Turning Pint Glass

[Chris Straub]

I'm working on turning a pint glass (6'' deep, inner 3 1/8'', outer 3 1/2'') for an order I have. So far have tried:
- ascending forstner bits but you get a different center than the chuck
- boring a hole and hollowing tools but 6'' straight down is long for my Sorby hollower
- taking 1/8'' or 1/4'' of the edge at a time with my scraper
- using carbide tools

So much experimentation but havent found the way that is easily replicable and efficient. I'll be using poplar, cherry, and walnut do not super hard woods.

Suggestions? Thanks!!

[Clint Baxter]

You could drill, using the forstner bits into a slightly oversized piece. Once you have it bored out, place your blank on a spigot chuck to reduce the outside diameter, which will the create a blank with your recess perfectly centered. You could then place it back into your chuck for any other required actions.

Clint

[Thomas Canfield]

Drill pilot using decending Forstner bit to start the hole to get the hole diameter and center established. Then use the live center and drive to turn the OD of piece. You can then go back and use Forstner bits, again establishing the hole diameter of any other bits, large to small, before drilling to depth and finish drilling with larger bits, small to large, until hole drilled. The Forstner bits in chuck should give support to drill centered hole. Possibly even better is to drill the full hole first and then use a cone on live center to support the piece to turn the OD. Good luck.

[Brice Rogers]

Assuming that I understand your post, I think that your challenge/problem is the large amount of overhand you have trying to bore and hollow out to 6" in. If you have 6" of unsupported tool, that is problematic and whether you are using a Sorby hollower (I presume that you are talking about a tool rather than a monster-like hollowing system) or a carbide bit, you are likely to get an exciting catch.

One solution: get a tool post that can stick into the opening perhaps 5" deep. I made one that is shaped like a diving board. No problem going in 5". I don't get chatter or grabbiness. These are also sold commercially but I forget what they are called.

edit: others correctly called it a box rest, which is the name that I couldn't remember.

[ALAN HOLLAR]

I think you would call them Box Rests. Best Wood Tools makes 2, maybe not 5" long, but a better platform than a traditional rest. Packard Woodworks has them, perhaps others as well.

[David Delo]

JT Turning Tools offers a 4" offset style that looks to be handy for that type of work.
JT Offset.jpg

[John K Jordan]

I think you would call them Box Rests. Best Wood Tools makes 2, maybe not 5" long, but a better platform than a traditional rest. Packard Woodworks has them, perhaps others as well.

I have the original box rest from Best Wood Tools and it is great. (I can't stand their round-rod rests.)

Chris, if I had a number of deep turnings like the one you mentioned I'd probably make an extended rest. You might also think about acquiring an additional tool or two. What kind of carbide? - the flat-topped carbide tools are low on my list of useful tools. Mike Hunter makes some that work far better. You can probably use any of the tools made for hollow vessels. The advantage of the wide opening on your turning is you can more easily check on the progress.

You can also hollow something like this with a scraper ground flat across the end and push straight into the wood from the end. The scraper would have to be well supported and/or quite heavy and you might have to avoid heavy cuts, i.e., drill a center hole first then use the scraper to widen just a 1/4" or so on each pass.

For a straight sided turning with a wide opening to clean up the sides and bottom you could use a heavy scraper ground as a box scraper with a relatively short angled cutting edge on the left. Any of the round or teardrop scrapers (such as the Sorby) often used to clean up somewhat closed forms will also work.

I don't understand when you said the the holes using a Forstner bit have a different center than the chuck. This shouldn't happen unless your lathe is sloppy, the bits are bad, or you are perhaps drilling all the way to the bottom with a smaller bit then trying to drill larger diameters towards the top. If so, to allow each bit to center properly you need to go the other way and drill the largest diameter hole first, then the next smaller, etc.

Also, I forgot to look at this in your photos - are you using end grain blanks (with the grain running parallel to the bed of the lathe? I hope so!

JKJ

[Chris Straub]

Hi John,
I am using end grain blanks - it'd be much easier but not a proper glass if I wasn't!

I did start using a scraper, I have a 1.5'' sorby and 1'' wood river as well as various box scrapers etc. It's actually the most reliable, and controllable, way of doing this and want to explore it more with an extended tool rest. I'm assuming the lathe didn't have a good center - it was explained to me that without a center for the drill bit to go into, that they can travel some. At the moment, I had a finished product with varying thicknesses between inner and OD, so I believed it. But will try it on a better lathe.

Thank you for your reply
Chris

[Dane Riley]

or you are perhaps drilling all the way to the bottom with a smaller bit then trying to drill larger diameters towards the top. If so, to allow each bit to center properly you need to go the other way and drill the largest diameter hole first, then the next smaller, etc.

JKJ

Absolutely. I found that out when learning to use a Beall tap for something to thread onto my lathe spindle (3520b). (in addition to generous use of CA before tapping) If you forget to drill the flat for the shoulder and the the clearance for the next part, you throw it away and start over.

[Brice Rogers]

Thanks David for posting this. I made my own box rest but it is straight. I like this one better. I'm going make one copying this design. I've been using hot-rolled surveyers stakes (about 1-1/2 x 3/8 thick) because they're dirt cheap. But for this design I'm going to add a re-inforcing rib at the bottom for stiffness. It looks like the JT tool is probably 1/2" thick???? I would be curious to know the thickness.

JT Turning Tools offers a 4" offset style that looks to be handy for that type of work.
JT Offset.jpg

[John K Jordan]

...I've been using hot-rolled surveyers stakes (about 1-1/2 x 3/8 thick) because they're dirt cheap. ...

Where do you find these steel surveyor's stakes? I've never seen them for sale or in use.

I like that design too - allows better entry near the edge.

JKJ

[Brice Rogers]

Hi John,

I get them at Home Depot in the section of the store near the concrete tools, rebar and tie wire. I call them surveyors stakes but they might also be called builders stakes. They are commonly used for pulling string lines for setting the lines for footings on a foundation. They come in different lengths up to perhaps 30". The end that would get pounded into the ground is drawn to a chisel edge. The only negative is they have a few holes drilled in them for tying string. But when I'm welding I will close the hole up and grind it flat. IIRC, they don't cost very much. They weld very nicely with my Lincoln (tombstone) AC stick welder.

[Doug Hepler]

Chris,

I have made a number of mugs of about the size that you describe. You can drill them out with a Forstner bit. If you drill the cylinder at once you won't lose your center. It is very tedious. You have to go slow to avoid overheating the bit (and the wood) and lubricate the side of the bit with wax. Then you can finish the inside with a heavy scraper, which removes any wax that adhered to the inside when you were drilling it. A spigot or mortise mount with a scroll chuck is the best way to mount the blank. A glue block is likely to fail and a screw chuck leaves a hole that you would have to fill with a dowel.

I find that making mugs from a solid blank is way too tedious. I make them with staves. Maybe you are not into segmented turning, but if you have many to make this method would merit serious consideration. Staves offer a wide range of design possibilities, including lamination. PVA is waterproof. I use stainless steel liners (available from Rockler) You can finish the inside of an unlined mug with food safe expoxy (Max Clr).

If you are interested I will be happy to provide more detail.

Doug

[ron david]

I'm working on turning a pint glass (6'' deep, inner 3 1/8'', outer 3 1/2'') for an order I have. So far have tried:
- ascending forstner bits but you get a different center than the chuck
- boring a hole and hollowing tools but 6'' straight down is long for my Sorby hollower
- taking 1/8'' or 1/4'' of the edge at a time with my scraper
- using carbide tools

So much experimentation but havent found the way that is easily replicable and efficient. I'll be using poplar, cherry, and walnut do not super hard woods.

Suggestions? Thanks!!

you said ascending forstner bits. if you are using ascending sizes then you will be lost for control. it is the centre point of the drill which keeps it in control. if you use a larger(ascending) bit in a hole you will have no contro of the bit. it will wander
ron

[Shawn Pachlhofer]

I made a number of these style glasses a few years back.

I used a single forstner bit all the way to the bottom, then came back wit carbide tool to remove all the excess material inside the glass