The Shop > Tools

Cutting a taper

**Dell**:

I am trying to make some arbors for my Pultra for diamond grinding wheels and I am having trouble getting the taper correct, I know the included angle is 30 degrees, the overall length of taper is 7.8mm large end 15.2mm small end 11.98 as best as I can measure and I have to convert to ratio for the Rocketronics so I input 7.6 being 1/2 large end ➗ by 15 degrees being 1/2 included angle into calculator like so

7.6 ➗ 15 tan = 28.363 input that into control panel but not getting the correct angle when turning on a bit of scrap aluminium, what am I doing wrong.

**awemawson**:

Tool centre height is very critical cutting tapers accurately - needs to be dead nuts on.

**philf**:

If you have a taper of length 7.8, Large diameter 15.2 and small diameter 11.98 you don't have a 15 degree half angle! It's more like 12 degrees. (11.605 degrees). For large diameter 15.2, taper length 7.8 and 15 degree angle the small diameter would be 11.02 - nearly a mm difference to what you measured!

According to the manual :-

If you're inputting the Cone Ratio (V). V = L / (D - d); V = 7.8 / 4.18 = 1.866

If you're inputting ZP & XP: ZP – This corresponds to the length of the cone. [= 7.8]; XP – The distance in X by which the cone tapers, i.e. (d1-d2)/2 [= 2.09]

It seems bizarre that you can't enter the angle!

**Dell**:

I said as best as I could measure, it’s not very easy with a calliper but I know the included angle is 30 degrees so I will cut another bit of scrap using what you posted.

**philf**:

--- Quote from: Dell on November 05, 2023, 02:19:24 PM ---I said as best as I could measure, it’s not very easy with a calliper but I know the included angle is 30 degrees so I will cut another bit of scrap using what you posted.

--- End quote ---

Dell, Don't use the figure I quoted - I used 7.8 instead of 7.6 - I since deleted that bit. Phil.

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