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Segmented pen blanks exploding frequently

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Forum topic by cjshrader posted 08-20-2019 02:08 PM 707 views 0 times favorited 17 replies Add to Favorites Watch
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cjshrader

4 posts in 29 days


08-20-2019 02:08 PM

Topic tags/keywords: turning pens explosions segmented

Hey all,

I wouldn’t consider myself a new turner but also definitely not an expert. I’ve probably made around 10-15 pens previously and then a few other random projects.

I would say about half of my segmented pen blanks explode while turning. I think I’m doing something fundamentally wrong but I just can’t figure it out.

I was hoping I could go through my steps and there’s something obvious I’m doing wrong. I hope it’s something simple as I’m just getting very frustrated as I put a lot of time into my blanks.

When gluing up the segments, I use Titebond 1 wood glue. I let it dry overnight at a minimum.

I then drill on the lathe, no issues there.

I then use StickFast medium glue to glue the tubes in. I put the glue on 3 sides of the tube and twist it and bring it in and out a little bit while putting it in the blank. The tube is pre-sanded. I let that dry overnight at a minimum, though for the most recent explosions they dried for weeks because it got very hot here and I didn’t want to go outside.

For segmented blanks, I do barrel trimming using sandpaper and punches on the lathe. An actual barrel trimmer might rip the segments apart so I avoid it, but wanted to share in case that’s important.

I then use a sander to sand off the corners and round it out a little bit.

For turning, I turn between centers. I have an Excelsior mini-lathe whose tail stock tends to slip, so I put a Bessey clamp across it and tighten that up so that I can then tighten the tail stock without slipping and get it tight.

I originally used the Rockler brand carbide tools but I thought maybe they were too cheap so bought this kind instead, which are well reviewed: https://smile.amazon.com/gp/product/B013KCGZAS/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I’ve barely used the cutter on this one but I do feel like it’s not cutting well and I have to push a little bit to get a cut. I’m using the square cutter. I am coming in at a perpendicular angle and lining the blade right or slightly below the center line of the blank. At some point it just feels like it catches and then a portion of the blank will fly off. What’s interesting to me is the break doesn’t start on a glue seam, it actually starts on just a random spot on the wood.

In this image you can see where there must have been a catch and a chunk was taken out, and then a bunch more broke too (I’m trying to glue it back together but I think it’s too late for this one):

I can post pictures of the other recent blank explosion too if we think it’s helpful.

I suspect most of you will hone in on the carbide blade. I’d really like to keep using them as I don’t know how to sharpen or use anything else. But I also don’t want my blanks to explode.

Thanks so much for reading all of this and I appreciate any advice! I really enjoy turning but I only have so much free time so losing all that time making a blank just to have it explode at the end is quite frustrating.


17 replies so far

View ibewjon's profile

ibewjon

902 posts in 3272 days


#1 posted 08-20-2019 03:06 PM

I like to use a round carbide tool so if I am a bit off square, there is no corner of the carbide to catch. Give round a try..

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RobHannon

304 posts in 1010 days


#2 posted 08-20-2019 03:32 PM

I have had this happen with mixed resin/wood blanks if I let the tool handle get too low. I ended up switching to a radius square cutter with a negative rake. Bit slower, but pretty forgiving.

Also in the pic, that segment that is glued in appears to have the grain running perpendicular to the rest of the pen blank. You are cutting across end grain there like you would be with a bowl. Sharp tools and solid anchor to the tool rest is going to be very important.

View TheDane's profile

TheDane

5669 posts in 4142 days


#3 posted 08-20-2019 04:30 PM

There is an oft-unspoken rule in segmenting … keep the grain running the same direction. Cross-grain glue-ups are a recipe for disaster, and turning against the grain will result in all kinds of tear-out.

I am not a fan of carbide tools … most of them are scrapers and tear the wood. Properly sharpened HSS tools slice the grain, leaving a cleaner finish.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

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cjshrader

4 posts in 29 days


#4 posted 08-20-2019 05:15 PM



I like to use a round carbide tool so if I am a bit off square, there is no corner of the carbide to catch. Give round a try..

- ibewjon

I’ll give it a shot, I never really considered the round tool for roughing. Thanks!


Also in the pic, that segment that is glued in appears to have the grain running perpendicular to the rest of the pen blank. You are cutting across end grain there like you would be with a bowl. Sharp tools and solid anchor to the tool rest is going to be very important.


There is an oft-unspoken rule in segmenting … keep the grain running the same direction. Cross-grain glue-ups are a recipe for disaster, and turning against the grain will result in all kinds of tear-out.

Thank you both! I think my logic was I wanted to prevent this so I was avoiding end grain to end grain glue up. However what you’re saying makes a lot of sense, I could see why this would give more of an opportunity for a catch. I made 10 blanks all at once, I hope some of them I made a little smarter but I’m not sure how much thought I was actively giving it.

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ibewjon

902 posts in 3272 days


#5 posted 08-20-2019 06:08 PM

Many people hate carbide, but like you I need to get sharpening equipment and learn to use it. My belief is that a sharp carbide scraper is better than a dull shearing cutter till that time.

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Wildwood

2717 posts in 2614 days


#6 posted 08-20-2019 06:55 PM

You would definitely have less trouble using conventional tools like roughing gouge or skew. JMHO might be pressing too hard on soft wood with you carbide tool like already mention might try round cutter just don’t press too hard! Just be little more patient! Also didn’t mention lathe speed but slowest rpm’s for me would be 1,000 rpm.

Think carbide tools excel at exotic hard wood, bone and stone on most domestic woods cannot beat convention tools. Know a champion bird caller uses his inexpensive conventional scraper on his calls normally exotic woods and domestic wood. He does do lot of sanding and doesn’t worry about sanding scratches. He sells every one he makes!
Good luck with it!

-- Bill

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cjshrader

4 posts in 29 days


#7 posted 08-20-2019 06:58 PM


Also didn’t mention lathe speed but slowest rpm’s for me would be 1,000 rpm.

- Wildwood

Whoops I did mean to mention this. I go at the maximum speed of the lathe, which is 3200 RPM.

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pottz

5960 posts in 1463 days


#8 posted 08-20-2019 09:31 PM

i use carbide tools all the time,love em,mostly the round.nice thing is when it gets dull loosen the screw give it a slight turn and you have a sharp tool again.i havn’t had any issues.

-- sawdust the bigger the pile the bigger my smile-larry,so cal.

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mel52

966 posts in 744 days


#9 posted 08-22-2019 03:23 AM

Just curious, but has anyone here rolled a carbide tool slightly to use it ( kind of ) like a shear type scraper. I have tried this and it does work on some projects with some woods. NOT trying to start an argument on if this is correct or not, just checking. Mel

-- MEL, Kansas

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gwilki

318 posts in 1953 days


#10 posted 08-22-2019 11:33 AM

If you don’t want to get into sharpening spindle gouges, think about getting a Hunter carbide tool. They cut. The ones that you are using scrape. You will never get the finish you are looking for off a scraper and as you have experienced, you will frequently get blow outs on segmented blanks.

-- Grant Wilkinson, Ottawa ON

View Andybb's profile

Andybb

2024 posts in 1082 days


#11 posted 08-22-2019 10:25 PM

This comes from many many many (20?) attempts at techniques that failed miserably after hours of building segmented blanks only to have them explode like a Hiroshima bomb.

1. Only use titebond if the segments are wood, otherwise use 2 part epoxy or thick CA. If you are letting them dry overnight you might as well use the 30 min kind vs the 5 min kind.

2. If you must use CA glue on the tube use copious amounts of thick, not medium. You will notice that even though you thought you used plenty of glue when the blanks explode off of the tube there is very little glue on there. CA glue has very poor shear strength so it separates from the blank.
Otherwise use Gorilla Glue or epoxy. If using Gorilla Glue wet the inside of the blank with a Q-tip as water activates it and it expands into the all of the little crevices.

3. Make sure to use compressed air (or your mouth) to blow all of the dust out of the tube.

I put plumbers putty in one end of the blank and coat the tube, stick and turn in one end then put more on the tube and stick and turn into the other end.

4. I haven’t used a barrel trimmer in years. Way too easy to tear a blank apart after spending hours building the segments. I use a disc sander.
It hasn’t ever failed me.

5. I only use the round and square radius carbide tools on segmented pens but some people love their standard HSS tools.

Then I switch to a VERY sharp Benjamins Best skew that I got from Ed at Exotic blanks. It gives me a 400 grit type finish. Then I use a flat strip if wood with some 400 grit stuck to it and run it back and forth or the blank for the final finish. When you get down to the end it’s just too easy to get a catch so sometimes I’ll even skip the skew and just use the sand paper.

The only sharpening tool I use is a cheap credit card sized hone on the skew and the carbide inserts. Just take the inserts off once in a while and with a circular motion rub them on the hone with a little oil (although I just use a little spit) for a few seconds. I have a low speed grinder that I have only used once or twice until I discovered carbide.

Keep everything sharp.



If you haven’t already join IAP for all things pen related. It’s like this site but for pens.

-- Andy - Seattle USA

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Andybb

2024 posts in 1082 days


#12 posted 08-22-2019 10:38 PM


Just curious, but has anyone here rolled a carbide tool slightly to use it ( kind of ) like a shear type scraper. I have tried this and it does work on some projects with some woods. NOT trying to start an argument on if this is correct or not, just checking. Mel

- mel52

Yep. But not on angled segments though as they can grab the seam and then BAM!!

-- Andy - Seattle USA

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Andybb

2024 posts in 1082 days


#13 posted 08-22-2019 10:57 PM

.

-- Andy - Seattle USA

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mel52

966 posts in 744 days


#14 posted 08-23-2019 01:06 AM

Thanks Andybb. Mel

-- MEL, Kansas

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Andybb

2024 posts in 1082 days


#15 posted 08-23-2019 01:36 AM



Thanks Andybb. Mel

- mel52

No problem. My choice for tubes is Gorilla Glue. No mixing like epoxy and it wont harden before you get the tube set like CA glue while you’re twisting and turning. Good luck. Let us know what works for you.

-- Andy - Seattle USA

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