Minimum thickness of bowl blanks?

[PolishPenTurner]

A friend of mine gave me a very nice piece of Purple Heart that is 1.75” thick x 5 1/2” wide x 7 feet long. In appreciation for him giving me this nice piece of wood I’m going to make him some bottle openers. However, I’d also like to make him a bowl out of Purple Heart which I think would look beautiful.

My question…..can I turn bowls from this wood when it’s only 1 3/4” thick? I’m fairly new to bowl turning and the different options that can be used to mount the blank onto my lathe…(ie…bowl turning threaded chuck and faceplates). The few bowls I’ve made have all been 3” or thicker.

If it’s not safe to turn this thin of a wood blank, can I laminate/glue two pieces of Purple Heart together to make a blank that would be 3 1/2” thick?

Thanks for any input. Wasn’t sure where to post this thread since it wasn’t related to pen turning.

 

[Gert Fitcher]

Hot melt glue is your friend. Glue the blank to scrap. If the blank is heavier put spacers between the blank and the scrap so you can get a heated knife between them to release it. The pro I knew used hot melt for blanks up to 100lbs, this one was done with it, it was reversed only once - it's about 75mm deep, the base looks flat but is about 3mm hollow.

 

[waterbuffalo]

Could you cut it into conical rings and stack them together. If you get what I mean

 

[PolishPenTurner]

OK....I apologize for my ignorance...but a few questions when using hot glue...
1. I assume the advantage to hot gluing a scrap to the blank would allow me more depth for the screws when applying the faceplate to the scrap?
2. Any particular kind of hot glue? I saw a video a long time ago (before I started turning bowls) about using hot glue...but I thought they said to use a specific brand or type of hot glue which had better adhesion.
3. How do you remove the scrap from the bowl when you're done? Do you just take a heat gun and re-melt the glue?

 

[Hallelujahal]

1. Yes
2. Not particularly, but it’s gotta be hot, I use a heat gun to warm up surface of the wood before application.
3. I just turn it off with parting tool

Just my 2p hope it helps

 

[Gert Fitcher]

Jeff -
In this instance two thirds of the outside (from the bottom up) was completely finished before turning it over turning the inside and the rest of the outside. I put 2mm spacers between the bowl and scrap purposely so I didn't risk digging into the finished surface.

1. I assume the advantage to hot gluing a scrap to the blank would allow me more depth for the screws when applying the faceplate to the scrap?
Yes you can use any thickness you choose - I tend to start quite thick as the face can be turned clean and flat and reused several times. You can also turn through the blank into the scrap if you need to.

2. Any particular kind of hot glue? I saw a video a long time ago (before I started turning bowls) about using hot glue...but I thought they said to use a specific brand or type of hot glue which had better adhesion.
I use a general purpose one I bought a lifetime's supply of (5Kg).

3. How do you remove the scrap from the bowl when you're done? Do you just take a heat gun and re-melt the glue?
You can turn through the visible stuff, being sure not to go overboard and see the blank fly off. Take a very sharp paring chisel and cut away most of the remnants, IPA softens anything left and it'll rub off. A piece of 320 or 400 abranet will remove any very slight marking.
That particular bowl was a bit of an excercise - so many bowls are spoiled by poor finishing on the base. I lost a little concentricity, but not enough to spoil the bowl, and I don't know quite how much of that was caused by the time lapse between the two operations, anyway.

The pro turner I knew used three hot melt guns at a time on blanks of up to 1cwt.

 

[Gert Fitcher]

1mm spacers folded in half. Easy to part with no damage.

 

[howsitwork?]

I would strongly suggest turning him a nice platter rather than a bowl and skip laminating the purple heart .

As to glue chucks , yes you screw into the scrap rather than the actual blank. General purpose hot melt glue will work well but pre warming the blank surface first is a good idea . Don’t skimp on the hot melt glue at all, you can easily turn it off .
Depending upon how thin you make your platter ( or shallow,bowl ) you can either turn most of it away or I use an old plane blade to insert and gently part the two. How do you intend to finish the base? Do you have cole jaws or something similar to grip the outside gently whilst you turn it or do you intend to finish the base first then remount ona further glue chuck and turn the inside, being careful with your recentering in that case?

 

[PolishPenTurner]

Hey folks,
I thought I had asked this (possibly in a separate thread...but can't find it)...but what type and length of screw should be used when screwing the faceplate to a waste block for turning bowls?
Thanks.