Level The Table?

[gubni]

Saturday I bought a 1979 JET-16. I am pretty excited about learning how to use it. The primary reason I got it is that I sell disc brake kits and sometimes I need to make a brake pad thinner. That should be pretty easy with a mill.

My problem is as I cut about 2" wide 8" long the left rear corner is about .05 deeper than the right front. The reason I bought a mill is that I wanted it exact from one side to the other.

I'm not sure if anyone can help unless you have the same machine, but I thought I would ask.

 

[Chipper5783]

Have you trammed the head? I don't know if there are any adjustments (looks like a mill drill)? Even if it does not, you still need to do a sweep so you know if it is out. Out of whack by 0.05" front to back is a lot (sort of a twist to it - you have something wrong). You may have to unbolt the column and re-align everything. In the mean time, you can shim your work.

Also, you won't get it "exact". You work to a tolerance (fancy word for "good enough"). You should have no trouble getting to ±0.0005" (still not exact, but probably good enough).

 

[gubni]

Have you trammed the head? -- Since I am not familiar with that term, then no, lol

I don't know if there are any adjustments (looks like a mill drill)? -- Yes it is

Even if it does not, you still need to do a sweep so you know if it is out. -- I did sweep the floor before before I set it up, but I have a feeling you are referring to something else.

Out of whack by 0.05" front to back is a lot (sort of a twist to it - you have something wrong). -- Well mostly right to left over 8" with a little front to back.

You may have to unbolt the column and re-align everything. -- Sounds like one heck of a job.

Also, you won't get it "exact". You work to a tolerance (fancy word for "good enough"). You should have no trouble getting to ±0.0005" (still not exact, but probably good enough). -- That would be very good.

Attached is a pic.

 

[Paul in OKC]

Are you holding the parts in the vise? May be 'rising' on you as you cut. If you are running left to right, and the part is flat in the vise, you should not have that much run out. A little concave-ness maybe. Are you thinning the pad, or the metal? May need to clamp to the table for a more rigid set up.

 

[chips&more]

A pic of your set-up please. Or you will get all kinds of random help/ideas.

 

[gubni]

First of all I attempted to level the C channel to use as parallels. I got it fairly close by trail and error. The pad in this pic is just one I have played with, so ignore the patterns in it, but it is typical size I would work with.

 

[gubni]

Are you holding the parts in the vise? May be 'rising' on you as you cut. If you are running left to right, and the part is flat in the vise, you should not have that much run out. A little concave-ness maybe. Are you thinning the pad, or the metal? May need to clamp to the table for a more rigid set up.

I was told this is a Wilton vice. I have checked after cutting and I don't think that's the case. I am going right to left. I am thinning the pad which is a relatively soft surface.

 

[4GSR]

I was told this is a Wilton vice. I have checked after cutting and I don't think that's the case. I am going right to left. I am thinning the pad which is a relatively soft surface.

That's a old Bridgeport vise.

 

[brino]

Hi gubni,

Welcome to the group!

First some terms:
By "tram the head" we mean get the spindle set accurately to 90 degrees to the table both left-right(x-axis), and front-back (the y-axis).
Some mills allow adjustment in various directions to allow special cutting set-ups. "tilt" and "nod" are commonly used terms.
On yours it doesn't look like you have these advanced adjustments. Don't worry, you can still do many of the same advanced operations, you just need to be more creative in your work holding, maybe using sine-plates, etc. But that advanced stuff can wait.
However, you still need to "tram the head".

By "sweep" we mean to place a sensitive measuring device in the spindle (and with the mill turned off!), place the indicator against the table and move the table to look at how the indicator reading changes. You want to place the indicator against a smooth flat surface, so you are not just measuring the table dings and holes (yikes!) left by the previous users.

The measuring device can be a "dial indicator" like this:

from here: http://littlemachineshop.com/products/product_view.php?ProductID=4285&category=

or a "dial test indicator" like this:

from here: http://littlemachineshop.com/products/product_view.php?ProductID=3709&category=

Note the difference between those two.
On the dial indicator the bottom plunger moves up/down to take a reading.
With the dial test indicator the lever-arm on the bottom moves back and forth, but you can change the angle that it covers.

Ideally, you want zero difference while moving the table, realistically, you need to determine what's required by the job and what's possible with the equipment.
-for x-axis you can put the indicator on the top of the table between the t-slots if the table is not too banged up
-for the y-axis you can still run the indicator on top the table, you just need to lift it over the t-slot gaps.

First get the table trammed in, and then introduce the vise.

For your machine I believe tramming requires you to install/adjust shims under where the vertical column bolts to the base.
I know it may sound daunting, but with some thought and effort I am sure you can get it.
I know there is a thread here about tramming a machine like yours.....though it may take me a while to find it.
When(if?) I do , I will post a link here.

Once the head is trammed to the table, then get the vise trammed in too. Bolt the vise down loosely to the table, run the indicators along the fixed jaw of the vise, and adjust it with little taps from your hand or a mallet. When it's right, tighten it down.

50 thou is significant....it should not be this far out. There is a problem that needs to be corrected.
However, I would not shoot for +/-0.0005 either; (that's 5 tenths of a thou.!) that would just drive you crazy.
For many automotive applications I have found 5 thou (0.005 ") to be plenty accurate.

Other thoughts:
Could there be some chips under one end of your work?
Could there be some chips under one end of your vise?

Good luck!
Please post back with any questions or progress.

-brino

 

[brino]

....oh and one more thing....

Do they still use asbestos in brake pads?
I have read conflicting answers to that question.

If they do be very careful!
I do not know what all the precautions should be, but I'd think a shop-vac may just make the particles air born.....making them more dangerous.

Play safe!
-brino