Thread: A Simple Tramming Ring for the Mill.

Nice work BT,
I would have to say the ring may have flexed at the point of cut. I always find a nice sharp HSS cutter works better in situations when the lathe/work is just not rigid enough for carbide.

As nice as it is to make one, a new brake disk makes a great tramming ring.....

Originally Posted by Anorak Bob

Why the slow speed while boring worked has me stumped. I imagine a more rigid bar would allow for boring at higher speeds.

...

The ring is out of whack thickness ( height) wise by 0.0003". Shabby chuck work assisted maybe by distortion when clamping a ring at 4 points?

I don't know if it would be feasible to try and scrape the error off. I could end up tail chasing. I don't know what I should expect to pay to have the ring ground. Any suggestions?

BT

I bought a diameter 20mm boring bar to try and minimise boring chatter myself. I end up taking 1mm+ DOC cuts (with no chatter) because I can.The rigidity of a boring bar is related to the diameter^3 I think, so it pays to use as heavy as you can. Deflection due to overhang has a similar relationship to bar length (^3 or ^4 from memory), so making your overhang as little as possible works wonders too.

Bob, is your mill table better than 0.0003" flat? Even if the ring was perfectly parallel, it will still sit on 3 high points on the table, which could change depending on what you have been doing. I find on my mill even when I have it trammed in (I use the table surface) the cutter patterns on the work will change if going L to R rather than R to L. On that basis tramming to within 3 tenths is fine.

Michael

Hi BT,
Looks like the Hercus is about maxed out and I cant find a pic of an AL-330.
Can you get on a lathe that lets you face both sides in one setting?

Blue it up and have a go, you can always grind it after.

Stuart

Originally Posted by Anorak Bob

The ring is out of whack thickness ( height) wise by 0.0003". Shabby chuck work assisted maybe by distortion when clamping a ring at 4 points?

I had a related problem while squaring off a 95 ID x 3 mm thickness ally tube in a 4 jaw chuck lathe. I held the tube under compression while squaring the ends.

Then I turned up 3, 12 mm thick discs to fit inside the tube and found they were binding on four symmetrically arranged places on the tube equivalent to the chuck jaw spacing. I didn't think I was that aggressive with the chuck key but obviously I was.

Bob,
If your happy enough to ship it, I know a bloke that is doing a lot of surface grinding lately and would be happy to put on for you .......

-Josh

Originally Posted by Brobdingnagian

Bob,
If your happy enough to ship it, I know a bloke that is doing a lot of surface grinding lately and would be happy to put on for you .......

-Josh

Definitely happy enough to ship it Josh. Thank you for your kind offer.

There will be some thinking quite correctly "you lazy bastard". A concern I have is that while I could scrape one side I could be left with the other side being slightly convex or concave or with four high or low spots where jaw induced distortion might have occurred. If I scraped both sides the indicator needle will jump all over the place.

The problem with the existing error and the universal table is that the ring can neutralise any minor ( ok, .0003" is FA ) by being rotated. Having the ring's faces parallel will remove one variable when tramming both the table and the head. Sure the mill is 50 years old and there is wear in the ways and undoubtedly some surface wear on the table top. Might be a while before I have the confidence to tackle making that wear good.

BT

You lazy bastard
You're assuming Josh's grinder is not only smooth(which is is) but flat and parallel.....I'd be asking for a calibration certificate

Toolpost grinder with the wheel dressed by a diamond on the faceplate....that would remove convex concave issues.......postage is starting to sound cheap.

When I get lazy with tram the cut isnt normally the issue, its the movement you get in X and Y when you use Z..whos the lazy bastard now?

Stuart

Certification. I would need access to a laser inferometer to do that... Last time I checked, after skimming the chuck there was a ~5 micron maximum deviation in parallel across the chuck (600mmx300mm).


Just to clarify what the surface grinder does. It would make the top and bottom of the ring parallel, it would not be capable of making it flat to that level as well ( using the mag will pull it flat against the chuck and any other work holding method I can think off would add more error.) so you would still have to break out the scraper to make one side flat first. And then we get into the problem of stress reliving the ring which you would want to do first.

The nice thing about a ground finish is that it is excellent to gauge off.

-J

Hi

Instead of using these fancy, and somewhat expensive gadgets .Why not just mill a flat on some scrap and watch for the cross-hatch pattern on the piece . Or am I on the wrong track again

Originally Posted by Brobdingnagian

Just to clarify what the surface grinder does. It would make the top and bottom of the ring parallel, it would not be capable of making it flat to that level as well ( using the mag will pull it flat against the chuck and any other work holding method I can think off would add more error.) so you would still have to break out the scraper to make one side flat first.

-J

Could you cast the ring into a wax or resin nest (set on a steel plate) that would let you grind one side 'flat' before removing it and using the flat side on the mag table to get the other side parallel? Mind you, as 5 microns is around 2 tenths, will it really be much better?

Michael

Originally Posted by morrisman

Hi

Instead of using these fancy, and somewhat expensive gadgets .Why not just mill a flat on some scrap and watch for the cross-hatch pattern on the piece . Or am I on the wrong track again

Mike,

The ring facilitates the use of the fancy, somewhat expensive gadgets. I could use a DTI and a mirror and leave the Centricator in it's nice little box but there wouldn't be much point. Especially after all the rooting around to safely mount it in the spindle.

The table on the mill in the photo is adjustable, it tilts on the XYZ axes. Whilst your suggested method of tramming would work, it would mean that the spindle was at right angles to the X and Y. Well and good on a fixed table but not on a table that could be out of whack on any or all of the axes.


Stu, Michael, Josh and Ewan,

I blued up my boy's version of a surface plate and the results show a whisker of distortion. There's continuous contact around the inner surface but a couple of non contact areas opposite one another on the outside. Hopefully not enough non contact to cause a problem with the mag chuck. Fingers crossed.

The concentric lines are interesting. That surface looked smooth. Maybe some harmonic thing?

BT

004 (Large).JPG

that was 5 micron across the entire table. smaller foot print would be better than 5 micron. how much better... hard to tell without doing a map.

Originally Posted by Anorak Bob

Mike,

The ring facilitates the use of the fancy, somewhat expensive gadgets. I could use a DTI and a mirror and leave the Centricator in it's nice little box but there wouldn't be much point. Especially after all the rooting around to safely mount it in the spindle.

The table on the mill in the photo is adjustable, it tilts on the XYZ axes. Whilst your suggested method of tramming would work, it would mean that the spindle was at right angles to the X and Y. Well and good on a fixed table but not on a table that could be out of whack on any or all of the axes.


Stu, Michael, Josh and Ewan,

I blued up my boy's version of a surface plate and the results show a whisker of distortion. There's continuous contact around the inner surface but a couple of non contact areas opposite one another on the outside. Hopefully not enough non contact to cause a problem with the mag chuck. Fingers crossed.

The concentric lines are interesting. That surface looked smooth. Maybe some harmonic thing?

BT

004 (Large).JPG

Is the distance between the concentric rings the same as the pitch on your lead screw?

Originally Posted by Brobdingnagian

Is the distance between the concentric rings the same as the pitch on your lead screw?

Yep. 0.125"