What Do You Indicate Off Of When Tramming Mill

[dmartin]

I'm sure this has been discussed before but I'm asking anyway. The thread about getting lucky when installing the mill vice prompted this question. I didn't want to hijack that thread so I'm asking here.
I was going to post in that thread about the time I had been using the mill with the head tilted and when returning it to vertical I got lucky and was within less than a half thousandth on the first try and was happy with that.
The question I have is what do you use to indicate off of when you tram the mill? I always sweep the top of the back vice jaw after running a stone across it to make sure there are no high spots.

I had been thinking about starting to use a parallel that is higher than the vise jaw but then again if the jaw is parallel and tight against the bottom of the vise I guess it is really doing the same as if I had clamped a parallel in the vise. So anyway, does anyone have a different way of tramming and if so what is the procedure that you use. While typing this question it occurred to me that since I recently got a surface plate it would probably be a good idea to double check the vise jaw to make sure that it is parallel. Other than that are there any other good practices to use when tramming? Thanks.

Dwight

[Paul Alciatore]

I sweep across the table itself. But then, I don't make a habit of keeping the vise permanently mounted on it.

I have seen rings that stand over the vise with their legs resting on the table used for this. I think they are sold by some of the tool suppliers. As to how good they are, I do not know.

[BCRider]

What you're describing is tramming the vise itself and not the mill in general. For tramming my vise I just reach down at an angle and directly run the pointer along the face of the fixed jaw a short way down from the top edge. The reading I get is reduced by the degree of the angle but we're just looking for zero anyway. I only go in about 10 to 15 thou so the tip can ride into and back up at the "V" in the middle of the jaw.

Tramming the mill table or head itself is a whole other issue. It involves multiple steps to first prove that the table is true to the ways for thickness and once confirmed to be "true" you can then use the upper table surface to tram the head tilt and nod.

[Mark Rand]

I use a ventilated car brake disk. They are surprisingly flat (maybe not so surprising, since they tend to be faced with a double sided tool post). The one I got is flat to less than a tenth, and rests on the table while I sweep the indicator around.)

[dmartin]

I wasn't clear in the my post that I know that in the other thread he was talking about the vice being true with the X axis and in this thread I am referring to the head being 90 deg or square to the vice top, or it being level.
I don't move the vice unless needed and then always check by sweeping across The FACE of the back Jaw before and after tightening it to be sure it is parallel to the X axis.

For the question I'm talking about sweeping the TOP of the vice jaw and was wondering if that is the best place to be checking to be sure the head is square and not tilted one way or the other.
I realize that there is more that comes into play with the table vs vice and my thought is that it is best to sweep the vice jaw but wanted to know if generally that would be considered the best practice if the table had been checked at some point in the past and it was acceptable. Thanks.

Dwight

[MichaelP]

I use large bearing races to tram the table or my Kurt vise. For the Kurt I place the race on the bottom between the jaws where the parallels normally rest. Sometimes, I use the above mentioned 3-leg tramming device standing above the vise on the table.

But, first, you should test your vise on a surface plate. Make sure the surface you're tramming to is parallel to the base (in this case, to the surface plate the vise is rested on). In my case, I bought my Kurt second hand, checked it, and had to grind the base to make it parallel to the surface the parallels rest on (put the vise upside down on parallels and grind the bottom on a surface grinder).

[A.K. Boomer]

If my tables true then so is my vice as my vise is true and always remains the same for height,

so I just true the table - and the trick to truing the table without having to use anything else (and avoid compound errors i might add) is to just set the depth of the indicator to .005" max, that way i can swing it around pretty quick past the tables chamfered lockdown grooves without even worrying about it catching or snagging or throwing it off, just a mild bump and then it's back to normal no big whoop...

[BCRider]

I wasn't clear in the my post that I know that in the other thread he was talking about the vice being true with the X axis and in this thread I am referring to the head being 90 deg or square to the vice top, or it being level.
I don't move the vice unless needed and then always check by sweeping across The FACE of the back Jaw before and after tightening it to be sure it is parallel to the X axis.

For the question I'm talking about sweeping the TOP of the vice jaw and was wondering if that is the best place to be checking to be sure the head is square and not tilted one way or the other.
I realize that there is more that comes into play with the table vs vice and my thought is that it is best to sweep the vice jaw but wanted to know if generally that would be considered the best practice if the table had been checked at some point in the past and it was acceptable. Thanks.

Dwight

Don't use the vise. If it's out then your tram will be out. Always sweep the table. If you want to check the top of the vise later on that's another topic.

But as I mentioned above this is sort of a two step thing. FIRST you want to ensure that the top of the table travels "flat" to the travel of the ways. Do do that a dial or test gauge in the quill is set up to read the table. This is the table not the head. Leave the head alone and move the table under the single point both side to side and in then out and look for any variation. It should be very little if any at all. You are checking the trueness of the table here and how parallel the top of the table is to the movement of the table ways. If it's out by much that indicates a bent table or a tapered table. There was a recent thread on one of the little Seig mills that had something like an .08" taper from end to end. The writer of that thread was going back to see if the vendor would work with him to get a replacement. So it CAN happen and it SHOULD be checked.

So assuming your table passes muster with only a couple of thou or less of variation through the whole range of travel. Next up would be to set up a gauge on an arm to sweep the table. But first draw a circle the size of the one you will use to sweep the table. Using that single point gauge in the collet check for any high or low spots in the four points where you will be focusing your sweep measurements and mark any significant differences. You'll add or subtract these from the sweep readings to aid you with setting the tilt and nod to a finer degree. So you may want to pick "0" to be the lowest point and the others all are either "0" as well or some value you subtract from the swept gauge readings.

This is a one time thing. Once you've proven a spot, ideally in the middle of the table's travel, make a diagram of the highs and lows at the 12, 3, 6 and 9 o'clock positions of the circle for future use. That's if you have any significant steps that are worth noting. If it's a tenth or two you might not want to bother. Or perhaps you're OCD enough to make the map. And if you're that far along you might even put a center punch spot at the middle of said circle that you can use to return to each time. If you center punch mark the table stone or file away the raised metal of course.

After this you at least know that your table is true to the travel axis of the ways and that the head is true to the table.... or at least the average if there's wear or some slight slanting of the able. At that point if you want to tram the top of the vise that's fine if it's something you need. But you would not move the head of the mill if it's out. Instead you would either live with it or send the vise out for surface grinding to make the top of the jaws parallel to the base which sits on the known to be true table surface.

Basically if you want a nice true and square house then the care starts with the foundation. If the foundation is out then the whole house is out as well. And for the mill the foundation is the table ways. The table's top surface is the surface of the first floor and the body of the table is the structure between the foundation and actual floor The vise is the walls and second story floor. And that relies fully on doing a good job on the other stuff below.

[Mcgyver]

agree with BC, best is take the vise off and tram the table. I use large granite parallel but any parallel will work, within reason the longer the better. I get the x on then check, using a dti with the needle pointing away from the direction rotation so it rides up on the parallel easily. After the x, I do y, snug things, go back to x, fix, go to the y, tighten and check one more time.

A disk would be easier, I'd use it if I had it, but my parallel is over a foot long; longer gives better accuracy or least makes things more pronounced. Obviously a disk is a source of error, bit of dirt between the table or the planes not being perfectly parallel....but I'd still like one, error is imaginable and I like the convenience. The parallel also could introduce some error, but its a very accurate bit of precision so I'm not worried about it. End of the day, its milling so you can't get too carried away I suppose.

[Lew Hartswick]

First off you said the "Mill" and then start to talk about the "Vise". Which are you really talking about???
...lew...

[3 Phase Lightbulb]

The first thing I do before I do any tramming is remove the vise and clean the table with whatever I have. I then take a fine machinist stone and knock off anything that might be protruding off the table. Then I clamp a 0.001 indicator in the spindle with a collet. The indicator has an arm with a radius of about 5-6" so I can turn the indicator in the spindle and sweep a ~12" diameter around the spindle. I tram the head so all 360 positions read the same value with the 0.001 indicator (at least where it touches the table, and doesn't miss the slots or edges). I then pull out the 0.001 indicator and replace with the 0.0001 indicator and again adjust head until all 360 positions average out to the same.

Then I mount a vise and align the back jaw with 0.001 then redo with 0.0001 indicator in X. Then I confirm Z is parallel which it always has been. I guess I'd shim the vise if it wasn't but I guess I've always been lucky as my Kurt has also been perfectly parallel with the table.

[CCWKen]

Rule 1: If you're working off the table, tram the mill to the table.

Rule 2: If you're working off a vise, tram the mill to the vise bed. If you have a Kurt, use rule 1.

[dmartin]

Wow, thank you guys for all the info. Due to some back problems that at times are quite severe I don't lift the vice off of the table any more. I can do it but will usually pay for it for the next few days so I don't risk it any more.
I do have a bearing race that is 8 inches in diameter and about 5 years ago soon after acquiring the new mill I did tram the head to the table. I then checked the tram to the vice and was happy with the results from the very beginning of owning the mill and vice. I don't remember the exact readings and though I am not as particular as some I am pretty picky, so I'm sure it had to be a fair amount less than 1 thousandths out, I'm sure I wouldn't have accepted anything near a whole thousandths. I also have trammed the table and vice the same way probably 10 times since with good results. I use the bearing race for the table and the fixed vice jaw to check the vice.

I guess I feel a bit guilty due to having only trammed it to the vice the last time I trammed it after having tilted the head. FYI the mill is a Grizzly G0730 with an 8"x30" table and Grizzly 5" premium vice. I only mention the "Premium" part because it is supposedly better with tight tolerances. I have milled a few parts since then, some being milled on 2 sides that were 90 deg apart and have had no problems. I double checked the parts with my good Starrett micrometer at several points because I had only trammed it to the vice and wanted to reassure myself that it was fine. I can use the bearing race to tram it to the table and then verify the vice as I have done in the past but it just takes longer. I use the engine crane and it's a tight fit but if I screw up the back by not using it I do pay for it over the next few days.

I was hoping someone here that has been using a milling machine for 40 years would say, yes if you trust the vice and table from past experience and only the head was moved it will be fine don't worry about it. I do overthink details sometimes but if I could be overlooking something that could cause problems I don't want to do that. Anyway thanks for all of the good information and I will probably go ahead and redo it and at a minimum I will start using the bottom of the vice between the jaws instead of the top of the fixed vice jaw. Thanks again for all the good information and have a good one. Oh, 3 Phase Lightbulb, you really use a tenths indicator? Wow kudos to you I figured that as busy as I think you are, you apparently have the patience required when it is needed, keep up the good work.

Dwight

[CalM]

Rule 1: If you're working off the table, tram the mill to the table.

Rule 2: If you're working off a vise, tram the mill to the vise bed. If you have a Kurt, use rule 1.

YES!

I used to clear the table and use precision stock to span the T-slots for the indicator sweep.
Anymore, I keep a pair of Kurt 5 inch vises on the table that have been thoroughly "qualified".

Now I sweep the bases of the two vises. With never a problem.

[Paul Alciatore]

Nothing is ever mounted to the TOP of the vise. So, IMHO, that is not what you want to tram the mill to. Now, the top of your vise may be 100% true, but do you know that? I doubt that the top surface of any milling vise is even specified.

The sequence is:

1. The top of the table should be parallel to the ways/slides.

2. The bottom of the vise should be a good, FLAT reference surface.

3. The top of the vise's saddle, which is what a part or your parallels that support your part are mounted on, should be parallel to the vise's bottom.

Due to the buildup of tolerances, it is not best practice to use any part of the vise for tramming the mill head. Number 1 above should be checked when the mill is new and at intervals after use. But that should be a "given" and should not have to be checked on a daily basis or even when the head is rotated and then returned to vertical.

As I said above, you should tram the head on the TABLE's top surface. And, as I said above, that is difficult if you keep the vise mounted all the time.

So, I suggested one of these:



It allows you to tram to the table's top while the vise is mounted on that table.