Tear-out -- how to avoid it?

[Robert Marshall]

The photo below shows a problem I've had with tear-out; this was on a stacked bowl of padauk and plywood. What do I need to do, to avoid this? I was using a square carbide cutting bit, to round this bowl; it was not new, but had been recently honed using a diamond sharpening plate.

The tear-out occurs in the end-grain; the rest of the surface is quite smooth.

To the extent tear-out can't be avoided, can this be filled before finishing with a fine sawdust (from sanding the padauk) and glue mix?

Thanks!

Robert

[David Walser]

You can try a couple of things to avoid the tear out: First, use a bowl gouge so you can cut the wood rather than scrape it. (Most carbide tools are scrapers.) Be sure you are cutting from the inside diameter towards the outside diameter. This avoids having the cut being 90 degrees to the rotation of the lathe. More importantly, it allows the fibers to be fully supported throughout the cut. In this case, your blank is basically a cylinder in shape. If that's the final shape, take a light cut from one edge or the other. You won't be cutting end grain, you'll be cutting face grain if you do this properly.

Sometimes not even that will completely work. Then, try shear scraping. Instead of having the cutting edge parallel with the bed of the lathe (which causes the scraping action to be at 90 degrees to the rotation of the lathe), cant the tool over about 45 degrees. Now the scraping action will be at a shear angle to the rotation of the lathe.

Hope this helps.

[Brian Brown]

Try this vid. It shows what David is saying.

dubdubdub.youtube.com/watch?v=7oeiVQLeOd4&list=PLKupw_lpbxJmdlpHN29tFXhk8SrfJftK2

[Steve Mawson]

Good advise from David and Brian. If you use glue and sawdust it will always show, if it is a piece you want to look nice I would avoid the glue and sawdust. Most end grain can be cut cleanly with the technique that David suggests.

[Thomas Canfield]

No one mentioned higher speed, but that will help. Main thing is to have a "sharp" cutting tool (gouge, carbide, scraper, ....whatever) and light cuts. A slice cut will tear less than a shear cut.

[Dennis Ford]

All good advise above. There is not a single fix for tear-out; preventing it requires doing several things right (including wood selection) and in some cases it requires doing many things perfectly.

[robert baccus]

This plagues everyone. I usually spray some water or lacquer on the tearout and wait maybe a minute. My go to is a 3/8" bowl or detail gouge honed to scarey sharp and take off tiny threads of wood at high rpm.

[Reed Gray]

From looking at the pattern of this tear out, it could be caused by rotten wood. When ever it gets soft, it will want to tear, and leaves the surrounding wood in place. A scraping cut, as in scraping tool flat on the tool rest and cutting edge at 90 degrees to the spin (yes, gouges can scrape too), will always pull more at the grain before cutting. A shear cut, with the edge at 45 or higher degrees to the spin of the wood will cut more cleanly. At this point, you may have to fill with glue, unless there is enough meat to turn it down a bit more. Lubricating with water, finish, or any oil does help lubricate the wood as you cut, and you take several passes to remove the tear out by cutting away the wet wood. If you are going to try to turn that out, flood with some thin CA glue first and let it set up.

robo hippy

[Randy Red Bemont]

I had a similar issue and I turned up the speed and that made a world if difference. I too am using carbide cutters. Good luck.

Red

[Bruce Lewane]

Yup. Padauk tears out like crazy when roughing out. A couple of thoughts from someone who works almost exclusively with carbides.
Padauk is fairly soft with an open grain. It loves to tear out.
The square carbide is really only good for a few things and getting a good finished surface is not one of them.
The round finisher works better but still not great for final cuts.
For finish cuts I use a Hunter Osprey, 1 and 2, that allows shear cuts. ( This is not an advertisement.)
Very light cuts at a pretty good speed.
Still not perfect but within sanding range.
When working with a laminated piece with a contrasting wood never wet sand.
Everything will turn red.
Hope this is helpful.
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[Stan Smith]

I've had some tear out, on a small scale, using carbide cutters and square in partticular. The wood was old wenge. The suggestion was to use a skew, taking very small and non-agressive cuts. That solved my problem. YMMV. Also, I finally learned to use a skew which produced a very smooth finish. I use oval skews. Again, YMMV

[robert baccus]

I'm turning box lids tonight out of very soft spalted sweet gum. I throw them in a butter tub with 50/50 lacquer and thinner to soak overnite. Dry for a day and it usually turns well with care.

[Geoff Whaling]

I turn a fair bit of Padauk / New Guinea Rosewood and don't experience those tear out issues at all. I turn smaller linear laminated bowls similar to Jim McPhail's wonderful "Small World" items but I use sharp honed conventional bowl gouges and the Sorby tear drop scraper at times to refine the inner surface.

Beware of advice to use speed to over come tear out from poor tool selection / control / sharpening issues. Higher turning speeds equate to higher risk and potentially more serious injuries should a mishap occur. Far better to sort out the root cause and learn to select more appropriate tools, sharpen etc.

[Scott Hackler]

I think we are loosing sight of Roberts real issue with the tear out. The laminated blocks are in side grain orientation and so, every full rotation of the lathe caused both ends and both sides of the board to come into contact with the tool. End grain is where tear out is prevalent. The second clue to Roberts issue is that is appears he uses an Easy Wood tool (or something similar) Those tools are scrapers, not cutters and although they can do an adequate job on side grain, a scraper will almost always tear at end grain. Sometimes very badly, sometimes not too bad.

So without the sharp cutting action of a traditional lathe tool (spindle or bowl gouge or skew) is can prove to be very difficult on this particular project or one similar. Robert, you could try a shear scrape with that tool where instead of coming straight into the wood, you tilt the cutter face 45 degrees to the work. That could help a bunch, but you might have to shear scrape a bunch to remove the tear out that you have currently. Light touch, shear scrape and faster rotation speed.

If you are not familiar with or own a gouge (or 12) I highly suggest you consider the traditional tools instead of a carbide scraper. I think you will find that after you learn how to use gouges (sharp ones) you will use the carbide scrapers less and less.

Good luck and keep us all updated on your progress.

[Geoff Whaling]

I think we are loosing sight of Roberts real issue with the tear out. The laminated blocks are in side grain orientation and so,

Scott good advice, but the end grain tear out issue is the same for bowls turned from face grain; stacked laminations of face grain blocks; or linear laminations of smaller timber sections with the grain all running parallel but in face plate grain orientation, i.e. long grain running across the lathe axis.

The amount of "end grain" is only different as a spindle orientation blank, grain running parallel to the lathe axis; or as a traditional segmented bowl, with the long grain arranged in a circular orientation.

The worst glue up grain orientation for tear out is a radial lamination or "pie chart" with the long grain aligned near radially - the outside is all end grain.

The real issues here are the tool choice in this particular application - scraping end grain; and the presentation of the tool's "cutting edge".

If the scraper, a carbide cutter in this instance, is presented in "shear scrape mode" it will produce a better cut with less tear out as the "scraping action" will not be as aggressive as lying the scraper flat on its back. Wether the still present tear out is acceptable is up too the user. However a well sharpened & honed bowl gouge on similar timber will produce a 240 / 320# finish off the tool. :)

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