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Rolling Metal Sliders

By Martin Preshaw
For The Pipers Review, Autumn 2007

The past number of years has 'enjoyed' a resurgence of traditional methods, techniques and tools employed in the manufacture of the Irish Bagpipes, more commonly known as the Union Pipes or the Uilleann pipes. These most noticeably have included incorporating hollow main-stocks, hand-forged keys and hand rolled ferrules and sliders, the subject of this short article. Bores fashioned from D-bits and shell augers and reamed with handmade flat reamers and spoon reamers are common place in modern day Uilleann pipes. I believe it is important to closely observe and study period instruments that have been fashioned entirely within the walls of one musical instrument workshop utilising the tools, methods and materials of the day. However, this 21st century creation of the past in modern day folk instruments, while perhaps enjoyable as an exercise in self-indulgence for both maker and customer is quite frankly, superfluous. While I am open to reasoned debate and welcome intelligent argument, I nevertheless remain skeptical about the musical and engineering merit of such antiquated practices. If a physician were to set-up a surgery today drawing entirely on the equipment, medicines and practices of the mid 18th century, business would be bleak. Medicine has advanced rapidly over the past 200 years and not for a moment would we want our doctors to practice any out-dated medical procedures on us. Similarly, there have been advances in all aspects of engineering yet our society, the Uilleann pipe society, seems to favour traditional approaches to our musical instruments above that most base of words 'modern'. Simply because we are commonly playing tunes that are 100+ years old does not necessitate that to play them any better or have an affinity to that period or their county and country of origin that they are played on musical instruments crafted in the manner of that day. If a chanter is misbehaving with an uncooperative reed, what matter that it is attached to a set of pipes with hollow main stock with hand rolled ferrules or a solid stock with ferrules fashioned from drawn tube? I am more than happy to embrace the new which includes gun drills driven by compressed air, which, incidentally, give a beautiful polished surface to any internal bore, unachievable with a D-bit. Spiral-flute reamers fashioned on precision CNC machinery, with tolerances simply not achievable by hand, and seamless drawn tube which is readily available, are all to be found in my shop.

However, there is one area which just recently in my career as a pipe maker I have come to learn that rolled tuning sliders are an essential. Latterly, I have arrived at the opinion that drones which are fashioned entirely from wood with a metal sleeve for protection on the sliders are much easier to reed, tune and balance than those that have commercial tube functioning entirely as the main tuning slider. The aesthetic of the instrument is an important consideration and commercially drawn tube which could sleeve the drone slides is too heavy and looks, clumsy. As I have been unable to source tube that fits the required taper of my flat pitch and concert pitch pipes that is aesthetically acceptable, necessity, the mother of all invention, has driven me to learn to make these. My method and approach to roll these slider components is an amalgamation of the technique kindly demonstrated to me by Mr. David Quinn, the article by Mr. Geoff Woof on this subject in SRS Vol I along with his advice and suggestions and the methods employed by Mr. Terry Tynan in his superb DVD tutorials on metal spinning. While my approach is an amalgamation, I do employ certain tools, machinery, equipment and technique that the above named folk do not use and in some instances, may want to disassociate themselves from altogether. However, all credit for my development and manipulation of this process is theirs entirely and it should go without saying that any errors or shortcomings in this approach are entirely my own.

I have used the following method to form sliders fashioned from stainless steel, brass, nickel silver and sterling silver. However, when learning how to form these pipe components I practiced long and hard on sheet copper. For all the above metals I would recommend that the annealed material is NOT quenched but rather allowed to cool off naturally. Finally, a word of caution in advance of any experimentation with metal spinning. Machinery with fast spinning parts does not interact well with human flesh and bone. Extreme care and caution must be exercised at all times when using any workshop equipment.

Tools, equipment and materials:

Photo 1 details the tools and materials which include home made mandrels for polishing the ferrules fashioned from threaded 6mm brass rod and fitted to boxwood handles, digital vernier, steel rule, engineers square, bees wax to lubricate the spinning metal, a piece of mild steel for truing up the seams, joiners mandrel with a sharp point for marking your chosen material, mandrels for the different slider sizes, files, raw-hide mallet, carbon steel wood turning gouge for spinning the metal, brushes for removing the flux debris, Tenacity #5 Flux and Silver Flo 55 hard solder, sheet brass 0.75mm thick, pliers, wet and dry paper 180 grit to 2000 grit, pen and notepad, garden wire and calculator - optional accessory depending on your mathematical acumen! Not included in this photo is a propane gas bottle and torch which are required for annealing the material.

Machinery:  

Engineers vice with soft jaws (photo 2)

Band saw for cutting material (photo 3)

Arbor press for pressing slider onto mandrel (photo 4)

Woodturning lathe for spinning slider (photo 5)

Metal lathe for truing/squaring slider (photo 6)

Double pedestal polisher with soap compounds for finishing (photo 7)

Method:

Opting for 0.75mm sheet the slider blank must first be marked out for cutting. The dimensions are arrived at using the following formula: (internal diameter + thickness of material) X 3.142

I use slightly different lengths for flat pitch and concert pitch sliders. In this case we are making a tenor slider and therefore I would aim at an o/a/l (overall length) of 65mm for flat pitches and 60mm for concert pitch. As it is a tapered slider we need to calculate the maximum and minimum widths of the blank over 65mm, i.e., two sets of figures using the above formula. My tenor mandrel has a taper of 13.8mm down to 11.8mm over 83mm and I like a finished slide of approximately 13.5mm o/d (outside diameter) to 14.5mm o/d over 65mm, and while this is determined to a large extent by the spinning and truing up processes, I need a set of figures to commence from, so I aim for internal diameters of 11.25mm and 13.25mm. My figures for marking out the blank are therefore as follows:

(11.25mm + 0.75mm) X 3.142 = 37.7mm and,

(13.25 + 0.75mm) X 3.142 = 44mm (rounded up from 43.988mm)

Therefore, my cut metal will have a width of 37.7mm at the narrow end and 44mm at the wider end. 

Mark out the blank using a sharpie, in my case a joiner's mandrel (photo 8)

Cut out the tapered blank, slightly oversize is better (photo 9)

Using soft jaws on a vice (photo 10) (soft jaws safeguard against marking the material) true up both sides of the blank with a file making sure the sides are straight, ie, without any bumps or gaps underneath the straight edge of the engineer's square, (photo 11) and within tolerances (photo 12)

File away some of the material on what will be the inside of the slider at an angle of approximately 45 degrees. (photo 13) This forms a gulley which allows the solder to run the entire length of the slider ensuring a sound joint in the finish.

The material needs to be formed around the mandrel initially by hand and then rolled into a tube. However, as the material is quite stiff at this stage it requires softening by the process of annealing. This is done by gently heating the material over a gas flame from the underside and with a gas torch from the top until it glows cherry red (photo 14). I let the material cool off naturally and preoccupy my time by cutting out several more blanks.

In order for the flux to work and allow the hard solder to 'run', the joint needs to be clean and free of all carbon deposits from the annealing process. The gulley is cleaned back to a polished finish with 180 wet and dry abrasive. (photos 15 and 16)

Place the blank in the centre of the mandrel (photo 17) and gently commence folding the edges up around the mandrel. (photos 18 and 19). Care needs to be exercised at this point ensuring that the bank lies centrally in the heart of the mandrel otherwise the join may run off centre and while it may adequately serve it's purpose as a protective sleeve over the tuning slide, it will look unsightly. The material may need to be gently persuaded to meet up by a combination of a hide mallet and gently opening and closing the jaws of the vice around the blank. (photo 20)

Roll the blank on a hard surface to roughly form it into a tube. I use a file with a safe face which prevents the material from being marked but an ebony square/piece or smooth piece metal will serve this purpose equally well. (photo 21 and 22). Burnish the seams of the blank with a piece of mild steel (photo 23) thus allowing them to lie snugly against one another when fastened with the wire. Snip 3 pieces of garden wire approximately 75mm long and form into a uniform U shape. Place the belly of the U underneath the tube and twist the wire with pliers until the seam closes. (Photo 24). It should be neatly closed along the entire length of the tube and straight (photo 25)

Mix the flux powder with a little water until it makes a paste with the consistency of clotted cream. (Photo 26) and apply liberally along the inside of the joint (photo 27). Some makers recommend applying the flux to both the inside and outside of the joint. However, I have found that soldering from the inside to be adequate and greatly reduces the risk of soldering fast the wire to the tube, which is extremely difficult to completely remove. Position the tube in such a way that it can be worked at one end and then turned 180 degrees and worked at from the other. I use an old frying pan propping the job with firebrick but have seen the tube buried into a steel bowl filled with pumice gravel which was perhaps much more user friendly.

Using the propane gas and torch, heat the tube until cherry red and apply a small dab of hard solder (Easy Flo 55) until it begins to run. Wasting no time carefully turn the tube 180 degrees and solder up from this end also until you can see the hard solder run the entire length of the joint. (photo 28)

Carefully remove the wire loops and clean out the crystallized flux debris with a stiff bristle brush (photo 29). Some solder depositing on the exterior of the slider is largely inevitable but can be removed by gently passing a file along the seam prior to spinning (photo 30).

Gently press the slider back onto the mandrel. Take care not to force it further than it wishes to go otherwise it will concertina. (photo 31) Place the mandrel in the wood lathe chuck and apply some bees wax while spinning at 1200 RPM (photo 32). Place the spinning tool underneath the slider and gently apply pressure upwards and work evenly along the surface keeping the tool continually on the move (photo 33). The spinning of the metal loosens the tube away from the mandrel and will periodically need to be returned to the arbor to be pressed on. The material will 'bump' on the tool until it runs smooth indicating the job is finished. The excess beeswax can be removed with a conventional woodturning diamond parting tool and then any residue goo cleaned of with meths and then gently applying the file to remove the stubborn carbon deposits (photo 34). This also acts to loosen the slider from the mandrel which makes it easy to remove (photo 35).

Measure and mark the slider to the appropriate length (photo 36) for removing the bulk of the waste on the band-saw (photo 37). True back the face of the slider to the correct length - 65mm for flat pitches and 60mm for concert and clean with a file and 180 grit papers. (photos 38, 39, 40)  

Return the slider to the wood lathe and place between centres and clean up to a satisfactory finish working from 180 through to 2000 grit (photo 41). Place the slider on the polishing mandrel and lock tight. (photo 42). I use two polishing soaps with the double pedestal polisher, the first is a blue compound and is a general cleaner used on a stitched mop and the second is a pink compound and when used with a loose leaf mop gives a high lustre finish (photo 43 and 44). I polish until I am satisfied that I cannot see either the seam or any of the abrasions left by the grit paper (photo 45). I also ensure the interior is clean (photo 46). The slider is now finished (photo 47) and awaits your preferred motif (photo 48).

The process is relatively straightforward and excellent results can be obtained after some practice. If I can be of any further assistance or help on this subject I can be contacted directly.

Martin Preshaw
Co. Fermanagh
September 2007

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