# Setting Angle of Bridgeport Head?

• posted

How do you accurately measure the angle when you rotate the milling head? Is there a relatively easy way to measure the angle? For example, if I want to cut a 65 degree angle with an end mill I can put a straight rod extending out of the spindle and use an adjustable protractor to set the angle of the head but what other methods are there?

Thanks,

Dave Berryhill

• posted

• posted

• posted

Set up a sine bar (or table) and sweep it with an indicator just as you would indicate the table when tramming the head.

Ned Simmons

• posted

It's a lot more complicated that it appears. Because Bridgeports have a turret, and the head can tilt in two directions, unless you have everything at dead right angles, the setting won't be proper because of the compound angles you generate. You begin by squaring the turret with the saddle ways and go from there. When you have everything in proper attitude, you can then dial the angle from a sine plate or bar, which must also be dialed true before use. Lots of setup and overkill, but that's how you set the angle properly. Some folks go by the marks and call it good enough. Sigh.

Harold

• posted

Thanks for the input. Although I didn't mention it, I did assume that the head would be trued before making any adjustments. Using a sine bar means using gage blocks too, right? I don't think I can justify buying a set for just one project but I'll see if I can find some imports on sale. I've never used a sine bar but I understand the concept. How about a "Reader's Digest" version of how to calculate the height needed for an angle you want to set it for?

As for James' idea about inspection angles, do you stack them to get an angle when there isn't one made for the angle desired?

Thanks again,

Dave Berryhill

• posted

You can get a "spacer block" set cheaper than gauge blocks, sometimes as low as \$25 for the set. They are round and have a threaded hole in the center, so you can stack them up on a long set screw, which is provided. I can't imagine trying to wrestle some item onto a sine bar supported by a wobbly stack of gauge blocks! Doing the same with a set of clamped- together spacer blocks is definitely better, but still a bit tricky.

Jon

• posted

Chuckle!

Wobbly stack of gage blocks? You apparently have never worked with them. While I'll openly admit the possibility of them tipping over, gage blocks that are properly wrung together are hardly wobbly. Further, the square variety have tie bars to prevent them coming apart. The only real issue is the stack tipping over, and you'd face that with any spacer unless it had a very broad base.

I do agree with your assessment of spacer blocks, however. Unless the angle desired is ultra critical, a spacer of proper length could be easily made from a piece of solid stock for any particular setup. No real need to buy a set of gage blocks, although they are a nice addition to any shop. Missing the length of the spacer by even a thou translates into such a small error that it's highly unlikely that a mill would have the necessary precision to make any difference.

The ultimate way to get around the wobbly situation is to work with a sine plate instead of a bar.

Harold

• posted

That part's pretty easy. All you do is refer to trig tables. Considering I have no mathematics aside from general math behind me, I'll leave it to the mathematicians to describe the process. I'm pretty clumsy at it.

Harold

• posted

A sine bar has a top plate mounted on two round bars (one pivots). The important number is the center to center distance of these two bars along the top plate. Five inches seems to be standard.

The formula is (distance between bars) times (the sine of the angle desired) equals (the height of the stack).

for 22 deg sine of 22 = .3746

5 x .3746 = 1.873

You need a 1.873 inch stack to get 22 deg.

Paul K. Dickman

• posted

While others have described the methods for setting the angle on the head, sometimes it is easier to leave the head square and set the angle of the work. Small stuff can be set on top of a sine bar in the vise, larger stuff can be held in a sine vise. ( The vise tips and is clamped in place.)

Often the setup depends on how much work is needed at an angle and the precision required. As an example if you were making an injection mold with rising detail a high degree of precision is required, but if you were making a vacuum forming mold and needed a draft angle so the part would release you could probably just eyeball the protractor scale and be fine.

• posted

Dave Yes you stack to get the proper angle. the sets usually come with

1 2 3 4 5 10 15 20 25 30 degree blocks. check out the KBC tools online catalog page 580.
There is a realy nice Brown & Sharpe set that has recesses to hold the part or other blocks. not cheap thought :-)

As Harold says about l>>It's a lot more complicated that it appears. Because Bridgeports have a

• posted

• posted

In article , dberryhill wrote: : : Using a sine bar means :using gage blocks too, right? I don't think I can justify buying a set for :just one project but I'll see if I can find some imports on sale.

Unless you need extreme accuracy, a set of adjustable parallels and a micrometer work just fine.

• posted

Excellent information!

Thanks for the help,

Dave Berryhill

• posted

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.