Heat shakes? -Moved

[Jay Coulson]

Hi all. I think that I just had my first dose of heat shakes...at least I think that;s what it's called. I was making a small bowl out of bloodwood. The piece was cut pretty cleanly so, I started at 180 and went up to 400 BUT, wasn't using any Briwax on the paper. I think that I created a little too much heat and, suddendly noticed when I stopped the lathe, that I had little lines (almost looked like cracks) across the grain. Is sanding with wax to reduce heat build-up the only way to avoid this junk?
Tks,
J

 

[Steve Worcester]

Heat checks can certainly be caused by sanding, the first thing is to slow down the lathe, and don't sand for too long. That way you won't get a lot of heat built up. You can use wax as a lubricant, but I would only do so if wax is the final finish.

 

[john lucas]

Ditto what STeve says. I keep the sandpaper moving constantly and use light pressure with slower speeds on the lathe. I don't use wax. If you find that you are sanding a lot with one grit then you should have started with a courser grit paper. You should only need to sand for a fairly short time with all the grits except the first one.

 

[Jay Coulson]

heat checks

First an apology...I think. Don't now about you guys but, on my computer, the word "heat" showed up in red letters. I didn't do that guys! Anyway, thanks for the feedback. I've been doing both things wrong...sanding at about 1500 rpm and, spending too much time doing it. The piece that acted up was red-heart (not blood wood) but, I am pretty sure the problem would have ended-up the same either way. I have seen and read that, one must be very careful sanding dense exoctics for this very reason. Some folks seem to sand with wax while others just make the sanding short and sweet.
Now, a question to hitch-hike on our theme. What to do if I have a piece that is cut pretty cleanly but, the end grain (inside and out) of a bowl for example, just won't lay down? As my turning speed has increased, my sharpening has improved and, my over-all technique is better, I still run into this type of occasional tear-out, regardless. I hate resorting to the "80-100 grit gouge" but, what other choice(s) do I have?
I'm all ears.
Tks,
J

Heat checks can certainly be caused by sanding, the first thing is to slow down the lathe, and don't sand for too long. That way you won't get a lot of heat built up. You can use wax as a lubricant, but I would only do so if wax is the final finish.

 

[GeorgeH]

You could resharpen your tools to create a razor sharp edge that does a better job of cutting the end grain than tearing it. But, unfortunately, it is often impossible to eliminate all evidence of tear out without sanding with some of that nasty coarse grit stuff. For tear out, IMO, 100 grit is not a shameful level to work from. 80? Well, IMO the tool need sharpening or the skill level needs to be developed a bit further. I've worked with some wood that refused to submit to my well sharpened, properly presented honed tool and reached for the 100 grit because I knew that I'd spend an additional unnecessary hour sanding if I started with 120.
Here's a method I use to determine if I'm getting the work piece too hot while sanding. I sand with a bare hand behind the sandpaper. If my hand begins to get uncomfortably warm, I'm either running the lathe too fast or applying too much pressure. Applying too much pressure actually causes more problems than it solves because light pressure, allow the sandpaper to do the work, actually gets the job done faster and with better overall results.
Using wax on the sandpaper, except for the final stages of finishing, is foreign to me so why you're doing that is unclear.

 

[MichaelMouse]

Jay, the standard friction equation does not include speed. It's coefficient of friction times normal force. Blaming speed should be so obvious a red herring that no one would bother repeating it, but they do. How fast is that ROS or that orbital running? 15-25 K, that's how fast. It doesn't make any difference which is moving, either.

DON'T PRESS when sanding. Lots of things working against you if you are hand sanding, like the paper wanting to run away, then there's power sanding with the heavy drill that wants to be braced against the work with pressure. Or even the work-driven sander with the delicate balance between drive and pure pressure.

Lots of folks forget another aspect of friction, that the squirm of their soft velcro pad adds to the friction, and thus the heat. It's not even mentioned in most threads on sanding, though the smell of herring hangs around all of them.

My solution is pretty simple. I use hard backing and support the sanding tool on the rest, not the work, so I can use it as a rotary scraper. Then all I have to do is remember not to be tempted into pressing. For the numbers types, the disk rotates at 1725 and the piece at 680 if you believe the maker of the motor and lathe. Once the piece is sanded to proper level and the grain raised, I can hand sand it with the grain for best surface.

http://s35.photobucket.com/albums/d160/GoodOnesGone/?action=view&current=150Sand-1.flv

That's the setup over on the far right. http://i35.photobucket.com/albums/d160/GoodOnesGone/P3140057.jpg

Lightening up keeps the paper cooler, diminishing heat checks. Minimum flex reduces loss of grit, lowering cost per piece, too. Plus, you can always set the warp-and-go stuff in your lap after it dries, hold with one hand, and sand with the other. Tough to do with a drill.

 

[Jay Coulson]

heat checks

Thanks Michael. Good video, tks. Assume that you were vacuum chucked when you were sanding. I see the sanding set-up in the right but, admit that I am unfamiliar with the power rig you have there. Please describe it in a little more detail. Bowl ended up looking very nice and even. Good job!
tks,
J

Jay, the standard friction equation does not include speed. It's coefficient of friction times normal force. Blaming speed should be so obvious a red herring that no one would bother repeating it, but they do. How fast is that ROS or that orbital running? 15-25 K, that's how fast. It doesn't make any difference which is moving, either.

DON'T PRESS when sanding. Lots of things working against you if you are hand sanding, like the paper wanting to run away, then there's power sanding with the heavy drill that wants to be braced against the work with pressure. Or even the work-driven sander with the delicate balance between drive and pure pressure.

Lots of folks forget another aspect of friction, that the squirm of their soft velcro pad adds to the friction, and thus the heat. It's not even mentioned in most threads on sanding, though the smell of herring hangs around all of them.

My solution is pretty simple. I use hard backing and support the sanding tool on the rest, not the work, so I can use it as a rotary scraper. Then all I have to do is remember not to be tempted into pressing. For the numbers types, the disk rotates at 1725 and the piece at 680 if you believe the maker of the motor and lathe. Once the piece is sanded to proper level and the grain raised, I can hand sand it with the grain for best surface.

http://s35.photobucket.com/albums/d160/GoodOnesGone/?action=view&current=150Sand-1.flv

That's the setup over on the far right. http://i35.photobucket.com/albums/d160/GoodOnesGone/P3140057.jpg

Lightening up keeps the paper cooler, diminishing heat checks. Minimum flex reduces loss of grit, lowering cost per piece, too. Plus, you can always set the warp-and-go stuff in your lap after it dries, hold with one hand, and sand with the other. Tough to do with a drill.

 

[Jay Coulson]

heat checks

Thanks George,
I am plenty sharp and, don't run into the tear-out problem nearly as much as I did when I started turning. But, as you say, ocassionally, you have a piece of wood that just will not behave, no matter how sharp you are and, how good your finishing cut is. I've had some pieces that evidenced a bit of tear-out on the outside but, not on the inside and, vice versa. Others...oily stuff like cocobolo, a breeze if you're sharp with good tool presentation. I've started at 320 and gone to 400 or, sometimes 600 in about 3 minutes and, all done.
but, there are the exceptions with certain types of woods. Such a pain when youve yaken your time with attention to a pleasing form only to find out that the finishing is going to be a chore...and possibly you never get as even and smooth as you would have hoped.
Tks,
J

You could resharpen your tools to create a razor sharp edge that does a better job of cutting the end grain than tearing it. But, unfortunately, it is often impossible to eliminate all evidence of tear out without sanding with some of that nasty coarse grit stuff. For tear out, IMO, 100 grit is not a shameful level to work from. 80? Well, IMO the tool need sharpening or the skill level needs to be developed a bit further. I've worked with some wood that refused to submit to my well sharpened, properly presented honed tool and reached for the 100 grit because I knew that I'd spend an additional unnecessary hour sanding if I started with 120.
Here's a method I use to determine if I'm getting the work piece too hot while sanding. I sand with a bare hand behind the sandpaper. If my hand begins to get uncomfortably warm, I'm either running the lathe too fast or applying too much pressure. Applying too much pressure actually causes more problems than it solves because light pressure, allow the sandpaper to do the work, actually gets the job done faster and with better overall results.
Using wax on the sandpaper, except for the final stages of finishing, is foreign to me so why you're doing that is unclear.

 

[MichaelMouse]

Thanks Michael. Good video, tks. Assume that you were vacuum chucked when you were sanding. I see the sanding set-up in the right but, admit that I am unfamiliar with the power rig you have there. Please describe it in a little more detail. Bowl ended up looking very nice and even. Good job!
tks,
J

Pin chuck mounted. I rough outside with pin then reverse to 4-jaw chuck. I use the same method to turn after drying. Makes an easy setup, because the hole for the pin chuck shrinks, requiring a 1" Forstner down the old hole to re-mount within a fraction of center. The 4-jaw mount is rounded, embellished if desired, and sanded before hollowing.

http://i35.photobucket.com/albums/d160/GoodOnesGone/Method-One.jpg
http://i35.photobucket.com/albums/d160/GoodOnesGone/Method-Two.jpg
http://i35.photobucket.com/albums/d160/GoodOnesGone/Method-3.jpg


The power is an old 1725 fan motor with a chuck and flex shaft. I used a Maytag motor until I decided I liked it with the longer shaft on my power strop.

 

[Odie]

First an apology...I think. Don't now about you guys but, on my computer, the word "heat" showed up in red letters. I didn't do that guys! Anyway, thanks for the feedback. I've been doing both things wrong...sanding at about 1500 rpm and, spending too much time doing it. The piece that acted up was red-heart (not blood wood) but, I am pretty sure the problem would have ended-up the same either way. I have seen and read that, one must be very careful sanding dense exoctics for this very reason. Some folks seem to sand with wax while others just make the sanding short and sweet.
Now, a question to hitch-hike on our theme. What to do if I have a piece that is cut pretty cleanly but, the end grain (inside and out) of a bowl for example, just won't lay down? As my turning speed has increased, my sharpening has improved and, my over-all technique is better, I still run into this type of occasional tear-out, regardless. I hate resorting to the "80-100 grit gouge" but, what other choice(s) do I have?
I'm all ears.
Tks,
J

Howdy Jay......

As Steve pointed out, slow it down a little! 1500rpm is pretty darn fast for sanding. For my bowls, I seldom do my sanding at speeds over about 500 rpm, or so.....and, often times, much slower than that.

You didn't say what it was you were turning out of Red Heart......a bowl?

The larger the diameter, the faster the surface speed will be.....and the more concern heat will become. Also, the finer grits tend to produce heat more readily than the coarser grits. You may have to adjust rpm, according to the grit you are using at the moment. Someone else pointed out that your fingers are a great way to judge how much heat your sanding is producing.

One particular point that hasn't been addressed, is moisture content. Any moisture in the bowl, regardless of your seasoning process, will be quickly eliminated at the surface through normal sanding. It's impossible to eliminate heat from sanding altogether, and there is that possibility you could be seeing heat checking that is caused by eliminating excess surface moisture too quickly. I'm not sure how dense your Red Heart blank is (and, I don't recall ever turning any RH), but if it's very dense, then moisture could be an issue.....because the denser woods tend to release moisture a little more stubbornly during the seasoning process, than other, less dense woods.

What method of drying (seasoning) your bowl blank do you use? If your bowl is roughed, sealed, and stabilized to about 10% +/- MC, or under, that's probably not your problem......

ooc

To address your secondary question: Yes, sharp tools produce less tear-out.....and as you know, often times it's impossible to eliminate tearout completely. Use the bowl gouge as much as you can, but you can clean-up tearout considerably by then employing the scraper as a follow-up to the gouge. You may not be able to get rid of it all, but you certainly can improve the situation to the point where sanding is much easier to do. I am going to assume you are aware of the technique of "shear scraping", so I'm not going to bother.

About that "80gt gouge".....don't be fooled into believing the expert turners don't have to use it once in awhile........but, the less you have to resort to very coarse grits, the better you can feel about how well your own skills are improving!

ooc

 

[Jay Coulson]

sanding anf tear-out

Thanks Odie. forgot about this thread that I started. Where this all started is with my partner and, the love of my life buying me a sampler package of 10 square , dry blanks of exotics. She didn't know what they were but, thought that I might like to try some of them. The only one or 2 that I was familiar with were cocobolo and mora (mara). The others...redheart, chechen, grenadillo, EI Rosewood and a bunch more...I had no clue. They all seem to be high oil stuff like coco so, they finish out pretty easy...sand 240 or 320 up to 400 or 600, a little sanding sealer , friction polish and I'm done. Unfortunately, none of this stuff was labeled so, the ones that are ending up decent...well, I don't know what wood they are. I did get a little bit of tear out on the red heart which is what prompted me to write to the forum.Finish gouge may have needed sharpening but, I doubt it. It's always possible that I made a bad finishing cut with the standard gring bg. Anyway, all of this stuff is very dense. So, sanding out a little tear-out was more than a notion. I'll get thru it. Yeah, I am familiar with shear scraping etc.
Later,
J

Howdy Jay......

As Steve pointed out, slow it down a little! 1500rpm is pretty darn fast for sanding. For my bowls, I seldom do my sanding at speeds over about 500 rpm, or so.....and, often times, much slower than that.

You didn't say what it was you were turning out of Red Heart......a bowl?

The larger the diameter, the faster the surface speed will be.....and the more concern heat will become. Also, the finer grits tend to produce heat more readily than the coarser grits. You may have to adjust rpm, according to the grit you are using at the moment. Someone else pointed out that your fingers are a great way to judge how much heat your sanding is producing.

One particular point that hasn't been addressed, is moisture content. Any moisture in the bowl, regardless of your seasoning process, will be quickly eliminated at the surface through normal sanding. It's impossible to eliminate heat from sanding altogether, and there is that possibility you could be seeing heat checking that is caused by eliminating excess surface moisture too quickly. I'm not sure how dense your Red Heart blank is (and, I don't recall ever turning any RH), but if it's very dense, then moisture could be an issue.....because the denser woods tend to release moisture a little more stubbornly during the seasoning process, than other, less dense woods.

What method of drying (seasoning) your bowl blank do you use? If your bowl is roughed, sealed, and stabilized to about 10% +/- MC, or under, that's probably not your problem......

ooc

To address your secondary question: Yes, sharp tools produce less tear-out.....and as you know, often times it's impossible to eliminate tearout completely. Use the bowl gouge as much as you can, but you can clean-up tearout considerably by then employing the scraper as a follow-up to the gouge. You may not be able to get rid of it all, but you certainly can improve the situation to the point where sanding is much easier to do. I am going to assume you are aware of the technique of "shear scraping", so I'm not going to bother.

About that "80gt gouge".....don't be fooled into believing the expert turners don't have to use it once in awhile........but, the less you have to resort to very coarse grits, the better you can feel about how well your own skills are improving!

ooc

 

[Jay Coulson]

Sanding...

Pretty neat Michael!. It never ceases to amaze me how ingenious people can be to achive their goals. An old Maytag motor...now that's something that would have never crossed my mind but, it makes perfect sense. An available motor to drive a sanding rig...so simple yet effective. I've read alot of stuff about people coming up with similar solutions for vacuum chucking. I've given it some thought but, I'm not real engineering minded and, in the case of whipping up a vacuum system, I'm a little apprehensive that, it wouldn't create sufficient holding power and, that I'd have bowls flying around the shop.
J

Pin chuck mounted. I rough outside with pin then reverse to 4-jaw chuck. I use the same method to turn after drying. Makes an easy setup, because the hole for the pin chuck shrinks, requiring a 1" Forstner down the old hole to re-mount within a fraction of center. The 4-jaw mount is rounded, embellished if desired, and sanded before hollowing.

http://i35.photobucket.com/albums/d160/GoodOnesGone/Method-One.jpg
http://i35.photobucket.com/albums/d160/GoodOnesGone/Method-Two.jpg
http://i35.photobucket.com/albums/d160/GoodOnesGone/Method-3.jpg


The power is an old 1725 fan motor with a chuck and flex shaft. I used a Maytag motor until I decided I liked it with the longer shaft on my power strop.

 

[MichaelMouse]

Time was most everyone saved the functioning parts of outmoded or outworn appliances. I think I picked up that one at the "GI Store" (dump) in Minot. Scored a mess of dexion, too!

With most things now molded in place, there's much less to scavenge.

 

[Bill Boehme]

First an apology...I think. Don't now about you guys but, on my computer, the word "heat" showed up in red letters. I didn't do that guys!

Funny, but it showed up blue over here. Just kidding.

My guess is that you were doing a search for your post and keywords used in the search show up red in the posts that are found by the search.