Coronet No 3 Bowl turning question

[Suffolkboy]

Gentlemen, Ladies,

I have just gotten in to Wood turning and have purchased an old Coronet No 3. It is in excellent condition and I am chuffed with it.

Being a beginner I appreciate that this post may seem a bit ahead of myself but bear with me.

I am going to be logging a rather large windblown oak later in the month and will be keeping the timber. The Coronet instruction book says that the maximum bowl turning diameter of the lathe is 30".

My question is, is there a weight restriction or limitation? The reason I ask I that I don't want to miss the opportunity to make some large bowl blanks ready to turn in a few years time when they have seasoned a bit and I have gained the experience. But I am worried that if I cut a blank say 30x15" it will be too heavy for the lathe.

Any advice would be much appreciated.

 

[Phil Pascoe]

I use one regularly, and I wouldn't like to try anything much thicker than a table top at 30". They might be physically large enough to handle it, but they are not very heavy. (IMO)

 

[Harry 48]

30''x 15'' of oak imho would be very dangerous with the head stock turned unless the lathe is bolted down to the floor it may tip over 15'' thick I don't think the bowl arm will take that thickness good luck if you try. I use a cl3 with speed control upgrade .

 

[paulm]

I used to have a CL3 (same machine essentially I think), and think you would find the motor would struggle to turn that size blank, or at least would stall easily when you try to take a cut with a gouge, as well as the reservations others have mentioned.

I upgraded to a big wivamac to be able to do larger items, although the CL3 was perfectly sound for small to medium stuff and even for larger stuff occasionally but not as large as that !

Cheers, Paul

 

[Suffolkboy]

Thanks for the reply's. My concern wasn't about tipping essentially as I can avoid that by by fastening to the floor, my concerns were for the physical capability of the machine to handle the blank, which it sounds like you guys are saying the machine probably isn't man enough.

I still don't want to waste the opportunity to make some big blanks from this massive tree but I will put them to one side for a day when I have a machine that can handle them, or, if not I can always reduce them, I may try a table top as well, ( I hadn't thought about that, thanks) and cut some smaller ones for the Coronet, maybe more like 20x10?

 

[Mark Hancock]

It's not for the feint hearted but the Coronet No 3 can manage large pieces BUT you need to set up the lathe to cope with it i.e. solid bench weighted and bolted to a concrete floor. And remember the bottom speed is 425 which is a lot for a large diameter piece.

The other issue is the headstock spindle. Being only 3/4 x 16 it is very flimsy and easily bent and crushed with a heavy weight on it - that's what happened to mine with a very large wet burr oak chainsawed 24" dia. bowl blank and the spindle was very expensive to replace and that was 20 years ago! I learnt from that experience to place a dead centre or morse taper from an engineering drill in the headstock spindle before mount large heavy blanks on it - You have to make sure enough of the centre/morse taper is protruding from the spindle to be able to remove it after use with pipe pliers/spanner.

 

[nev]

Put an unbalanced 12x6 oak blank or similar on the lathe, stand back and turn it on. :shock:
Then
1) decide if you want to stand in front of it poking it with bits of steel, and
2) multiply a number of times (to estimate the 20x10, 30x ?) its efforts to leave the lathe or move the lathe around the workshop and decide if you'd like to stand in front of that poking it with bits of steel.
3) ask yourself - will my facemask protect me if it flies off the lathe at X00 rpm?

Not wishing to put you off, and by all means cut some larger ones and store them away to dry (after all they wont be ready for a few years ) but work your way up in sizes and you will find what the lathe (and you) are actually capable of handling.

 

[bogmonster]

You would be a braver man than me - proceed with extreme caution...

I have turned about a 24" bowl on a lathe that went down to about 325 to 350 RPM and that was exciting enough when the lump was unbalanced. The other thing to consider is what are are you going to do with a bowl that size?

If you do tackle it, work up to it slowly

BM

 

[Suffolkboy]

Thanks Nev, Bogmonster,

I will cut the bigger blanks and put them away for a few years, (or more) if after that time I feel I am Brave enough then I may consider attempting them, whether by then it is on the Coronet or not will be a decision I make at the time. Probably, given what Mark Hancock has said about the headstock spindle and the RPM's it probably won't be.

What am I going to do with a bowl that size? Put stuff in it!

 

[Mark Hancock]

I will cut the bigger blanks and put them away for a few years, (or more)

IMHO You'd be better leaving the timber in the round. If you prepare bowl blanks now and leave them they are almost certainly going to split and crack especially with it being oak.

 

[Suffolkboy]

That's a fair point Mark,

I was thinking of size/weight considerations when it comes to moving and storing.

I suppose also it will give me a bit more choice when I do come to turning it though.

 

[Mark Hancock]

You could cut the logs through length ways through the pith to help reduce the weight. Alternatively rough slab at around 8 inches thick which would give you a suitable depth for the size of bowls you are considering and put in stick.

 

[Suffolkboy]

many thanks Mark.

 

[Normancb]

15 in is 1.25 ft, so the volume of a 30 x 15 cylinder is 3.14 (pi) x 1.25 x 1.25 x 1.25 = 6.1 cubic feet.

The density of dry oak is about 45 lb per cubic foot, so your blank will weigh 276 lb.

That will challenge all but the very largest commercial lathe and will destroy a Coronet. I know someone who turns stuff that size - his lathe weighs a couple of tons!

Bear in mind that a lump of oak that size will never dry fully so will be even heavier when mounted.

 

[Spindle]

But I am worried that if I cut a blank say 30x15" it will be too heavy for the lathe.

Hi

I would not entertain trying to turn an unbalanced blank of that size on any lathe that doesn't have a variable speed control down to about 50 RPM - you can bolt a lathe down as rigidly as you like, the weakest link is going to be the attachment of the work to the face plate, (or the face plate itself), or the spindle in the case of a 1MT, (a 1MT spindle is certainly not up to the task).

I'd estimate a 15" blank is going to take 10 plus years to air dry - plenty of time to learn to turn and save up for a suitable lathe :wink:

Regards Mick

 

[finneyb]

At 276 +lbs you will need a car engine hoist to position the wood on the lathe.

Using the formula
Diameter in inches x rpm = 6000 to 9000 (use 6000 ie lower value for roughing)
RPM comes out at 6000/30 = 200 rpm

And I would at least halve that value to start with ie 100 rpm max.
ie you need a lathe with electronic variable speed.

HTH

Brian

 

[Suffolkboy]

Many thanks for the advice guys.

I think common sense told me most of what you have confirmed. Its not every day I get to log a tree this large so I didn't want to miss the opportunity.

I intend to cut some very large blanks for the future, in the way that Mark suggests which if I never get around to doing anything with I can always reduce in size, after all I cant glue them back together once they are cut.

The rest of the wood I will process into smaller, more normal sized pieces and use them accordingly.

Everything else is destined for the wood burner.

 

[boomerang bender]

Hi I am new to turning but would it be possible to remove as much of the blank as possible by drilling the bowl centre down to bring the weight of the blank to a safe weight for this lathe. Obviously the balance of the reduced blank would have to be taken into consideration,

 

[Ridethewave]

when you cut the oak with a chainsaw into rounds, remember that its the length of the round that will end up being the maximum diameter of your bowls. if you cut it to 30" you wont be able to pick it up.would probably take 4 guys to pick it up. if you find someone with a very long bar on a large powerful saw then you could plank it in situ once its felled. the grain in the planks is then going in the correct direction for turning bowls.

I've only been turning a few weeks myself with a coronet minor and have only been turning bowls so far.
I would never consider turning anything that diameter. the speed at the outside would be more than considerable. Take a look at large platters that the experienced guys turn. they know what they're doing.

hope that helps...John

 

[Phil Pascoe]

My lathe is much heavier than yours (and has a slower starting speed), with a hundredweight of sand, a hundredweight of scrap iron and the bricks from eight night storage heaters in the base. I wouldn't entertain a blank of that weight.