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Dimple die help

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Laytonnz

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#1
Hey,

I have had go at making 2 dimple dies, but I got the angle portion wrong I keep machining it too big before I cut the angle, hope that made some sence

It is such a simple task but I just can't seem to get it right.

I machined it in steps then tried to cut the angle on the male die but either come up too short or too big

If I was on a PC i would draw something to explain what I'm doing wrong
 

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Desolus

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#2
Lathe or mill, if lathe cnc or manual?
 

Laytonnz

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#3
Thanks for the reply, manual lathe.. i got it figured out about 5MM seems to work before turning the taper.
 

RJSakowski

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#4
I had that problem machining a tapered shoulder and neck although my diameters were around 6 mm. What I did was first machine the cylindrical sections. I then set my tape om the compound and started to remove material. When I was getting close to the intersection with the neck, I used a 50X microscope to close in on reducing the remaining face between the taper and the neck to zero.

In your case, I would turn cylindrical sections equal to the neck diameter, the major tapered shoulder diameter, and the base diameter with lengths appropriate to the length of the various sections. Then I would set my compound to the correct angle if I had not already done so, blue the appropriate surfaces and begin cutting my tapered shoulder as described above. Setting the compound angle correctly and doing the math accurately are crucial to everything hitting on target. The compound angle setting is probably the most difficult to hit. There are a number of ways to set that angle, the most accurate being with a sine bar. If, as you get close to the final cut, you see that your angle is wrong, you can make small corrections then.
 

Wreck™Wreck

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#5
Tool Nose Radius compensation perhaps, if you touch the tool off in the X and Z axes it will cut a taper at a different position on the tool nose.
The points of contact are at 2 different positions on the tool because of the nose radius, see drawing below. Click for a larger view
In order to compensate when turning a taper from the compound you will have to do a bit of Trigonometry to figure out where on the nose radius the actual cutting happens, this is easy with 45 Deg. angles not so much at others.

On a CNC lathe there are 2 or 3 G-Code instructions for this reason, this probably explains it better then my limited patience allows http://www.cnctrainingcentre.com/news/cnc-lathe-tool-nose-radius-compensation-part-2/

 
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