# Dust system tapered cone connectors. Build the missing pieces!



## Colosnoball (Oct 16, 2021)

I came across these instructions many decades ago and have had many occasions to use them to create custom length tapered two diameter flared sheet metal fittings that transition between two different sized diameter pipes. I make them out sheet metal flashing rolls. Using 3’ rosin paper, I layout a paper template for taping onto the sheet metal. Then I use a sharpie to trace the pattern for subsequent cutout with tinsnips.
Referencing the attached drawings:
The drawing shows a template for making a 7” large diameter tapering to a 4” small diameter fitting that is 5” in overall length.

To discover the arcs needed for the template, start the layout with a large building square to draw angle CAB.

The length of line AB is the planned large ID cone end.
The length of line AE is the overall desired fitting length.
The length of line EF is the planned small ID cone end.
Lines AB and EF are parallel and 90° to line AC.

Using points B and F, strike a line ( create the hypotenuse of triangle ABD) to intersect line AC now identifying point D.

Set your compass/dividers to the radius length identified by the line AD. This length is transferred to the secondary arc drawing to create arc JJ with the radius centered at point H.

Set your compass/dividers to the radius length identified by the line ED. The length is also transferred to the template arc drawing to create arc KK with this radius too, centered at point H.

Line AD strikes arc JJ using line HJ as the radius. Make a semi-circle.
Line AE strikes arc KK using line HK as the radius. Again, make a semi-circle.

Now for the tricky part:
Divide line AB into 7 exactly equal segments regardless of your large diameter measurement for line AB.

Setting your compass/dividers to this one segment distance, set out along the path of arc JJ— 22 increments derived from the incremental 1/7 of line AB.This determines the end points for each end of the arc at J and J. It may be easier to plot 11 increments left and 11 increments right from the top center of the arc.

After finding the arcs end points J and J, connect the JJ points to point H.
The pattern is then given sufficient additional edge as shown by the dotted lines, for overlaps for fastening. I generally use 1/2 inch extensions and use rivet or screw assembly and duct tape the OD and ID of the cone.

I hope you find these directions useful for your shop needs.


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## Colosnoball (Oct 16, 2021)

Using a temporary custom length--as needed--beam compass on the roll of rosin or newsprint paper will allow you to make larger diameter and longer cones. Sometimes a nice open floor space is a good idea for layouts on larger pieces.


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