Tramming a hobby mill

[WilliamG]

I have a Craftex CT129N mill/drill from Busy Bee.

http://www.busybeetools.com/products...ADOUT-MT3.html

Similar to if not the same as this Lathemaster.
http://www.lathemaster.com/Lathemast...%20Machine.htm

As a newbie I understand the process although I can't find an answer to the following questions. And yes I have both a dial test indicator and dial indicators c/w holders.

1) Should one use a collet or go with the drill chuck?

2) Am I right in thinking one must tighten the mill head locks, quill lock, table locks, and release the fine down feed before tramming a mill with the table?

3) What is an acceptable degree of error as it relates to measurements?

4) Now I've tried with everything at rest meaning none of the locks tightened and then with all the locks tightend and there's a huge difference. Can't seem to find the answer in my books so what am I missing here?

Please remember I'm a newb and this is my first crack at squaring a mill.

Bill

[AllThumbz]

I am in the same experience category, i.e. tramming a mill for the first time, so I would love to see the procedure explained. I know that the AGI series on milling goes through this, as does Rudy K's tape on milling, but more information is always a good thing.

I'd love to see some step by step pictures showing how it's done. We have so many experts here, this should be an easy one for them.

Looking forward to it.

[photomankc]

I have a PM25-MV and it's quite similar to what you have there. If you are using the locks then yes, it's going to move around. The quill lock will cause you to get pushed a bit to one side since it just jams the quill against the other side to lock it. That will add a degree of tilt. Also the Z locks on mine cause a shift and slight tilt in the saddle when they are engaged so......

Determine how you will be performing tram sensitive operations and make sure you are trammed to that condition. When I mill with it, the head is locked, and the quill is locked. I raise/lower the head with the crank using a custom fit DRO and then re-lock. I rarely use the quill for Z depth changes in milling so it is also locked in normal operation. I then make sure that it is in that condition when I tram to the table. I use the indicol type clamp-on indicator holders so I can swing a ~6.5" circle on the table. I then adjust the head tilt till I'm under 0.001" over that distance in X, I have to live with about 0.002 for Y. I would go with a collet or the clamp on type holder over a drill chuck for holding the DTI.

The pain is there is no way to pull out that forward/backwards nod in the head in these machines. You have to shim it out betwen the head and the saddle, live with it, or add extra bolts to the head/saddle interface to allow you to pull the head up a bit. Also keep in mind that if your cutter is right on the edge of a profile and you release the locks to move the quill or the head you will almost certainly dig in a little and leave a mark. For that reason I try to be certain that any time I have to move in Z that I have some space between the cutter and the walls of the part.

I'd like it to be more solid with how the locks work but in a few months when I finally go to CNC on the Z axis that's going to be a moot issue. I would probably only ever use the quill for occasional manual drilling.

[dp]

I have an extremely simple method to test tram on my smallish mill.

http://www.youtube.com/watch?v=ZfioLDhBNBQ

Adjust for 0 deflection of the coaxial indicator. In this configuration it is a protractor and is indicating angle of the perpenducular surface.

That is a VW rotor, new, and quite parallel between the surfaces.

[TR]

I find this tram tool useful. 0 out and 4/1000" out.

[dp]

Nice looking tool - what is the distance between the probes? I have a very narrow table to work around. Does it come with an alignment fixture or is that done in situ? And who is the vendor?

[whitis]

This video, about half way in, shows tramming the head.
http://techtv.mit.edu/videos/127-machine-shop-4
I would not recommend using a parallel in the vise, as shown, though, until you have proven that your vise is parallel to the ways and you can clamp stuff in the vise and keep it parallel. Parallels can provide a smoother surface than the table to indicate against.

Here is another vid by tubalcain (one of several who have gone by that psuedonym):
http://www.youtube.com/watch?v=JfANyiS8Hs4
There are a number of others on youtube.

Table locks shouldn't significantly affect the tram, if they do, your machine has some issues. Like loose gibs. Table X should be centered to balance out the weight of the table ends. Tables are meant to be able to slide unlocked and still be precise (but you lock when not in use so machining forces don't take out the backlash on you unexpectedly).

Head swivel you should lock or almost lock (just loose enough you can move the head with a mallet) when testing tram since you will be machining with it locked and these aren't likely to be designed to be a precision pivot when unlocked.

Quills tend to be sloppy. Lock it; it should be locked when doing critical machining operations.

Drill chuck or collets should be ok. The way a dial test indicator is used doesn't require any great accuracy in the holding just that it doesn't move.

Acceptable error: I would try to get about as close as your indicators will allow, if reasonably possible, as tram error affects fly cutting and the perpendicularity of surfaces. You can relax that a bit if you know you won't be doing anything critical between now and the next time you tram the head - you should be checking it frequently. Don't go crazy trying to get it to within 0.000050" over 12" when doing a job where it doesn't mater if you are off by 0.005". But a fraction of a dial division on a 0.001" dial test indicator over 6" diameter circle should be possible side to side (front to back on that machine would require shims where the column mounts to base) and you could probably use the practice.

[GadgetBuilder]

Here's what I did using a DTI:
http://www.gadgetbuilder.com/MillTram.html

You'll know whether you got it right when you fly cut something, poor tram shows up dramatically there.

John

[photomankc]

Don't shim the column to fix front to back tram error on that machine. If it's already square then all you did was trade Y positional error for no tram error. Check that the column is square by running a DTI over a known good square, clamped to the table, moving the head up and down the column. Check in X and in Y. If that is good DON'T MESS WITH THE BASE/COLUMN. If you then have front/back error you can add a little shim at the top or bottom of the head/saddle joint to correct it.

Yep, My Z gib is messed up. Seems to be a not uncommon issue with the BF types. Measure tram with it locked. You need to lock it to mill anyway because vibration can let the crank handle move if it's in the right position and then you end up slowly decending deeper as you are cutting.

One day I hope to make my own gib that's better but for now it will absolutely move around a little when locked, even if I tighten the gib till it stick-slips down the ways.

[WilliamG]

Don't shim the column to fix front to back tram error on that machine. If it's already square then all you did was trade Y positional error for no tram error. Check that the column is square by running a DTI over a known good square, clamped to the table, moving the head up and down the column. Check in X and in Y. If that is good DON'T MESS WITH THE BASE/COLUMN. If you then have front/back error you can add a little shim at the top or bottom of the head/saddle joint to correct it.

Yep, My Z gib is messed up. Seems to be a not uncommon issue with the BF types. Measure tram with it locked. You need to lock it to mill anyway because vibration can let the crank handle move if it's in the right position and then you end up slowly decending deeper as you are cutting.

One day I hope to make my own gib that's better but for now it will absolutely move around a little when locked, even if I tighten the gib till it stick-slips down the ways.

Great replies and videos from the list. 'photomankc' puts it well into perspective and I shall work at finding the best process to square up my mill. Realize nothing is perfect and a small degree of error is anticipated. Simply a matter of trial and error to find what is acceptable and what is not. Thanks guys!

Bill