Scratches and tool chatter

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RVA_Tyndall

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Mar 14, 2019
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I have been noticing that my tool rest might not be well seated and that the banjo might be moving when I run my lathe at high speeds.

I am not happy with my recent pens because of the scratch marks and CA Run. Here is what I did:
1. Shaped with carbide cutter
2. Sanded with mesh 400 paper and then 600 (slow speed on the lathe and then with the lathe off sanded with the grain)
3. Sanded with micro mesh and walnut oil
4. Applied CA using paper towel. Used thin CA from Smith Industry. Wiped on 8 coats alternating starting from left to right. I think my lathe was at 500 rpm.
Image1553990927.512452.jpgImage1553990938.467277.jpg

Any suggestions for me?
 
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Dehn0045

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If the scratches/marks are visible before CA, then they will most likely be visible after CA. Sanding with 400 should remove tool marks but will leave behind 400 grit sanding marks. If you still have tool marks then spend more time sanding, or work your way up from larger grit. I use a skew with a light scraping cut to avoid needing sandpaper - both methods have their pros and cons.

I avoid putting anything that won't evaporate on the blank prior to CA. I know that BLO/CA is fairly common, but I just don't trust it.

I don't see a need to sand a blank above 800 grit prior to CA (maybe 1500). While I don't think MM before finishing will cause problems, I think it is a waste of time and effort.

Are you doing any sanding/polishing/buffing after applying CA? I also use Bob Smith Industries thin CA, I find that it cures quite hard so requires a bit of sanding to get smooth prior to MM. I usually go with 800 unit I don't see any shiny spots (low spots stay shiny), then I go to 1500 prior to MM. All sanding and MM is wet with water. If the grain is open or there are other holes, I will sand with 400/800/1500 and then reapply CA.

I find that number of coats of CA is somewhat arbitrary, since different methods and different CA will apply differebt amounts of CA with each coat. I shoot for a finish that is about 0.007 to 0.010 inches. This is usually about 8 coats with BSI thin using open cell foam as the applicator. I'm thinking that you are probably getting adequate thickness of CA, but you may want to check with calipers.
 
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Probably going to get lots of replies on this one.
The scratches in your pics appear to be NOT tool marks. I'm thinking they are surface scratches in the CA.
When you sand over 400, consider sanding wet.
Consider sanding with MM wet (water is fine).
Pay attention to keeping the grits "uncontaminated" with debris from previous grits.
MM gets old like any abrasive and needs to be replaced (although not as often)
 

jttheclockman

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Many things here. First do not sand with MM before doing the CA finish. Wasting time and ruining your MM pads. Never add walnut oil when sanding before finishing with CA or any other finish. Oil under a finish will have an effect on the finish and that is including CA. You may not see it at first but over time it will peel and crack on you. If you start with 400 grit than make sure you sand with the length of the blank to help get sanding marks out. Also before you go up to 800 grit you better do 600 grit or again you are wasting your time. I would stop at 600 if you are doing a CA finish because it will not be any benefit going higher. Again though make sure you sand with the grain of the wood after all said and done. Make sure you wipe the blank down to rid it of any grit from sandpaper. I like to use acetone in case there is any oils from wood or fingerprints left on blank. Some people use denatured alcohol.
As far as CA finish, there are about 100 different methods so will leave that to you. But I will use 3 coats of thin and sand with 1200 grit. wipe down and then use med CA for usually 4 to 5 coats. Depends on my caliper measurements. I do not wipe back and forth. I wipe once each way and leave it alone. The more you try to be perfect with it the more chance of a mess.

Good luck and just for you to know these are my opinions only.:):)
 

RVA_Tyndall

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Probably going to get lots of replies on this one.
The scratches in your pics appear to be NOT tool marks. I'm thinking they are surface scratches in the CA.
When you sand over 400, consider sanding wet.
Consider sanding with MM wet (water is fine).
Pay attention to keeping the grits "uncontaminated" with debris from previous grits.
MM gets old like any abrasive and needs to be replaced (although not as often)


What is the best way to clean the MM? I don’t have running water
In my shop and rely on rain water. I might need to increase my water supply.


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RVA_Tyndall

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Many things here. First do not sand with MM before doing the CA finish. Wasting time and ruining your MM pads. Never add walnut oil when sanding before finishing with CA or any other finish. Oil under a finish will have an effect on the finish and that is including CA. You may not see it at first but over time it will peel and crack on you. If you start with 400 grit than make sure you sand with the length of the blank to help get sanding marks out. Also before you go up to 800 grit you better do 600 grit or again you are wasting your time. I would stop at 600 if you are doing a CA finish because it will not be any benefit going higher. Again though make sure you sand with the grain of the wood after all said and done. Make sure you wipe the blank down to rid it of any grit from sandpaper. I like to use acetone in case there is any oils from wood or fingerprints left on blank. Some people use denatured alcohol.

As far as CA finish, there are about 100 different methods so will leave that to you. But I will use 3 coats of thin and sand with 1200 grit. wipe down and then use med CA for usually 4 to 5 coats. Depends on my caliper measurements. I do not wipe back and forth. I wipe once each way and leave it alone. The more you try to be perfect with it the more chance of a mess.



Good luck and just for you to know these are my opinions only.:):)


Thank you for the feedback. I should have mentioned that I use the denatured alcohol to clean the blank between sanding levels. I also think I got my sanding levels wrong. I have a pen turners pack and just use two grits from it 400 and 600. I read somewhere that starting lower is inviting trouble

I will drop the MM sanding before the CA when I go that route. The oil under the finish is probably a bad idea. Makes sense to me. I like the feel of the wood on some pens so I will continue to mix it up.

Thank you everyone for the suggestions. I appreciate the help as I work to improve my pens.


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mark james

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In addition to all the above excellent comments. When sanding, I find it especially important to use a light touch, and move the sandpaper continuously (I actually use abranet exclusively, but the technique is the same).

A very worth-while trial: Turn 3-4 scrap pieces of wood round and just go through the finishing process. An old broom stick will suffice. Some boring hard maple would be better as it will hold any scratches longer, for you to see your progress in technique.
 

EdM

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Another item to try which will improve your finish is to switch to GluBoost CA.
Check out the pen finishing video on their website, and Exotic Blank's Ed Brown's GluBoost videos on YouTube.
I just started using this product, and it is amazing !!!!!
 

jttheclockman

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One other thing I would like to add here in case others are following this, is in the sanding process. You see countless videos and many times it is written here as well about taking strips of sandpaper and sanding away on such a small object that is spinning at least 500rpms Not a good idea in my opinion and I keep having to put this disclaimer in because I get jumped here too often when I make suggestions.

But when sanding a spindle which this basically is, you want to avoid dips and valleys especially if you are starting with course grits of sand paper because they can show up later in the finishing stages. To do this never present the sandpaper using your fingers as a backer . This is much more relevant with soft woods or woods that have hard grains such as oak or spalted woods. Burls can present this problem also. What happens is your fingers are soft and round and when you hit a soft section of the wood you can press harder into that area than surround areas where the grain can be harder. Add to this the speed the wood is spinning at, can sand those areas down very quickly.

To avoid this you can use two different methods. One is which is the one I like to use, back you sandpaper up with a block of wood. Now when you press to the spindle you apply same amount of pressure all around. The second is to present the sand paper to the spindle in a half wrap fashion and hold the ends of the paper as the spindle spins inside the sandpaper . Do not wrap the paper all the way around the wood because if it catches it will pull your hand toward the work piece.

But with both methods you need to keep the paper moving side to side. Then stop lathe and sand lengthwise and clean blank so no left over sanding grit is left for next grit.

May seem trivial to some but it could mean the difference between a mediocre finish and a great one. Take this advice for what it is worth. :):)
 

jttheclockman

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leehljp

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John. T's comment about calipers is one of the best things one can do to improve the matching of fittings. Get a good set of calipers. Harbor Freight has their calipers on sale about once every 3 months or so for about $9.95. For some people they like the fraction-MM-inch ones and use that in a variety of circumstances.

https://www.harborfreight.com/6-in-digital-caliper-with-sae-and-metric-fractional-readings-63731.html

One caution - don't get the plastic/composite calipers, they have to much give/slack in them.

As to the CA being wavy, a good scraper or radiuses square carbide blade used with light touches will smooth out the waves. It is much easier to smooth out the CA that way than with sandpaper. You will be surprised at how smooth the scraper will make it.
 

RVA_Tyndall

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Good feedback! I have the plastic calipers and find there is a lot of slack depending on how hard I press the ends.

Question about MicroMesh sanding:
Do you stop after each color and sand with the grain or do you just move on to the next color?

Curious if I have to stop the lathe after each color or just move through the grits.


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leehljp

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Good feedback! I have the plastic calipers and find there is a lot of slack depending on how hard I press the ends.

Question about MicroMesh sanding:
Do you stop after each color and sand with the grain or do you just move on to the next color?

Curious if I have to stop the lathe after each color or just move through the grits.



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IN my understanding MOST experienced people here (at least with the ones that give regular feedback) stop, and sand with one grit and then the next.

I learned long ago without any help - and rarely sand lengthwise. But that is my own technique that does not always work for others. I go from one grit to the next to the next on the lathe while it is turning at about 750 RPM. Others seem to have, or are able to see circular scratches when they do this, therefore they sand lengthwise. I don't know what I do different that there are no circular scratches on mine. I just do it. One thing that may be different is that I finish the turning with a very fine scraper which makes it already super smooth and then use 600 at the least and often 800 to start sanding. Very little swirls with this. John T often recommends starting no lower than 600 grit sandpaper. The higher one starts, the less swirls you will find. But the key is preparing the CA by bringing it into shape and smooth with the scraper or skew, which ever one is the most proficient with.

Edit in: BTW, chatter can have several different causes but in general (to me) it is the result of a little too much pressure and a slightly dull tool. Chatter is good in some turnings as it produces a wanted visible wave (mostly in bowls and turnings larger than pens). Sometimes it is the result of too much distance between the tool rest and pen, sometimes not holding the tool tight enough, sometimes dull blade, sometimes too much force on a flexing stock/blank or mandrel. Sometimes it can be from incorrect angles too.
 
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jttheclockman

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Yes with the MM and sanding lengthwise. I will expand on what Hank quoted me on and that is starting with a high grit of paper. I say this with all sincerity in that you can get to almost that ready for finish stage if you learn to use your turning tools properly and keep them sharp.i push the skew as the most useful tool in a pen turners arsenal because it can get you to that perfect stage where no sandpaper is needed at all and finish can be applied. I have shown many examples of it when I make segmented blanks that any sandpaper would cause contamination of colors. If you have to start sanding with 100 grit or 150 grit your tool technique needs lots of work. This is an area that is easily corrected. I see many times here people suggesting newbies buy some cheap dowles or some cheap wood and just turn and practice technique. This is good advice if you use wood that does not have hard grain running through it. Practice practice practice is what gets you to Carnegie Hall. :):)
 

penicillin

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Here is what I do, based on what I have read from others, refined with personal experimentation:

* Turn the blanks to a very close match with the bushings or desired caliper dimensions. I use a round carbide and a gentle touch to do the final matching. Your fingers (or the calipers) are the best test. Be careful and pay attention, the round tip can cut a tiny cove in the blank behind the bushing. The goal is to get a smooth shape with the tools, not the sandpaper.

* Cut up old rags from the garage into a bunch of small pieces. I cut 'em up with scissors. We have a bin in the garage full of old t-shirts, etc.

* Before sanding, rotate the tool rest completely out of the way or remove it. Mount the blanks on non-stick plastic bushings. This exposes the blanks end-to-end, and eliminates the concern that metal grains will be pulled from the bushings and ground into the blanks.

* Sanding should be mostly about finishing, not shaping. With each sanding, I run the lathe on a slow speed, and do not spend more than a few seconds. I hold the strip behind the blanks, pinching the strip from above and below. Move the strip up and down and back and forth quickly as the blank turns. Do not pull very hard or you may bend your pen mandrel. Do not allow the sandpaper to roll over the ends of the blanks or you will round them and make them too small. Do not sand too much, or your blank will be smaller than the pen parts. This is where experience comes into play.

* Preserve the unused the top and bottom "pinch areas" of the sandpaper unused. Stop the lathe and use the pinch areas to sand along the length of the blanks with your right hand while you slowly rotate the blanks with your left hand on the rotator-wheel-thingy-on-the-left-side-of-your-lathe. Your goal is to remove or reduce the circular scratches. Inspect the ends carefully, that's where I usually find the "rings." When you sand the ends, don't let your sandpaper bend roll over the end of the blank.

* After EVERY sanding, make sure the lathe is off, then pick up a clean rag piece and wipe off all the dust and grit from the blanks. Throw the rag in the trash.

* If the blanks are plastic or finished with CA, then I do the same thing with all nine Micro-mesh pads, but I sand with them wet. (Wet sand with lathe turning slowly for only a few seconds, moving quickly back and forth, again laterally with lathe off while rotating the blank by hand, and then wipe with a clean rag.)

True confessions:

I don't always use a fresh rag piece for every wipe. Sometimes I am lazy and use the same rag piece for two or three "adjacent" grits, but never more than that. When you are done with one, throw it in the trash so you don't mix it up with clean ones.

I don't need to start at 150, especially with acrylics, but I do anyway. I can't explain why.

I am getting better at using the skew chisel, even on acrylics, but I still resort to the scrapers at the end. I always practice with the skew chisel when the rounded blank is large, but when I get close, I switch to the other tools - spindle gouge, rounded square carbide, and round carbide to do the final shaping and bushing matching. Someday soon I hope to shape a smooth pen with the skew chisel all the way.
 
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