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View Full Version : How to indicate off a tilted workpiece?

beanbag
07-07-2011, 05:35 AM
I'm going to be drilling some diagonal holes in the flat face of a cylinder. There will be a concentric hole in the center of the cylinder and the edges will be chamfered. I need the slanted hole to come in at one position and pop out the other side in a relatively precise location. Setting the tilt angle is not the problem, but how to set the x y position? The cylinder will either be held in a hexagonal collet block or put on a tilted rotary table / 4th axis.

Edit: Actually, I think there will be a bolt that needs to go thru the cylinder's center hole in order to hold it down.

winchman
07-07-2011, 06:25 AM
If the location of the hole on the side of the cylinder is more important than the its location on the flat end, start the hole on the side. Use an end mill to create a flat-ended recess, and drill the hole from there.

You should put a piece of scrap under the cylinder for the drill to run into so you won't scar the RT.

easymike29
07-07-2011, 11:54 AM
How is the x/y position defined in the original drawing?

Gene

3jaw
07-07-2011, 12:04 PM
How is the x/y position defined in the original drawing?

What he said plus a tooling ball in the center of the end of the bar and a little trig should get you where you need to be.

easymike29
07-07-2011, 02:24 PM
What he said plus a tooling ball in the center of the end of the bar and a little trig should get you where you need to be.

Disregard my rebuttal.

Gene

easymike29
07-07-2011, 03:28 PM
What he said plus a tooling ball in the center of the end of the bar and a little trig should get you where you need to be.

Can you provide the readers with an example of how you perceive the solution? A CAD drawing maybe?

Gene

3jaw
07-07-2011, 05:59 PM
Can you provide the readers with an example of how you perceive the solution? A CAD drawing maybe?

Sure, but I would like to see a drawing of the part in question to make sure I'm on the right track first.

beanbag
07-07-2011, 06:10 PM
Once I get stupid Inventor figured out I will make a drawing.

Dave S.
07-07-2011, 10:01 PM
Is this what you are doing more or less.

Dave

http://i132.photobucket.com/albums/q3/Dave_Sohlstrom/cylwithholes.jpg

beanbag
07-08-2011, 12:44 AM
more or less, except that my cylinder height is much shorter.

winchman
07-08-2011, 01:25 AM
Wow. I certainly wasn't expecting the holes would go completely through the cylinder if there was a bolt there holding it down. I thought you meant the holes angled outward from the flat face to the OD of the cylinder.

Dave S.
07-08-2011, 11:45 AM
You will then need to turn a bolt to a very close fit for the bore of the cylinder. The bolt will need to be the same material as the cylinder. As was suggested earlier you will need to use a end mill to make a flat spot for a small center drill in order to get your drill started without it skiding off where you want the holes to be. First hole will be the most accurite because the drill has to pass through a void at the center of the bolt where the first hole removed material and will want to skid when it gets to the far side of the void. It will get worse with every hole.

What is the OD,ID,height, drill size and angle you are working with. I'll change the drawing to those sizes.

Dave

beanbag
07-08-2011, 02:51 PM
The cylinder is short enough that the holes don't poke out thru the center.

winchman
07-08-2011, 04:34 PM
So, the holes start on one flat face and come out on the other flat face of the cylinder?

beanbag
07-08-2011, 05:30 PM
yes

But does this really matter in terms of indicating?

Toolguy
07-08-2011, 05:52 PM
Can you edge find the opposite side of the part, then draw a triangle to see how far to go to the center of the hole you are drilling? The diameter of the part and the angle of the part are presumably known dimensions.

derekm
07-08-2011, 06:13 PM
.measure the x distance between the two edges. The ratio between the that measurement and diameter, gives you the scaling factor in that direction.
example cylinder diameter is 5 measured in x is 4. PCD is 4. x dimension of PCD is 4 * 4/5 =3.2. pcd is 0.4 in x dimension in from edge.

Dave S.
07-08-2011, 06:35 PM
No but it gives us a better idea of what you are trying to do.
From the information you have given I think you are looking for something like this.

http://i132.photobucket.com/albums/q3/Dave_Sohlstrom/cylwithholes-1.jpg

http://i132.photobucket.com/albums/q3/Dave_Sohlstrom/cylwithholesbottom.jpg

If I'm close then you can use your edge finder to get the spindle ccentered over the part.

http://i132.photobucket.com/albums/q3/Dave_Sohlstrom/cylwithholesdrawung.jpg

I hope this helps

Dave

winchman
07-08-2011, 06:42 PM
Since you know the heigth of the cylinder and the slant angle of the holes, you can compute the measurement from the OD of the far end face of the cylinder to the center of the hole you want to drill on the near face. You can use a regular edge finder to pick up the edge of the far end face, move over the required distance, and commence drilling operations as previously discussed.

You can put a slightly undersized standoff under the cylinder so the edge will be accessible. The standoff can be stepped on both ends so it can be used to locate the cylinder on the RT center hole. The bolt holding the cylinder will pass through the standoff.

Edit: Dave came through with a drawing for what I was thinking.

easymike29
07-09-2011, 12:04 PM
What he said plus a tooling ball in the center of the end of the bar and a little trig should get you where you need to be.

I agree. However, if there's a bolt down the center then what? Maybe a recessed bolt?

Gene

3jaw
07-10-2011, 03:58 PM
You can use a regular edge finder to pick up the edge of the far end face, move over the required distance, and commence drilling operations as previously discussed.

Edge finding off of a corner is not a good practice if you are trying to locate something accurately. Any amount of chamfer or burr will throw you off.

I agree. However, if there's a bolt down the center then what? Maybe a recessed bolt?

Or he could drill the angled radial holes before he bores the center hole. Just drill and ream a hole in the center for the tooling ball shank. There are other ways to go about it if the hole is already bored in the center.

moldmonkey
07-11-2011, 07:38 AM
When doing similar parts i have edge found the "non-tilted" axis having stoned off any burrs of course and picked up the center mark for the tilted axis with the pointed end of the edgefinder. Having laid out the hole location previously.

If you edge find the tilted axis, you will have to do the trig to find the correct move over distance. Depends on your tolerances for which method you use.

I used to do alot of similar work drilling water and air lines in molds. Often we would use a ball-endmill feed slowly to spot to save the extra step of spotface and center drill.

Edit: Being a round, I would use a indicator to find the high spot of the radius on the non-tilted axis before edge finding and then edge find from both directions to find center.

beanbag
07-13-2011, 02:01 AM
In this case, edge finding off the OD edges will not be good because they will be chamfered by me on the manual lathe, which means the chamfers will only be approximate depth.

If I instead grip around the OD, then I guess I can end find the tilted edge of the center hole. The center hole is already there, and I plan to drill the slanted holes.

I'm not sure how to use a tooling ball in this case. I guess I can use it to press against the center hole, but how can I tell if it is fully engaged around all the edges?

One other option I thought of was to have a close fit pin stick out of the center hole, and then hold a triangular piece of material of the same tilt angle against the pin. This would give me a vertical surface to indicate off of.