Here's how I made my mast foot to mate my new SailCraft mast to my old IYE mast foot (with 2" ball) on my Tornado.
NOTE: I am *not* an expert. Mimic what I did at your own peril. I assume no responsibility for injury to you or your equipment.
I used the following woodworking tools:
- Chop saw
- - with *carbide* tooth blade.
- Table saw
- - with zero-clearance insert and
- - with *carbide* tooth blade.
- Belt Sander.
- Drill Press with
- - 1/4" and 1/2" speed bits.
- - a 2" hole saw.
- WD-40 and a respirator.
- Router
- - with 1/2" round-nose *carbide* blade and
- - with a set of router collars
- - on lowest speed setting.
- A bucket of water.
- A flat file.
- A compass. (Dividers with a pencil on one side.)
- A hot glue gun (or double-stick tape).
- A shop vac.
First, I matched the mast outer profile as follows:
I started with some 1.5" thick T6061 alloy tooling stock from imsmetals.com, my local metal supply house. I cut off a block a bit wider than my mast using my chop saw with a carbide tooth blade (images 145, 146). I used a scratch awl to trace the outer profile of my mast and mast web (the front wall of the track) onto the block, and used the chop saw to cut the rough outline, leaving about 1mm of extra material all-around (image 147). Then I sanded to match the traced mast outline plus an even 1mm reveal all-around (images 149 & 148). The reveal must be even all around for a good internal fit. Frequent quenching was required to keep the AL cool enough to handle.
Next, I created a rabbit (a.k.a "rebate") all around so the foot would fit inside the mast. First I installed a sacrificial fence on my table saw. (That's just a piece of plywood taped to real fence, so it's OK if the saw cuts away part of the sacrificial fence.) I installed a zero-clearance table saw insert for better support (image 150). I marked the center (high point) of my blade in pencil on the table of my saw. I then cut a small test rabbit the width of my saw kerf at the very top of the foot, and tested the fit against my mast. I adjusted the saw height until I had a snug fit in the mast.
Once the blade height was set, I removed the sacrificial fence and started cutting the rabbit in successive passes, moving the fence 1/16" per pass. I skipped about 1/8" at the top of the foot to act as a support for the other passes, and cut it away last (image 150), but in retrospect it was not necessary.
The trick to cutting an even rabbit depth is to keep the curved surface of the foot touching the table where you drew a line marking the high point of the blade.
I had to round the aft corners of the rebate with a flat file to match the inside of my mast. I achieved a nice snug fit.
Next I made and secured a template to the bottom of the foot as follows: I cut a template in 3/4" MDF with the 2 1/8" whole saw. With the compass, I marked a ~1/2 inset line on the bottom of the foot, to act a a visual guide. Then I hot-glued the template in place (temporarily), and glued and screwed blocks to the back of the template to hold the template in place over the foot (images 152 and 153).
I removed most of the metal from the hole with a 1/4" speed bit in my drill press, after setting the drill to the recommended 3000 RPM for soft metals. I set the depth limit on the press to stop my bit 3/8" above my drill press table. I drilled evenly space holes around the perimeter just inside the edge of the template, lubricating with WD-40 spray lubricant while wearing an organic vapor respirator. Cutting oil would have been better. I drilled out as much as I could without the holes intersecting. Then I switched to the 1/2" bit, adjusted the RPM down per my drills instructions (2180 RPM, if memory serves), and re-set the depth stop for the new bit, and drilled out as much as I could with that, centering the drilling on existing 1/4" holes, and making sure my 1/2" holes did not intersect each other(image 154).
Finally, I finished the mast foot hole using my router (set to its lowest speed) and 1/2" round nose bits and router template collars. I started with a collar large enough that my bits would fit through, and removed material in 1mm passes, first going clockwise around the template edge. Once I got deep enough that the router cutters were below the collar, I switched to a 1/2" router collar and re-cut all the way flush with the edge of the template, again removing material in <1mm passes, vacuuming out shavings between each pass, and lubricating with WD-40. Eventually, the whole was complete smooth, except for the pre-drilling around the edge (image 165) because I was using a round-nose cutter and didn't want to remove more material. If I had it to do over, I would not have pre-drilled quite so deep around the edge.
Note: I am very glad I pre-drilled. Removing the edge material works well with the router against the template, but removing material in the middle of the hole is a bit squirrelly, especially in the last couple of passes, which did not benefit from the pre-drilling de-bulking having removed most of the material.
The mast foot is more substantial in all respects (including weight) than my old IYE step, so I'm sure it's much stronger than it needs to be. Additional material could be removed by cutting a dado within the rabbit, and by removing material from the aft solid region. I will just KISS, however.
I will, however, be bolting an auxiliary plate to the bottom of the step to attach downhaul blocks, and to mate with my mast rotator control arm. I'll document that build similarly.
--Glenn [img]
http://www.catsailor.com/forums/download.php?Number=141315[/img]