Power Sanding Mandrels

Power sanding mandrels come
in many different sizes

Overview: Many years ago in junior high woodshop class, I hand sanded every project I turned on the lathe. At the time, this was the only option available to me. While the rest of the class were using large stationary drum sanders, horizontal sanders, oscillating spindle sanders and belt sanders to sand their flatwork projects, those of us who preferred lathe work had abrasive cloth strips for sanding.

Thankfully, those days are long past! We now enjoy a plethora of tools for sanding our projects on the lathe including rotary tools, random orbit sanders, dual action sanders, inertia sanders, in-line sanders, pen sanders and more. Oh, how I would have loved to power sand a bowl back in the day! Although there are many different tools to choose from in every price range, one of the most useful tools you can own for sanding is an ordinary rotary or pneumatic drill, equipped with a Velcro backed abrasive disk.

Not only will using mandrels save your fingers, they can actually produce a better surface than hand sanding in most situations. They are also easier to use when working deep inside larger projects, where you may not be able to hand sand. Through the years, I've used and made more than a hundred sanding mandrels and have found that some designs work much better than others.

Design Considerations

Sanding mandrels are manufactured with straight sides or tapered sides. At first glance, you might think both would work fine for any sanding tasks you might throw at it, but this is not the case. Each design has its own advantages and disadvantages.

Standard mandrels
feature straight sides

Straight-sided mandrels can easily
mark beads when power sanding

  • Straight Sided Mandrels feature a 90-degree sidewall construction, with a Velcro or PSA (Pressure Sensitive Adhesive) face. These mandrels work well for projects like shallow open bowls, platters and other projects without much intricate detail. The straight side becomes counter-productive when trying to use the mandrel near design elements like beads. When you try to sand next to the bead, the side of the mandrel can touch the bead, causing the foam to melt and mark the surface of the wood. Although the mark is easily removable with mineral spirits, it can be easily avoided by using mandrels with tapered sides.
  • Tapered/Angled Sided Mandrels feature sides that have been tapered (angles vary by manufacturer) to reduce the potential for contacting adjacent design elements when sanding. When using a tapered side mandrel, it's easy to sand right up to the side of a bead without touching, or marking it. For all around use, a tapered side sanding mandrel is a better choice for power sanding most woodturning projects.

Tapered sanding mandrels are a better
choice for most power sanding needs

Tapered sanding mandrels can sand next
to beads without marking the bead surface

Mandrel Sizes

Mandrels are available in numerous sizes, including these 1", 1.5" and 2" versions. These are excellent for power sanding smaller projects and for cleaning up bowl and platter bottoms

Sanding mandrels come in a variety of sizes including 1.0", 1.5", 2.0", 2.5", 3.0", 3.5", 5.0" and 6.0." For most woodturners the 1.0", 2.0", 3.0" and 3.5" mandrels are the most useful. You need several sizes on hand so you can match the pad to the size of the project you need to sand. For example, if you need to power sand a 16" round Mesquite salad bowl, a 3.0" or 3.5" mandrel would be a good choice. You could of course sand the bowl with a 2.0" pad, but it would be much harder to maintain a smooth, fluid curve.

These mandrels feature precision machined arbors that fit The Sanding Solutions inertia (self-powered) sanding tool

You always want to use the largest pad size possible to sand your project, as long as it will follow the contours on your project. This will give you a more uniformly sanded surface, versus using a pad that's too small. The smaller 1.0" and 1.5" sanding mandrels are great for removing the last little bit of nub on the foot of bowls before finishing. A shallow carving knife can easily remove the bulk of the nub (where the tailstock's ball bearing center was placed) before using the sanding mandrel to smooth the remaining surface.

These tapered sanding mandrels from the
www.thesandingglove.com measure 5" in diameter
and are available with medium density and soft density
foam hook and loop pads

Foam Pad Density

The density of the foam pads on mandrels varies from manufacturer to manufacturer. Some are quite firm, others are medium density and some are very soft. Knowing which pad to use at any given time is the key to achieving sanding success. If the pad is too stiff, it may not be able to follow the contours you created which can lead to flat spots on your profile. If the pad is too soft, it may create undulations in the surface by sanding away the early wood areas (springwood) more than the late wood areas (summerwood).

These tapered sanding mandrels feature soft
foam faces that easily conform to curved surfaces

I like to keep a variety of different mandrels on hand with varying pad densities, so I can match the pad to the project I need to sand. If you do not have several different pads on hand, you can still achieve the same effect by using an interface pad between the abrasive and the face of your sanding mandrel.

Interface Pads

Interface pads (also known as backing pads) are foam core pads with Velcro faces that allow you to vary the density of the sanding mandrel by simply changing the interface pad. Interface pads are inexpensive and if used regularly, they can extend the life of your sanding mandrel almost indefinitely. If you use an interface pad on all of your mandrels and the Velcro face becomes worn, you simply replace the interface pad for a few dollars and you're back in business.

If you use a sanding mandrel without an interface pad and the Velcro face becomes worn or the hooks melt off, you have to replace the entire mandrel or try to resurface it. For most of us, it's much easier to just rip off a cheap interface pad and replace it rather than trying to resurface the pad.

Resurfacing Velcro Faces

Eventually the Velcro face on your sanding mandrel will wear out. Since many turners tend to use the edge of the pad more than the face, the edge is usually the first part of the pad that wears out. If you get the pad too hot when sanding, you will soften the hooks and they eventually wear off. They can also wear from the action of pulling the abrasive disks on and off the Velcro face.

If your Velcro face is worn, you have two options… Buy another mandrel, or resurface the face. You could just buy a brand new mandrel of course, but most mandrels are a tad bit expensive to replace. When you consider that the metal arbor and the foam face on your worn mandrel are probably still in good order, it's much cheaper to just replace the Velcro face.

Replacement Velcro faces are inexpensive, but they do require you to remove the old facing and prepare the foam surface for the new pad. I use a long razor knife like the ones sold for cutting wallpaper to remove the old worn pad. Once the pad is off, I smooth the surface if necessary with sandpaper and blow off any residue before gluing the new pad to the foam face.

The replacement Velcro faces do not come with an adhesive backing. I use E-6000 adhesive, which remains flexible when cured to secure the new Velcro pad onto the freshly prepared foam face. The adhesive should fully cure for at least 24 hours before using the pad for sanding.

PSA to Velcro Upgrade Kits

If you've got some old PSA faced sanding mandrels lying around and you prefer to power sand with Velcro backed abrasives, you can purchase an inexpensive PSA to Velcro upgrade kit that will convert your mandrels to Velcro faces. Since few abrasives are available with sticky backs, switching to Velcro faced pads will make it easier to sand your projects.

Make Your Own

These sanding mandrels have arbors made from
bolts with plywood backing plates and are
covered with a dense foam Velcro facing

If you're the type of person that enjoys making your own tools and accessories, you might want to consider making a few of your own sanding mandrels. Although new sanding mandrels are not particularly expensive, they are not inexpensive either. For folks on a budget, or for those who just enjoy making some of their own tools, making a few mandrels can be a nice way to spend a Saturday morning in the studio.

One advantage of making your own mandrels is that you can control the quality of materials you use to construct the pads and if you use recycled materials, the pads cost next to nothing. There are several ways to make your own mandrels. One way is to make everything from scratch. Another way is to find an el-cheapo sanding mandrel and modify it to suit your needs.

Making Mandrels from Scratch – If you take a look at a sanding mandrel there are only a few components -- the arbor, a stiff backing plate, the foam pad and the Velcro facing. For the arbor, you can use an ordinary bolt (not all thread), which costs a few pence at any home centre.

The backing plate can be made from numerous materials and turned to shape with a drilled hole to accept the arbor. Scrap Corian, or any good hardwood works just as well. I have used Baltic Birch plywood many times for backing plates. Almost anything will work; so feel free to use what you have on hand.

The foam pad is a little harder to scrounge. I have used dense foam scraps that were used as packing material and scraps from custom foam fitted luggage interiors. You can also buy dense foam pads from any foam manufacturer. Old mouse pads can also work. Some woodturning clubs purchase some bulk foam and split the cost among club members to keep the price low. Then, they have a "sanding mandrel party" to make up mandrels for everyone.

The Velcro faces must be purchased, but they cost a lot less than a complete new mandrel. These usually come without adhesive on the mounting side. I use a flexible when cured adhesive like E6000 for mounting the Velcro face to the foam disk. Let the adhesive fully cure for 24 hours before using the mandrel.

If you're using scrap foam or you need to taper the sides, simply mount itl on the lathe in a Jacob's chuck. A sharp skew can easily cut the foam to shape. Use another sanding disk mounted with a course abrasive (180-grit) to further refine the sides of the foam and smooth it out. If you use scrap materials, your sanding disks will cost $2.00 or $3.00 tops and you will have a nice new tool to use in your studio.

Modifying El-Cheapo Manufactured Mandrels – Another way to make your own mandrels is to buy a cheap manufactured sanding mandrel and modify it to suit your needs. Most cities have stores like Big Lots, Harbor Freight and similar stores that sell large rubber backed sanding disks with a 1/4" arbor. These are usually offered with a thin foam face made for using PSA (sticky backed) abrasives. A 5" PSA sanding pad can cost as little as $3.00. You can even find them two for $3.00 on sale.

Simply purchase a few of these and cut them down to the proper size on the lathe using a skew chisel. Once the mandrel is cut to size (for example 3") simply apply the foam (if necessary) or the Velcro face and you're good to go. You can taper the pad, or sand it to smooth any rough surface using an abrasive disk. This approach is faster and easier than making a mandrel up from scratch, but it does cost more. Either way, you will end up with some nice mandrels for a few pence.

Safety Note: Always follow all manufacturers safety instructions before working with your lathe, or any of the tools or products you may use. If you are unsure about any operation, obtain competent professional instruction before proceeding. Use and wear all necessary safety devices during turning and observe safe woodturning practices to prevent accident or injury.

Steven D. Russell is a professional studio woodturner, teacher and writer. He has written numerous articles for international woodturning magazines, which have been published in more than 78 countries around the world. Steve has demonstrated in numerous cities across the United States. His studio, Eurowood Werks, specializes in bowls, platters and hollow forms with unique visual and tactile treatments.

Steve is also the current and founding President of the Lone Star Woodturners Association, Inc., an AAW member chapter. The LSWA is a 501(c)3 non-profit educational organization dedicated to teaching and demonstrating the art and craft of woodturning.

Steve is also a featured writer for the Guild of Master Craftsman's "Woodturning" magazine, published in London England. Woodturning magazine is the world's leading magazine for woodturners. Look for his articles covering technical topics, or project based articles in an upcoming issue.