How can I eliminate side play in PM940V quill?

[john.oliver35]

It could also be that the head is not perfectly trammed. If the spindle is extended, or table moved to a different position when drilling the hole to using the indicator, then any variation in tram will move the center of spindle wrt a workpiece mounted on the table.

 

[scattermaster]

Hey guys,
Thought I'd follow up and let u know my progress.
I tried drilling in steps and just ignored the shaking and the out of round and offset holes I got.
I only drilled up to 7/16" and that helped a whole lot. Then I followed with end mills. 1/2" and 5/8". They went in like cutting butter. Nice and smooth. After that I finished up with the boring head.
When I do the actual work there will already be 12mm holes, so I won't have to do any drilling at all.

I bought some 16mm removable dowel pins to use as go gauges. They are .0007" smaller in diameter than the pins that actually get used.
That way I get a chance to do a test fit. I can push the gauge pins in with my fingers, about 1/4" or so and that's about all. They tap all the way down with several light taps with a 16 oz ball peen. When it's like that, the real pins go in with 8 or 10 slightly harder taps. Perfect!
Oh, and i discovered how to set my cheap import boring head. I started mounting a mag base indicator right on the side of the head and use an indicator that has .0001" graduations. Now I can make very small changes reliably. That was a major confidence builder.
thx for your input.
Jim

 

[scattermaster]

I have ran Big Devlig jig boring machines and even a SIP. .002" is about the best you can hope for with twist drills and a reamer, especially if your doing it with a drill chuck. Many jacobs have that in runout!. Using a er collet tool holder will help as will higher end carbide drills but still you will have consistency issues due to the limitations of twist drills.

The boring really needs to be done over two or three passes to true it up. If you try do it all in one pass you will have run out issues. Maybe a quick change tool system like tts can have 2 different boring heads set up so your not adjusting them?

As far as play, if doing precision work on a machine with a less than ideal quill, lock it and move the knee on the critical passes.

Firebrick,
Unfortunately I didn't spring for a knee mill. I have the PM940V-PDF. It is like a mini mill but it's 1700 lbs.
I can't really lock the head because, 1 I'm constantly moving it up and down, and 2 I can't get it to consistently be in the same vertical place when I lock - unlock - and lock again. Sooo, I'm doing all of my work with it loose. It seems like its weight hanging on the dove tails keeps it lined up.
OH, and not using drill bit's at all, changed everything.

 

[mksj]

One of the major pitfalls of bench top mills, in particular with heavy heads is the gibs will wear more on the bottom over time and you will get some head nod and some movement with pressure. Without locking the Z axis in a fixed position and just using the weight of the head will most likely result in repeated work inaccuracies. My previous bench top mill which was around 800 lbs, the head sagged inward unless locked and accounted for at least a 0.001-0.0015" change in position when locked. It also caused some misalignment in trying to get perfectly parallel bores in multiple holes. Some people add a counterbalance system with cables or a chain with a weight on the back or a gas strut system to balance the head weight. You could look at a quick change TTS system if you need to switch out indicator/tooling.