HRW guidance needed!

[jriechel]

Hey,

Here's the deal; I love honduran rosewood, but the stuff hates me.

Case in point:

This happens EVERY time. Usually the chunks are big enough that I can glue it back together and continue, but seriously, I'm really getting frustrated. Every other material I've tried, I've eventually made it work, but not HRW.

I am using a carbide Woodchuck and turn at 2200 rpm. I use the very corner to get it down to almost the finished diameter, then switch to using the trailing 1/4 of the cutting edge. To cut down to the final diameter, I start with the bevel on the wood, then gradually raise the handle until it's barely cutting. It's almost like dust the cuttings are so fine. As I move across, everything is going great, then wham, the edge catches and the chunks fly. This isn't fun.

Any suggestions from those who've tamed this beast?

Thanks for any help.

Jeff

 

[PedroDelgado]

Is your cutting edge right about center? What glue are you using and is it covering the entire tube? Is your mandrel balanced? Any vibrations? Try reducing speed down a bit. I turn plenty HRW and never had a problem.
Good luck, don't give up!!!

 

[greenmtnguy]

With burls, sometimes it is better to get it close and sand to final size. I finally figured that out on anything delicate. I turn soapstone with a rasp and then sand to size. Pretty much guaranteed to blow up using a tool to final size.

 

[1080Wayne]

Good practice on burls is to seal with thin CA to harden up the softer areas , bark inclusions, etc . You may need to do that several times on a blank . Sometimes it takes a while for the CA to cure if parts of the blank are quite punky , and it may be wise to let it cure for several hours .

 

[Hendu3270]

Good practice on burls is to seal with thin CA to harden up the softer areas , bark inclusions, etc . You may need to do that several times on a blank . Sometimes it takes a while for the CA to cure if parts of the blank are quite punky , and it may be wise to let it cure for several hours .

I do this on all burls as well, even if the wood seems ok.

 

[jfoh]

You can soak the drilled hole with thin CA and let it cure. Then redrill. It gives the wood some internal strength so when you get it turned to a thin final size it will hold up better. I also flood the external several times when turning. It shows cracks and soft areas that need to be dealt with a little extra light touch. A "sanding skew" will work but you have to watch heat build up.

 

[bwftex]

I had the same experience with a batch of amboyna burl. They were beautiful pieces but most nearly unturnable. Try to take your wood to round lightly and as far as you dare with a carbide R2 or R4 blade never letting the end cut in. Then use files or sand paper to shape and do the rest. It can take a long time to turn hardwood this way but I don't know what else to do with material that does this. Even so there is still a chance of failure and even stabilized stuff can explode. This can help though if the wood is too hard and brittle, nonuniform in hardness or too soft. I turn European style fishing floats with balsa and have to use sand paper from start to finish or they tear to shreds.

Consider too that even if everything works out and you end up with a perfect pen out of delicate material of this nature just one short drop is often enough to do it in. Certain woods or certain particular batches of wood like real ivory are not ideal materials for small thin durable turnings. They may make a beautiful pen it may be best to avoid them.

 

[robutacion]

I had the same experience with a batch of amboyna burl. They were beautiful pieces but most nearly unturnable. Try to take your wood to round lightly and as far as you dare with a carbide R2 or R4 blade never letting the end cut in. Then use files or sand paper to shape and do the rest. It can take a long time to turn hardwood this way but I don't know what else to do with material that does this. Even so there is still a chance of failure and even stabilized stuff can explode. This can help though if the wood is too hard and brittle, nonuniform in hardness or too soft. I turn European style fishing floats with balsa and have to use sand paper from start to finish or they tear to shreds.

Consider too that even if everything works out and you end up with a perfect pen out of delicate material of this nature just one short drop is often enough to do it in. Certain woods or certain particular batches of wood like real ivory are not ideal materials for small thin durable turnings. They may make a beautiful pen it may be best to avoid them.

Oh...! but I do...!:wink::biggrin: look here

Good luck,

Cheers
George

 

[George Watkins]

I think your problem is a mixture of the tool and the speed-

I'm not a big fan of using carbide tools with either wood or resin as they tend to grab and want to pull into the material.

I know that some like to turn at high speeds but I personally can't see the point of turning a pen at any speed over 1500rpm- any higher and your just introducing excessive heat and if you do have a dig in it just happens allot faster!!

I love turning all burrs (burls) especially HRB but can't seem to find any at the moment- I use epoxy glue, lathe speed at 1250>1500rpm and a ¾" wide negative rake scraper.

Negative rake is an extremely easy tool technique to use, it leaves a glass like finish on most resin and dense woods.
Just take a normal scraper and grind a bevel on the top edge then sharpen/grind the bottom bevel as normal, this will raise a burr and it's that burr that does the work- use the tool horizontally (don't lift or lower the handle) dont push it into the work just gently present it and you should get ribbons of shaving and don't forgot to replenish the burr often as on some materials it won't last long.

Here's more info on neg rake on page 24 here

and here's a short video of me using a neg rake on a resin box

hope this helps

 

[jriechel]

Thanks for all the suggestions. It's some comfort to know that I'm not suffering by myself.

I can give the CA hardening a shot right away. The negative rake idea is intriguing, but I actually don't own a scraper, so that will be something to work on once I do have one.

Also, I have been using polyurethane glue for my tubes on everything. I may go to epoxy for rosewood burls just for the heck of it, but what I really need to do is eliminate catches. I use a new carbide edge for the final cuts, so using a sharper carbide tool isn't possible. I'm liking the looks of the neg rake as a definite possibility.

Back to the shop I go!

Jeff

 

[paintspill]

i've done some research on rosewood while working on a guitar and i think i came across that it was an oily wood, might be causing a bonding problem with the glue. i could be off on this but i want to help any one i can when ever i can, might be something as simple as a solvent wipe/wash before glue up.

 

[JerrySambrook]

Your picture appears to show three different glue failures.

Toward the right, the tube is "shiny", and show lack of glue on the tube. This would then mean there is noglue joint in that area and it creats a weak spot.

Just to the left is a whitish area of glue, which means the oil in the wood did not allow it to cure properly, and therefor, be a week joint as well.

Just to the left of that, shows an area where the glue is evident on the tube, bur the glue has a slick surface, which would indicate that the glue did not adhere to the blank, either due to no contact, or to the oils in the wood not penetrating the glue, but also not letting the glue contact and penetrate the wood.

For oily woods, try using two part epoxy, and washing the insides of the blank with alcohol. But remember, if you wash with alcohol or acetone, and let the blank sit around too long, the oils come right back to the surface, although usually thinner, and will still give you a problem.

addition: I think if you look at the large piece that came off, you will find it shiny, and it will show a lack of glue on it,

 

[mick]

Jeff, I've got to agree with everything Jerry said. It's not necessarily the rosewood but a matter of taking a little more time prepping for gluing. Swab the drilled hole with acetone or accelerator to wash some of the oils from the gluing surface and use good practice gluing the tube in. Make sure the hole is completely covered with glue and there's glue on the tube. Then insert with a twisting motion. This will greatly improve your record of blowouts!

 

[edstreet]

Hey,

Here's the deal; I love honduran rosewood, but the stuff hates me.

Case in point:

This happens EVERY time. Usually the chunks are big enough that I can glue it back together and continue, but seriously, I'm really getting frustrated. Every other material I've tried, I've eventually made it work, but not HRW.

I am using a carbide Woodchuck and turn at 2200 rpm. I use the very corner to get it down to almost the finished diameter, then switch to using the trailing 1/4 of the cutting edge. To cut down to the final diameter, I start with the bevel on the wood, then gradually raise the handle until it's barely cutting. It's almost like dust the cuttings are so fine. As I move across, everything is going great, then wham, the edge catches and the chunks fly. This isn't fun.

Any suggestions from those who've tamed this beast?

Thanks for any help.

Jeff

As some others may have said this is not a single failure. The things that I see wrong is
a) Glue joint fail, Not enough, not the right type of glue and not in the right areas. It appears the glue is drying before it fills up the voids and all those tiny areas they need to get into, this also may indicate there is some problem(s) with your drill bit.

b) Speed appears to fast. I personally endorse slower speed turning but that is for another topic. which leads to

c) Wrong type/direction and angle of cutting from the chisel. If you jab it in or put to much pressure or put the wrong direction of pressure then, well $#!@ like this happens.

Possibly getting in to much of a rush while turning? Look at the direction of the grain and what type of grain it is. Burl can/will have soft and hard spots all over it and you have to be on your toes with some of it. Move to some better epoxy like the 5 minute or the 2 hour epoxy's and give it full 110% coverage

 

[JerrySambrook]

I need to ask Ed,

How can you tell the speed is too fast by the pics?
And also, where is the grain direction on that piece of burl?

From my point, it looks like a glue joint failure caused by a slight catch.

Even bad joints can stay together if a real good technique is used throughout the whole turning process.

 

[edstreet]

I need to ask Ed,

How can you tell the speed is too fast by the pics?
And also, where is the grain direction on that piece of burl?

From my point, it looks like a glue joint failure caused by a slight catch.

Even bad joints can stay together if a real good technique is used throughout the whole turning process.

Sure we can go there if you want ....

Part 1)

I am using a carbide Woodchuck and turn at 2200 rpm. I use the very corner to get it down to almost the finished diameter, then switch to using the trailing 1/4 of the cutting edge. To cut down to the final diameter, I start with the bevel on the wood, then gradually raise the handle until it's barely cutting. It's almost like dust the cuttings are so fine. As I move across, everything is going great, then wham, the edge catches and the chunks fly. This isn't fun.

What do we know.
1) we have a block of wood with variations of hard and soft spots all over it.
2) our burl tube is moving 40 MPH, yes that is miles per hour.
3) Dust and small chunks of softer areas are coming off plentiful.
4) "the trailing 1/4 of the cutting edge" <- So approx 1/8" wide flat bit, assuming this is the 15mm inserts (I got that from the website fyi)


Lets look at a few things.

Honduras Rosewood
Average Dry Weight (?) : 59 lbs/ft3 (940 kg/m3)
Janka Hardness (?) : 1780lbf (7918 N)
Specific Gravity (?) : 0.96

Note this is not burl, this is heartwood only. so burl will be somewhere around ((heart_strength+sap_strength)/2 - other stuff) as for Janka test goes. Keep this in mind. 'other stuff' would be adhesion to adjacent wood fibers, think of this as your wild card variables in burls.

In perspective balsa wood is 100.
Amboyna burl is listed at 2170lbf (9653 N)
Hickory / Pecan, Satinwood is 1820. So lets compare to to pecan or hickory sapwood for the minimum strength.

In short this is quite soft.

Part 2)

From the above it sounds like the direction of chisel impact is about 90 degrees from the rotating shaft. Now lets test a few theories.
a) buildup on top of the chisel falls into irregular cut spots and adds torsion, one section hangs on and you are forcing all of that into a limited space while moving 40 miles per hour and it blows out.

b) a section of softer material comes out while cutting and the chisel does a 'chatter' as in bounce back and is pushed back into the wood where it hangs on the gap and causes the section to blow out.

c) due to lack of glue support a chisel push that is greater than the tensile strength of the burl breaks through and hangs causing a blow out.

d) the bur on the chisel is to great and hangs in the softer spots and pulls the rest of the chisel in and causing a blowout from rotational speed and impact strength.

bservations:
a) the biggest solution is to use sandpaper as the crap coming off the wood at this point is classified as an abrasive material.

b) we still have abrasion and add in irregular pressure on the chisel (from hand holding) and the 40 MPH speed the solution would be to change the angel of the chisel to not allow chatter to fracture, reduce the speed and deal with the abrasion (read sand paper).

c) a glue support deficit in that great of an area is, well I am not buying that large amount but I will say there is more than just glue going on, you would have to glue just the ends practically, which we do not see in the photo. Now this also poses the question of tensile strength compared with impact force of the 40 MPH burl, which is greater?

d) a change of chisel both in shape, size, weight and cutting stroke would be in order. Or at least a change in some/most of those areas. Also cut direction and pattern would be needed.

Now in truth there is likely a blend of a, b, c and d above.


Part 3)
:What can we do to fix this:

a) Use sandpaper for final shaping, take it down so much then use sand paper, 80 grit does some amazing things if used properly. You could also take a good amount of it down with sandpaper if you wanted. The softer the material is the more sandpaper becomes your friend. It is soft and molds to the shape and yields extra support.

b) stabilize soft/irregular/non-uniform wood. The stabilizing material actually will even out the hard/soft spots some, provide density, increase tensile strength greatly in the weaker areas due to more soaking, a.k.a. wick effect. I would go even further and say stabilize anything you can, it is that good and makes that big of a difference.

c) Change angles of the chisel compared to direction of rotation. i.e. go from perpendicular to the shaft to parallel and you eliminate chatter causing push back recovery.

d) Change speeds to something lower, lower rpm = lower MPH = lower impact force = better on fragile materials.
2200 rpm = 40 MPH,
1500 rpm 27 MPH,
1200 rpm = 21 MPH,
1000 rpm = 18 MPH,
800 rpm = 14 MPH.
Biggest speed reduction for impact force will likely be going to 1500 or 1200 rpm. 2200 to 1500 is a 31% reduction, 2200 to 1200 is a 45% reduction.

As for abrasions goes, particle that are removed from the material can be captured and used then discarded, not only does it provide gap filling but support. The biggest drawback is heat build up. Which is why I suggest hand sanding, you can feel the heat.

I believe someone mentioned thin CA as a coating for the thinner passes. This may work good but it's not a substitute for stabilizing. Nor would this provide missing glue support. But this is a very wise choice.

JerrySambrook, I hope this answers your question.

 

[robutacion]

Wow, and then I was thinking that only I, like to be "detailed" with my answers....! well, not any more...!:wink::biggrin:

Cheers
George

 

[JerrySambrook]

Ed, good answer job you did.
It is a nice long dissertation.

However,
Janka hardness testing is to test the resistance of impact on a wood and for abrasion resistance. It has almost nothing to do with the cutting characteristics of wood. It does have some bearing on abrading or sanding the wood.
To refute a few items in your dissertation though.
2a) this is where speed becomes your friend. More speed also decreases the amount of time spend in the air, or on a soft spot. This is in turn also decreases the lateral movement or pushing of the tool into air spots or soft spots. This creates less time to "get a catch" due to the nature of "scraping" as the original poster does.
2b) The increased speed amounts to less depth of chatter per surface foot, but does increase the frequency. However, in the case, the frequency does not matter, as it is only the quickness of the occurance of the chatter, and not the physical violence of the chatter.
2c) please refer to 2b, or 2a or actually both. The physical violence of each "chatter" is lessened, which means less transfer of the physical violence on the wood, but with the violence of the chatter getting transferred back to the operator because of the increased frequence, not the increased amplitude.
2d) please refer to 2c.
Observations on 2
a) Wood is always more responsive to a clean cut or scrape rather than the jagged on created by sanding. Does this mean sanding is not a viable option. NO, It is a viable option, but should not be used as a substitute for good cutting techniques. Ask any good flatboarder, and you will almost always get the answer that a good scraping job is much cleaner, nicer and easier than a good sanding job.
b) Increasing the speed will give a better cut/scrape as noted above, and with the lathes we all typically work with, we cannot get too much of a surface speed for the size of the work being referenced here. (Larger items will have greater surface speeds, and yes that is where it becomes detrimental.
c) YOU do not have to buy into a void that large, but if you actually read what was written, you will see there were THREE different items occurring there at once. The visual of the tube alone was enough to tell the story. This hypothesis came about due to experience.
d) Conventional tooling would have been and almost always is a better choice due to the more practical cutting nature and the lack of rigidity out bodies have. However, weight is a puzzling one, unless the operator is overextending his tool. Which then reverts back to proper turning techniques.
e) Your conclusion for part 2 was exactly what was written in a previous post. So why you feel you had to refute it and reword it is beyond me, but hey, we all have our quirks.

3a) it is always more efficient to cut rather than sand, but once again, sanding is NOT to be discluded as a viable option either
3b) stabilization was not an option here, as the original poster asked for a reason why this failure occurs.
3c) Increasing speed reduces "pushback" since there is less time to push in. see way above.

As for the final part about sanding. The British have an excellent saying about the American technique of woodturning. "Americans turn too slow, and sand too fast". If you are feeling heat while sanding, you are sanding using too much pressure, too much speed, or both. This increases friction, and thus increases heat. And in this is very detrimental to the sanding process in more ways than one.

Once again,, thanks for taking the time to explain the way you looked at it.

Sincerely
Jerry Sambrook

 

[sbell111]

I don't doubt that the previous couple of posts were on to something, but I got bored and didn't make it very far into them.

I agree with others that this looks like a glue issue. I'd switch to epoxy or CA. Also, I wonder how the tube was prepped prior to gluing.

 

[edstreet]

Why I personally was picked out of 5 posters in this thread who said the same thing is somewhat troubling, almost seems as if there was some personal reason behind it. Putting that aside and ignoring that aspect.

However,
Janka hardness testing is to test the resistance of impact on a wood and for abrasion resistance. It has almost nothing to do with the cutting characteristics of wood. It does have some bearing on abrading or sanding the wood.

Looks like you so missed the boat on this subject, nice try tho but please go read up on what it is and after that go read up on how chisels work and you will clearly see how a chisel is an impact device.

The second area you missed the boat on was durability relationship.

Janka is a variation on the brinell test and yes it is mostly for the flooring aspect but we can gain valuable insight as well. By not tossing Janka aside like a used condom and some simple google searching we can see things like this.

The Janka hardness test measures the force in pound per square inch required to embed a 0.444" steel ball to half its diameter in a 2" x 2" x 6" piece of wood. This test is a good measurement of how a wood product will withstand denting and wear. By the same token, it's also a good indicator of how hard a species is to saw or mill. The Janka test is also a good indicator of how hard it would be to saw or nail into a species of wood. The higher the Janka measure, the harder and more resistant it is to denting.

As for the fast speed I just need to direct your attention here
[yt]http://www.youtube.com/watch?v=zPrHMYU4y0s&feature=share&list=PL091F70C14001D9EF[/yt]

Amazing how much blowouts we see from just a very small distance traveled. Yet many think that higher speed results in better cutting. What they dont know and dont understand is at higher speed it is more brute force impact strength that does the cutting, *NOT* the cutting edge of the blade.

Yes this is particle board and structurally it is not much different to that of burl.

[YT]http://youtu.be/4Pvs5oClgpg[/YT]

Here note 0:19 to 0:23 note the bouncing effect then ponder the softness of the wood. THIS is why your blanks are exploding.

 

[JerrySambrook]

a chisel is an impacting device, but the impact is done with a cutting edge, not a ball or blunt end. And that alone is what takes woodturning tools out of the Janka hardness scale useage.

If it was relevant, then not many people would be able to cut Lignum Vitae, as it is the second hardest item on your list, yet, it responds to turning and scraping very nicely.

 

[alphageek]

Woah... Hold on guys - Chill a bit. No need to bury Jeffs thread in your back and forth.

As for my take on your question Jeff... Here is my view on how I get past the issues you've stated (only pointing out differences from what you do to me)...

1) Try changing speeds. I know some above are advocates of slower. Personally I like pens as faster speeds. I'm not going to debate what was said by others, but for me faster works better (very light cuts with a sharp tool).
2) I have a carbide tool but I don't really like it as a finishing tool. IF I use the carbide tool, its for roughing out (But lately I use a spindle gouge for that more than the carbide tool).
3) Try a skew or different tool.. You haven't told about "position" of your carbide tool, just leading/trailing edge - but if you're still using it "flat" its still acting mostly like a very sharp scraper... it wouldn't take much of a catch at all to cause grief.

 

[LagniappeRob]

Sure we can go there if you want ....
...

TLDNR

 

[edstreet]

It would appear that 2 links that I posted did not show up properly

table saw particle board 1200fps - YouTube


is the first one

Mini Lathe in Slo-Mo - YouTube


Is the second one.

 

[JerrySambrook]

Just what do either of those two videos have to do with a failed glue joint?

The mini lathe video could be related as the operator in the video used extremely poor turning techniques.

 

[jriechel]

Thanks for all the information and attempts to analyse what's going on. Lots to think about there, but theoretical must yield to practical outcomes when I'm in the shop. Fun to think about, but I just want to do a better job turning burl rosewood.

All the words about glue failures warrant a comment. I'm skeptical that I'm doing a poor job, but perhaps. If a joint is going to break, it's going to break somewhere. I suppose wood left on the brass tube would look better vis a vis my gluing ability, but it still amounts to a catch and blowout to me. I want to know how to turn this stuff and use my tools so this is more unlikely to happen.

Nevertheless, you all inspired me to not give up. In fact, just before I wrote off that blowout in my original post, and tossed it in the appropriate container, I went back and tried a repair. I used turquoise to fill the chunks that I couldn't find (I don't know if that was a good choice-I'll find out if it sells, I guess), then used sandpaper to complete the final shaping. I used my Woodchuck on the lower barrel only to rough size, then finished it again with sandpaper. It feels like cheating, but it got the job done.

I still want to learn how to actually turn HRW properly, but at least this way I am getting better results. Almost at the same time, I had a Thailand Rosewood burl blank do almost the same thing. Still inspired by you all, I repaired it too, rather than tossing it, but I used epoxy to fill the gaps.

Anyway here they are. They came out alright, though my next ones will be better.

Thanks again for the help. I got a couple of pens out of it that otherwise wouldn't have even seen a coat of finish!

Jeff

 

[Hendu3270]

I think they turned out great. You learn from each failure and most failures can be salvaged into something great, as you've shown. Good job.

 

[robutacion]

Thanks for all the information and attempts to analyse what's going on. Lots to think about there, but theoretical must yield to practical outcomes when I'm in the shop. Fun to think about, but I just want to do a better job turning burl rosewood.

All the words about glue failures warrant a comment. I'm skeptical that I'm doing a poor job, but perhaps. If a joint is going to break, it's going to break somewhere. I suppose wood left on the brass tube would look better vis a vis my gluing ability, but it still amounts to a catch and blowout to me. I want to know how to turn this stuff and use my tools so this is more unlikely to happen.

Nevertheless, you all inspired me to not give up. In fact, just before I wrote off that blowout in my original post, and tossed it in the appropriate container, I went back and tried a repair. I used turquoise to fill the chunks that I couldn't find (I don't know if that was a good choice-I'll find out if it sells, I guess), then used sandpaper to complete the final shaping. I used my Woodchuck on the lower barrel only to rough size, then finished it again with sandpaper. It feels like cheating, but it got the job done.

I still want to learn how to actually turn HRW properly, but at least this way I am getting better results. Almost at the same time, I had a Thailand Rosewood burl blank do almost the same thing. Still inspired by you all, I repaired it too, rather than tossing it, but I used epoxy to fill the gaps.

Anyway here they are. They came out alright, though my next ones will be better.


Thanks again for the help. I got a couple of pens out of it that otherwise wouldn't have even seen a coat of finish!

Jeff

Hi Jeff,

I don't think that using "sanding" to shape/size a pen blanks is cheating, at all. People use files, rasps and all sorts of gadgets, and I like to use the flap disc for difficult/fragile/temperamental blanks, particularly when blowing outs is the repeated results from "traditional" gouge use.

I read that you want to be able to turn the HRB blanks into successful finished pens, using your tools, based on this, I'm sure you own a 4" grinder so, buy yourself a 40 grit flap disc and give it a go, unless you do, you will never know what it does and will be fine if you don't like it after you tried, that is no cheating nor anything to be ashamed of or embarrassed about, if only everyone would be honest enough to admit and divulge what sort of stuff they do to get the job done...!:wink::biggrin:

Cheers
George

 

[sbwertz]

My mulberry does this a LOT because it is so fragile. The first thing is did was switch to gorilla glue for gluing in the blanks. If they can't break loose from the blank, they can't shatter.

The second was to use my little air sander like a turning tool. It has a little 1" foam head that takes peel and stick sandpaper I use it with the lathe turning to finish shaping the fragile blanks. (Sort of like the flap sander Leroy suggested.) (Actually is is a little air die grinder that I converted to a sander.)

With turquoise inlay in the blank, I have to use carbide, since the turquoise EATS steel tools, but the carbide can really tear up a fragile blank. This works for me. (the old 80 grit gouge technique)

 

[jriechel]

George,

Actually, I don't have a grinder, but I could get one without too much trouble. What causes me pause, is the thought of how you get to final size without touching the bushing? And this is precisely where I'm currently having trouble. With that spinning flap disk, it seems that the slightest touch could ruin them.


Jeff

 

[robutacion]

My mulberry does this a LOT because it is so fragile. The first thing is did was switch to gorilla glue for gluing in the blanks. If they can't break loose from the blank, they can't shatter.

The second was to use my little air sander like a turning tool. It has a little 1" foam head that takes peel and stick sandpaper I use it with the lathe turning to finish shaping the fragile blanks. (Sort of like the flap sander Leroy suggested.) (Actually is is a little air die grinder that I converted to a sander.)

With turquoise inlay in the blank, I have to use carbide, since the turquoise EATS steel tools, but the carbide can really tear up a fragile blank. This works for me. (the old 80 grit gouge technique)

I'm pleased that you have the courage to disclose your use of the rotary sander, those air tools are quite good and small, the only problem is that they require more air than most small compressors can produce...!

The major difference between normal round sanding disks and the flap discs even if the same grit is that, the flap discs cut 3 times faster, this can be quite handy if using the sander starting from the square blank. The bigger the disc diameter, the more/faster it will cut/sand however, find 4" flap discs is quite easy and inexpensive considering getting flap discs for the 1" and 2" diameter pads as these are more specialized tools and therefore a lot more expensive to buy, tools and discs, unfortunately...!

This is the reason why I suggest the 4" flap disc on a normal 4" grinder that is our days can be purchased for about $20 to $40, the Chinese versions, off-course the better brands still cost a lot more.

As for the Turquoise true crashed stone (there is an artificial one ", man made), red oxide discs wont cut it but, you can buy the stone discs (normally blue) that also work on steel and aluminium, that's what I use when I use the true stone crashed "powders".

There is one great advantage of those 1" and 2" sanding pads and the air sanders/grinders, the tools are always smaller the the electric ones and the smaller pads/disks are easier to work in small areas...!

Cheers
George

 

[robutacion]

George,

Actually, I don't have a grinder, but I could get one without too much trouble. What causes me pause, is the thought of how you get to final size without touching the bushing? And this is precisely where I'm currently having trouble. With that spinning flap disk, it seems that the slightest touch could ruin them.


Jeff

Hi Jeff,

The flap disk system is above all "a system" to remove/sand wood and other materials, is the principle that I'm trying to offer/suggest as a solution for situations like yours, more detail in here. You have options and you need a little practice with any of those options, as you would need with any other tool, there is a reason why I suggest to invest on 2 sets of bushings, one as your sacrificial one for the flap disc and the other for the final hand sanding.

You can get away with the spare set of bushings and the replacement in the mandrel as the result, one turn of masking tape over the bushing, can be all you will need to carefully work with the flap disk, it will serve 2 purposes, one to minimise the damage of the bushings if you touch them with the disk and will serve as your measurement of how far you should go with it, the rest is hand sanding work to avoid any tool catches.

Do not feel that using a flap disc for turning some blanks, makes you less than a pen turner, there is no such thing as a "fixed" definition to what a pen turner should be, nor you should worry about such rubbish, I can use any wood turning tool with the most efficiency possible however, I use the flap disk when I don't feel worth to risk destroying a good blank and everything else that goes with it just because, only because of what "others" may think.

What do you prefer...???

Cheers
George