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A weekend of utter faliure.

Pastor of Muppets

Full Member
Joined
Dec 5, 2017
Posts
279
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Oxford (ish)
First Name
Andy
Morning ladies and gents,

I had an awful weekend in the workshop this weekend......

I went to the shop Friday evening and cut, drilled and glues a number of blanks up (2 siroccos, a mistral rb, a Chairman fp, and a few 7mm twist pens of various names.) I drill on the lathe using my nova chuck and Nova's pen jaws. The tubes were scuffed with 200g and are pretty a pretty snug fit and then glued in place with a decent amount of gorilla glue (the foamy expanding stuff).
I went down Saturday and trimmed the blanks using an end mill in a hand drill and due to family obligations left it at that.
Sunday morning comes and I have a day to myself to spend in the shop. Hooray!! I put one of the sirocco blanks on the mandrel with enough spacers that I can screw the knurled nut down to hold it in place then put the mandrel saver over the end and tightened it down gently. then started to turn.
I am using carbide tools and had put them across the diamond stone that morning before starting. All was going well the wood was turning into shavings beautifully and shaping was coming along nicely and I was getting close to the bushes. Then suddenly at the left hand end (headstock) the blank cracked and came away from the tube.
A few naughty words later I turned the rest of the wood and glue off the tube and put it back in the box. the Next sirocco blank went on the mandrel in exactly the same way and exactly the same happened ( the definition of insanity is to repeat a process and expect a different outcome!).
So I took the mandrel out and popped my centres in to check the alignment of the head stock and everything was fine.
So on to the first of the 7mm twist pens..... I'm imagining by now you can guess where this is going three blanks all at the headstock end giving way in exactly the same way.
At this point I looked at my Mistral blanks a pen I'm turning for myself and decided it to chuck up an ash bowl blank about 6" square and reduce it to sawdust just because!
I'm now hesitant to turn the mistrals because I am obviously doing something very wrong to lose so many blanks in exactly the same way.

Any help and advice is greatly received!!

Cheers

Andy

P.S. Apologies for a a very wordy post
 

Gregory Hardy

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Jul 7, 2017
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454
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Upper New York State
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Greg
I also use the expanding nasty Gorilla glue so that this doesn't happen. The few times it did, I realized that though squared (using a mill in a drill press) to the tube, they were not trimmed all the way down to the end of the brass tube. The compression with the bushings was then on the end grain of the wood, not wood and tube. Is this a possible explanation? Sorry the weekend wasn't a better one for you!
 

rayf6604

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Narrowboat dweller Willington, Derby
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You said you screwed the nut on the end of your mandrel then brought up the mandrel saver. I don’t think you need the nut, the mandrel should go inside saver right up against the bushes, otherwise the threaded part is slightly narrower than the mandrel shaft and you could be getting movement of the shaft inside the saver. That’s what I always used to do anyway.


Sent from my iPhone using Tapatalk
 

Penpal

Grand Master
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Peter
Andy I tend to have a loose not snug fit after drilling,it allows the Gorilla Glue to expand and do its job properly. Also the G Glue company suggest damping the to be glued area with water to ensure complete setting. Blank end squaring using a sanding disk is far less likely to start fine cracks etc than an end mill in most timbers,also it is very difficult to judge pressure using them in a mechanical way with hand drills or lathe chucks etc. Getting close to fully turned I use a Skew Chisel flat on the tool rest just below centre with great results. I tend to turn each end gently then face the rest of the blank. All of this by instinct including a 1/2 inch gouge. For sensitive timber I like to cut the square edges back,there are many ways to do this,the easy careful way is a large sanding disk. The times you cut down the square edges can cause havoc with the blank. I wrap elastic bands around the blank from end to end to remove any stray movement of the blank. Be absolutely careful as you remove excess glue when it expands, try not to overdo the amount of glue you use in the first instance. Always use suitable gloves Gorilla Glue is nasty on the hands. If you can give more time from glueing to trimming. Trust these few things may assist you overcome the log jam of problems mate.

Kind regards Peter.
 

Bammer

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Joined
Oct 5, 2015
Posts
1,482
Location
Cambridge
First Name
Brad
Andy, I've never used that type of mandrel so can't advise you on that.

I have an Axminster evolution so the mandrel goes into the saver and tightens up on the bushes.

I square my blanks on a sander using a magnetic v block and transfer punches so I can't advise you on the milling either, tried it and didn't like it.

What I can advise you on is the Beaufort kits all come with TBC bushes, so you use a dead centre drive and a live centre tailstock. NO mandrel required.

I also use Gorilla polyurethane glue for all my wood blanks, just make sure you get a decent covering, and excess is easily sanded off when squaring and any in the tube is removed with a quick rub of a file. I regulary do 40+ blanks a week and have no problems. I also abrade all my tubes, just because I always have

So, plenty of glue, square them up to the tube, decent mandrel or TBC ...

Only other thing could be technigue. Lighter cuts when you get close to finished size.

Brad
 

Pastor of Muppets

Full Member
Joined
Dec 5, 2017
Posts
279
Location
Oxford (ish)
First Name
Andy
I also use the expanding nasty Gorilla glue so that this doesn't happen. The few times it did, I realized that though squared (using a mill in a drill press) to the tube, they were not trimmed all the way down to the end of the brass tube. The compression with the bushings was then on the end grain of the wood, not wood and tube. Is this a possible explanation? Sorry the weekend wasn't a better one for you!

Now this is something that I hadn't considered. and begs the question what should I be doing to square the blanks? I had considered using the radial arm saw but dont trust myself to be accurate enough.
 

Pastor of Muppets

Full Member
Joined
Dec 5, 2017
Posts
279
Location
Oxford (ish)
First Name
Andy
Andy I tend to have a loose not snug fit after drilling,it allows the Gorilla Glue to expand and do its job properly. Also the G Glue company suggest damping the to be glued area with water to ensure complete setting. Blank end squaring using a sanding disk is far less likely to start fine cracks etc than an end mill in most timbers,also it is very difficult to judge pressure using them in a mechanical way with hand drills or lathe chucks etc. Getting close to fully turned I use a Skew Chisel flat on the tool rest just below centre with great results. I tend to turn each end gently then face the rest of the blank. All of this by instinct including a 1/2 inch gouge. For sensitive timber I like to cut the square edges back,there are many ways to do this,the easy careful way is a large sanding disk. The times you cut down the square edges can cause havoc with the blank. I wrap elastic bands around the blank from end to end to remove any stray movement of the blank. Be absolutely careful as you remove excess glue when it expands, try not to overdo the amount of glue you use in the first instance. Always use suitable gloves Gorilla Glue is nasty on the hands. If you can give more time from glueing to trimming. Trust these few things may assist you overcome the log jam of problems mate.

Kind regards Peter.

Thanks Peter I have discovered the evils of G glue I still have one black fingernail and black patches on my hands! I think i am definitely going to scrap the end mill though. Would a sanding disk in the lathe i.e. a board on a faceplate covered in abrasive and a drill chuck in the tailstock with a transfer punch in it do the job? or would the centre of the disk be moving too slowly in the centre?
As for the skew I have watched it used so many times but still have a a huge amount of fear of using it. it sits in the tool rack and I look at it every time i'm down at the shop and its always "not today".
 

Pastor of Muppets

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Cheers Brad. I will definitely try not using the knurled nut, how much pressure do you put on the bushes?
I was looking at these for turning between centres and avoiding the bowing of a standard mandrel.
could you show me a pic of your sanding set up? as i think this is going to be my next step in my journey
 

Gregory Hardy

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454
Location
Upper New York State
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Greg
Now this is something that I hadn't considered. and begs the question what should I be doing to square the blanks? I had considered using the radial arm saw but dont trust myself to be accurate enough.

If you are squaring on a drill press, make sure you have bushed the barrel correctly, and then cut (square) until you can see that you brass tube has "cut" (shows "shiny" all the way around the perimeter of the brass tube). Use your drill. Just get down to the tube at each end. Not sure that's the problem, but it's worth a check, eh?
 

Pastor of Muppets

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Andy
Thank you all for your advice I have to admit I was pretty downhearted sunday afternoon but hopefully i'll get back on the right track now.
with dampened blanks better squaring and not using the knurled nut!
 

Gregory Hardy

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Upper New York State
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I would also recommend a pass-through bearing-driven tailstock fitting. Get rid of as many "spacers" as possible. Every joint between spacers is a spot that can create wobble...one of those cases where "less is better."
 

Pastor of Muppets

Full Member
Joined
Dec 5, 2017
Posts
279
Location
Oxford (ish)
First Name
Andy
If you are squaring on a drill press, make sure you have bushed the barrel correctly, and then cut (square) until you can see that you brass tube has "cut" (shows "shiny" all the way around the perimeter of the brass tube). Use your drill. Just get down to the tube at each end. Not sure that's the problem, but it's worth a check, eh?

"bushed the barrel"? I'm obviously not doing something i ought to be!!
I dont use a drill press just a vise and a hand drill. I think im going to shy away from the end mill from now on though.
 

Pastor of Muppets

Full Member
Joined
Dec 5, 2017
Posts
279
Location
Oxford (ish)
First Name
Andy
I would also recommend a pass-through bearing-driven tailstock fitting. Get rid of as many "spacers" as possible. Every joint between spacers is a spot that can create wobble...one of those cases where "less is better."

is that the mandrel saver where the mandrel passes through centre of the tailstock? and that makes a lot of sense about getting rid of the spacers, I'll add that to the list!
 

Gregory Hardy

Graduate Member
Joined
Jul 7, 2017
Posts
454
Location
Upper New York State
First Name
Greg
"bushed the barrel"? I'm obviously not doing something i ought to be!!
I dont use a drill press just a vise and a hand drill. I think im going to shy away from the end mill from now on though.

If you are squaring with a 7mm mill and the tube is bigger than 7mm, you need tube bushings. Penn State sells sets - worth the money...an get a mandrel saver tailstock live center too.
 

Penpal

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Andy the idea of using a large disk to face blanks I find is the ability to use the outside for rapid removal and toward the centre for the last finish at the slower speed.

Peter.
 

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