Earlier Review of Passive Sanders
Lyn J. Mangiameli
>Here is the passive sander portion of the comprehensive review I did on sanding devices for More Woodturning.
1. Passive Rotary:
I�m completely set up with electric and pneumatic sanding systems, but I still find that passive sanding tools are often my first choice. The abrasive pad is rotated by the action of the object turning on the lathe. The more the sanding disk is pressed against its own periphery (as opposed to flat against the wood), the faster the disk will turn.
Put briefly:
Passive sanders have these advantages
� They are quiet
� They tend to strew less dust around
� They tend to operate slower and cooler, making it less likely to have heat checking and
more likely to achieve longer abrasive life.
� The rotational direction of the sanding pad/head is easily reversed by changing the way the
pad is applied to the work. By changing the direction of rotation both sides of the abrasive
particles, the effective life of the abrasive disk is greatly increased.
� They have no power cords or air hoses to tangle and pull, or bump into your turning.
� They are lighter
� In general, they are smaller and some handle shapes are much more conducive to working
inside narrow forms.
� Some models allow for a the head to be adjusted over a 340 degree angle, allowing
them to work somewhat under lips and in confined spaces.
� Some passive sanders are capable of extending deeper into narrow vessels than any
powered drill/sander
� A single unit will cost less than most powered drills, and is essentially maintenance free.
� They can be used for wet sanding without fear of electrocution or equipment damage.
� Some find they offer more feedback from the wood and more control over the sanding.
Passive sanders have these disadvantages:
� They require the lathe to be turning for them to operate.
� There is yet to be a single handle shape optimal for both internal and external use.
� They are not really adaptable to rotating shaft extensions.
� They have limited ability to be used with the entire abrasive disk flat against the wood.
� Some make changing/replacing the basic pad difficult to impossible to achieve (Vic
Woods style), or the interchangeable parts are not commonly available (Grip-a-Disk).
There is a small range of styles and sizes of pads that are available or suitable for
most that do allow replacement.
� They are more expensive compared to already having a suitable drill or sander. Particularly
if you feel you need more than one.
a. Grip-a-Disk:� This British Sander comes in models with holders to take either two or three inch sandpaper discs. Included with the sander is a mandrel that will allow you to transfer the holder to a drill chuck for power sanding. The holder will take either thick soft foam backed abrasive disks also called �Grip-a-disk� or regular Velcro backed ones. I usually use a subsidiary Innerface backing pad that helps preserve the Velcro on the sander and will fly off if the sander gets rapped badly (which I see as a feature).
One advantage of this passive sander is that it has an articulating head that can be set at numerous angles so you can position the sanding head at roughly right angles to the handle to deal with external sanding or internal sanding up near the wings of natural edge bowls, or set it inline with the handle for the bottom of bowls. However, while the Grip-a-disk allows for articulation, it is slightly troublesome and time consuming to adjust (though it locks really well, once set). The two inch version is better than the three inch version for dealing with the inside of most bowls, though the 3 inch is slightly easier to use on the outside. The included holder is thin and hard, allowing it to get into narrow under-clings and grooves. When more padding is desired, use the foam backed Grip-A-Disk abrasives or just add one of the Performance Abrasive Innerface pads to obtain the padding of your choice. The mostly wood handle is approximately 9 inches to the pivot point of the head. The drive shaft is coupled to the head via ball bearings.
b. Sorby has introduced a passive sander very similar to the Grip-a-Disk, and like it, is available in both 2 inch and 3 inch versions. Though it resembles the Grip-a-Disk, and may be easier to find, I find it is much the inferior of the units. The Sorby pad is very thick (almost 3/4 inch), which limits the spaces it can enter into, and offers less control of density. The locking knob that adjusts the head is massive in comparison to the head and the knob gets in the way of properly positioning the head within some forms (but does make for quick and easy adjustment of head angle over a range in excess of 90 degrees). One could substitute an Allen head bolt to reduce the bulk of the locking mechanism, but at the price of giving up the ability to easily lock the head with your fingers. The bearings are phosphor bronze sleeves that Sorby says should be regularly oiled (leaving the slight possibility of transferring machine oil to the wood of your turning which can stain or interfere with some finishes). The rotating shaft protrudes from the end of the head, which makes it awkward to grip the sander at the back of the head. It just amazes me that this copy of the Grip-A-Disk is so inferior in design to the original. Please don�t judge the performance of passive sanders by this tool.
c. VicWoods: This passive sander has been available in a couple of configurations over the years, sometimes having a handle of fine hardwood and more often a plastic handle. The handle is short, at a little over six inches, and for one handed use is functionally shorter as the drive shaft is permanently affixed at a right angle approximately 4.5 inches from the end. However, this location makes it easier to use a two handed grip (one on each side of the drive shaft) for external sanding. The short drive shaft is couple to the handle through sealed ball bearings, and ends in a thick rubber holding pad of roughly hemispherical shape. The thick pad can develop tears after extended use, but I�ve always been able to repair them successfully with Barge cement. The tool with its 3 inch diameter holder is best suited for external sanding using a two handed grip. It works very well, and I find it to approximate the efficiency of a powered sander, but without the noise.
d. Soren Berger: Soren Berger offers two versions of what he calls his �Free-Wheel Sander.� I have not used these, so I am basing my description on the information from his web site. He makes a short handled version, that sets the drive head at 45 degrees, and an 18 inch long handled version where the head is fixed inline with the metal handle. The long handle is notable in that it is hollow and allows one to attach a vacuum to the distal end. According to Soren, when a small hole is made in the center of the abrasive disk, the long hollow handle can effectively channel a lot of the sanding dust directly into the vacuum. Both heads use a thick, tapered, foam pad and are meant to take 3 inch Velcro backed abrasives. Apparent drawbacks to these devices are that their head does not articulate, which I find essential for interior work, and the large heads limit the size of the curve they can follow.
e. LJM Passive Sander: A passive sander with double ball bearings and all metal head that can use almost any size sanding pad, can mount to a broad range of handles and shafts, and can be used for both internal and external sanding. Directions and diagrams for construction are included in a side bar.
Until recently, neither the commercial nor homemade passive designs dealt well with the interior of small bowls, deep vases, semiclosed forms, and fairly narrow mouthed hollow forms. In these settings, a design I developed works best, and often is likely to be the only design that will work at all. The tighter internal curves, the more constrained shape of the forms, and the narrower mouths of hollow forms and vases require a smaller sanding pad. One and 1.5 inch pads often will work in these settings when others will not (though a 1.5 to 2 inch abrasive hemisphere might be about perfect). For internal use, one may need to be able to adjust the angle of presentation, sometimes several times, and other designs, do not allow for the articulation that is necessary for these forms, nor do they address the need for a smaller pad in the more constrained places.
Thus the advantages to the design I offer are multiple. It allows for easy replacement of pads and easy conversion between pad sizes. It allows for quick, easy, and wide adjustment of approach angle, it allows for easy movement between various handle lengths and styles. Just within the Stewart family you can use a straight handle, a pistol grip handle (which works great for small to medium hollow forms), an Omnitool or SuperOmni for deep forms, and you can even bolt it up to the Hooker (and if you want, you can add a Sorby RS2000 side handle). It also will fit the Jamieson boring bars. Using such shafts and handles, it will work well over a standard toolrest (almost essential for interior work on hollow forms) and works wonderfully with the gated and pin style tool rests. If you don't like or have the Stewart style handles, you can make your own out of some steel rod or even hardwood dowel.
Thus this design will perform more tasks and interchange between them more quickly than any other passive or active system I am aware of. You can go from a 90 degree short handle with 3 inch hard pad to a 45 degree long shaft on a pistol handle using a 1 inch pad, and make the entire change in less than 30 seconds. I'm not trying to promote this design as wildly original or desirable for every turning use, but I have found it to be one of the most useful sanders in my arsenal.
f. Commercial Internal Passive Sander: Recently a device has come out variously called the �Infinity Boring Bar Sander� or simply the �Angle Sander.� This appears to be a commercial approximation of the free plans I�ve offered for several years. It is made up of an aluminum head with dual ball bearings and is supplied with two 5/16 inch shanks; one angled, one straight. These shanks should fit in most boring bars (e.g., Jamieson, Omnitool Scorpion Straight shaft), but the head is not set up for attachment to a Hooker like tool. The 2 inch sanding pad is replaceable, and a 3 inch pad may be substituted.
g. Home made: Passive sanders are an easy project. Herman de Vries has long offered directions on how to make your own ( http://www.hdv.net/ ), and there are additional plans to be found on the forums and newsgroups. Joe Fleming has suggested a very easy to make version which involves simply mounting a round Velcro disk holder to a rollerblade wheel. I haven�t tried these, but they offer a very inexpensive way to conduct your own experiments with passive sanding.
