Is there a trigonometry solution to this question?

[Janderso]

Hey all,
I have a paying job!!
These are leveling blocks for Super Duty front ends. I get $100 a pair.
My question is, how can I accurately duplicate the same length of bevel on each piece?
The 35 degree angle depth has been duplicated by me measuring the width of the cut. I sneak up to .480”.
I have a DRO on my lathe. I tried to zero out the axis and watch how far I moved toward the headstock but it was not consistent.

What are your thoughts?

 

[Alexander McGilton]

This taper is decorative I take it, though needs to be somewhat consistent enough to match all others.

Start with a form tool to make a chattering mess to Over sized.

I would use the x and z axis and a sharp tool to scribe a belt line on all samples in one operation, then in a new clamp up, use the compound to make the finish pass to the scribe belt line. Use a Z bed clamp, a the cosse slide to a number, and don't even look at the numbers on the compound.

You could put a center point in the tail stock and somehow use it as a reference point. Then SinCosTan your way over to the part. But time is money, and getting a decorative bevel to the. 010 to .001 to .0001 cost exponentially more.

 

[RJSakowski]

Accurately measuring a bevel can be a challenge since there is no simple way to measure the position of an edge on the bevel. One way to measure it would be to move the carriage until it just kisses the edge of the squared part and zero the z axis DRO. Then without changing the cross slide or the compound, advance the carriage a distance L where the width of the bevel, W = L/cosΘ with Θ being the angle of the bevel relative to the spindle axis. If you also zero the x axis, you can back the cross slide off to make multiple passes, returning it to zero for your final pass. For a 35º angle and a bevel width of .480:, I get a distance for L of .393". Actually measuring the result will prove to be the difficult task.

 

[Ischgl99]

Joe Pie has a video on this with multiple techniques that would probably work for you.

 

[pontiac428]

If you cut .275 in from the face at 35 degrees, you will get a .480 bevel face, because of the law of sines.

Law of Sines Calculator

Calculate angles or sides of triangles with the Law of Sines. Calculator shows law of sine equations and work. Calculates triangle perimeter, semi-perimeter, area, radius of inscribed circle, and radius of circumscribed circle around triangle.

www.calculatorsoup.com

 

[Janderso]

You guys are the best.
Some good ideas here.
The question was to see what others may do to produce the same part.
The bevel fits into a pocket to center and seat the block. It needs to be fairly accurate.
RJ, you immediately discovered the difficulty in measuring the bevel.

""For a 35º angle and a bevel width of .480:, I get a distance for L of .393". Actually measuring the result will prove to be the difficult task.""

I think for kicks and giggles I'll give this a try a couple times to see how it turns out.

The form tool is interesting.

 

[Janderso]

If you cut .275 in from the face at 35 degrees, you will get a .480 bevel face, because of the law of sines.

Law of Sines Calculator

Calculate angles or sides of triangles with the Law of Sines. Calculator shows law of sine equations and work. Calculates triangle perimeter, semi-perimeter, area, radius of inscribed circle, and radius of circumscribed circle around triangle.

www.calculatorsoup.com

RJ came up with .393".
Maybe I'm not understanding this. Wouldn't be the first time.

 

[extropic]

They are BOTH correct !!! Dependent on the orientation of the chamfer (which you didn't specify) and whether you are measuring the cross slide travel or the carriage travel.

Is your 35° back (toward the chuck) from the flat face or in (toward the workpiece centerline) from the OD?

 

[Ischgl99]

Instead of measuring in process to see how much needs to come off, you are better off using a consistent process that you can verify is accurate. The easiest way to stay consistent and accurate is setting a consistent zero starting point for the final pass. Method #5 I think it was in Joe’s video gives you a consistent starting point so you don’t need to measure in process to see how far off you are, your final pass is from that point. If you don’t want to leave material that needs to be faced off, I have extended the angle line to get a point a set distance away from the face to start. By using that same point each time, every piece should be identical within a few thousandths. Say you want to use 0.010“ away from the face, calculate what the distance on the angle line that additional distance would be for X and Z, touch off on the face and the OD and then move your tool to your calculated point for the final pass if you can’t do it in one pass. As long as your compound is at the same zero as when setting the zero point when you start your final pass, you will be consistent on each part. It sounds complicated, but actually pretty easy to do.

 

[Alexander McGilton]

The bevel fits into a pocket to center and seat the block. It needs to be fairly accurate.

How accurate are we talking?

Loose tolerance you may inspect the item by placing it, end face down on the surface plate then bringing the scriber end of the height gauge to the edge, then measuring one leg and not the hypotenuse.

More precisec you could make or commission some chamfer gauges. A silhouette profile cut into a small square of metal. You would have a key chain ring and multiple depths of champfer to look at and compare.

Further more precise than that where a line of sight is not reliable enough. You may get a flush gauge or a dial gage on a specially saddle to measure distance of the convergence of the end and side to the hypotenuse.

Other methods include replicating a thread wire approach with a micrometer. Place the end face down as before on the surface plate. Then have two gauge pins pinch the taper and touching the granite. You will need to-do more trig in this method, as well as calibrating the prior methods.