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Little Help Please! Tung Oil, Grind Angles, and Polyurethane, Oh My!

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Forum topic by MoreWoodPlease posted 11-28-2010 11:50 PM 3124 views 1 time favorited 9 replies Add to Favorites Watch
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MoreWoodPlease

94 posts in 1924 days


11-28-2010 11:50 PM

Topic tags/keywords: polyurethane tung oil grind angles turning tools

Been trying to regrind turning tools. What are the correct angles for: Skew, Bowl Gouge, Spindle Gouge, and Scraper?
Can you apply Poly over “Tung Oil Finish”, not the 100% tung oil, but the Home Depot version?
Can you use Polyurethane on bowls that may hold fruit? And if not, what do you use to finish bowls?

Thanks all.
Wes

-- Integrity is who we are when no one else is watching.


9 replies so far

View Scott Bryan's profile

Scott Bryan

27251 posts in 2573 days


#1 posted 11-29-2010 02:04 AM

Wes, you have a pretty complicated question in the second one. But, can you apply poly over a Tung oil finish, the answer is yes. The HD version is a wiping varnish so it is ok to apply poly over it. If I were doing this I would scuff sand the tung oil with 320 after it has cured and apply a few coats of wipe on poly.

Can you use poly on bowls for fruit? That is a topic that has been hotly debated at times. One school of thought holds that any finish is safe for food contact once it has cured since the toxic elements of the finish are the solvent carriers. Once the solvents evaporate only inert materials are left behind. There is an equal number who advocate only using “approved” food safe finishes such as mineral oil, walnut oil, Behlen’s salad bowl finish, to mention a few.

-- Challenges are what make life interesting; overcoming them is what makes life meaningful- Joshua Marine

View dbray45's profile

dbray45

2618 posts in 1528 days


#2 posted 11-30-2010 08:37 PM

Walnut oil can flavor – and some people may be sensitive to it.
Tung oil 100% pure, is food safe but has a flavor and smell (all oils except mineral oil can have a smell and taste)
Minwax Tung oil finish must cure and like poly will chip.
Mineral oil doesn’t have a taste but can be “heavy”
Pure Beeswax won’t last against water – will “whiten”
Poly and lacquer can chip and leave cut marks
Poly will cover tung oil – lightly sand and wipe it down with mineral spirits first – haven’t tried it over the other oils.
Shellac will disolve with alcohol

When I use mineral oil and beeswax I will heat the piece (usually butcher blocks) in the oven at out 125 – 150 (F). You have to be careful about the glue getting soft but it allows them to be absorbed into the grain.

-- David in Damascus, MD

View peteg's profile

peteg

3006 posts in 1574 days


#3 posted 12-02-2010 02:29 AM

Hi Wes,
The standard sharpening angles for turning gear is (angles given)
Bowl gouge 55
Roughing gouge 45
Spindel gouge 35
Skew 22 ea side & the rake about 65
Parting tool 60
These are the nominal angles taken as a standard, however its your tool and what ever you feel happy with is what you should stick with. (Just make sure you dont have any shoulders to cause dig ins)
I’ll leave the other questions for the other guys

-- Pete G: If you always do what you always did you'll always get what you always got

View Lochlainn1066's profile

Lochlainn1066

138 posts in 1528 days


#4 posted 12-02-2010 09:33 AM

Like Scott said, there’s debate about whether finishes are food safe. I’m of the opinion that they are once they dry.

If you want one proven safe, use one of the common shellac and wax turning finishes, like HUT. Shellac is a common food additive (puts the shine on candy, for example), it’s alcohol based, and carnauba, paraffin, and beeswax are all nontoxic/indigestible.

-- Nate, thegaragestudio.etsy.com

View hObOmOnk's profile

hObOmOnk

1381 posts in 2879 days


#5 posted 12-02-2010 01:59 PM

“Tung Oil Finish” is a wiping varnish, not raw tung oil.
“Poly” (so called) over TOF is varnish over varnish.

-- 温故知新

View jockmike2's profile

jockmike2

10635 posts in 2998 days


#6 posted 12-03-2010 05:53 AM

THE WELL KNOWN FINISHER AND AUTHOR BOB FLEXNER ALSO SAYS THAT ONCE POLYURETHENE, OR VARNISH HAS DRIED, THERE IS NO DANGER OF TOXICITY. THERE IS A WARNING ON MOST FINISHES THAT THEY ARE TOXIC OUT OF THE CAN. HOWEVER, ONCE DRIED, THERE IS NO DANGER. I WOULD THINK THAT OTHER THAN MINERAL OIL, SHELLAC WOULD BE THE IDEAL FINISH, SINCE IT COMES FROM THE LAC BUG, AND ALCOHOL, THERE SHOULD BE NO DANGER ONCE DRY NOR SHOULD THERE BE ANY ODOR OR FLAVOR IMPARTED TO THE CONTENTS OF THE CONTAINER, WITH THE THREAT OF LEACHING FROM PLASTICS THAT I HAVE RECENTLY READ ABOUT, I WOULD TRUST THE NATURAL FINISHES OVER WOOD THAN THE PLASTIC CONTAINERS ANY DAY.

-- (You just have to please the man in the Mirror) Mike from Michigan -

View DrDirt's profile

DrDirt

2597 posts in 2493 days


#7 posted 12-03-2010 06:49 AM

I agree mike – in fact shellac is applied to medicines to keep them slick and/or have them be “time release” So we eat shellac all the time, and the ethanol is the same stuff we drink (+ the denaturang) but both have evaporated before use.

Wes, you never mentioned why you wanted to apply polyurinate :-) on your piece anyway?
I usually avoid it since especially for kitchen use one expects it to get beat up a bit because it is usually hard/impossible to repair without stripping back to bare wood.
It is a very durable finish but hard to work on. I go a littl less durable (Laquer or shellac) and can ‘freshen up’ the piece years down the road

-- "If we did all the things we are capable of doing, we would literally astonish ourselves." Edison

View hObOmOnk's profile

hObOmOnk

1381 posts in 2879 days


#8 posted 12-03-2010 01:34 PM

Shellac is good stuff. It is very safe to use, it is far more durable than “internet echoers” claim and it is easy to fix and maintain.

Common shellac myths, aka “Internet Wisdom” (repeated until believed by the masses):

1. All shellac is edible because shellac is used in food products and medicines.
Truth is that “food-grade” shellac and “medical-grade” shellac are highly purified and approved for their intended purposes. The stuff in the can from the hardware store is not guaranteed to be consumable, although it is generally safe for casual contact. Take a look at the raw shellac flakes that many artisans use to mix their own finishes. It can be quite nasty.

2. Denatured alcohol is completely safe because it evaporates and leaves no residue. While methanol and similar evaporative chemicals are used to denature alcohol in the USA, this is not true in other countries. Non-food approved residues may result.

Analogy: Some water is drinkable therefore all water is drinkable.
Truth is that less than 1% of the Earth’s water supply is drinkable as is.

-- 温故知新

View Bill White's profile

Bill White

3587 posts in 2711 days


#9 posted 12-03-2010 05:05 PM

If you don’t use polycrapathane at all you will be a better finisher. Why not a good wiping varnish over BLO?
Bill (Want to know what I REALLY think?)

-- bill@magraphics.us

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