Turning a CrushGrind shaft grinder without using glue

Transcription

1 Turning a CrushGrind shaft grinder without using glue A step-by-step approach to removing the apprehension 1 Chris West

2 Content Introduction 3 Robert Sorby CrushGrind Recess Cutting Tool 4 Required tools and accessories 4 Drawings for the project 5 Preparation 6 Drilling the grinder - base section 7 - top section. 9 - top section s wood insert 10 Assembly of the top of the grinder 10 Shaping the grinder 11 Finishing the grinder s body 11 Assembly of the base of the grinder 12 Shortening the grinder s shaft 12 Maintaining the mechanism 13 Supplier 13 Additional Reading 13 About the author 13 2

3 Introduction Many people believe that the CrushGrind with its ceramic grinding mechanism is the best on the market; few would disagree. Developed by IDEAS Denmark in 1992 the mechanism is designed not only for salt and pepper, but also for spices and herbs. For this reason the CrushGrind Shaft mechanism Fig 1 has become a favourite in the woodturning community. Just as popular is the CrushGrind Wood mechanism Fig 2. Somewhere along the line the approach of using glue with the CrushGrind mechanism was introduced which is not how it was designed to be assembled. Grinding the lugs off a CrushGrind mechanism and using glue might have been introduced by the professional whose livelihood depends on speed. However this was not the way the Crushgrind designers envisioned it would be fitted into a grinder. To quote from the IDEAS - Denmark website¹ it is a Press and Click mounting mechanism without usage of glue or screws. To achieve this a special tool designed by Brian Fitzsimmons of Constable Woodcrafts and produced by Robert Sorby is used to cut a recess 3/16 (5mm) wide and approximately 5/32 (4mm) deep for the spring clips which locate the mechanism in the main body and in the top. Fig 1 The particular mechanism being discussed in this guide is know as the CrushGrind Shaft. Fig 1. Fig 2 A following guide will be written for the shaftless version of the CrushGrind Wood model. Fig 2. The following instructions differ from articles often found in woodturning magazines in that the illustrations and photographs clearly show the order of drilling for you to easily make yourself a grinder which you can be proud of. From this point on the words CrushGrind may be shortened to CG for brevity. 3

4 Robert Sorby CrushGrind Recess Cutting Tool Below is the tool portion of the Robert Sorby CrushGrind Recess Cutting Tool which is critical to the process being described in this guide. Required tools and accessories 8 CrushGrind Shaft mechanism Forstner drill bits: ⅞, 1, 1¼, 1½ & 1¾ Sorby CrushGrind Recess Cutting tool. Live centre #2MT Jam chuck blank Wood blank 3 x 3 x 12 Spindle gouges of your choice Finish of your choice 4

5 Drawings for the project Shown below are the two main drawings of the grinder. Diagram A shows the dimensions of the holes required for the CrushGrind Shaft mechanism. Diagram B shows the shape and dimensions of the grinder itself. Diagram A Diagram B 5

6 Preparation As mentioned earlier the objective of this guide is to show how to: drill and form the necessary holes Properly cut the two required recesses for the CrushGrind mechanisms lugs. Spalted beech is the chosen wood for this grinder. The two blank sizes should be rough turned as shown in Diagram C. Step 1 Shown are the two halves of the grinder with their tenon and spigots rough turned. Step 2 The top of the base is held by its tenon in compression jaws with the tailstock in place and when it is running true face off what will be the bottom of the grinder, sand and seal. Diagram C The next stage is the drilling of the holes for the base of the mechanism. This is not a process you should approach with apprehension. Just stay focussed and everything will work out just fine. Remember the old saying Measure twice, cut once It is surprising how short a time it takes. Then you can say to yourself. What s all the fuss about? 6

7 Drilling the grinder base section The top of the base should still be held in compression jaws. The speed of the lathe should be around 450 rpm. On the shaft of a 1¾ Forstner bit wrap a piece of masking tape round and mark a depth of ⅞. Step 3 Drill to a depth of ⅞. On the shaft of a 1½ Forstner bit wrap a piece of masking tape round and mark a depth of 2-3/16 [⅞ + 1-5/16 ]. If your ⅞ distance was different take this into account when marking the depth to be drilled. Step 4 Step 4 The recess for the three lugs on the CrushGrind mechanism is now cut using the recess tool. Depth of cut should be a min of 1/8. Step 5 Note: It is NOT recommended that the lugs be cut off and the mechanism glued in. The tool rest is locked at right angles to the lathe s bed such that the tool is at centre height. The tool is rested flat on the toolrest. The lathe speed should be around 700rpm depending on the type of wood and the length of the blank from the headstock. The recess tool is pushed in until it reaches the bottom of the hole. It is pulled along the toolrest towards you until it rubs against the side of the blank s 1½ diameter hole. You will now have a recess 1/8 (3mm) deep. 7

8 After the recess has been cut the area for the grinder s salt or pepper can be drilled using a 1 Forstner bit. Note: It is NOT recommended that the lugs be cut off and the mechanism glued in. Step 6 Step 7 Remove the base from the lathe. Change the chuck jaws to expansion jaws. Remount the base holding the bottom 1¾ hole in the jaws. The tailstock should be place when the base is running true. If you have used a tenon rather than a dovetail, remove the tenon using a parting tool. Mark out the required overall length 6¾, part off, sand and seal. Finish the 1 drilling by drilling to meet the existing 1 hole if it did not come all the way through. Remove the tailstock and use a ½ skew chisel to open the 1 hole to 1¼ for a depth of ½. Shown on right; the completed drilling. Step 8 The drilling of the base is complete except for Step 21 below which is completed after the base has been finished with your choice of materials. 8

9 Drilling the grinder - top section Step 9 The spigot on the bottom half of the grinder top was rough turned earlier to a diameter of 1⅝. Hold the tenon at the top of the grinder in compressions jaws and ensure that it is running true. Bring the live centre in the tailstock up to the top and face off. The small diameter stub shown on the right hand side on the photograph is removed. Finally remove the live centre ready for drilling in the next step. Using a piece of masking tape on the ⅞ diamter drill shaft mark a depth of ¾. Drill ensuring that the depth is accurate. Step 10 Note if the wood is particularly hard you might want to consider using a 15/16 drill instead of the ⅞ drill to avoid splitting the wood when pushing the mechanism in. The recess for the thee lugs on the CG mechanism is cut using the recess tool. Refer back to Step 5 for further details. Step 11 Finally drill a ⅞ hole to a depth of ¾ + ¾ i.e. 1½ to house the top of the mechanism s shaft. Remove from the compression jaws. Step 12 9

10 Drilling the grinder - top section s wood insert Step 13 This grinder s design includes a dark wood insert in its top to identify the grinder s contents as pepper. Hold the top by its 1⅝ spigot and ensure it is running true. Next action is the drilling of a hole suitable for an insert. The hole should be around 1¼ in diameter for a depth of around ¼. The top of the grinder s insert will be glued in Step 18. Assembly of the top of the grinder Step 14 Find yourself a piece of plywood ½ thick, around 2 square. Drill a ½ hole in the centre. The purpose of the ½ hole is primarily to allow the mechanism s shaft to pass through and into the tailstock barrel when the base is assembled. This will become clearer in Step 21. Place the plywood between the barrel of the tailstock and the top half of the mechanism and when it is square to the grinder s top wind in the barrel forcing the mechanism in. If the wood being used for the top is dense you may want to cut two opposite spines off the mechanism and add a small amount of glue before pressing the mechanism home. Step 15 Remove the top from the lathe and turn an insert to fit the hole in the top of the grinder. It should be parted off to around ⅜ thickness. Use wood or an acrylic of a colour which gives an indication of the contents of the grinder. Do not glue the insert in yet. Step 16 Remount the grinder s top by holding it by the insert hole drilled in Step 13. Reduce the diameter of the top of the grinder s spigot to be a tight fit in the base of the grinder. Push the top and bottom of the grinder together aligning the grain as you do so. 10

11 Shaping the grinder First turn a drive plug as shown in Diagram D below. The bottom of the grinder s base will fit into the drive plug and a live centre in the tailstock. This is a dual purpose plug that will also be used to fit the mechanism in. Diagram D Step 17 The dual purpose plug is held in compression jaws and the grinder is held between the plug and the live centre in the tailstock. It can now be shaped with tools of your choice. Note that the very top of the grinder cannot be completed at this time. When complete, pull the halves apart and hold the top in expansion Jaws in order to reduce the diameter of the spigot to be a loose fit in the bottom half of the grinder. Step 18 Remount the grinder s top by holding it by its spigot and smear PVA glue in the insert s hole. Try and align the grain of the grinder s top and the wood insert and tap in. Once dry the shaping of the insert at the top of the grinder can be completed with the tailstock giving support until the very end. Remove the tailstock to remove the final nib and sand the top before finishing to your choice. Finishing the grinder s body Step 19 Sand down to 400 grit with the lathe speed set around 500 rpm. Seal using a 40:60 mix of cellulose sanding sealer and cellulose thinners. At this point I sprayed the two halves with 3 coats of gloss acrylic lacquer. Between coats, de-nib the finish using either White Webrax or a soft high grit sandpaper. The grinder was buffed using white diamond and finished with renaissance wax polish. 11

12 Step 20 Hold the grinder s base by the 1¼ hole in the top of the base. Ensure that the base is running true. Using a ½ skew chisel widen the bottom at an angle as shown in the drawing. The reason for this is to allow your fingers to get a better grip on the grey wheel when adjusting the grind. When complete remove the base from the chuck jaws. Assembly of the base of the grinder Step 21 The dual purpose jig is reversed and placed in compression jaws. Place the base of the mechanism square onto the jig and the grinder s base into the mechanism as shown on the left in the photograph. Use the piece of ½ plywood and place it between the top of the grinder and the barrel of the tailstock. The protruding mechanism shaft may pass through the ½ hole and into the barrel of the locked tailstock. Ensure everything is square then slowly begin to wind in the Shortening the grinder s shaft Step 22 Having fitted both parts of the mechanism, push the top over the shaft as far as it will go. Measure the gap between the two halves of the grinder; the shaft needs to be shortened by this amount, plus an additional 1/8 to 1/4. Remove the excess using a small hacksaw. Finally, file a champfer on the top edges of the shaft. You may find in this instance that you do not need to shorten the shaft Congratulations you have created a CrushGrind grinder without the use of 12

13 Maintaining the mechanism Spice will build up on the grinder. To clean this I use either salt or warm water. Using Salt Using a course salt, grind the grinder and this will clean the ceramic grinding stone inside the grinder. Using warm water and a stiff brush Unscrew the grey adjusting wheel, remove the ceramic cone. Clean both halves of the grinder with warm water and a stiff brush. If you feel so inclined the cone can be put in the dishwasher. Important: Before re-assembling make sure that all of the parts are completely dry. Information supplied by IDEAS Denmark Additional Reading Turning Salt & Pepper Shakers and Grinders by Chris West. Published by GMC, 2011 About the Author: Chris West Although he has attended many classes with professional turners, Chris West describes himself as a self-taught club turner who has been enjoying his craft for over 30 years. During the last dozen or so Chris has specialized in designing and turning salt & pepper grinders and shakers. On leaving school he started his career in the computer industry, serving a 5-year apprenticeship as an electromechanical engineer; yes, computers did have moving parts in those days! One aspect of his work was the necessity to work within tight tolerances. This gave Chris helpful skills required for turning matching pairs of grinders. He remained in the industry until he took early retirement, and now spends a good deal of his time in his workshop. Chris s schedule also includes taking his woodturning experience to outside groups by giving talks and demonstrations to interested social organizations. Many of Chris s grinders have appeared in the UK s Woodturning magazine and The Woodturning Design magazine in the USA. He hopes that by producing this guide he can share his knowledge and experience with many budding and experienced woodturners. Chris is an active member of the Hampshire Woodturners Association, the Test Valley Woodturners in the UK and the American Association of Woodturners (AAW). Chris can be contacted at chris@westwoodturnery.co.uk Copyright 2014 Chris West all rights reserved 13