Tramming a BP head

Monafly · Jun 22, 2006

Some time ago (and quite possibly some other resource) someone posted some info about tramming a BP head that included the distance to the various pivot points and thus how far to move the head to correct the measured deviation. I can't find that note and rather than reinvent the wheel, thought I'd ask again.

Toms Wheels · Jun 23, 2006

I read that post and tried it, found it way too slow. You lower the quill 3+ inches, set a DI on the table with the point horizontial against the side of the quill, zero the dial, then lower the knee 3" and read the dial, that reading X3= amount the quill is off. move head that amount to correct. Its cranking the knee up each time to remeasure that kills it for me.

my wheels don't slow me down, except when cranking the knee

JRIowa · Jun 24, 2006

Tom, that "assumes" that your knee travel is square with everything.

Tramming a BP takes practice. After you've done it a couple of thousand times, it's very fast. I never used any formulas, just moved the head. I don't think it takes me 15 minutes to check and move mine. You also have to remember, how close do I need to be. For some jobs, 0.001" is good enough. On others, you might want to be less than 0.0005".
JR

boozer · Jun 24, 2006

I have an S shaped 3/4" rod, and i mount a DI on the end of it, and turn the spindle, adjusting the head until i get the same reading all the way around.

Monafly · Jun 26, 2006

Tom-that's the method. I subsequently found my copy of the method. Don't know where I got it so can't give credit to the originator.
JR-isn't it a pretty valid assuption that knee travel is square? I've always thought that was supposed to be a given, just as X and Y are orthogonal. If these conditions aren't true it's got to be awfully hard to make anything come out right.
What I liked about the method is that it gives one a clue how MUCH to move the head to get it aligned. I don't like cranking the knee up and down either and this takes the trial and error and repeat out of the procedure.

"HOW TO QUICKLY TRAM A BRIDGEPORT MILL"

Extend the quill a little over 3" and lock it.
Place a 0-1" dial indicator so that it rests against the top of the quill.
Adjust the table to read a preload of 100 thousandths.
Crank the table down exactly 3" using the dial on the crank.
Multiply the reading times 3. (the indicator is now ~9" below the pivot point of the head and you read 1/3 of that)
Adjust the head in the opposite direction the indicator moved by your figured amount.
Check your work by doing it again, it should be dead on.
This works for both directions.

JRIowa · Jun 26, 2006

Monafly,
I've seen some BPs that, because of wear, have some spots that are terrible as far as repeating squareness.

I use an Indicol and a 312B InteRapid indicator. I just sweep the table. I've worked in a bunch of different shops and never seen anybody do it different. If I need to get real close, I've got a ground and lapped 12" dia. ring that I put on the table.
JR

The real Leigh · Jun 26, 2006

The procedure posted by monofly has one basic flaw: It assumes (and requires) that the head is already trammed correctly on the other axis.

The quill is a cylinder. If you expect to check it for squareness of rotation, i.e. tramming the X-axis, then it must already be vertical in the Y axis, otherwise the two points of measurement on the circumference of the quill will not be directly inline.

IMHO this method requires a lot more effort to achieve acceptable results than more traditional methods. Other folks might disagree

Like JR, I use an Interapid 312B on a tramming bar, thus:

Leigh

pepo · Jun 27, 2006

Sweep the table.Dont indicate the quill or crank the knee up and down.I can guarentee you that some knees dont crank up "straight. Indicate a hole in and then drop the knee 4 inches and reindicate. Some machines will be very close and some wont. If the knee isnt exactly 90 degrees you will see an error. When you tram the head the idea is to get the spindle exactly perpendicular to the ways. We use the top of the table because its supposed to be parellel to the ways. Sweep the table,it eliminates any errors. Why would you want to indicate the od of the quill in with the knee ways? Youre forgetting about that thing in between them,the table.

[ 06-27-2006, 03:29 AM: Message edited by: pepo ]

boozer · Jun 30, 2006

Pebo
That interesting but yet confusing, I always indicate the rotation of the quill, but now in in the process of restoring and old ram mill, and thinking about how im going to set it up before i resurface the table,
Do i rotate the quill and adjust to that, or should i set the quill by raising the knee?
If i set the quill by raising the knee, and then indicate the cross feed, and its different. Then what???
Im not in favor of resurfacing the table, but i really have no choice, ive seen welding benches in better shape than this mill.
My thought is indicate the quill, because more times than not im raising and lowering my quill for boring, and drilling than what i am raising and lowering the knee.

pepo · Jul 1, 2006

Boozer,Im not sure what you mean when you say "I always indicate the rotation of the quill." The quill doesnt rotate,the spindle rotates inside of the quill,the quill just goes up and down with the quill lever that you use when drilling a hole. If your goal is to get the head "trammed" or square to the ways but you cant because the table is too hacked up to sweep I would suggest that you set it as good as you can with any method you see fit. You are there looking at it and Im not. Resurfacing the table with a cutter is not the best way to do it,Im sure you know this. If you decide to go ahead dont try to use a flycutter or anything too large in diameter. This will only magnify any error in the head tram. Id use a 1 inch or 1 1/4 carbide end mill and run all over with it. It wont be as pretty as the flycutter but it will be truer to the ways. Im sure you realize that you cant recut the whole table no matter what you use,not enough travel.

The real Leigh · Jul 1, 2006

Im not in favor of resurfacing the table, but i really have no choice, ive seen welding benches in better shape than this mill.

Hi Boozer,

If the table is in bad shape, have it reground. There's no way you can resurface it on the machine with any reasonable accuracy.

Leigh

boozer · Jul 1, 2006

The more i think about it, when i get the mill back together, i probabbly wont bother with the table, 99% of my work is done in a vice anyway, and resurfacing it, would really only be cosmetic.

pepo · Jul 1, 2006

You could always screw a plate on the table with counterbored cap screws and put a pattern of tapped holes in it. Make it a size that you can fly cut if you need to. It would save time and give you some choices in the future.

harrytm · Jul 2, 2006

JrIowa pretty much nailed it when he said"You also have to remember, how close do I need to be."

Getting within .001 on a Bridgeport can be done.But getting closer is a task that will be done by much diligence and will be closer than a Bridgeport was ever designed to be.

Sometimes you just have to sit back and look at the real world and think about what .001" really is.

I don't think that (other than size) you really want to be trying to get any closer in location or squareness than that.

I'm sure many will disagree with me as in the past, but from my 28 yrs. of experience, if you want it that close, you better be going to a jig bore or Wire EDM or jig grinder.

Again, just my 2 cents worth.

harrytm · Jul 2, 2006

JrIowa pretty much nailed it when he said"You also have to remember, how close do I need to be."

Getting within .001 on a Bridgeport can be done.But getting closer is a task that will be done by much diligence and will be closer than a Bridgeport was ever designed to be.

Sometimes you just have to sit back and look at the real world and think about what .001" really is.

I don't think that (other than size) you really want to be trying to get any closer in location or squareness than that.

I'm sure many will disagree with me as in the past, but from my 28 yrs. of experience, if you want it that close, you better be going to a jig bore or Wire EDM or jig grinder.

Again, just my 2 cents worth.

Larry Condon · Jul 6, 2006

I have to agree with JrIowa and harrytm.

Larry

Jackmo · Jul 6, 2006

If the table is too damaged to sweep with an indicator use 4 1" gage blocks on the table set indicator on one then sweep to all the others this should give you a good average.

DaveC · Jul 8, 2006

"If the table is too damaged to sweep with an indicator use 4 1" gage blocks on the table set indicator on one then sweep to all the others this should give you a good average."

I use a single 1-2-3 block, moving it around to follow the indicator as I sweep the table. Also, you can use a stone to remove the major bumps from the table.

DC

afmcorp · Jul 17, 2006

harrytm

i understand what harrytm is saying. i use a double gage system, the ol best test and a plunger type DG. i've worked for an hour or more trying to get my head trammed to not make a dragging tool mark when using a standard 4fl cc niagara type end mill and forget about it. i have had to give it up. i can get a better finish when using an indexable endmill where the corners are rounded and overlap on a pass by. but being anal i would just like my customers to see a nicer finish when i use a standard type end mill.

JRIowa · Jul 18, 2006

OK, I had 5 minutes last night, so I took a picture. Here's what I use to tram a BP.

That's an Indicol model 178 clamped to the quill. I use one because you don't have to remove a cutter to indicate. They save a lot of time and are worth every penny they get for one. Available at MSC or ENCO.

The indicator is an InterRapid 312B. IMO, the best indicator for the money (I've got 3). Auto reverse, and 0.060" travel. I used to have "Last words" and Gems, but no more.

The bearing race came from an amonia compressor and has been checked for flatness and parallel.

I try never to have the quill extended by more than 3 inches when I tram. The quill, table, saddle, and knee are all locked. I always do side-to-side first. If you have to loosen the 4 front bolts to move side-to-side, the head will usually nod anyway. If the head is off very much, you need to repeat the steps.
JR
JR

Tramming a BP head

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