Question about tramming a bridgeport

[D.sebens]

Also, when you mill your next test piece, indicate the surface along the y-axis after you mill it to see if it indicates that it's flat.
When you remove the piece (or before you install it) indicate along the y-axis of one of the vise ways. If that shows a slope the taper is likely in your vise (assuming the table was trammed and remains in tram).
If your vise has no taper, and the part has no discernible taper before you remove it, it's either a problem seating or holding the part, or your vise jaws. Putting a ball bearing or a block of wood between the part and the moving jaw of the vise will better allow the part to seat firmly against the fixed jaw, which is your desired reference.
If you tightened your knee gib when tramming, tighten it for your cut. If you did not, then don't. Doing so is the better practice. I can't imagine this being the cause of so much taper, but it's worth noting.

GsT

Edit: clarity

Wouldn’t I expect it to be completely flat after milling the top if I indicate from the spindle? If the head was out of tram it would still cut a surface level to its own level right? I will still check it though

 

[tjb]

I would clamp a piece of flat stock (e.g., 1"x4" or 1"x6" aluminum, 6"-ish long). Get it as close to parallel to the X-axis as you can; then mill the front two or three inches down along the X-axis. If the result is square, you know the problem is the vise. If it's not, you have another issue.

Regards

 

[tjb]

P.S.: Should have stated more clearly, remove the vise and clamp the piece of flat stock directly to the table. Then proceed.

 

[GeneT45]

Wouldn’t I expect it to be completely flat after milling the top if I indicate from the spindle? If the head was out of tram it would still cut a surface level to its own level right? I will still check it though

Yes, you'd expect it to be completely flat. But it isn't, so something is not what you'd expect. When troubleshooting this sort of thing the first step, as with debugging many things is: check your assumptions.
On your existing sample, is the tapered top square to the side that was against the back jaw? It should be...

GsT

 

[Firstram]

Putting a ball bearing between the part and the moving jaw of the vise will better allow the part to seat firmly against the fixed jaw, which is your desired reference.


GsT

Edit: clarity

Important to grind a flat spot on the ball to avoid dents in the vise jaw!

 

[RaisedByWolves]

I keep cutting a taper in the y axis. I haven’t had much time to investigate but it’s consistent. I need to double check tram. I’m using a 1/2 endmill on aluminum. I trammed it the. Tightend down then rechecked. Something could of slipped. The vise operates nice and looks like it hasn’t been damaged but it’s very old. It looks likea Bridgeport vise without the bridgeport name. I’ll give it all another once over see where I’m coming up.

This is all trying to square stock. It’s tapping the stock down against a parallel and using a copper wire on the moving jaw. I keep the first faced side against the stationary jaw the face the “top and bottom” sides still using the copper wire. Does this sound like the right process?

Lock the knee and try again.

 

[Parlo]

Check if your parallels are the same or damaged.

 

[D.sebens]

I’m going to do more testing but here’s what I’ve found so far.

The fixed jaw is true to the x axis to .0007” ish. The bottom of the vise is true to y axis to .0005”. When clamping a large block in the vise I get less than a half thou of change(did not tap anything to seat it since I was just measuring).

My process appears to be flawed and I will continue to practice squaring until it works.

 

[Shotgun]

Mount the indicator to the spindle and indicate your fixed jaw in the z direction. It may not be vertical.

 

[D.sebens]

Made good progress! I got 7 of the eight measurements(measuring all faces of the cube on each end) to .003” difference and the other to .004”. I think my issue is I need to figure out how hard to tap the part right and when. I think it’s bouncing up a bit when tapping it in.

I have two questions, one should I tighten it fully before tapping the part down? Two, when squaring stock should I use two parallels or one if the bottom face isn’t machined yet? I assume use two but it’s possible it won’t touch both if out of square?

I’ll keep fiddling with it. It seems to be operator error.