, but also just stupid. Gunner Asch

Reply to
Gunner Asch

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if that's the case, he doesn't have to get tricky about leaving room. I'd still go with this encoder route

Karl

Reply to
Karl Townsend

I'm curious, if its a QC, why the hollow spindle shaft?

karl

Reply to
Karl Townsend

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