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Forum topic by Mainboom posted 03-08-2019 10:31 PM 1178 views 0 times favorited 27 replies Add to Favorites Watch
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Mainboom

92 posts in 807 days


03-08-2019 10:31 PM

first off new turner. I bought some turning blanks online. they are waxed big time so they are still wet. the blanks that have went flying were both tulip poplar or poplar if you don’t wanna be fancy. first one outside was turned and finished. was cutting out the inside had a catch and heard a crack. At the time I was using a half round 3/4 scraper. the walls were 3/8 thick and I had about 3/4 still to get out of the bottom. I had a 1/8 dovetail in the bottom and expanded the chuck into the dovetail. im using a nova g3 chuck. I didn’t get it monkey tight or anything but I was turning at like 1400 rpm. which I must have missed in the instructions it says not over 600 so my bad.

Second bowl…. basically the same thing.Except I was only turning about 400 rpm. I had the tail stock in this time when I started to cut out the inside for more support. got about 1 1/2 into the bowl. and I hear crack and the bowl goes flying. This time I was using my 3/8 gough. I did get a catch this time as well. my dovetail was exactly 1/8 maybe more I measured it 5 times.

So am I just not making the dovetail deep enough or what ? Or is it just me getting a catch ? My lathe is sitting kinda high right now on my bench because my stand has not come yet.my blanks are 6×6x3 so I don’t want to make a giant hole if I don’t have to. is it because the wood is wet and drying as it spins or what ? im at a loss. I got mad after this happened and cut up a stack of plywood made blanks and glued them together and im gonna practice cutting dove tails till I get it right. its birch ply and I have seen it turned but I don’t want to turn any more of these blanks till I figure out what im doing wrong. like I said the instructions say 1/8 dovetail depth and clean it out that deep which I do.

I have never turned wet wood so if im doing something wrong please let me know. Other then the catch’s which ill admit has happened more then once. Or is it just because im getting a catch a few to many times ?

-- CRANE OPERATORS START EARLY because iron workers need their heros ready when they wake up


27 replies so far

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MrUnix

8502 posts in 3248 days


#1 posted 03-08-2019 10:48 PM

I personally prefer tenons… particularly on bowls. With a recess, it’s too easy for me to expand the wood to the point where it fails; while it’s difficult to do the same with a tenon. Never had one go flying yet. I also like to use threaded glueblocks, which are even stronger.

Also, I would look for alternative sources of wood besides mail order, especially since you are just learning. Where you are, I imagine you have an unlimited supply of wood all around you if you look.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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LeeMills

702 posts in 2351 days


#2 posted 03-08-2019 10:57 PM

Since you had the tailstock the second time I assume it was due to the catch.
That said, Nova states up to 1/4” deep for the 50mm jaws. I go overboard my self and make the recess (or tenon) about 3/8 but I am not buying blanks so it isn’t like I am wasting any money.
Probably the wet wood, which is easier to split than dry, along with a shallow recess both contribute along with the catch. In dry hard wood you can get by with a more shallow recess or shorter tenon.
Stuart Batty has three excellent videos on chuck, jaws, tenons, and recesses; each about 12 minutes.
https://vimeo.com/woodturning/videos/sort:alphabetical/format:thumbnail

-- We cannot solve our problems with the same thinking we used when we created them. Albert Einstein

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Mainboom

92 posts in 807 days


#3 posted 03-08-2019 11:27 PM

@ mr unix my first bowl I ever did I used a tenon it seemed stronger. I do have wood all around me but its not “legal” to take it.

@leemills ill check out the videos. I was just following instructions basically I think using a tenon might be a better idea. I just don’t wanna use up the wood if I don’t have to

-- CRANE OPERATORS START EARLY because iron workers need their heros ready when they wake up

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SignWave

472 posts in 4085 days


#4 posted 03-09-2019 01:18 AM

The issue, based on what you’ve said, is that you got a catch. I’m guessing that the wing of your gouge ended up going into endgrain, which leads to the catch, then the flying part. Unless you were totally negligent in mounting your workpiece (and I don’t get that impression), then I really don’t think that’s where you need to focus.

There’s a learning curve for understanding how to work the grain. I think your idea to practice more is spot on. I wouldn’t use laminated plywood though, because it doesn’t have a single grain pattern, so it will be hard to learn to work the grain. Instead, I suggest working on spindle oriented pieces, between centers in a moderately soft wood with even grain and no knots. Turning spindles makes it much easier to see the grain and understand terms like “downhill”. Turning between centers is generally safer because the wood is supported on both ends.

When you go back to cross-grain (e.g. bowls), you’ll have to re-orient yourself with regard to technique because the grain is different. But the understanding that you gained during your spindle practice will be a foundation for the bowl turning.

-- Barry, http://BarrysWorkshop.com/

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Mainboom

92 posts in 807 days


#5 posted 03-09-2019 01:57 AM

So would cutting up some maple i have and making up blanks with that for spindles be better ? i can cut it all from the same piece and glue it so the grain is basically the same. would that be better ? im still gonna probably use the ones i already made so i can practice cutting a good dovetail and so on. id just prefer to use what i have on hand. what i have on hand to make blanks is a lot of birch ply and about 15 board foot or more of maple.

-- CRANE OPERATORS START EARLY because iron workers need their heros ready when they wake up

View Wildwood's profile

Wildwood

2954 posts in 3184 days


#6 posted 03-09-2019 11:50 AM

If turned a recess with dovetail its not the problem it’s your turning technique and that Poplar wood trying to turn. While Poplar listed as a hard wood its pretty soft, so need sharp tools and don’t get a catch and don’t force the tool!

I use either a recess or tenon turning bowls depending upon size of the wood whether wet or dry. Recess probably better for wet wood. Harvest my own wood so turn mostly wet wood bowls but spindle turning wood at EMC.

-- Bill

View OSU55's profile

OSU55

2770 posts in 3039 days


#7 posted 03-09-2019 02:25 PM

Look around your area for arborists, tree cutting services, logging companies – dont cut the tree down, get what someone else doesnt want. This spring/summer chances are good a storm in your area will take some trees down.

Its probable that using a mortice and getting catches combined to losing the bowls. You said you heard a crack when you got the catches – are the bowls cracked at the mortice? I lost a couple that way when I started. I prefer tenons – crushing fibers together vs splitting apart.

Work hard on the catches part. Be a good idea to make deeper mortices or longer tenons – 1/16 to an 1/8 less then the jaw allows, until you get more experience. There are many good sources for avoiding catches – study them and make proper tool control a habit. After years of turning I still get the occassional catch, due to not paying attention.

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Ripper70

1379 posts in 1958 days


#8 posted 03-09-2019 02:43 PM

You can scan CL in the free section for wood that may be suitable for turning. Listings like this one may yield a trove of usable material. The trick is all in the timing.

-- "You know, I'm such a great driver, it's incomprehensible that they took my license away." --Vince Ricardo

View SignWave's profile

SignWave

472 posts in 4085 days


#9 posted 03-09-2019 07:24 PM

Poplar is a nice wood for turning because it has even grain and is not too hard. I’ve also used dimensional lumber for spindle turning blanks. Not Soft Yellow Pine, but another variant (spruce, perhaps?) that has more even grain.

-- Barry, http://BarrysWorkshop.com/

View gwilki's profile

gwilki

365 posts in 2523 days


#10 posted 03-09-2019 10:23 PM

How are the bowls coming off the chuck? Are they pulling out of the jaws or is the blank splitting?

If they are pulling out, but the recess is still in good shape, I would suggest that you are not remembering to stop the lathe and re-tighten the jaws frequently. Wet wood is going to move as you turn, so you need to open the jaws into the recess every few minutes.

If the blank is splitting, you may want to go with a bit deeper recess. Plus, make sure that you have a lot of wood around the recess. Don’t make it too big, leaving only a small margin between the recess and the outside diameter of the bottom of the bowl.

Finally, as others have said, try to figure out what you are doing to cause you catches, and stop doing it. :-)

-- Grant Wilkinson, Ottawa ON

View Lazyman's profile

Lazyman

6916 posts in 2437 days


#11 posted 03-10-2019 02:19 AM

Personally, I have had more failures with tenons than with recess mounted bowls, especially in brittle woods. I have had the tenons simply snap off. One mistake that new turners make when making their recesses for mounting is to not getting a good sharp corner in the dovetail. You need to make sure that the sharp corner of the jaw fits snugly into the corner of the recess but without compressing the wood at all. If the inside corner is rounded at all, even a minor catch can send it flying. One other thing that is often done wrong is to make the recess or tenon too large for the jaw set. Ideally, you should size the recess or tenon so that its diameter is a small as possible and still fit inside or around the recess or tenon. Basically, this is the diameter where the jaws form a perfect circle. This gives you the most surface area against the jaws which makes it almost impossible to come out without breaking apart and also spreads the stress evenly around the diameter making it less likely to break. If when you remove the bowl from the chuck you see pressure points from the ends of each jaw, you made the recess or tenon too large for that jaw set.

BTW, My absolute favorite wood for turning is Bradford pear. It is a dream to turn, finishes beautifully and makes a beautiful bowl. It is great for tool handles too. Even the bark turns nicely and sands to create a really cool pattern on the wood. In the DFW area, it pretty commonly planted and you usually find it on trash piles after an ice storm or heavy winds because it has a very weak branching pattern that is prone to breaking off. Except when I wait too long to turn it and it developed cracks, I have rarely had one fail, even with a nasty catch.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Mainboom's profile

Mainboom

92 posts in 807 days


#12 posted 03-10-2019 02:25 AM

the crack happened almost right where I got the catch. and once that happened im guessing it became to lose to hold and slipped off. I stop the lathe frequently to check things out and I do retighten the chuck. I have been watching the stuart batty videos that Barry(signwave) suggested. And learned as a few have said. Yes a tenon is way better then a recess. Also there is a lot to look at when making a recess and a tenon both to make them correctly.

Another thing I have learned was. I was taught to use the area between the tip and the wing on a gouge. From what I see and hear stuart batty saying use mostly the tip or center of a gouge. if doing a push cut and to put more down pressure on the tool rest then on the gouge itself and to more glide the bevel instead of riding the bevel.
Now I may have lost a little in translation but I did learn what im doing wrong mostly. I have been using to much wing ( which could be main cause of getting a catch) and using less tip of the gouge. Which I should use mostly the tip. Unless im hearing that wrong. Secondly im pushing into the piece instead of down on the rest and trying to make sure the bevel is “riding” and not losing contact. Which I should let it glide And im putting way to much power into it. Which im going to assume is causing undo side pressure. And causing the recess to crack on me. Also since im using way to much towards the wing of the gouge its causing me tons of tear out. But when I use a scraper im not getting the tear out I am with a gouge. So ill watch his videos again to be sure im hearing it correctly but I think I was given kind of lazy instuctions at first and left to my own to quickly. So ill try a new way and see how that goes which most of it seems pretty logical.

-- CRANE OPERATORS START EARLY because iron workers need their heros ready when they wake up

View SignWave's profile

SignWave

472 posts in 4085 days


#13 posted 03-10-2019 05:13 AM

FWIW, it was LeeMills who recommended Stuart Batty, but I second the recommendation.

I’m glad you’re learning from Stuart’s videos. He’s a great turner and a great teacher. Keep in mind that his techniques are based on the grind that he uses for his gouges, which is primarily a 40/40 grind.

Another common ground is the Irish/Ellsworth grind, which has more swept back wings. It’s a more advanced subject, but the different grinds make more of a difference in how the tools are used than you might imagine from looking at them. Keep this in mind as you watch different turners.

For whatever reason, I ended up using more of a 40/40 grind than swept back grind, so I resonate more with Batty’s teaching than Ellsworth. I happened to see a demo by Ellsworth, and he’s incredibly skilled (and also a good teacher). Different ways of doing it.

As for scraping, make sure the edge meets the wood at less than 90 degree angle to avoid catches. If you’re working the outside of a radius, then moving the toolrest down will help. If you’re working inside (like inside a bowl), then raising the toolrest will help.
https://www.youtube.com/watch?v=Pq5uUDMFi5M

The woodturner in the previous video (Brian Havens) makes some very useful videos. He hasn’t posted in a while, but his explanations of how the tools interact with the grain are very good.
https://www.youtube.com/watch?v=N2Onfm2CXHo
https://www.youtube.com/watch?v=vztW0uzJDlI
https://www.youtube.com/watch?v=0x9ItWv9Ibw
https://www.youtube.com/watch?v=iRvIpiOQ1T4

-- Barry, http://BarrysWorkshop.com/

View OSU55's profile

OSU55

2770 posts in 3039 days


#14 posted 03-10-2019 02:15 PM

Mainboom, congrats it sounds like you are making some great headway. Yes a push cut uses only the center section of the bevel. Swept wings are use as scrapers (and in a pull cut at a sharp angle but dont go there yet). Stuart is a great resource, as is Lyle Jamieson. Its good to use several resources so you get different opinions – typically there are several legitimate methods to do things.

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Mainboom

92 posts in 807 days


#15 posted 03-11-2019 06:54 PM

So I turned a bowl with the birch ply I cut up and glides together using mostly stuart battus techniques. Came out pretty good for plywood lol. I used alot less effort for one and I didnt have any catches. I did notice my spindal gouge has one wing higher then the other. So I’ll be grinding that out. I’m using a 120 grit wheel and it almost seems to be getting the steel to hot. I do dip them in water before and after and limit grinding as much as I can. They are the psi Benjamin’s best. So we will see.
Also I pulled up to work today and one of the other companies tore down a bunch of trees. So I went on over and got a truck load of free wood. I’ll be getting a chain saw and the excavator and digging out and cutting up all the good wood I can over the next few weeks or days till they have to load it out. It mostly a bunch of soft maple I think but to practice with I really dont think I can beat it

-- CRANE OPERATORS START EARLY because iron workers need their heros ready when they wake up

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