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View Full Version : Tramming a ShopMaster Elderado Bridgemill



TeaMan
02-09-2013, 03:58 PM
I have read through many threads on tramming and think I have a general understanding. I checked my ShopMaster Elderado Bridgemill today before I take on the task of milling my tool holder for my Lathe down to fit the lathe properly. I need to remove about 1/4" to achieve center.

Anyway on to the tramming. My machine doesn't have knuckles and adjustment screws as I have seen on other machines online so easy isn't in the equation. I have four mounting bolts on the lower part of the arm that can be loosened and I suspect shims can be inserted to achieve a proper tram. I'm wondering if anyone has trammed a machine such as this and how you went about it. Second I'm wondering where a person finds shim stock to do the shimming. And third, is there a simple mathematical way to calculate the amount of shim stock needed in either direction to get it into tram.

My measurement putting the dial indicator in a 1/2" collet was .030 in the X direction, making it .015 in the Y direction. I would think this is bad enough to want to correct it. The dial indicator was slightly loose in the collet, but it tightened with no problems.

I'm thinking this will be a slightly big job since I need to loosen mounting bolts and add shims, so any advise from you experienced guys is greatly appreciated.

Thanks
TeaMan

TeaMan
02-15-2013, 11:19 AM
How good is good enough? I know this is a somewhat loaded question and will hear how precise do you want to be, but I know those with more experience have a good feel for how good is good enough. I have a difficult machine to tram. I have four mounting bolts on a quadralift, pretty much 4 shafts the mill head or Bridge on my machine ride up and down on for gross movement. The mill itself has Z axis movement of about 6" that is more fine. Anyway the quadralift has about a 1" plate of steel the 4 shafts mount on that is bolted down to the cast body of the machine. I have to loosen the 4 bolts and shim under the plate to move the tram both X and Y. I spent about 4 hours last night and went from .030 in the X and .015 in the Y to under .001 in the X and about .0015 in the Y. It seemed that every time I loosened the bolts and tried a shim somewhere else or a very small addition to shims I already had, it got worse not better.

I'm considering building myself a tramming fixture to mount on each side with 4 fine bolts and a nut similar to a Gib screw to have the quadralift plate ride on that I can have simpler adjustments than the shims and hopefully much less frustration. But until I get there, any help with the question.

TeaMan

danlb
02-15-2013, 03:02 PM
The answer is based on a few things.

First is that you need to say how far apart your measurements are. Is that .001 in one inch travel (terrible) or .001 when sweeping a 12 inch circle? .001 over 12 inches is pretty good. It sounds almost like you might be measuring from one end of the table to the other.

The tram will impact how deep the marks will be when overlapping passes of the tool, so the larger the tool diameter the more impact the tram will have.


Dan

TeaMan
02-15-2013, 03:25 PM
Thanks Dan, If I'm not mistaken, my table is 8" wide, and that was near the very outside of the table in both directions. Makes it about an 8" diameter circle, pretty close anyway. I guess I could put the collet over the left edge of the table and use the Y as the main dimension. I think I could get almost a 16" circle. Maybe that would be easier. I definitely need a better way to adjust it though. Going to get some metal tonight to build a fixture for both sides. Trick will be to find a fine threaded 1/2" bolt around here somewhere.

TeaMan

mixdenny
02-15-2013, 04:18 PM
You need to tram the Shoptask in two stages. First is to make sure the head travels straight up and down on the 4 rods. You do indeed shim under the bottom mounting plate to accomplish this. Measure with an indicator on the mill head, with the indicator against a vertical surface. Do the X and Y planes.

When you are satisfied with that, move on to tramming the head. Mount an indicator on the spindle bottom or in the chuck. Indicate against the table. Sweep the indicator around in a circle as large as the table is wide (lift the tip carefully over the T-slots). The mill head is secured in the Quadra lift with several bolts, these need to be loosened and the head tapped into place and retightened. This is not a precise method and can take quite a while. I needed to enlarge some of the bolt holes. Shims can help hold things secure.

I found that my millhead rocks a bit when the lift travels up and down. If your does, mark the leadscrew so that you can return it to the same orientation for best accuracy.

Dennis

TeaMan
02-16-2013, 10:48 AM
You need to tram the Shoptask in two stages. First is to make sure the head travels straight up and down on the 4 rods. You do indeed shim under the bottom mounting plate to accomplish this. Measure with an indicator on the mill head, with the indicator against a vertical surface. Do the X and Y planes.


Dennis

Thanks Dennis, PM sent for more detailed info. Thanks again. Teaman

mixdenny
02-16-2013, 11:28 AM
I'll attach some photos and a bit more description on tramming the Bridgemill. First, let's determine how the Shoptask is different. On the Bridgemill the millhead is bolted into a stage that travels up and down on four rods instead of a simple round or square column like a mill/drill. The stage has four 6" long, close fitting, DOM tubes that act as bushings, they ride on each rod. These tubes run between the upper and lower plates of the stage. The whole stage/tube thing is one welded assembly, the millhead fits between the upper and lower plate of the stage. Shoptask calls this assembly a Quadralift because of the four rods. It was an option on the Eldorado, and became standard on the Bridgemill.

Thus, there are two places to tram. One is the addition of shims under the bottom plate that holds the entire Quadrlift assembly. This tilts the Quadralift in the X and Y planes and is used to make the assembly vertical, so the millhead/stage travels straight up and down. Do this first. One photo shows this setup, a dial indicator rides on a vertical surface (I used a angle plate ground on all edges) as the stage is moved up and down. Measure the X and Y separately

The second is in between the actual millhead and the stage that rides up and down the four rods. On mine (there are later variations), the millhead has four bolts through the lower plate of the stage, and one through the upper plate of the stage. By loosening these bolts and twisting/tilting the millhead, and placing shims to help hold it, the circular tramming is accomplished.

There is no precise way to do this, I had to enlarge some of the holes and even used one of those small jacks to force the millhead into place while the bolts were tightened. Tightening sequence had a huge effect.

Now, the Bridgemill has one more feature. The overarm rides up and down against a vertical column at the tailstock end of the lathe bed. A clamp secures the overarm to the column, and when this clamp is tightened, it can pull the millhead sideways and disturb the tramming. After the Quadralift is vertically trammed in the X and Y planes, you must check and address this clamp.

The column needs to be adjusted so it is vertical and does not influence the overarm. And the overarm must ride against the column with zero gap or else tightening the clamp will move things. On mine (I made my own Bridgemill setup), I needed a special shim between the overarm and the column. This shim thickness was determined with feeler gauges and is tapered in two planes, i.e., the shim is different thicknesses at each of the four corners.

All final measurments during tramming should be done with the clamp tightened.

Dennis

P.S. Hmm, seems I cannot add attachments according to my posting permissions. How can I add a photo? Does the moderator need to change my permissions?

TeaMan
02-16-2013, 11:49 AM
Dennis, I had to create a photobucket account, put the pictures there and use the link button to attach the link to the photo's.

This post explains how. I had the same problem with permissions, this is another method someone helped me with. It's the second sticky under general forums.

http://bbs.homeshopmachinist.net/threads/29277-Posting-pictures-with-photobucket

TeaMan

mixdenny
02-16-2013, 12:08 PM
I tried to get a Photobucket account, but when I slide the arrow to verify I am human, it does not accept it. I contacted the moderator to see if my posting permissions can be changed.

Dennis

TeaMan
02-16-2013, 02:42 PM
Thanks, let me know when you get it figured out. I'd like to know how to just imbed a picture. It would be much convenient than using photobucket. I had problems gettting my photobucket account too. Same issue, can't remember what the final solution was anymore. Sucks to get old, memory goes fast...