Rebarreling and Home-Shop Machining

Tramming the Mill Head

I needed to machine the face of the cross arm of my new fifth column to be parallel to the quadralift and quill travel and perpendicular to the bed so that it would not affect the milling machine alignment much when I tightened it down. Here are the steps that I took to align the milling head first.

Level the Lathe

First I leveled the lathe bed by using the new leveling feet on the sturdier milling table. I used a machinery level directly on the bed. One graduation on this level is about .002 inch over the length of the level so you can measure to about .0002 inch with it. The new sturdier table allowed me to shim the right side of the lathe bed and remove a slight twist in the bed that was evident with the level. I was aware of this problem previously, but could do nothing about it. The level also let me determine that the milling table was parallel to the bed over its short dimension but slightly out in the long dimension. See photo 1 of the level on the milling table. I will take care of the milling table problem later.

Plumb the Quadralift

After the lathe was leveled I tested the quadralift in order to make it’s movement perpendicular to the bed. This would make it so adjustments of the quadralift would not affect a machining setup. It’s probably a good procedure, though, to do all the machining without moving the quadralift and fifth column clamp. I had good luck here. Less than .001 inch over six inches. See photo 1 and 2. I measured the movement on the Y axis directly from the bed. Also less than .001 over six inches. Both squares were tested against each other and a third square on the surface plate. All agreed well. If I needed to adjust the quadralift I would put shim under the bottom plate of the quadralift and retest until it was plumb.

Tram the Mill Head

Then I aligned or ‘trammed’ the mill head using the setup in photo 3 with the indicator on the bed. The indicator setup resembles a tramming cutter used to cut circles or a trammel used to draw large circles. I had recently installed the quadralift by first tightening the bottom bolts on to the bottom plate which secures the mill head and with gravity taking its course on the flexible bottom plate, then I attached the top shouldered stud. There was considerable tilt on both axis. The top bolt hole that clamped the mill head to the quadralifts movable top plate was large enough so that I could loosen the stud to make an adjustment. I clamped my fifth column support to the cross arm. I applied some downward pressure with the quadralift to tilt the mill head up. Then I, retighten the top bolt. I was within .001 inch along the length of the bed after this. Then I loosed the bottom bolts and moved it the additional .001 inch. When the error along the length of the bed was at .000, I stopped. I will correct a small error that still exists on the axis perpendicular to the bed when I finish the fifth column project. Unfortunately adjusting the milling head by canting it in the mounting fixture affected the plumb of the quadralift. I describe its readjustment in the section below.

Screw Jacking the Mill Head

I made a final alignment of the Mill head. What is needed to align the mill head in the quadralift seems to be an accurate method of positioning the top stud on the mill head mount. FirstI added a .003 inch shim under the front edge of the bottom plate of the quadralift to replumb the quadralift. Then I placed a screw jack under the cross Arm with the indicator positioned to tram the mill. See photo 4. I flexed the arm upward .010 inch with the screw jack. I Loosened then tightened the top screw which holds the mill head to the quadralift. I achieve a zero indicator movement along the bed when I flexed the arm up .020 before loosening the top bolt. Make sure and release the screw jack before remeasureing. The mill head was also twisted slightly which gave me an indicator movement across the bed. I put a second screw jack to push the bottom of the top stud in the correct direction. See photo 5. At the same time i used the same .020 inch upward tension on the other screw jack. Then I loosened and tightened the stud. I repeated with 1/4 to ½ turn more tension on the screw jack. If I needed more movement I loosened the bottom bolts. I got within .001 all around so I was satisfied with the method. I rechecked the plumb on the quadralift and it was still good after the shimming of the quadralift and retramming of the mill head

Test the Quill Travel

After you have trammed the mill head you can retest the vertical spindle travel (quill travel) at the mill head instead of at the quadralift to see if it is parallel to spindle rotation. Use the setup in photo 1 and 2. Any problem here would be hard to correct, as far as I can think right now. My quill travel was good.

Check the Mill Table Flatness

I then tested the milling table for flatness by putting the same indicator setup in photo 6, on the edge of the table and running the milling table along its full travel. I tested both sides. It was flat. The only correction for this is to reqrind the table flat or to use a tilting vise whose fixed jaw is always indicated true to the spindle travel.

Tram the Mill Table

I also trammed the surface of the mill table using the same circle diameter that I used on the bed. I took four readings (approximately on the inside edges of the bed rails) on the mill table. See photo 6. Any difference in this reading and the reading at the bed indicates a problem at the circular surface that allows the milling table to rotate (if your milling table is flat). This can be corrected by removing the mill table and scraping this circular surface to remove the high spot. Your should first clean, deburr, and inspect this surface and the carriage to bed contact and retest, before your remove any metal

Quadralift Alignment Moving Up or Down

I noticed that the mill head trammed differently depending on whether the last movement of the quadralift was up or down so I had a choice to make over its last movement before locking it down rather than try to adjust this out. I decided to move it down and then lock the mill head with the fifth column. This would give the mill head the greatest rigidity against deflection upward. Also, it just so happened that this resulted in good plumb on the two axis, about .001 inch over 6 inches, and a good tramming test of about .001 on the y axis and .000 on the x axis along the bed. I ended up with a .003 inch shim under the base of the quadralift on the chuck side of the lathe spindle support and a second .003 inch shim under the near side of the base to correct plumb on the X and Y axis.

Quadralift Stop.

When I made the last adjustement of the quadralift down, I used a screw jack to act as a stop under the mill head mounting plate to act as a stop and prevent slack from developing. This screw jack can also be moved around up bit to make small adjustemnts of your milling head into alignment for a precision job. Photo 7.

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