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This article was published in the April 2011 (#30)  edition of  Woodturning Design.

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Drill Guide in a more printer friendly (7 pages) pdf format

 

 

Drill Guide

Introduction

One-Way came out with a woodturning accessory called a Drill Wizard several years ago.  I bought one and liked what I could do with it (to the extent that I dedicated an extra drill and foot switch to it), but in a stock configuration it won’t fit on my One-Way 1018 lathe, much less other mini-lathes.  This article describes a Drill Guide that can do most of the Drill Wizard functions but is engineered quite differently.  Instead of mounting a drill on a moveable cradle, it takes advantage of the low speed bearing capabilities, both rotary and linear, of Ultra High Molecular Weight Polyethylene (UHMW is easily workable with woodworking tools).  Being home made, the Drill Guide is also quite inexpensive, if you discount your time.

 

A UHMW block is mounted on the lathe via the tool rest banjo.  A ¾” shaft is held in the adjustable UHMW block.  The shaft has a ½” NF drill chuck at one end and a stud for mounting a 3/8” drill on the other.  Shaft collars serve to set the Drill Guide at lathe center height and as a depth stop.  Center drilling the shaft allows radically choking up on small drill bits to avoid deflection especially when drilling at an angle to the work.

 

The Drill Guide can be used both for drilling mortises for assembly and for a variety of decorative effects.

UHMW Block

The core of the Drill Guide is a block of UHMW polyethylene.  A Google search will reveal numerous sources for UHMW—I used an Industrial Supplier, McMaster-Carr. You’ll also be able to get a bolt with ½-20 threads and locking collars there. Starting with a 2” x 2” square rod of UHMW, use your table saw (you could also use a band saw, but the table saw gives a reliably more square cut) to cut a block 3” [check] long as in Fig01.

 Fig01

Fig1                Crosscutting the UHMW block to length with table saw and sled.

At this point if you have a small lathe you may wish to measure the distance between the top of your tool rest banjo and center height of your lathe, as well as the thickness of your locking collar and locking nut.  The lathe banjo/center distance minus the thickness of the locking collar and nut should be more than the distance between the bottom of the UHMW block and the center of the shaft hole.  If you have to move the hole less than 3/4” from the bottom of the UHMW consider other means.  You could leave off the locking collar, or lengthen the UHMW block to 4” and cut a step into it so you can lower the shaft height.  Look at Drawing1.

 Drawing1

 

Drawing1 A drawing of two alternatives for locating the drilling holes.  Use the left hand version if you have adequate distance between your tool rest banjo and lathe center, if not use the right hand version.

Now mark the UHMW block for drilling as in Drawing1.  Pencil doesn’t do well on UHMW, so I used a ultra-fine line marker.  Pencil on masking tape would also work well.  On one long face measure in 1” from the center of a shorter edge and mark for tap drilling for the attachment post.  Then measure in 3/8” from the opposite short edge and 1/2” in from each long edge and mark for the adjustment bolts holes.  Last on a long face at right angles to the already marked face, measure in 1” from center of the adjustment hole end and mark for the shaft hole.  The marked UHMW block is shown in Fig02.

 Fig02

Fig02  The UHMW Block marked for drilling.

Clamp the UHMW Block on your drill press table with the shaft hole marked face up.  Mount a 49/64” drill in the drill press chuck and drill through the block at the mark as in Fig03.  If you do not have nor wish to buy a 49/64” drill bit, there are two alternatives.  You could use 47/64 drill rod for the shaft and use a ¾” drill.  You could also use a ¾” drill, and then after drilling the adjustment holes and slotting the UHMW on the tablesaw, compress the slot slightly with the adjustment bolts and redrill with the ¾” drill.

 Fig03

Fig03                       Drilling the shaft hole in the UHMW Block.

Re-clamp the block so that the other marked face is up.  Set the height of the drill press table so that you will be able to fit the tap and mini-tap guide as well as the drill without disturbing the set-up.  Insert the drill that is the proper tap size for a bolt that will fit in your lathe banjo (my 1018 uses a ¾” mount so I used a 21/32” drill bit).  If your lathe uses a tool rest post larger than 1” you may wish to use drill rod for the post and add a ¾” stud to hold the UHMW as taps larger than 1” start to get rather expensive.  Drill through the UHMW block with the tap drill as in Fig04.  Without moving the block or drill press alignment remove the drill bit and insert the min-tap guide in your drill press.  Place the tap in the drilled hole and lower the drill press quill to compress the internal spring in the mini-tap guide as in Fig05.  The point of the mini-tap guide should be in the center dimple of your tap or tap handle.  Turn the tap to cut the threads.  The mini-tap guide will keep the tap aligned and yield much more accurate results and is well worth its moderate expense.  It is possible to chuck the tap in the drill press itself or use some other spring loaded device but I strongly suggest getting the real thing

 Fig04

Fig04                       Drilling the tap hole for the mounting bolt.  Doesn’t the curly swarf from drilling look like it would make neat Christmas ornaments?

Fig05

Fig05                       Tapping for the mounting bolt.  The mini-tap guide keeps the tap aligned and vertical for accurate threads.

After completing tapping the threads remove the tap and mini-tap guide and insert a ¼” drill bit in the drill press chuck and drill through holes at the marked locations for the adjustment bolts as in Fig06.

 Fig06

Fig06  Drilling for the adjustment bolts.

Place the block on your table saw sled and set the height of the blade so that it will cut a slot intersecting the drilled shaft hole as in Fig07.  Use the stop block to center the blade on the hole as in Fig08 and cut the slot.  It is probably risky to do this operation without a sled, so if you don’t have one forego neatness and use your bandsaw or even a hand saw instead.  Fig09 shows the completed UHMW block.

 Fig07

Fig07                     Setting the saw height to create an adjustment slot.

Fig08

 

Fig08                       Sawing the adjustment slot.

Fig09

Fig09                    The UHMW Block after drilling all the holes.

Insert ¼ x 2-1/2” carriage bolts into the adjustment holes of the UHMW Block and use a hammer to set the square shoulders into the UHMW.  Place locking nuts on the bolts.

 

Select a partially threaded bolt that will fit your tool rest banjo.  Cut off the head of the bolt at an appropriate length for your lathe.  You can use your tool rest post as a guide. Chamfer the cut end of the bolt with your grinder so that it will be easy to insert.  Check to insure you can both insert the bolt and lock it in place as bolts are not exactly made to extreme tolerances.  If the bolt fit is too tight you can easily adjust it at this time by chucking it on the lathe and filing with the lathe on at a slow speed.  The completed mounting bolt with locking nut is shown in Fig10.

 Fig10

Fig10                  The beheaded mounting bolt with locking nut.

Thread a nut onto the bolt.  If you have limited distance between the tool rest banjo and lathe center you may wish to use a thinner locking nut.  You can also counter sink for the nut.  Insert the bolt into the UHMW Block and tighten the nut to lock the bolt in place.

Shaft

Prepare a drive stud for the Shaft.  Select a partially threaded 3/8” bolt and cut off the head, and trim the threaded end if necessary.  You need to allow ¾” or so to thread into the shaft and a long enough stud exposed to chuck up a drill.  Neaten up the cut ends with a grinder.  The completed drive stud is shown in Fig11.

 Fig11

Fig11                       The completed drive stud (beheaded 3/8” bolt).

Prepare a threaded stud to mount the drill chuck.  I used ½ x 20 threaded rod because I had some, but it would be cheaper to buy a ½ x 20 bolt and cut off a threaded section.  You need enough length to strongly attach to the shaft and chuck.  An inch to 1-1/2” would be adequate.  Thread a ½ x 20 nut on to the threads before cutting so that you can easily clean up the threads.  Cut the threaded length and then chamfer the ends with a grinder.  Clean up both ends if necessary with the nut.

 

I used ¾” steel drill rod for the shaft.  It’s durable, and reasonably cheap, but doesn’t machine easily with woodworking tools.  If you don’t mind spending more, brass is easier to work, and is certainly strong enough for the task.  Cut a piece of your ¾” rod 5” long.  I used a cut-off saw, as in Fig12, which gives a fairly square cut.

 Fig12

Fig12                       Cutting ¾” drill rod to length.

Chuck up the 5” piece of rod on your lathe.  You can use any sturdy method that works.  Fig13 shows the rod chucked up in a 4-jaw chuck with the top jaws removed.  #1 Jaws would also work.  Fig14 shows the rod chucked up in my favorite chuck, the Beall collet chuck.  First start a hole that will be exactly centered by using a combined drill and countersink, which is too rigid to deflect when drilling starts.  After starting the hole remove the combined drill and countersink, and chuck up a 29/64” drill bit.  Drill, as in Fig15, about an inch deep.  Use a slow lathe speed and cutting oil if you have some.

 Fig13

Fig13                       ¾” shaft mounted for drilling in a 4-jaw chuck with top jaws removed.

Fig14

Fig14                      The ¾” shaft mounted in the (preferred) collet chuck for drilling.  The hole has been started with a combined drill and countersink.  The combined drill and countersink is very short and rigid so it will start a well centered hole instead of deflecting.

Fig15

Fig15                       Drilling the shaft with the tap drill.

Remove the drill and chuck up a mini-tap guide.  Place the end of the ½ x 20 tap in the drilled hole, and use your tailstock center to compress the mini-tap guide as in Fig16.  Lock the spindle and tap the threads.  It is possible to substitute something else for the mini-tap guide.  It is equally possible for your spouse to open tin cans or dig holes for crocus bulbs with your best bowl gouge.  Set a good example.

 Fig16

Fig16                     Tapping the shaft for ½” NF threads using a mini-tap guide.

Drilling accuracy or run-out, depends on the face of the shaft being perpendicular to it’s axis.  Even the cut-off saw isn’t good enough—it’s just less work to clean up.  Use a scraping technique to true the face of the shaft.  HSS will cut drill rod if you slow the speed and cut gently.  To save re-sharpening I used a ¼” cobalt steel cutter in a handle as in Fig17.

 Fig17

Fig17                 Face turning the shaft so the drill chuck will mount aligned.

Screw the mounting stud into the shaft now.  Optionally use a combined drill and countersink to start a hole and then drill through the shaft with a 3/16” or ¼” drill as in Fig18.  This will let you choke up on small drills to reduce deflection, especially when drilling at an angle.

 Fig18

Fig18  Drilling through the mounting stud with a 3/16” drill so that small drills can be choked up on to reduce deflection.

Screw the drill chuck onto the shaft temporarily and mount a small drill in the chuck.  Turn on the lathe and visually check for excessive run-out as in Fig19.

 Fig18

Fig19                      Visually testing for run-out.

Remove the drill chuck and reverse the shaft in your chuck.  Use the combined drill and countersink to start the hole and then use a 5/16”drill bit to drill about an inch deep into the shaft.  After drilling remove the drill bit from the chuck and insert the mini-tap guide.  As before insert the tap into the hole and use the tailstock to compress the tap guide in the back of the tap or wrench.  Then tap the threads.  Fig20 shows tapping the drive stud hole in a make-shift fashion using a spring loads center punch instead of a mini-tap guide.

 Fig20

Fig20                    Tapping for the drive stud using a sub-optimal center punch instead of the mini-tap guide.

Fig21 show the shaft parts ready for assembly.  Assemble the shaft assembly by threading the mounting stud into the shaft, and then threading the chuck onto the mounting stud.  Thread the drive stud into the other end of the shaft.  Fig22 shows the assembled shaft.  Insert the shaft into the UHMW block, then place the locking collar on to the shaft.

 Fig21

Fig21               The unassembled shaft.

Fig22

Fig22                       The assembled shaft.

Mount the Drill Guide in your toolrest banjo and tighten the banjo and post securely.  Tighten the nuts on the adjusting bolts until there is no play in the shaft, but not so tight that it can’t be rotated or slid in and out.  Mount your drill on the shaft as in Fig23 and test the assembly by running the drill.  If there is no play in the shaft but it feels like it’s running rough, it could be that the drive stud is not quite mounted co-axially, say from using a center punch instead of a mini-tap guide.  If this is the case then remove the shaft and remove the drill chuck from the shaft.  Mount the shaft in your chuck and turn or file the drive stud true.

 Fig23

Fig23                       The Drill Guide  mounted on the lathe with drill attached.

When all is working well set the height of the Drill Guide so that it is at lathe center.  Chuck a small drill in the Drill Guide chuck and adjust the height of the mount in the toolrest banjo until the drill lines up with your tailstock center as in Fig24.  Lock the locking collar at this height.  If you didn’t do the math right and there’s not quite enough height, countersink the locking nut a bit.  Fig25 shows the completed Drill Guide.

Fig24

Fig24                      Set the adjusting collar so that the Drill Guide is at the center height of your lathe by comparing to the tailstock.

Fig25

 

Fig25                  The assembled Drill Guide.

Using

You can use the Drill Guide for both structural (such as mortises for stool legs) and decorative work on the lathe.  In general the shorter the drill bit the better the results, both because there will be less tendency of the drill to deflect, and because with mini-lathes the movement of the banjo from lathe center is limiting.  Forstner and brad point bits are often superior for this use.  However ordinary twist drill bits will give good results if you choke up on them to prevent deflection.  There are also available very short bits called spotting and centering drills, however they will not enter as cleanly when drilling at acute angles, and drill far from flat bottomed holes.

 

To use the drill guide, place the drill you want to use in the chuck.  Align the Drill Guide to the placement and angle of the hole and lock the tool rest banjo securely.  Attach a portable electric drill to the stud.  Push the shaft in with the drill off until the drill bit touches to confirm placement.  With the bit still just touching the wood adjust the locking collar on the shaft so that it is the distance from the back of the UHMW block that you want to be the depth you drill.  Withdraw the shaft a bit, turn on the drill, and push the drill in.

 

Fig26 shows drilling a hole for inlay in a practice spindle at a right angle to the spindle.  The drill is choked up on to prevent deflection.  The locking collar was set on the shaft to limit the drilling depth.  Fig27 shows drilling with the same twist drill in the sample spindle with the Drill Guide set up at about 45 degrees to the spindle axis.  Even at this angle with an ordinary drill bit the bit didn’t deflect because the chuck supports the drill close to the tip.  Fig28 show the results after filling with inlay.  The top spindle, with black nylon inlay, shows both a circular dot from right angle drilling and an apparent ellipse from drilling at an angle.  The bottom spindle shows pewter wire inlaid in angled holes.

 Fig26

Fig26                       Drilling a hole square to spindle stock.

Fig27

Fig27                       Drilling a hole at an acute angle to spindle stock.

Fig28

Fig28                       Practice spindles with inlay.  The top spindle has black nylon inlay in holes drill straight and angled.  The lower spindle has pewter wire inlaid in angled holes.

Fig29 shows drilling into a construction pine “bowl” with a twist bit.  Fig 30 shows the clean hole obtained with a spotting and centering drill.  Fig30, however, shows the ragged entrance the spotting and centering drill produces when drilling at an acute angle.  The Forstner bit, in Fig31 shows a much cleaner hole when angle drilling.

 Fig29

Fig29                       Drilling for inlay in a construction pine practice “bowl”.

Fig30

Fig30                       Drilling square to a practice bowl with a spotting and centering drill.

Fig31

Fig31                       Drilling at an acute angle to a practice bowl with a spotting and centering drill.  Note that it didn’t do very well.

Fig32

Fig32                       Drilling at an acute angle to a practice bowl with a Forstner bit.

Fig33 shows a square-in-circle inlay mounted in an angled hole.  Fig34 shows 1/8” aluminum wire with right angle holes on the top, and angled holes on the bottom.

 Fig33

Fig33                      Square-in-circle inlay in an angled hole.

Fig34

Fig34                       Aluminum wire inlaid in holes drilled square on top, and angled on the bottom.

You can get interesting effects particularly with fairly figured wood by using a homemade hole drill.  Fig35 shows a hole drill made from a pen tube.  Cutting the tube with a hacksaw near the end yields a ragged edge that will cut in a short distance.  A steel center fills the back part of the length to prevent the drill chuck from crushing the tube.  Drill in a short distance and don’t push hard, as this may turn the hole drill into a wood burner.  Then glue in segments of matching tubing with CA glue.  Cut off the excess tube with a saw after giving the glue a chance to set.  You can level the inlay with gentle cutting with ordinary turning tools and sand as usual.  Fig36 shows brass pen tube inlay in Zebrawood.

Fig35

Fig35                       Pen tube drill.  It’s just a piece of pen tube cut near one end reinforced with a steel insert to keep it from collapsing.

Fig36

Fig36                  Pen tube inlay in Zebrawood.

Tools and Supplies

2” x 2” UHMW square rod

Table saw with sled preferred

Drill press

49/64” drill bit

Tap drill bit for bolt that fits your tool rest

Tap for bolt that fits your tool rest

¼” drill bit

Mini-tap guide

Two 1/4” x 2-1/2” carriage bolt

Two ¼” locking nuts (nylon insert)

Partially threaded Bolt, locking collar and locking nut that fits your tool rest

Partially threaded 3/8” bolt

1“ of 1/2 “ x 20 threaded rod (buy a bolt or threaded rod) and nut

½” capacity drill chuck with 1/2x20 NF mount

5” of ¾” drill rod or brass ¾” rod

Saw (cut off saw preferred)

Lathe chuck (collet chuck preferred)

Combined drill and countersink

29/64” drill bit

½ x 20 tap and tap wrench

5/16” drill bit (optional)

¾” locking collar

Various drill bits and inlay stock

Author

David Reed Smith is a Basement Woodturner, tinker, and Meme Slave living in Hampstead, Maryland.  He welcomes comments, questions and suggestions via email at David@DavidReedSmith.com.  This article, along with about 50 others will be available on his web site www.DavidReedSmith.com.