Center finding question

[walterwoj]

I am making a bench block out of some 3.25" round stock approx 1" thick. I have drilled all the holes and all I have left to do is make a 'V' groove down the center. I don't have the right cutter for making the groove the easy way so I am going to tilt the sock in the vice 45° and use a regular end mill. So here is the question: how do I find the center of my round stock when it is tilted 45°?

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[Ken226]

Assuming that with a bench block your not looking for a high degree of precision, and want something quick n easy

Paint a little layout fluid on the top, chuck it in your lathe and use your toolpost/cross slide to drag a cutting tool lightly across the face. Just a light touch to scribe a line.

Lathe motor off, obviously

 

[walterwoj]

Ken, that is indeed a good Idea but I was hoping to do it in the mill vice so I don't loose my setup, I want the groove to be in line with the holes.... and I'm way too lazy to try lining that up in the vice again If I loose it... (unless I have to) I'm hoping there is some clever, genius way to do it.

 

[Firstram]

Everyone should have a center square, useful for so many things.
Random cheap set

https://www.amazon.com/AccusizeTools-Combination-Protractor-Graduation-0000-8101/dp/B00HS2WICG/ref=sr_1_8?keywords=Center+Square&qid=1640646126&sr=8-8

 

[Ken226]

Assuming the part is in the mill at a 45° angle.

If you can measure the diameter across the top face, top/inside of the chamfer.
Then touch off that point with the corner of an end mill. it's easy to calculate the distance along the X axis, to the center.

For example, 3" diameter = 1.5" radius. In the example, the hypotenuse is 1.5" long.

So, cos(45°) x 1.5" = 1.0607”

Then drop Z down to touch. The corner of the end mill tooth used to touch off will be on center.

Of course, in my example, 3" was just an example. You'll need to know your actual diameter across the point you intend to touch off.

Cos of 45° is .7071. so, multiply .7071 x the radius of the part at your touch off point to get the distance to center along X axis.

Then you will have to keep plunge depth increments = to X movements, to keep that endmill corner on center as you make cutting passes.

I'll draw it in CAD right quick, so it's easier to visualize.

 

[RJSakowski]

You need to look aty tooling balls. A tooling ball is a known diameter ball fixed to a dowel pin. The center of the ball is a known distance from the bottom of the base flange. You can determine the center of the ball with an edge finder or other means. Knowing the angle of the surface, you can locate a line through the center of the pin hole at the inclined surface.

Joe Pieczynski did a video regarding tooling balls and their uses.

Since you already have your center hole, I would machine a bushing to fit the hole and the tooling ball pin. If starting anew, I would make the hole for the pin and cut the groove and then machine the center hole.

 

[main_cogg]

If you have a lathe, you can turn a center that is a close slip fit in the center hole. Then with the point on plane with the top surface , set the end mill to the point. That will get you centered. If I'm thinking straight, as you cut you'll have move in x and z to keep the bottom of the groove centered.

 

[Ken226]

Hopefully this is helpful.




Once the corner of the end mill is centered, move it left and down = distance, to your desired depth and cut it. As long as each z- and x- move is =, the corner of the end mill will be in center.

 

[walterwoj]

Ken, That was the exact clever/genius trick I was looking for it's too late tonight to try it but I'll try tomorrow and let you know how it goes. Thanks!

 

[walterwoj]

Ken your truck works great, I got the groove in:

Then I recessed the back.

Here is the finished item:

Now I have to decide if I want to blue it.

For those wondering, this is a cheap project only if you ALREADY have all the drill bits, otherwise the bits cost about 2x the cost of a commercial version.

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