Tag: woodturning

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Getting rid of sanding scratches

Many bowl makers use sanding discs in an electric drill to sand bowls. The idea is to start with a coarse grit disc, then use a succession of finer grit discs to remove scratches left by each previous one. Each disc leaves its own scratches, getting finer and finer as you work through the sequence. But it can be hard to tell whether a scratch was made by the current disc or the previous one. If you sand with 120 grit, then go on to 180, which disc are the scratches from? If you go from 120 to 100 or 150 grit, those discs will be more effective than the 180 at getting rid of sanding scratches. But the smaller the interval, the harder it will be to tell them apart.

Sometimes you can overlook the deepest scratches until the last stage, or even until after you have applied the finish. If you miss the deep ones from the coarser disc they can show badly later.

There is a simple method to distinguish between them. A particle of grit on the upper part of the disc will be moving from left to right as the disc spins clockwise. If the part of the bowl being sanded is moving upwards in the lathe, the scratch that particle makes will run diagonally from top left to bottom right. The angle will depend on the relative rotation speeds – running the lathe slowly will make the angle easier to see. If you reverse the rotation for the following disc, its scratches will run from top right to bottom left. When you can’t see any scratches running the other way, that disc has done its work. Reverse the rotation again and go on to the next one.

You can reverse either the lathe or the drill to give this result. You can also switch between the upper and lower quadrants of the sanding disc. Either way, you will be able to spot deep sanding scratches more easily.

Another benefit is that reversing the direction helps remove projecting fibres. This applies also to hand-held sandpaper, which leaves vertical scratches. This method of getting rid of sanding scratches is not applicable to hand sanding.

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Turning spindles on the Titan 315

It’s possible to turn small items on any big lathe, but it may not be as user-friendly as a small machine if the tailstock and toolrest are heavy and clumsy. Most of my work is quite small and I knew I would be getting rid of my smaller lathe, so I made a point of turning spindles when ‘test driving’ the Titan 315 before I bought it.

Turning spindles

Now I’ve had time to turn different items in my own workshop, I’m very happy with the result. I made a batch of long spindles. Because I don’t have another rest the right length, I used the long asymmetric one. It needs a wooden strut at the thin end to stop vibration, but with this I had no trouble at all. The rest holder and the tailstock slide freely and lock securely. A little bit of WD40 on the bed helps with this. A rub of wax on the top of the rest lets the tools slide smoothly. The spindles were rock solid between the centres. I didn’t feel at all that a smaller machine would be better for the job. I did find I shall have to take extra care if I go on loading the blanks without stopping the lathe when turning spindles. The powerful motor, heavy toolrest and solid grip mean I really don’t want to get my fingers caught!

Then I set up a larger piece – a reclaimed baluster made of pine, 500 mm long with a maximum diameter of 200 mm. I wanted to reshape it for another purpose.

I tried earlier to do this on my old Tyme Classic lathe but found it tough going. The Titan makes it easy, although the wood is very gritty and full  of cracks.

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More work on the large redwood globe stands

Some time back I posted about making a pair of large globe stands from reclaimed redwood. I made the leg sections, but put the feet on hold because when cut up I found the wood too wet. Cut to length, with exposed end grain for the moisture to escape, they are now dry enough to finish turning them.

Each blank, about 200 mm  long and 180 mm square, was rough turned to a cylinder with a small spigot on one end. I held the spigot in a chuck while drilling a 12 mm hole right through using an auger with a T handle. I then transferred the blank to my homemade chuck with the tapered steel insert (which is proving very useful for this type of work) and turned the foot with tailstock support. Fairly straightforward, but a little nervy, as there is no spare timber – no mistakes allowed! I double checked all measurements and used a spindle gouge for most of the cutting. 8 feet turned and ready for finishing.

The next job was the central pedestals that support the globes. Two are needed, cut from a 600 mm length of 300 mm square redwood beam. The block was only just big enough, I had to cut it in half with a handsaw – it was too big for my bandsaw, and I didn’t think a chainsaw would have cut straight enough even if there was enough length spare for the kerf. Then I used the handsaw to cut off the corners, a total of about 8 feet of sawing. Redwood is quite soft, but seemed to be getting harder as I went on.

The initial sawcut that divided the block left a reasonably flat end grain surface on each piece, on which I could fix a faceplate. On my Graduate lathe, I could drill the axial hole at low speed, then support the block with the tailstock while I shaped the pedestal. I removed some of the surplus wood while still on the faceplate as it gave a very positive drive. Then I switched to my homemade chuck with the tapered insert. When I did so, I found, as expected, that the axial hole was not so axial after all. The auger had wandered a little. On the taper insert, I was able to true it up and continue with the shaping. The redwood is a little soft, and the maximum torque given by the friction was only just enough on a piece this large, so light cuts were essential.

I did not have a pattern for the pedestals, so to some extent I was designing them as I went along. It was very useful  to be able to remove and replace them on the tapers without losing accuracy.

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Hunter Hercules tool

I turn quite a lot of mdf and gritty reclaimed hardwood, both very abrasive and hard on the tools. The mdf turns quite well with HSS or even carbon steel scrapers, but they soon blunt. The gritty timber sometimes strikes sparks from the edge of a steel scraper, and knocks the edge off a gouge after just seconds of cutting. So I have been looking out for a tool that would hold up better. One day I shall try diamond tips – you can get diamond router bits, so perhaps they are available for fitting to woodturning tools, or perhaps a router bit could be adapted. I’ve tried various tungsten carbide scraper tips (though so far not the well-known Easywood tips), but found them to blunt quickly and not cut as well as HSS even when new.

The other day I purchased a Hunter Hercules tool. This has a little round cupped carbide tip set at a forward angle on a very robust, heavy steel shaft with a substantial handle. The tips are silvery-bright polished carbide and when new will catch on your thumbnail as sharp tools should. 

It has three modes of operation. Used with the tool shaft horizontal and flat on the rest, perpendicular to the surface and cutting on the very tip, it gives a semi scraping cut that is quite aggressive. If the handle is twisted and the side of the tip used, it shear scrapes and can give a good finish. It can be used for a bevel rubbing slicing cut that also gives a good finish. 

I tried the tool on some edge-grain mdf. In semi scraping mode, it cut freely for a while before the edge lost its initial keenness. But it kept going. The small tip penetrates easily and whether semi scraping or slicing it keeps on taking off the waste. Even on the mdf face-grain, which with normal scrapers produces shavings, the waste was very dusty indeed. The finish produced was not brilliant, but adequate after a little sanding, and I shall normally make the final cuts with HSS tools anyway. I made several complete components with the tip still going strong.

I found the tool quite catchy when going into a spindle cove in semi scraping mode. To avoid problems, the tool has to be swiveled and the cut kept on the front third of the tip’s circumference, say between 10 and 2 o’clock. The  inclined edge at 9 and 3 tends to catch on the sides of the cove and run back. I found it can catch and run in this mode on a flat surface or a hollow on faceplate work too. The best way to prevent runs when semi scraping is to push rather than pull the tool. The small diameter of the tip means that it is not so easy to get a sweeping, regular curve – the tip penetrates easily so any additional pressure makes a dip in the surface.

It is easy to ride the bevel in a straight line or round a curve. This gives a controllable cut and clean surface just like a gouge, but only light cuts can be taken as the tip is small.

Shear scraping with the Hunter is similar to with a normal scraper, but the small diameter tip makes it a little harder to get an even sweep.

Replacement tips are not cheap, though they may last a long time on easy timber. The maker hopes they will be considered disposable, but I hope it will prove possible to sharpen them. Flat carbide tips can be sharpened on their upper surface with a diamond hone, but this would flatten the top of these cupped tips. I intend to try three alternative methods – hone the top and afterwards use the tip as a normal flat tip scraper; mount the tip on the end of a rod like a dop stick (or just pin it on the end of a rod using the tail centre) and hone the bevel while it spins in the lathe; and hone the groove in the top using a very small diamond ball point in a Dremel, also while spinning the tip. I doubt if any of these will equal the original grind, but  shall report the results in due course.

So I am pleased with the tool so far. Quite impressed.

If it cuts mdf, I’m sure it will cut ordinary wood. I tried roughing down a small oak spindle blank in semi scraping mode and it worked well, though it did leave small feathery shavings not completely severed if traversed too fast, due to the small tip diameter. I have not yet tried it on the gritty stuff but shall update in due course. I have however roughed out a number of boxes in some unknown but hard and very abrasive wood. I have not yet changed or sharpened the cutter, though I have turned it through 180 degrees to a fresh edge, and it is still cutting quite well – HSS would have needed many sharpenings in this time.

It will not replace my gouges and scrapers. I shall use it on difficult materials as a roughing tool, and be grateful for the long edge life. When really blunt, the edge becomes badly chipped and eroded, and then will not give a good finish. No doubt others will use it on more tractable timber and get nice polished surfaces straight off the tool, but for me it is too slow-cutting for routine use – I get on better with normal gouges and scrapers that are more free-cutting.

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Homemade chuck

A common problem facing woodturners is how to hold pieces in the lathe. The usual options, such as faceplates, scroll chucks and spur drive centres deal with almost everything perfectly well. But sooner or later there is something different needed. Often in these cases I use my homemade chuck. This is simply a holder, made of steel and mounted on the lathe spindle nose, into which a variety of special purpose inserts can be fitted.

I often have to turn items with a half inch diameter axial hole. In these cases it is usually best to drill the hole in the blank before the turning is done. If the hole is used as the location for turning, it remains true in the finished item. How to hold it in the lathe so the hole is central? Till now, for larger holes, I have either used a conical tail centre in the headstock to drive by friction, or a counterbore with a pin to locate in the hole. Both are liable to slip on larger pieces.

So I made a taper pin for the insert chuck. I cut a piece of mild steel rod about 2.5 inches long and 5/8 inch in diameter and used my old Atlas metal turning lathe to reduce the diameter to 1/2 inch over part of the length, to fit my insert chuck. Then I reversed it in the lathe and turned a gentle taper, leaving it just under 1/2 inch at the end, so it would slip about 1/4 inch into a 1/2 inch hole.  Then I filed a flat on the shank where the locking screw bites, and the job was done. An insert like this could also be made from a soft steel morse taper with enough length to turn the taper on its nose, a job that could be done by hand in the wood lathe. For light work, it could be made from hardwood.

The taper has to be right, though I haven’t measured it. It’s not really critical, but too steep and it will not grip well enough, too gentle and it can split the wood. A little steeper than a morse taper but not as steep as a tailstock dead centre is about right. If the drive does slip, I can just tighten the tail centre a little more.

I used the chuck to make some wooden cylinders about 4 inches in diameter. Mounted on the taper, with the tail centre to keep them in place, they turned easily and accurately.

Taper insert for homemade chuck

 

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Tungsten carbide woodturning tools

Tungsten carbide is a very hard but brittle material used for cutting tips in metalworking. It is now used in woodturning too. I first made some tungsten carbide woodturning tools many years ago. They had a use, but I had to use them fairly forcefully to make them cut. I could not make them sharp enough to cut wood at the lathe, even though carbide has long been used for saw teeth. Recently there has been a lot of publicity given to tungsten carbide woodturning tools. They normally have replaceable carbide tips. They are supposedly formulated to be sharper. However, they are apparently less robust than other grades.

Several companies are now selling tipped tools, and users report very favourably. The tools are expensive, and without information about the carbide grade, you have to take the quality on trust. I would like to make some tipped tools with this woodturning grade carbide. I’ve bought some tips from various sources but the ones I have tried so far don’t keep their edge very long when cutting MDF. MDF is very abrasive and hard on sharp edges. A long-lasting edge is the main reason for using carbide. After a bit of use, the carbide edge feels rough to the touch, and like a sawblade when tried with a fingernail,

Yesterday, I bought a micrograin carbide tip from Robert Sorby. I fitted it to one of my homemade tools to try. First impressions are not good. It didn’t do well on MDF, which I turn a lot. Very likely it would work well on ordinary wood though. And at least the tip has a very generous thickness to allow sharpening with a diamond hone.

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European Woodworking Show

I went to the European Woodworking Show in Essex today. It’s a great venue, with ancient timber barns and a walled garden. It’s a bit different from the usual type of woodworking show. There is less emphasis on machinery and more on hand tools and traditional crafts. I saw displays of blacksmithing and axe woodworking as well as woodcarving.

There are two kinds of woodworker – those who like machinery and those who like hand tools such as planes and travishers (those special planes for making chair seats). I’m a machine man myself. Turning is a hybrid in which the turner’s hand holds the cutting tool and the wood spins in a machine. So I was glad to see some turning-related stands. I chatted about ornamental turning with a gentleman on one of the stands. He had brought along some examples of turning, including a little decorated oval box. Also some of the equipment such as drills (which, in ornamental turning cut profiled shapes, not simple holes). They had the specialised sharpening kit needed, including a goniostat. I also saw a Magma Titan lathe, which looks a first class machine. Expensive, but I feel strangely compelled to buy one sometime.

I bought an old-fashioned carbon steel skew chisel for just £4. There was a big box of them, many years old, but unused. They are a victim of the takeover of high speed steel. I also bought a Tormek tool bar holder to fit to my high speed grinder. This will let me use the same gouge grinding jig on the Tormek and on the high speed machine.

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Noisy lathe bearings fixed – Woodturning by Terry Vaughan

My spindle lathe is a Tyme Classic, a good quality cast iron machine that I have used for many years now. Some time ago, it developed noisy lathe bearings and I replaced them. It was a fairly straightforward job. But it was not easy to dismantle the components as the pulley had seized on the shaft. Those bearings were poorer quality and after a while they became noisy too. So I dismantled it all once more (it was easier this time). I put in some SKF bearings, which are as good as any. All was well.

Bearing misaligned

But recently the noise returned. On investigation I found that if I slackened the retaining ring at the spindle nose the noise disappeared. But when tightened up again the noise came back. It was an alignment problem, but I couldn’t work out how to fix it. Noisy lathe bearings are a real nuisance. You want to concentrate on the turning, and a good lathe is a quiet one. The noise was quite disturbing when running the lathe at normal speed. I had to do something, but what?

Hit it with a mallet

Today I consulted Derek Pyatt, at Pyatt Woodworking. He specialises in woodworking machinery of this kind, although he was not very familiar with the Classic. It’s quite an uncommon lathe. Derek advised me to put on the faceplate, run the lathe, and hit the centre of the faceplate with a mallet. That should seat and align the bearings properly. That is what I did, and after a couple of bangs the noise was much reduced. So thank you Derek! Now if only it would work on the dust extractor!

 

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Buffing cord pulls

Today I buffed the latest batch of cord pulls. I turned them a few days ago and  they have been oiled and given enough time for the oil to harden properly in the wood. I use the Beall buffing system. Tripoli first followed by wax. I don’t use the carnauba wax but apply microcrystalline wax from a block as it is more durable, particularly for something like a bathroom light pull that will frequently be wet. I made some in teak, some in oak, and some in plum wood, which have come out very well – the plum has a very rich colour.

I also made some more decorative wooden cones. Some are now ready to finish, but others will need time for the wood to dry before final turning. I removed the centre mark with a dremal cutter and sanding disc, and shaped the point with a chisel by hand.

Visit my web site for more information about woodturning

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Turning wooden cones

A discerning person has bought my remaining stock of wooden cones, leaving me sold out. These cones are decorative items, non functional except perhaps as paperweights, but I think they look good. A while back I took one to the woodturning club show and tell, and other members made some for the following meeting, so they must have something to recommend them!

Now I have to replenish stock. The difficulty is finding suitable blanks, they need to be well figured and of suitable size. I found several nice bits of pear wood with some ripple grain and darker patches. I’ve used this for making bowls previously and know it finishes well. I also sorted out some spalted sycamore and horse chestnut, but this is too wet to use at present. I spalted it myself, simply by wrapping it up in plastic bags for about a year. It certainly is heavily spalted, some of it too much so, but I won’t really know till it’s dry. I roughed out some cones from the spalted wood and put them aside to dry. The pear is good to go now, so I made a couple of cones with that. More tomorrow I expect.

Turning wooden cones is fairly simple. The blank goes between centres and I turn a tenon at one end for the chuck. Then I can turn and finish the taper, with the point on the end. The problem comes when the tenon has to be removed. How to hold the cone? I put a rubber bung in the morse taper. The bungs are sold for use by wine makers. The cone’s point goes in the hole in the bung and the tail stock supports the other end. Friction provides enough drive force for the tenon to be turned away. The bottom is undercut a little with a small gouge so the cone stands straight, and then sanded.