Problem Solving Products: Issue 31Comments (0)
This article is from Issue 31 of Woodcraft Magazine.
Quick support for lathe work
Hold Fast Vacuum Chuck Turning System
Helping a woodturner quickly mount turned work on the lathe without having to form a tenon and leave chuck marks sums up the function of a vacuum chuck. In the case of the Hold Fast Vacuum Chuck Turning System, you can choose from a 3" or 6" vacuum head. I tested the latter, noting that this system differs from most in that it uses an air compressor (rated at a minimum of 2 cfm at 65 psi) rather than a costly (but quieter) vacuum pump to create vacuum pressure—an advantage if you already own a compressor; not so, if you don’t. Too, the Hold Fast employs a Venturi system; it’s less efficient than a vacuum pump. Specifically, the Hold Fast system generates 19" Hg of vacuum where a vacuum pump generates 26" Hg of vacuum. For secure holding power, 12" Hg is recommended.
The system includes a vacuum generator and gauge and a vacuum adapter that let me connect it to my lathe and compressor in about 20 minutes. The biggest challenge often faced when using a vacuum chuck is centering the work. Registration marks indicating the center of a piece prove helpful when using the tailstock in aligning the work with the chuck. Here, centering is easier by using a centering adapter such as the Hold Fast Chuck Reversing Adapter.
I used a variety of bowls to test the Hold Fast system, including bowls of various species and wall thicknesses. Depending on a wood bowl’s wall thickness and porosity, the vacuum pressure changed significantly. Open-pored woods like ash or red oak allow air to pass through the pores, limiting the vacuum pressure. You can overcome this rather easily by sealing the pores with finish, wrapping the piece with plastic wrap, or by padding sawdust on the bowl while suction is created. When I placed a walnut bowl turned to a 3/16" thickness onto the chuck, the vacuum draw registered only 11" Hg (below the recommended amount for safe turning); after applying a quick coat of paste wax to the outside surface of the bowl, the vacuum immediately increased to 16" Hg. The vacuum draw on a bowl with a 3/8" wall thickness cored from the same walnut bowl blank was 19" Hg with or without wax. To remove the bowl, simply stop the lathe and shut off the Hold Fast regulator.
Vacuum chucks are most useful for remounting turned work for touch-up turning, sanding, or finishing, and for mounting natural-edge bowls for turning the bottom. Since vacuum chucking requires a sealed system, you may not be able to achieve a vacuum on a bowl that is out of round. Defects such as voids are also a concern, although smaller defects can be sealed with tape or plastic wrap.
Overall, I found the Hold Fast System performed up to expectations, and it worked well for applications where a vacuum chuck is the chuck of choice. It sets up quickly, and it’s reasonably priced. If you already own an air compressor and would like an out-of-the-box vacuum chucking system, the Hold Fast is a good option.
3" Vacuum Chuck Kit 11/4" × 8 TPI
6" Vacuum Head 11/4" × 8 TPI
Reversing Adapter, 11/4" × 8 TPI - #2 taper
#149370 $32.99 (optional for centering work)
Tester: Kip Christensen
A square with all the angles
When you add a few more angles to the common square, you likewise add more functionality and value. That’s the thinking behind the coated steel Modified Square made by a company having the same name. Having 1" and 11/2" blades, the tool measures 81/2 × 121/2" and includes a 19/16" opening that’s 31/2" long for marking studs on plates or stair stringers.
Other than holding the square to a workpiece in one of several ways, there’s no setup to speak of. You’ll want a sharp pencil on hand for marking assignments.
Here’s where the Modified Square gets interesting. I found that the zero/zero center finder along the inside large blade serves as a quick way to measure and mark out a circle or desired workpiece width. It’s terrific for marking out equidistant hole locations. By setting the narrow right-angle blade on the edge of a board, I could mark square cutlines like a try square. For scribing a notch or a toekick on a piece of plywood, I simply lined up the needed dimensions on the Modified Square with the edges of the workpiece and marked, proving the tool’s value in layout work.
While the Modified Square may not match the extreme precision of a high-priced machinist’s square, it can perform multiple tasks in centering, squaring, and general layout functions above and beyond the scope of a try and/or combination square. Carpenters may find it a good addition to their toolbox for locating fasteners and laying out studs, although it’s not something they can carry around conveniently in a tool belt.
For project building and tool setups, a woodworker will like the Modified Square’s versatility in that it makes quick work of many measuring tasks. It may not, however, measure up to those tasks requiring extreme precision.
Tester: Jim Harrold
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