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A Jig For Turning Masts
A Jig for Turning Masts and Yards
By Dave Nelson
It can be a challenge when turning masts and yards for a ship model to get a consistent taper over their length and to retain a circular cross section throughout. These considerations become more of an issue with small spars as they are prone to bending when pressure is applied by a cutting tool. To circumvent these problems I have created a jig that allows the model shipwright to turn the mast or yard with almost no pressure on the wood resulting in a smooth, consistent result.
The jig consists of three main parts:
A bed that sits along the front of the lathe. The bed can be angled to allow the cutting tool to remove more material at either end of the mast/yard producing the desired taper.
The Dremel cart. This cart holds the Dremel or other high-speed tool, and slides on the bed allowing the cutter to travel the length of the work material.
A locking disk located on the drive end of the lathe. This disk allows you to lock the work material in any one of 16 positions so the 8- or 16-sided section in the middle of a yard can be shaped.
I am providing pictures of the jig but do not feel there is any value in providing measurements or dimensions as these will be dependent on the specific lathe and high-speed tool being used.
The jig bed provides a platform for the Dremel cart to ride on. It must be long enough to allow the cart to travel beyond the capacity of the lathe so that you can cut the full length of any piece of material you might put into the lathe. The vertical end plates provide a means of locking the ends of the bed in position. Hanger bolts at each end of the jig bed extend out through slots in the end plates and a wing nut and washer are used to clamp the bed to the end plate. The end plates are fastened to the lathe bed abutting the ends of the jig bed at any slope of the jig. The height adjustment screw controls the slope of the bed and resulting taper in the mast/yard. The jig bed is fastened to the lathe bed with a hinge that can be moved to position the hinge pin in line with the point on the mast/yard where the diameter is largest. The hinge is moved by unfastening it then re-installing it in the desired position.
The Dremel cart holds the high-speed cutting tool and controls the depth of cut. The cart bed and hold-down block are contoured to the shape of your high-speed tool and lined with foam so when the block is screwed down to the cart bed the tool is held firmly in place. If the tool wobbles in the cart you will have gouges in your mast/yard. One end of the cart rides on the jig bed while the other end is supported by the height adjustment. The height adjustment is a threaded screw that is securely fastened to a metal rod to form a “T”. The crossbar of the “T” slides on the jig and the screw is threaded up through a T-Nut [pallet nut: ed.] inserted in the underside of the cart bed and secured by a wing nut on the top. By loosening the wing nut and turning the screw to move it up or down you control the vertical position of your cutter in relation to your mast/yard. A half turn of the height adjustment, as described here, will change the amount of material to be removed from the spar by 0.025". A piece of card stock or paper inserted under the other end of the cart will reduce the change in the depth of cut to less than the 0.025”. The cart side panels keep the cart in position on the jig bed.
The locking disk (above) is fastened to the drive end of the lathe’s headstock and spins with it. It has 16 holes drilled at equal intervals near the outside edge. By inserting a pin through a hole in the disk and into a hole in a metal plate fastened to the lathe bed you securely hold your work piece in a fixed position. Note: The
LATHE MUST BE KEPT OFF
when this pin is in place.
The photo at top shows a T-Nut [a.k.a. pallet nut: ed.] and a hanger bolt. They can be obtained at any good hardware store. The photo below shows the cutting tools I use. I found that the steel burr did not work well. The coarse cutting teeth caused the work material to oscillate resulting in uneven cuts.
How to Use the Jig.
Prior to turning any mast or yard, determine the length of each spar required then select a range of work material lengths that are close to the various spar lengths. For the yards on my
I determined the lengths of source material to be 28”, 24”, 18” and 12”. Now make the necessary screw holes and slots in the lathe bed so the jig bed hinge can be positioned at the largest dimension of the work material you are going to turn. This makes it easier to set the slope on the jig bed to produce the desired taper in the yard. In the case of a lower mast you want the jig bed to pivot at deck level as lower masts taper in both directions from this point. If the mast or yard you are turning has a single taper from one end to the other it does not matter where the jig bed pivots.
Select a piece of work material that is larger in diameter than required for the spar, cut it to slightly over finished length and insert it into the lathe. Set the tilt of the jig bed so that it is parallel with the work material. With the carbide tooth cutter in the tool set the depth of cut so it is just above the work material at the lathe tail piece. Turn on the lathe and high- speed cutter and slowly slide the Dremel cart towards the head stock. Lower the height adjustment on the cart and repeat the pass over the work material multiple times re-setting the height until any imperfections have been removed and the diameter is 1/16” larger than the spar’s finish dimension. If you are starting with square work material, take the corners off with the lathe turned off using thelocking disk. Rotate and hold the locking disk by hand and make a pass with the cutter. Repeat with the cart set lower and the lathe at different rotations until the work material is almost round.
Put a piece of masking tape on the lathe bed and mark it with the center point and quarters of the spar. At each of these points mark the desired diameter to provide a quick reference when checking your progress.
If you are making a yard, lock the rotation of the work material using the locking disk. With a coarse then fine sanding drum on the cutting tool, make a first cut on one of the flat sides. Lock the rotation at 180 degrees from the first cut and cut that flat side. Repeat these cuts while increasing the cut depth until you have the desired diameter. With the height adjustment unchanged, cut the remaining flats using the locking disk to index the angles. Remove the pin from the locking disk and, with the lathe running, turn a short section of the yard outside of the flat sections.
Tilt the jig bed to start tapering the work material. If more than 1/16” of material is to be removed start with the carbide tooth cutter then switch to sanding disks as you get closer to the desired diameter. Continue to make passes over the work material until you have the desired taper and slightly larger diameter of the work piece that that required of the spar. Do not try to use the high-speed cutter to get to the final diameter because any slight tipping of the cart may result in too much material being removed.
With the cart removed and the lathe turning use a file to remove the final small amount of material to get the desired diameter of the spar. Hold a piece of sand paper against the work material and slide it back and forth over the length of the round sections.
Remove the work material from the lathe and cut to final length. Run sand paper lengthwise of the round sections to remove any marks made while it was in the lathe. File the flat sections of the yard to make them smooth.
These pictures show the finishing process using file and sand paper. Note: You should always have your fingers opposite the file or sand paper when working with small diameter spars. The block seen behind the lathe is used to provide extra support for long work pieces when turning the small diameters at the outer ends. This block secures to the lathe bed and has an adjustable “V” block on top of it for the work piece to ride in. The “V” block adjustment consists of a hanger bolt in the top of the main block and a T-Nut with its spikes removed which is turned to adjust the height of the “V” block. This “V” block should not be used until the work piece is made round and straight.
has recently completed a 1:48 model of HMS Victory, pictures of which can be seen at
He is currently working on HM Schooner
from the War of 1812. An avid wilderness canoeist, Dave Nelson lives in Toronto.
is a trademark of the Robert Bosch Tool Corporation.
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