Turn Your Drill Into a Spindle Sander Using a Homemade Mandril




Sanding the inside of a hole can be horribly aggravating, especially on a pocket hole that doesn't go the whole way through the piece. You can try using a round file, but its hard to get consistent results, and a short range of motion really slows down progress.

In my case I needed to widen every hole in a handrail by about one millimeter so the spindles could be pushed further up inside. The holes were just slightly bigger than my pinky, so doing it by hand just wasn't an option, and I didn't want to use a drill bit, which would have splintered the edges of the hole.

The solution to this was to create a mandril that could be used in a hand drill, basically turning it into a hand-held spindle sander. I made mine at http://techshop.ws

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Choose an Appropriate Dowel to Make Your Mandril Out Of

Each task is unique, so you get to tailor your tool to the task you want to use it for. I like for my mandril to be a little bigger than half the diameter of the hole I'm sanding. That makes it big enough that it won't get easily hung up in one spot and create a trough where it sanded away too much at once, but its still small enough that you can maneuver around inside the hole and give attention to where it's needed.

Step 2: Cut Your Dowel to an Appropriate Length

Again, you're making a custom tool for a specific job, so the length of your mandril will be determined by how deep you need to get sandpaper into the hole. Take that length, add a half inch or more that will act as a spacer between the sandpaper and the drill, giving you some maneuvering room while sanding, then add another inch or more that you'll clamp into your drill chuck.

If the dowel you're using is too large to fit into the chuck of a drill, you'll need to decrease its diameter where it it will be clamped into the drill chuck. The concentricity of the two different diameters is very important if you want your tool to be balanced as it spins, so while you maybe could shave it down by hand, I doubt you'd get really good results. The obvious solution would be to use a lathe to remove the excess material.

Step 3: Cut a Slot for the Sandpaper

The slot should have a slight twist to it as it travels up the shaft. This will help push the sandpaper towards the base of the mandril where it clamps into the drill instead of getting spun off the tip. That assumes, of course, that the drill is spinning in the intended direction.

Use a coping saw or scroll saw with a rough toothed saw blade where the teeth extend slightly to the left and right of the blade. This will allow the blade to be able to cut the slight corkscrew we're trying to achieve.

Use a simple jig to keep the dowel centered on the blade as you make the cut by clamping piece of scrap wood to the saw table to push the dowel against to keep it stable.

Be sure not to twist the blade or you'll be likely to snap it. If you're having trouble cutting the twist, try alternating angling the blade slightly to the left and to the right as you progress, creating a slot that is wider than the width of the blade.

Step 4: Install the Sandpaper

Cut a strip of sandpaper whose width is the length of the slot you cut in the mandril. I prefer the fold and tear method instead of dulling a knife by actually cutting sandpaper, but you can mangle your own tools however you see fit.

The slot being at an angle can make it tricky to insert the sandpaper. I find it easiest to lay one end of the sandpaper over the slot and put a crease in it with my thumbnail, giving it the proper angle. It can then be folded and inserted into the slot. Wrap the sandpaper around the mandril and repeat the crease process for the second end of the strip. Trim off any excess sandpaper from the second end that won't fit down into the slot. If your slot is narrow with respect to the thickness of the sandpaper, it may be easier to (after creasing both ends of the strip) curl up the strip and slide it down over the mandril with tabs in the slot.

For additional security a rubber band can be wrapped around the sandpaper. Put the rubber band as close to the base of the mandril as possible to keep it out of the way.

Clamp the mandril in the drill chuck just like you would any drill bit. Make sure it is centered in the teeth as you clamp it down.

Keep the speeds low as you use your new sanding tool to help prevent the sand paper from being slung off of the mandril.



    • Indoor Lighting Contest

      Indoor Lighting Contest
    • Make It Fly Challenge

      Make It Fly Challenge
    • Growing Beyond Earth Maker Contest

      Growing Beyond Earth Maker Contest

    16 Discussions


    4 years ago on Step 4

    Great shop idea. I can't hardly wait to use it! Thanks for the build.


    4 years ago on Introduction

    Awesome take on this; I've been doing something similar for years but am digging the slotted dowel aspect.

    My version is a base layer wrapped around a nail (of whatever appropriate size), 100 grit and glued on. I have "wraps" at the ready to throw over the top of that -- the sandpaper grips the new twist, so usually extra no adhesive required.

    From there, I run it through a hole block...literally a block full of holes, haha! Running it slowly backwards (depending on the direction of your twist) will tighten the whole shebang up quite nicely!

    Once twisted to the correct size, reseat the sandpaper edge in your chuck, and off you go!

    Attached pic shows currently used twist in the chuck, a "post traumatic twist sitting on top, and one getting shaped courtesy an old hollow anti-vibration drum stick. Oh, and a hole block in the background. :-)

    They look rough, but the project didn't require precision...my apologies for the poor example!

    I WILL be trying your dowel mandrel next time. Thank you kindly!

    1 reply

    Reply 4 years ago on Introduction

    Thanks for the kind words, and for sharing your version!

    One thing I'd modify about loading the sandpaper into the dowel mandrel, instead of 'stubbing' the sandpaper into the slot, run the strip of paper a fair way bit through the slot then wrap both layers around the outside. That should help prevent the centrifugal force from pulling the sandpaper out of the slot, which is prone to happen when the paper is just stubbed down into the slot. It will make it more like a flap sander, though, so the accuracy of the sanding will be decreased somewhat. A rubber band or some glue to hold the flap down against the dowel might help with that.



    5 years ago on Introduction

    Great idea! Seems like it might help if the sandpaper extended into the chuck 1/8" or so. Gonna try that--I'll let you know if it works.

    1 reply

    Reply 5 years ago on Introduction

    Thanks, and please do post your results. It might be wise to wrap a heavy sheet of paper around the sandpaper that extends into the chuck to protect the chuck fingers from being abraded. Also, having a 1/8" section at the tip of the fingers that is thicker than the rest of the mandril's handle may cause the mandril to be able to spin slightly off-center, so wrapping the whole handle either in sandpaper or a paper of similar thickness might be needed to stabilize it. I'm probably way over-analyzing it, so fill us in on how it actually goes!


    5 years ago on Introduction

    In the early 70's a Buddy bought a new Yamaha 650 twin (4 cycle). It kept having valve guide problems. No Yamaha dealers around S/W Mt. could ever fix it. He got so mad He found the address of the President of the Yamaha Co and wrote Him a letter, "No computers then". The President of Yamaha sent a letter back saying "use a Tinker Toy stick and sandpaper". Yup.!

    spark master

    5 years ago on Introduction

    Try putting the slit side into the drill chuck for bettererer tightness! Nice concept, I have a HUGE slow speed drill mounted to a work bench using a piece of 1/2 black iron pipe into a flange. Maybe it is like 500 rpm's. I call it my whale, and you can put a rather large piece of wood dowel in it, or a piece of EMT with a slot, you can use rubber cement to make paper stick and removal is easy.

    Regardless of size, however, if you use very fine expensive paper AND slow it to 90 rpm's, you can sharpen small blades on it, or grind the edges of hand cut glass (or course in all cases you need to know about safety procedures, wear gloves and glasses, face and chest protection.

    nice though


    5 years ago on Introduction



    5 years ago on Introduction

    I totally did this to sand out the last ring I made! I didn't think to cut a slit in the dowel and just taped it, but I find it cool someone else had the same idea as me....

    2 replies

    Reply 5 years ago on Introduction

    Sounds like a good idea, especially if there isn't a saw on hand to cut a slot with. What sort of tape did you use, and how well did it hold up?