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View Full Version : Milling A Vee... setup on center how?



Derek13
10-30-2005, 07:03 PM
My questions is this!

For milling out a 90 Degree Vee in say the top of a 1-2-3 block or something... when it is tilted on 45 degrees... how do you find your center so you know you're in the middle of the block?

The only way i can think of is to use blueing and scribe some lines and mill by sight... or rig up a stop and flip it... or wait untill grinding and then flip the block while at the same depth. But lets say you didn't want to grind it, or have a grinder... how would you do this?

Also if you want your V to be a certain depth... how do you calculate your zero from?

Much thanks!

Paul F
10-30-2005, 07:34 PM
How would I do it?

I'd buy or make a 90 degree cutter, put the 1-2-3 block flat, and then center the cutter for height... cut the 90 degree V.

Either that, or I'd just buy my 1-2-3 block with a V already in it http://bbs.homeshopmachinist.net//biggrin.gif

Hope this helps!
Paul F.

spope14
10-30-2005, 08:12 PM
First off, scribe the line in to keep your frame of reference. I am using a 90 degree included angle V-Block holding set-up for my example.

Measure block width. Set at 45 degrees in V-Block. Divide block width by 1/2. Multiply answer x .7071068. Touch off on top corner with the bottom of the cutter using a doubled up piece of paper. Touch off on side corner of the part on the side of the cutter using the same method. Make moves to match your answer, but add .007 to each move - the width of a doubled up piece of paper.

For example - 2 inch block width. 1" x .7071068 = .707 for our purposes. Touch off on top, realize the final movement of .707 down +.007 for the paper On the side corner (bottom corner), touch off is basically the same using the side of the cutter. Move into vlock after raisong and re-referencing the top measurement - move over .707 + the .007 for the paper. This is hard to explain, a bit hard to keep track of, but the idea is over the same as down. Should get you into the park within .005 or better if you are careful.

Movements during cutting are sideways the same as depth - for example if you are using the X axis, move over .005, then the Z drops .005 equally.

Check measurements with an indicator for centrality.

[This message has been edited by spope14 (edited 10-30-2005).]

[This message has been edited by spope14 (edited 10-30-2005).]

Leigh
10-30-2005, 09:53 PM
Easy way {no measurements or calculations) (assuming an accurate block to start with):

Scribe lines on each side of the V, parallel with the V and the same distance in from each edge. These define the upper edges of the V.

Vise the block on a 45° sine bar or whatever is convenient and accurate enough, with scribed lines horizontal.

Select a regular end mill large enough to cut the full depth of the V. Drop the cutter about .025" below the upper line and cut in from the side until you touch the line. Cut the length of the V.

Feed the cutter straight down a reasonable amount and take another full-length cut. Repeat until you reach the second line.

Relieve the apex of the V by sawing a slot. Alternatively you can create a relief before you mill the V by drilling a 1/4" through hole.

If you want the slot accurately centered, better than you already have:

Fixture a hardened rod (dowel pin or some such) horizontally against the fixed vise jaw, high enough that the V-block will clear the bottom of the vise when laid on its side. The rod diameter should be large enough that it comes above the block by a very small amount. The lower it sits in the V, the less deformation will occur when the block is clamped in the vise and the more accurate the positioning.

Clamp the block in the vise with the rod in the V, taking care that the block bottom (opposite the V) is flat against the movable jaw and that this jaw is parallel with the fixed jaw. Face off the first side. Turn the block over and without changing the cutter position face off the other side.

Your V will be centered within <.0005" unless there's something wrong with your vise or mill. And both sides will be perpendicular to the bottom within the tolerances of your vise. This technique requires that your movable jaw be quite rigid, or that you can measure and compensate any inaccuracies.

------------------
Leigh

[This message has been edited by Leigh (edited 10-31-2005).]

Paul Alciatore
10-31-2005, 01:37 AM
First, consider if the block is for set-ups, the important considerations are that it be uniform and if you are making two blocks, that they both be identical. The precise depth and centering are not as critical. Also, holding the groove parallel to the sides of the block may be more important than those considerations.

Paul A.

smoke
10-31-2005, 01:39 PM
What you need to do first is scribe a line down the center of the block to be machined. Then set it up in a vee block,sine plate or 45deg. angle block. Begin by setting your cutter on the center line you have all ready scribed. When you have milled down equal amounts in both directions take a piece of drill rod or simular piece of material that fits down into the vee and set it in the vee. Take a calipers and measure from one egde of the rod to the out side edge of the block, repeat this process from the oppisite side. Adjust your cutter or table to bring it on center. Remember if you take off .010 from one axis do the same in the other. By measureing from one side and then the other this should get you very close to the center on your block. It's not that difficult once you get the cutter on center. If you take off .005 from both axises your vee will drop the same amount.
Smoke

rkepler
10-31-2005, 02:38 PM
The easiest thing is to do what the woodworkers do to make sure things are on center - simply mill both sides on the same fixture and tool setting. Make one cut, pull the block and reset the cutter to the start and replace the block set to cut the other side and take the other cut. That way the V pretty much has to be in the center of the block.

[This message has been edited by rkepler (edited 10-31-2005).]

Derek13
10-31-2005, 07:05 PM
Thank you all very much for your replies!!

Leigh, the method with the roundstock sounds interesteing... but i'm a tad confused. You say the block must clear the bottom of the vise, why is that? Also... do you fix the block under parallels? How do you make sure the round stock is going back in the same place thus pushing the V block up to the same zero? (ie if the round stock is lower in the vice or higher the block will sit that way will it not?)

Also how do i mill/grind it to an exact size? My V must be .900 wide at the top opening.

Thanks Much!!!

Leigh
10-31-2005, 09:01 PM
<font face="Verdana, Arial" size="2">Originally posted by Derek13:
Leigh, the method with the roundstock sounds interesteing... but i'm a tad confused. You say the block must clear the bottom of the vise, why is that? Also... do you fix the block under parallels? How do you make sure the round stock is going back in the same place thus pushing the V block up to the same zero? (ie if the round stock is lower in the vice or higher the block will sit that way will it not?)

Also how do i mill/grind it to an exact size? My V must be .900 wide at the top opening.</font>

Hi Derek,

The trick with the dowel pin (rod) requires that it be mounted rigidly against the fixed vise jaw. This usually requires that you make a fixture of some sort to support it. It must stay in position accurately through the entire machining cycle.

You must have clearance between the lower side of the V block and the vise below it because the rod is supposed to support and position the block, not the vise. This is the key to the accuracy of the setup.

If the rod is positioning the V in the block, and the block bottom (opposite the V) is vertical (the movable vise jaw must be so), then by definition the upward-facing side of the block must be horizontal, or will be after you face it off.

When you face both sides with the cutter in the same position, the two sides are equidistant from the center of the V, as defined by the rod. As long as the rod did not move when you repositioned the block, the two dimensions will be equal.

If I were going to make an accurate 0.900" block, I would start with 1" material, cut the V, then cut the sides down a bit at a time, measuring the thickness after facing both sides using the rod method.

This method would take .050" nominal off of each side, so take a first cut of .020" from each side and measure the block width. Adjust your second and final cuts as needed to reach desired size.

------------------
Leigh

[This message has been edited by Leigh (edited 10-31-2005).]

Al Messer
11-01-2005, 10:38 AM
I would scribe the two parallel lines as suggested, clamp it in the Shaper vise with the head set at 45 degrees and down-feed the head, making several cuts until it reached center, note the readings on the feed screws, flip it around in the vise and cut the remaining side until the readings matched the original readings.

kap pullen
11-02-2005, 06:23 AM
rkepler has it down pat!


<font face="Verdana, Arial" size="2">Originally posted by rkepler:
The easiest thing is to do what the woodworkers do to make sure things are on center - simply mill both sides on the same fixture and tool setting. Make one cut, pull the block and reset the cutter to the start and replace the block set to cut the other side and take the other cut. That way the V pretty much has to be in the center of the block.

[This message has been edited by rkepler (edited 10-31-2005).]</font>

That's the way to do it.

Forget all the layout lines, height gauges, pins, etc, etc.


Made many a vee block, and vee pulley this way.

Kap