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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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Chuck sizing template for bowls

Chuclk tenon sizing template

This is a very simple workshop aid. So simple that I hesitated to post about it. But it eliminates the risk and possible errors associated with using dividers. I made some of these chuck sizing templates to help beginners during my bowl turning classes, but they are so convenient that I now use them for my own work too.

A chuck sizing template helps you to make the chucking tenon or recess on a bowl the right diameter for the chuck. It should fit when the chuck jaws are almost closed, because that’s when they have the best, non-marking grip.

The usual method is to use dividers set to the correct diameter to scribe a circle on the work. If the dividers are set correctly, if both points fall on that circle and if the points are on the diameter (that is, not too high or too low on the work), the circle will fit the chuck. This method works well, but takes practice. It can be risky, because only the left point should touch and it’s possible for the points to catch in the spinning wood.

As an alternative, I made some templates from offcuts of 6 mm MDF. They are just small rectangles, with widths to suit the chuck jaws. You could add a millimetre or two to the ‘correct’ size to give some allowance for error when cutting the tenon or recess. They aren’t adjustable, so each set of jaws needs its own templates for marking a tenon and recess.

Using the chuck sizing template.

The end of the template has a mark in the middle. I hold that mark to the centre of the spinning wood, which can be highlighted with a pencil if necessary. Then I use a pencil to make a circle the same diameter as the template’s width.

It only takes a moment to mark the circle. And it’s the same each time with no need for measurement or setting dividers. You need separate chuck sizing templates for each set of chuck jaws. But a benefit of that is you can try the templates against the bowl blank to select the best size.

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Drying bowl blanks

Drying bowl blanks on racks indoors

Probably most bowl turners generally use blanks cut from green wood. They either make green turned bowls or rough outs to be turned again when dry. Some work with dry, seasoned timber, from which a bowl can be made in one session. Drying bowl blanks for that purpose may be easier and quicker than you think!

Most of my own work uses green wood. But in my bowl turning classes I rely on dry bowl blanks that I buy from turning suppliers. My students generally work with a blank of about 7 inches by 2 inches (175 mm x 50 mm), which I find is a good size for a beginner to make a useful small bowl. These blanks cost a significant amount, and sometimes turn out to have defects. So I now make my own. Cutting and drying bowl blanks is a process that I quite enjoy.

Cutting the blanks

I start with a log big enough to yield the size needed. 250 -300 mm diameter is useful, and as long as I can handle. The longer the better because there is always some waste due to end splits, but I don’t have lifting equipment. I use a small Alaskan chainsaw mill and my band saw to cut planks. There are plenty of videos on YouTube showing these mills in use, and even how to make them.

My mill is a commercially made one. I made a simple wooden “ladder” that I attach to the log. The mill slides along the rails as the chainsaw makes the first cut, clear of the pith which is the main source of cracks in the timber. The saw cuts straight, leaving a flat surface that guides subsequent cuts. I use an inexpensive electric saw from Screwfix. It’s self sharpening, which is very helpful, because ripping is tough on the saw and grit in the bark soon blunts it. I haven’t found it necessary to use special ripping chain.

On larger logs, I use the mill to make further cuts, but if the pieces are manageable I take them to my Startrite 352 band saw. On the band saw, I trim the pieces to about 180 mm wide, then saw planks 50 mm thick. I turn the log to its best orientation for maximum yield, and can usually go on to saw spindle blanks from the off cuts. The saw is somewhat underpowered, but does a good job as long as the blade is sharp. It’s quicker than the chain saw and makes a narrower kerf, minimising waste. I use a 12 mm 3 TPI blade.

Drying the blanks

I seal the ends of the planks with two or three coats of PVA, then stack them outdoors under cover, with spacers to allow air to circulate. After a few months, I cut discs from the planks, cutting clear of any cracks that may have developed. I microwaved a few discs in an attempt to speed drying, but not only was this a slow process, those discs all split. I allow the other discs to finish drying indoors, but don’t seal the edges or give them any other protection.

Until I tried drying bowl blanks like this. I would have expected all the discs to crack. But the process has been very successful. The woods I have used so far are apple and oak (both from standing dead trees, so probably already with a reduced moisture content before planking), ash and cherry. I weigh the discs at intervals until they stabilise, which seems to take about three or four months. I now have lots of bowl blanks either fully air dry and ready to use, or well on their way. Hardly any have cracked, and those used in my classes have been very satisfactory. All are similar in size. It may be that the process would not be so successful if the blanks were larger.

Some of the blanks warped as they dried, but I expected this. They are still usable.

Encouraged by this, I sawed some beech and cut some of the planks into discs immediately with no preliminary drying. Most of those discs cracked after about three or four weeks indoors. No surprise there!

It remains to be seen whether the beech planks now drying outdoors yield useful material. But I should be able to cut spindle blanks, if nothing else.

Conclusion

I shall continue to experiment, but at this stage my conclusion is that the discs should not be cut from wet wood. Some preliminary drying is necessary, but the planks don’t have to be fully dry. The total drying time is measured in months, not years. 

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Dust extractor maintenance

I’ve written before about the need for regular dust extractor maintenance. An extractor with a filter is not ‘fit and forget’. My extractor is a cyclone unit and since I removed the internal wire grid that avoids the low risk of accidental contact with the fan, it is less prone to blocking up. After considerable use, it still seemed to be working OK. But when I checked the filter recently I found a great deal of fine dust in it. After cleaning it, the extractor worked a great deal better. Not really a surprise!

The deterioration in performance had been so gradual that I had failed to notice it. I needed an objective measure of performance and a proper dust extractor maintenance schedule. Just putting my hand in front of the inlet now and again to see if there is still suction is not good enough.

Measuring air flow

Performance equates to air inlet velocity and filter effectiveness. Dust build up in the filter actually improves its effectiveness, but it cuts the air flow. The flow can be assessed by measuring the vacuum in the pipe. A vacuum gauge permanently installed as part of the system, with an easily visible readout, would be ideal. However, I opted to measure the speed directly with an anemometer. A digital anemometer can be got very cheaply. I bought this one from Amazon.

It was impossible to get a consistent reading from it just by holding it in my hand. I folded a bit of steel strapping to make a holder for it, with a hook that clips on the edge of the extractor inlet to secure it at a fixed short distance inside. I take it out again after each reading.

The reading itself is less important than changes in the reading over time. So I noted the indicated air speed just after I had cleaned the filter. I can take further readings at intervals as dust starts to build up again. This will tell me how long it takes for the speed to drop by, say, 20%. Then I can schedule a regular filter clean in my calendar.

It was interesting to see how far from the inlet the suction extends. The answer is not very far at all. A small diameter inlet is only effective when very close to the dust source, which is not easy to achieve at the lathe. The 7 inch inlet I have at the lathe does provide quite good air flow at the tool tip where the dust is generated.

Cleaning the filter

Cleaning the filter was straightforward. I took the cartridge outdoors and stood it on end. Tapping it with a wooden batten dislodged the dust cake and it fell to the bottom. In some places the pleats were close together, and those areas took more tapping. I also used compressed air. At first, the supply of dust coming from the filter seemed almost infinite, but eventually it slowed down.

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Taking up woodturning

Using a lathe, you can make objects that are both beautiful and useful, often taking only a few minutes from start to finish. The process is fun, and no other form of woodworking is so immediate in its results. But if you are thinking of taking up woodturning, how do you start?
There are four things you need to become a woodturner: a workspace, the equipment, some timber and the necessary skills.

The workspace

This you probably have already, or you would not be considering taking up the craft. The space determines what you can do. Woodturning can be messy, and you need somewhere to store materials and valuable equipment, so the workspace is the first thing to sort out. A proper building that is secure, insulated, heated, powered, dry and well lit is ideal. But most people get by in a garden shed, basement or garage, and do great work.
Whatever you have, do your best to allow nothing in your workspace that does not relate to turning – no bicycles, lawnmowers etc. They take up the space that you as a turner will need, and detract from the proper dignity of the craft. And unless your workspace is large, try to find somewhere else protected from the weather for the wood pile.

The equipment needed for taking up woodturning

When you are taking up woodturning, the essentials are:
  • A lathe with a stand or a bench, and a chuck. The lathe should be the most substantial one possible. If you start with a cheap, flimsy machine, you will soon want to replace it. If space and budget are limited, a good quality mini lathe is fine, though it will restrict what you can do. A good used machine is much better than a poor new one.
  • A grinder for sharpening. Blunt tools will not give you the results you want.
  • A sharpening jig for gouges, though you can learn to sharpen gouges freehand if you take the trouble.
  • Some basic turning tools – a good start would be a small spindle roughing gouge, a 3/8″ spindle gouge, a small and a larger bowl gouge ground at different angles, a square nose scraper, a round nose scraper and a parting tool
  • An instructional DVD or book.
  • A face shield and dust mask
  • Sandpaper and the usual workshop tools – screwdrivers, power drill, tape measure etc.
With these, you can make bowls and vases, boxes, all kinds of spindles, and lots of shavings. Later, you may need a bandsaw, a chainsaw, a drill press, a dust extractor, power sanding equipment, additional turning tools, buffing equipment and lots more. No woodturner ever has all the equipment they would really like.

The materials

In the beginning, you can buy ready-made turning blanks. It’s what many people do when first taking up woodturning. But this is the most expensive way to buy wood. It is better to convert small logs and branches to turning blanks yourself, at no cost. You will enjoy turning unseasoned timber, and found timber can be the most beautiful. A band saw will pay for itself. You will soon find you have more timber than you can turn, and will need somewhere to store it, protected from the weather while it seasons.
For practice, almost any timber will do. But it is easier to turn wood that is straight-grained, free of large knots, decay and splits, and not too hard. It’s a mistake to buy tropical hardwoods when you are starting out. They are beautiful, but harder to turn than species such as oak and ash, which are just as attractive.
You will also need finishing materials, such as a can of danish oil.

The skills

A turner must be able to prepare the wood, sharpen and use the turning tools properly, and come up with pleasing shapes for the finished items.
When you are taking up woodturning, you have to develop these abilities. Study the books and magazines, watch the DVDs, take lessons from me or anyone else with the experience, and join a turning club. If you practice, you will improve. Practice some more. Eventually, practice makes perfect. Learn from people who have gone before, then go your own way to establish your own style.
There are two options for a turner. Some people use a lathe simply as a means to an end. They use any turning methods that get the result they need. As scraping tools are comparatively easy, that’s what they use. It’s a pragmatic approach that can make a lot of sense. With a little practice, and on suitable timber, scrapers can give excellent results. But they can sometimes leave a very poor surface, so that heavy sanding is needed. This can show in the finished product.
Others set out to learn the more difficult tools – gouges and chisels, as well as the scrapers. They value the craft for its own sake. These tools are quicker and more versatile in use. There are very competent turners who rely on scrapers and get great results. But getting to grips with the other tools pays off in the end.
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New website

Until recently I operated a website at www.turnedwoodenbowls.com. Because of technical problems with it, I set up my new website here. I think it already looks and works better for visitors than my old one, which I have now closed. It’s easier to manage too, though I still have a lot of work to do on it. I haven’t yet republished all of my old posts, and I still have to transfer some images.

I have migrated my list of subscribers. So if you are one of them, you will be notified when I add new posts, and I thank you for your interest.

I’ve published a couple of new posts here so far, on sharpening and on dust extraction. More will follow, so if you haven’t yet subscribed, please do.

Most of the wooden bowls and other things on my product pages here are new. In due course I shall list stock from my old site here. If you are looking for a specific item, just let me know.

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Getting organised in the workshop

Since my new Titan 315 lathe arrived the workshop has been in chaos. I still have both my old lathes. The Tyme Classic will go off to its new home in the next couple of weeks. Until then it is taking up space and getting in the way. The new lathe is bigger and I have had to move quite a lot of stuff around to make room for it. The process is not yet finished.

I’ve decided I can do without a cut-off saw. Until now I had a cheap Erbauer from Screwfix. I got it chiefly to cut lathe spindle blanks and to make segments for globe horizon rings. It did the former well enough, but was not very accurate for the latter. This was probably at least in part because I did not prepare the blanks well enough before cutting the angles. Its blade had got very blunt and I recently fitted it with a new one. Unfortunately the blade guard shattered when the new blade picked up a small off-cut. Spares are not available for these machines. Rather than replace the saw I have purchased an Incra mitre fence for my table saw. I shall use that instead.

The saw lived on top of one of my homemade chests of drawers. Without it, I was able to stack another chest of drawers on top of that one. It seems to work OK there and the move has given some welcome floor space. But I shall have to re-arrange the drawer contents so that the things I want most often are more accessible. A helpful suggestion from my daughter is to turn the higher drawers upside down so I can see what’s in them from below.

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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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Magma Titan 315

Yesterday I posted about turning a bit of 2″ diameter mahogany in my new Magma Titan 315 lathe and had to admit it wasn’t much of a test. Today though I put an 11″ diameter, 17″ long freshly felled log between centres. It would not have fit on either of my old lathes. This was quite a heavy chunk, and its ends were not cut square. I lined it up by eye, not very accurately as it had a definite heavy side that gravitated downward.

Vibration

I thought I would try the traditional vibration test, so balanced a £1 coin on its edge on the headstock, stood well back, and started at the lowest speed on the fast pulley. The Magma Titan 315 is not bolted down, but the coin didn’t begin to wobble until I took the speed up to about 430 rpm. I turned the speed down to about 275 rpm to begin the turning – this was not a piece that I wanted to come loose.

I used the long (about 600 mm, 24″) asymmetric tool rest. It was disappointing to find it distinctly flexible towards the unsupported end.  I was not really surprised at this, although I had been assured that it would be rigid.

Tool rest

This rest is heavily built, but it only has one stem and overhangs too far to be rigid. This makes anything but light cutting at that end difficult or impossible. Perhaps it would be better with a steel web welded at right angles to the main rest bar. This would give it an inclined T or L shape in cross section. However, a loose wooden strut slipped under the end braces it either to the floor or the lathe bed. It then becomes much more solid and will certainly be very useful. The taper helps with this as it allows for some height adjustment.

I turned a ball from the log. It will live in the garden next to the workshop door.

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Titan lathe – smooth and vibration free, with a better finish from the higher speed.

My new Titan lathe is up and running, though I haven’t had time yet to do much with it. I started with a bit of mahogany about 50 x 150 mm between centres. Not exactly challenging, but I didn’t have a usable chuck or faceplate yet). The tailstock ram has a nominal 200 mm travel. With a four prong drive centre in the headstock, the No. 3 MT ram felt as if it could happily force its way right through the mahogany and out the other end. The blank felt rock solid. There was nearly a foot of clear space between the blank and the bed. I switched on.

Titan lathe noise level

The Titan lathe has two different ramp speeds, one that reaches full speed almost immediately, and a slower one that gradually winds up to speed and down again, safer for large blanks. The lathe made a bit more noise at full speed (3000 rpm) than I hoped, but not excessive. At about 1000 rpm it was quiet. I suppose large bearings cannot run silently at speed.

I took a cut with a roughing gouge and in two or three passes made the blank into a cylinder. There was no hesitation or vibration whatsoever. The toolrest is very heavy (40 mm stem) and too deep for the underhand grip that I use. If I don’t get used to it I can easily make up some smaller rests for detail work.

Chuck insert

My Vicmarc 120 chuck had an insert threaded for the Graduate lathe. I remember that I had trouble fitting this insert originally. Because it sometimes came loose when unscrewing the chuck, I used some Loctite bonding agent in the thread. This worked perfectly – so well that even with a large pair of Stilson grips it was impossible to remove. Warming the insert with a small blow torch softened the cement and it was then easy to undo. Loctite doesn’t seem necessary with the new insert.

I screwed the chuck on the Titan, but found a small amount of run-out. This is not a problem with the lathe, it means the insert is not seated properly in the chuck. I was too impatient to correct this, so loaded a small bowl rough-out for a trial cut. This was smooth and vibration free. I compared a cut at about 1000 rpm with one at full speed. There was a big difference at high speed, with much less tear out. The surface was slightly burnished, without ripples.