Traming improvements on Clausing 8520 mill

[gard]

Following is a description of some tips and improvements for tramming a Clausing 8520 mill. This may work for other similar ones like grizzly G0696 round ram head mil or perhaps A1S mill-Drill units like HF 40939.

I found it important to have the clamp bolts as tight as possible when adjusting the head, this reduces movement when it is finally clamped tight.I chucked up a drill rod and adjusted the clamping bolts (one at a time) to the point where I could just barely tilt it by hand then marked the bolts. At this point I found I could move the head with a long wood stick, prying the extended quill or motor mount against the mill column. This seemed a little more repeatable than tapping on the head with a plastic mallet.

There are lots of recommendations on the web for how to measure Tram, I used a DTI held in a collet and rotated the quill between 2 different 123 blocks. Start with the indicator just barely contacting the lower block, carefully rotate to the other block and move the head so the needle moves 1/2 way back to zero. It only took a couple of iterations to get the same reading on both blocks. I find it works best to tighten up the back clamp bolt first, then front. The DTI does still move a little as the clamp bolt is tightened so there might be some trial and error.

I decided to make a fine adjustment attachment for the mill. After a couple of quick calculations, I started with 1.125 shaft (actually annealed torsion spring from an old Astro van) and 2 ea 0.25 thick plates. I welded together then bored the 2.995 holes to fit the mill ram shaft. This took awhile, probably would have been quicker to grind a treepanning bit? I have used hole saws but they are pretty slow also.



Next welded on the other parts and fit a couple of 10-32 adjusting screws and sawed the assembly in half vertically. Probably should paint it but can't wait to try it out.

A little adjustment and fits perfectly.


The opposing adjustment screws made it very easy to adjust the tram. The adjustment screws are 6 in below the ram and offset from the center of the vertical bars by 2 in
The thumb screws snug up but do not flex the assembly too much. If both screws are left snug there is little change in the tram as the ram clamp bolts are tightened. The entire tramming process took about 5 minutes not including photographs.

The new assembly can be loosened and moved with one nut on the top (same nuts used in the mill table clamping kit). It can be easily removed or moved to the front of the column if more ram adjustment is needed.

There are a couple other things that can be checked. The above tram checks that the spindle is perpendicular to the table surface in one direction, it can also be checked front to back (nodding) but there is no easy adjustment on this mill (short of shimming or scraping).

The parallelism between the table top and bottom dovetails can next be checked by setting the indicator on the table (or a parallel block) and cranking the table in X and Y.

Deflection of the mill under load can be checked by using a fly cutter or large face mill and fine adjusting tram to get the desired cross hatch pattern. If the pattern changes depending on cutting load or direction it suggests some deflection in the machine frame or spindle.

For years I have gone to every contortion possible to avoid changing the head because it was such a pain to get it trammed back in. I wish I had made something like this long ago. With this mill I can move the head closer and further from the column as well as rotate the ram and rotate about the column so that will help being able to locate the head over a variety of parts. I am sure many others have done something similar but a search did not find any, (probably a good indication of my poor search skills) so I figured I would share.

[nc5a]

Pretty ingenious fixture. I don't have your style of milling machine but I can see why you would design something like it to help with tramming. And yes a treepanning operation would probably have been faster. Well done.

Coming up with the right search terms when trying to find specialty tooling is a challenge because you never know what the maker might call it.

[oxford]

Pretty ingenious fixture.

Yes, nice job. I’m sure after using it you are wondering why you didn’t do it years earlier.

[kev74]

Very nice! That beats rapping the motor mount back and forth with a plastic hammer!

[gard]

Thanks for the comments, now I am trying to work out an improved simple way to tension the belts. I always like the way my designs tend to improve and generally become simpler as I mull them over in my head for a week or more before I start cutting

[J Tiers]

That's an effective way.



I have a Benchmaster mill with the same problems adjusting it. Something along similar lines to yours, but a bit more complex was in the magazines a few years ago. I started out to do something similar, but ended up doing it different. Between the motor and the column is a housing and you can see the end of a screw.



What is inside of that is this:

[Doozer]

The thing I experience with my Clausing 8520 is because the
turret housing is split where it pinches the ram, the ram ends
up moving a little when you tighten the pinch bolts.
Mine moves one and a half thou (arbitrary measurement)
in one direction. It is predictable, so I just offset my head tram
to the direction that it pulls to compensate. Then I snug down
the pinch bolts and side to side is perfect. It is not difficult.
Just measure what it does, and pre-plan the offset to
counteract the movement before tightening.
Tapping my head left and right with a urethane hammer is
standard procedure. It is not something odd. It is something
that is done in machine shops every day.

-Doozer

[J Tiers]

The best technique I have found is to snug down the clamps before final adjustment. That way the movement is almost nothing, since you are not really moving the clamps, just changing the tightness. The Benchmaster was totally unpredictable in how much it would move.

....................
Tapping my head left and right with a urethane hammer is
standard procedure. It is not something odd. It is something
that is done in machine shops every day.

-Doozer

No wonder machinists are so grumpy!

[Doozer]

I always throw a good beat'in on myself
just to keep myself in line.
I mean, in tram.

-D

[oxford]

Tapping my head left and right with a urethane hammer is
standard procedure. It is not something odd. It is something
that is done in machine shops every day.

-Doozer

Is that before or after you are done talking with engineering?

[Doozer]

I am engineering.

-Doozer

[gard]

LOL, I was also the engineer also until they decided it was time for me to retire. I do use the soft hammer a lot. The biggest improvement in the entire process for me was to get the clamp bolts just tight enough before adjusting one way or another (like J Tiers and Doozer). I think I may take them out and mark them with a thin cut with the slitting saw (instead of the sharpie on there). If the bolts are too lose the head moves like 5 mils when tightened, if just right its only 1/2 or 1 mil. It seems like with the the thumb screws snug the head moves vertically a small amount but the tram does not change as the ram clamp pinch bolts are tightened. Those bolts have to be quite tight to really hold the head in place on my machine.
The Benchmaster mod looks pretty slick. With my adjustment screws I can move the head about +/- 5 degrees and that seems enough. Any further than that it is just a matter of loosing the one clamp bolt on the top of the adjusting mechanism.

[old mart]

The Tom Senior light vertical mill head is on a long steel shaft which allows tilting both ways and also extending forward to increase the throat depth by up to 6". Unfortunately the clamps are wrap around with the bolts on the left side of the machine. The whole lot turns when the bolts are tightened. A mod like gard's might be the answer. Since the mill has been refurbished, we have trammed it only the once, that shows what a **** job it is.

[J Tiers]

Refurbishing was what did it for me.... I was taking out and re-tramming every day, it seemed like, when I was re-scraping the various slideways. It got to be such a pain that I made the thing just to get the nasty job of tramming down to a somewhat reasonable amount of trouble.