Thread: Aust Wood Review article on bowl mounting

What a pack of pussies you lot are - this thread had the makinbgs of a good ol stoushe but no you are like a few old chaps - oh my knee - my arm-brace - i use tenons not recess's - i prefer glue blocks - oh you agree do you - bah get into it and tell him what you really think.

Bloody chaps you lot - and we know what the "rules of the shed " say about chaps

I find this discussion really interesting, especially since I am a novice turner. I supect that many of us find a way that works for us and then refine it. I have used both expansion and compression methods (as well as glue blocks etc) and with due care all work well.

Curently my preferred method for a bowl is to
1.Bore a hole the required depth with a forstner bit into the top of the bowl (will become the inside) and mount it on the chuck with dovetail jaws. Plenty of wood thickness/diameter to avoid it splitting.

2. Shape the outside and produce a tenon on the free end (to become the foot of the bowl) I prefer this for the reasons some have discussed already.

3. When the outside is finished, reverse chuck it and hollow out the inside and finish it.

4. Often use a disk sander (bench type) to take most of the tenon off and then reverse mount it to clean up the foot (often use a jamb chuck or Cole Jaws (esential for ME to wrap duct tape around the mounting blocks to avoid finger injuries, especially if I slip while sanding))

Any comments/advice appreciated.

Chipman

Originally Posted by Tim the Timber Turner

Thank but no thanks Ern.

I'm too busy making things on my lathe.

Cheers

Tim

Are you?

So tell me, how much do you like sanding?

There's busy, and there's efficient

Burrs are ########!! I remember bringing this up before!

If you take a tool straight from the grinder with a burr edge on it, that burr will last not time at all once the tool is applied to the work. To pretend, theorise and think that it does otherwise must bring your cognitive and reasoning powers into question.

Must also agree With Ken's comments on the recess. I noted this earlier on in the thread. Some judges simply will not countenance any sign that the work was somehow held in order to complete it.

Is this only true of woodturning judges?

The difference in burrs on tools is like the difference in profiles on gouges, there are many variations.

Scrapers will cut fine with the burr honed off. You can do scraping cuts (both pics in the attachment are scraping cuts), you can ride the bevel, and shear cut with it.

There are huge differences in burrs from grinders. If you just kiss the bevel on your grinder wheel, you get a very delicate burr that is gone in seconds. If you use a bit of a push into the grinding wheel, you get a more durable burr. With my CBN wheels (see thread on diamond grinding wheels), I get a burr that is as durable as any cutting edge on any of my gouges. Excellent for heavy roughing, riding the bevel cuts, and shear/finish cuts.

Then, there is the burnished burr. Hone off the grinder burr, then use a burnisning tool to create a burr like on your card scrapers, which most of us who do flat work are familiar with. I was never able to get a good burr from a round burnisher (screw driver rod, drill rod, or other really hard metal like shock ablsorer struts). With a trinagle burnisher, I can raise a good burr. Lee Valley/Veritas tools has a table mounted burnisher with carbide rods that you can buy. If you gently kiss the surface of the bevel, you get a dainty burr, that is great for shear/finish cuts, but not so good for roughing cuts. If you press harder, you get a more sturdy burr that is excellent for heavy roughing and finish/shear cuts. The burnished burrs seem to curl over more than the ones from the grinder, and don't work as well for riding the bevel.

Now, I know some of you are wondering about riding the bevel of a scraper. I may be crazy, but I'm nuts. It is a specializes tool I have for the center bottoms of the inside of my bowls. The profile is a quarter round, or swept back design to the left side like an 'inside' bowl scraper though it comes to more of a point. It is almost like half of a swept back profile on a gouge. I would never use a round nose scraper for this cut as I want to be cutting on the tip of the scraper, not high up on the center of it as this will have a high risk of catching. Bevel is steep like a bottom of the bowl gouge, and gives a high shear angle. I could use it on the outside, but don't, as a shear cut with a scraper or gouge is easier.

I need to win the lotto, so I can ship myself and a container of my woods to you, and return with some of your woods. I did a trade once with a guy there who makes penny whistles and he was looking for American woods with specific gravity of 1.0 or higher. I had some Mountain Mahogany (not mahogany, just called that because of the color) which was growing at 8500 feet just outside of Las Vegas. On the flooring hardness scale, Oak is about 8, bubinga is 12, and lignum is 20. This stuff is at 18. He was telling me about heading out into the desert for some acacia with a specific gravity of 1.5. Does your postal service have flat rate shipping boxes like ours? I can send 20 pounds max for pretty cheap, and would be willing to trade.

robo hippy

Originally Posted by artme

Burrs are ########!! I remember bringing this up before!

If you take a toll straight from the grinder with a burr edge on it, that burr will last not time at all once the tool is applied to the work. To pretend, theorise and think that it does otherwise must bring your cognitive and reasoning powers into question.

As RH says, burrs ain't burrs, but one of the first studies, done by Farrance, indicates that on a spindle gouge the burr off a dry grinder was hard, compacted, difficult to hone off, and lasted several minutes on ash (Fraxinus). If you'd like to test your own reasoning powers by studying the test report, PM me your email address.

PS I did my own microscopic edge study of a scraper burr raised on dry grinder. Then compared it with the same tool slammed into a bit of hardwood. No detectable diff. Partly this was a test of the old chippy's way of getting rid of a burr or wire edge after sharpening a bench chisel, and it's not the same bevel angle we're talking about, but it was enough demo for me of how hard the burr can be.

Originally Posted by rsser

Are you?

So tell me, how much do you like sanding?

There's busy, and there's efficient

Ern

I don’t think I have ever met anyone that enjoys sanding, not for any length of time anyway.

As for being efficient, I must have been doing something efficiently because I have made a very good living for 20 years, all with things I have made on my lathe.

In these 20 years I have educated my kids and built a small business with regular customers in 10 overseas countries. All this with stuff I made on my lathe.

I wouldn’t have achieved any of this if I spent all my time worrying about what sort of burr I had on my scraper.

Having said that I will defend to the death your right discuss and research scraper burrs for as long as you live.

Whatever rows your boat. We all get something different out of our hobbies or in my case a hobby that got out of control.

Woodturning has been very good to me; I make a good living; I have a great lifestyle and have met and enjoyed the company (along with a few glasses of red) many hundreds of like minded turners from many parts the world.

Duty now calls and I’m heading off to York Peninsular fishing for a few days. That’s a lie really, I’m not that keen on fishing. A white sandy beach, a good book and maybe a small glass of red. Or two. Life can be tough at times.

Cheers

Tim

Sounds good Tim; hope the weather is kind to you.

FWIW, I was a honing sceptic re turning tools in general and have posted against it in this forum. Wasn't what I learned; didn't see any professionals doing it. Only one ref to it, in one of Darlow's books. Was happy with my way of doing things.

Well I've had to eat my words. When a turner like Alan Lacer does the microscopic studies of edges and resulting finishes, I take notice. When our local pro's, Ken W and Vic Wood, in the shear scraping thread, mention that they lap the top of their scrapers, that's worth reflecting on.

As my hands are slowly weakening due to age (give or take a broken wrist in the meantime), anything that'll give me a cleaner finish off the tool and reduce sanding is worth a close look. Shear scraping is light work; wielding a power sander is heavier work.

Originally Posted by rsser

This is a bit beside the point re this discussion but for many of our woods (even green) roughing out with a scraper would be an exercise in frustration. They're just too hard. I was gobsmacked when I read Nish's Creative Woodturning about this use of scrapers.

As for a gouge actually scraping when you use it to hollow, as far as I'm concerned if the bevel is rubbing it's cutting.

To be a bit provocative, a scraper taken straight off the dry grind wheel is also cutting, with a jagged edge standing upright (aka the burr).

The gouge, because of the rounded nose, and wings can be scraping (wings) and shear cutting (nose) at the same time. You can have the tool at the same angle, and make the same cut, rubbing the bevel, or not rubbing, depending on where the handle is relative to the cut and wood. This can be done only on the outside of the bowl, and not on the inside, because of the differences between the concave and convex surfaces. Well, maybe you could do it on the inside, but it would be difficult, and you couldn't do it down inside the bowl. The wood doesn't really care if the bevel is rubbing or not, the angle the cutting edge is presented to the wood and its rotation is what makes the difference in how the wood cuts, Rubbing the bevel or not doesn't make any difference in how smooth the surface is, or how clean the wood cuts. The only difference I have been able to notice is if the bevel is rubbing, you burnish the surface of the wood, which does make it more shiny.

The differences between a pushing cut and pulling cut comes in here when done on the outside of a bowl. Almost all cuts on the inside of a bowl are push cuts, while on the outside, you can do either. A pull cut you generally are not rubbing the bevel, while on a push cut, you do rub it. You can again, get the same finished surface with either cut.

I do know that I am pretty much alone on this thinking, but think about it a while. It may make some sense.

Boy, did we get side tracked or what?

robo hippy

Originally Posted by robo hippy

I had some Mountain Mahogany (not mahogany, just called that because of the color) which was growing at 8500 feet just outside of Las Vegas. On the flooring hardness scale, Oak is about 8, bubinga is 12, and lignum is 20. This stuff is at 18. He was telling me about heading out into the desert for some acacia with a specific gravity of 1.5. Does your postal service have flat rate shipping boxes like ours? I can send 20 pounds max for pretty cheap, and would be willing to trade.

robo hippy

Looks like your desert acacias are on par with our desert acacias, then, in the 15-20 range. But specific gravity 1.5... are you sure? IIRC haven't seen any here over 1.3. Can anybody confirm either side?

Did we get sidetracked?

Yep, most enjoyably ;-}

Whatever unconscious competence I had with expansion mounting is now blown out of the water and next time I do it I'll be thinking about all the things that might go wrong which is not a bad thing.

Originally Posted by rsser

Shear scraping is light work; wielding a power sander is heavier work.

Ern,

In that case you might be interested how TTIT has his power sander set up with a long flexible shaft.


Must be easier to handle.


Peter.

Thanks Sturdee.

I did try to copy Vern's neat idea but couldn't find a shaft to take a chuck big enough for my discs that wasn't also junk.

Now I use a 90 degree angle drill which I don't have to fight so much to keep in the right place as with a std lekky drill.