Horizontal borer setup for table rotation

Hey everyone,
Iv got a job to do on my horizontal borer that involves boring either end of a long pipe that is welded to a larger assembly.

The job has to be bored from one side and then the table rotated 180 degrees to bore the other side.
The pipe will be held in v blocks.

My question is, firstly how do you guys find centre of the table? My borer has a 90mm hole in the middle of the table.

Secondly how to you get perfect 180 degrees and back to 0 again?
The crank for the table is graduated in minutes, but seems near impossible to get a perfect 180. I’m getting on average .30mm or 12 thou runout when I get to 180.

Is there a procedure for aligning parts on the table centreline?

I’m sure one of the experienced members on here will be able to point me in the right direction.

Cheers






Sent from my iPhone using Tapatalk

If it's close tolerance work I wouldn't rely on table settings etc etc I'd be clocking from known datums etc etc

This guys vids are (IMHO) excellent and show all sorts of borer work including setting up YouTube

Bryce.R said:

Hey everyone,
Iv got a job to do on my horizontal borer that involves boring either end of a long pipe that is welded to a larger assembly.

The job has to be bored from one side and then the table rotated 180 degrees to bore the other side.
The pipe will be held in v blocks.

My question is, firstly how do you guys find centre of the table? My borer has a 90mm hole in the middle of the table.

Secondly how to you get perfect 180 degrees and back to 0 again?
The crank for the table is graduated in minutes, but seems near impossible to get a perfect 180. I’m getting on average .30mm or 12 thou runout when I get to 180.

Is there a procedure for aligning parts on the table centreline?

I’m sure one of the experienced members on here will be able to point me in the right direction.

Cheers






Sent from my iPhone using Tapatalk

Click to expand...

.
grid shift adjustment. normally put a test bar in the spindle with indicator and magnetic base on the rotary table and touching test bar side at runout average indicator is zeroed. move in Z til clear and the rotate table and move in Z and read test bar. X axis is adjusted as needed usually by parameters on a cnc or the work offset zero is adjusted or the common work offset is adjusted.
.
Y is check if you got 2.0000 dia test bar and go to Y2.0000 than the test bar side should be 1.0000 off the table checking with a gage block remember measure at test bar runout average
.
Z is checked using indicator but you need to know test bar length if you zeroed indicator to side than at 90 degree table rotation it will show a 1.0000 difference (if 2.0000 dia test bar) from the test bar length. usually use a tool presetter (different machine) to measure test bar length
.
B axis or rotary table zero check usually indicating front of the pallet is parallel to X axis
.
is rotary table or any of the slides has backlash you might need to always move from the same direction
.
remember if you got tram error and or column is leaning than the longer the test bar in spindle and what height above table you measure the grid shift can be different. and if you use many pallets or tables on the same machine each pallet/table can vary from one to another. tram error if indicator set up on test bar side as you move in Z the indicator will vary. if you see more than a .0010" per 10" change along the test bar you got a problem. remember to measure at test bar runout average. its rarely perfect. hard to describe
.
typically i check B axis everyday and check XYZB monthly on a horizontal cnc. some machines with backlash or zero return repeating problems might have problems repeating. that if every time you run zero return or home the machine the grid shift might be different. thats often a sign of a mechanical problem. obviously if you record measurements you will see if day to day and month to month if things are holding steady or always changing. i keep records so i can look up adjustments going back months and years
.
i can then see if pallet 5 and pallet 10 always gives a B axis difference of .0005" per 28" more clockwise on pallet 5 compared to pallet 10. thus if machine uses 26 different pallets might try to adjust B to the average of the 26 different pallets. hard to describe. just saying might not be able to get .0002" per 40" grid shift if each pallet varies more than that. and can easily get different numbers if you measure 20" above the table then measure at 40" above the table. that is the machine alignment is rarely perfect. if you had a granite square on the table you can measure its not moving perfectly at 90 degree angles X to Y and Z. you can also indicate table top to see if its parallel to Z. pallet can be leaning (sitting on X axis). or column that Z moves on can be leaning or Y travel can be leaning. hard to describe
.
other thing to be aware of is at high rpm and very low rpm you might find the spindle picks up and shifts to side .0002" to .0004" due to oil moving in the spindle bearings, hard to describe but if holding a .0002" tolerance usually you start to notice it

How long is the part compared to your table size? What’s the part doing exactly?

How are you checking the runout currently?

Positioning the part central about the table is not required. The choices I’ve made are either indicating the table beforehand, and aligning part true to Z axis, or indicating part true to Z axis, and clamping a piece of bright mild steel on the table, indicating it true to the relevant axis to use as a reference. I found it easier to use the reference clamped on the table as you can turn that table to set the job with the job clamped. If you can indicate the part once the table is turned it won’t be required, but being pipe it won’t happen. That way you can dial in either the table or the bright mild steel reference to ensure it’s correct. To align each end it will depend on how long the part is. One way is to zero your readout or scale for the x axis when the spindle is on center of table rotation. Typically this is done with the quill stuck out and a mag base indicator on the table, and you swing the table around indicating the quill until it’s central. My preferred way would be to use a finger dial in the spindle and indicate the table edges with the quill up short but the machine I used to run wouldn’t take the spindle down that low. That requires some leg work anyway to verify the table edges are central to the rotation, and indicate the table square so it’s correct.

Having the quill out far enough to reach the center of the table, if you can, assumes the quill is true to the z axis, so check that also. Why I prefer a short quill length.

Once that’s set and the job is true, set and bore your hole, noting the x axis position set over from center, and turn the table, shift the x axis the same amount off center, but the other side, and you should be ok.

Depending on how long the part is there are better ways. I never liked the method I describe but sometimes it’s whats required. I would usually double check by other means depending on the part. The machine I used to run was well beyond it’s best days.

Limy sami’s suggestion of datums is a good one and how the old fella I used to work with did things where he used to work, different class of work though. How and where depends of your parts requirements.