PDA

View Full Version : Chatter, chatter .... grrrr ..... chatter



thumb trimmer
30th May 2010, 10:07 PM
I've just started turning my first goblet, and by 'just' I mean I've only rounded the blank and am about 4mm into hollowing the 'bowl' of the goblet.
The blank is (well and truely) dry huon.

The reason the goblet isn't finished yet, is that I started to get chatter as I tried to hollow the bowl of the goblet, causing major tearout.

The blank is about 2 or so inches in diameter, and the blank is approx 210mm long. I've got it 'secured' in a nova G3.

I've sharpened, and then re-sharpened both my spindle gouge and bowl gouge. Still chattering. The tools aren't 'catching', just chattering.

I was initially using the method outlined by Richard Raffan in his books, that I've also seen people use successfully in videos on youtube. I've also tried the sort of cut I'd make for a bowl ... all no good.

It appears that the blank is moving ... not sure how though?!?

Please help ... any advice would be appreciated.

TT

Broda
30th May 2010, 10:42 PM
the cup should be the first part you do otherwise it will not be supported if you do the stem and base first. Make sure you've got the blank only a little bit longer than you need it otherwise there is too much unsupported wood
maybe you've got some spindle runout?? whats you're lathe?? has it been abused??
hope this helps

Cliff Rogers
30th May 2010, 10:46 PM
What is your lathe & how good are the spindle bearings?

How are you holding the blank on the lathe?

Any up/down movement at the end of the blank where you are working will cause problems when trying t hollow end grain.

Oops, Broda beat me.

rsser
30th May 2010, 11:09 PM
Yar, that's a long bit of wood for a 50mm grip at the base.

Got a steady?

Or consider doing most of the hollowing with a saw tooth bit and then taking v. light cuts with a gouge or scraper.

Jim Carroll
30th May 2010, 11:20 PM
What jaws are you useing on the G3 chuck.

If the standard jaws then these will not give you enough support.

You should be using spigot jaws (http://www.cws.au.com/shop/item/nova-spigot-jaws-js-sp35) which will give you more support.

As others have indicated only do the goblet part first before moving onto the stem.

tea lady
30th May 2010, 11:25 PM
I had problems with chatter with my old lathe cos the head stock flexed a bit. It was a home made job. It got reinforced with some more metal and was great, then t got passed on to someone else when I got a chance to buy an even better one.

Does it only chatter when hollowing? Or when you are away from the head stock? It is quite long for hollowing the end, on quite soft wood. :think: Maybe a steady would help. :shrug:

rsser
30th May 2010, 11:25 PM
And don't grip the blank square. If you haven't already, turn a tenon with a shoulder for the jaw faces to butt against.

John Lucas
31st May 2010, 08:10 AM
You definitely should have a round tenon with a shoulder. Also don't bottom the blank out in the chuck. The shoulder of the tenon should sit on the top of the jaws and the bottom of the tenon should be just a little shy of the bottom of the jaws. This will give the most stable support.
At that length with only 50mm of support you will probably still fight chatter unless you take light cuts. You didn't mention if you were hollowing the goblet from the center out. If it's end grain you should be. If you are hollowing by starting in the middle and going straight across you will get more chatter. make a small hole in the middle and hollow at about 45 degrees from the hole. This way the middle is always deeper and you are hollowing in a cone shape. This applies less sideways force so it reduces the chatter. You are also cutting with the grain which again reduces chatter.
You should leave the goblet stem as fat as possible until you have the top almost hollow. I turn the cup portion but just as soon as I start to round over the bottom I stop and then I hollow. When I have the goblet hollow down to this point then I finish up the bottom of the cup but still try to leave the stem pretty fat until I have goblet completely hollow.

oldiephred
31st May 2010, 09:02 AM
I drill the inside of the cup with a forstner bit a bit smaller than finished size then make a stub that is the same dia as the drilled hole and the stub has a shoulder on it about 3-4 mm larger in dia than the drilled hole. Place the stub in the hole and use the tail stock center to support the work while rough turning the outside.
Finish turning the inside, reinstall the stub shaft and finish the outside.
It is easier than my explanation but , sorry, no pictures available.
Best of luck.

thumb trimmer
31st May 2010, 02:58 PM
Thankyou to all that have replied so far. Your insight is always helpful and appreciated.

re: turning the bowl before the stem and stem thickness - I've only just turned the blank round and a tenon to mount in the chuch; ie. I've not yet turned a stem. :~

re: turning a tenon - yes I did turn a tennon on the blank first, however :think: now that I think about it, I don't think the shoulders are butting up against the chuck jaws - I'll cut the tenon down a bit so that the shoulders are in contact the the jaws, and the end of the tenon is not 'bottoming out'.

re: blank only a little longer than you need - I was hoping to make a goblet approx. 200mmm (or so) tall by about 2" (or so); so I only made the blank about as long as I need/want.

re: standards jaws - yes I am only using the standard 50mm jaws on the G3.

re: steady rest - I've given it some thought previously, but maybe now is the time to make one.

re: chatter only when hollowing - yes and no, this is the first time I've had noticable chatter; however, I did do a rectangular edged bowl about a month ago which ended up with 'ridges' on the external sides adjacent to the square faces. I just assumed this was because I couldn't maintain a steady grip on the tool as the tool went from contact with wood to air to contact with wood as the 'square' faces came and went past the tool rest.

re: hollowing from centre to outside edge - yes I've tried this method (ie. as mentinoed following instructions from one of R.Raffans books). And yes, I've also tried only taking light cuts. - I haven't yet tried, but I will try the 45 degree/cone shaped cut.

re: using a forstener bit - hmmmm, sounds like an option worth looking at, with the exception that I can't fit a jacobs chuck and drill bit to my tail stock. :~ Bugger

re: lathe model - I've often considered ... or should say, am constantly considering the fact that I've exceeded the capacity or ability of the lathe :flog: ; but I've always tried to live by one of my grandfathers sayings "don't blame the tool, take a look at the user" (or something to that affect). I've also got to consider the fact that my financial controller (SWMBO) may not authorise the purchase of new lathe ... I'm trying to build a feasiblity study to support my arguement, but I seem to be losing that one a bit ... which I'm sure many can sympathise with. So, yes I need to admit that I have one of those cheap chinese bar bed style lathes, which up until now has (mostly) been ok for learning this addiction (or affliction, if you will) that is called wood turning. I've reasonably successfully turned about a dozen or so pens, a captive ringed rattle, four bowls (less than 200mm dia) and a terrrible looking mushroom.

So ... moving on , and hopefully ... with the exception of a new lathe ... are the above (re: making and using a steady and having the shoulders in contact with the jaws) likely to help reduce or eliminate the chatter?

Thanks again
TT

rsser
31st May 2010, 04:28 PM
Yes.

Huon's fairly soft so may be more liable to flexing than other choices of wood. That rather than tool chatter is prob your main challenge. I've done something with a shorter thicker piece of Horizontal and that was so whippy I didn't get v. far.

If you can get the bowl formed then bring the tailstock centre up with some kind of cone over it to sit in the bowl so you can finish the stem with less flexing.

thumb trimmer
31st May 2010, 10:26 PM
:cold: ...and it ain't the cold.

I've just tried another piece of timber, a peice of myrtle ... and I still am getting chattering. :~
(thanks to Ern for suggesting using an alt timber)

I've butted the shoulders of the tenon up against the chuck.

I've also made the blank shorter (albeit by 30-40mm).

After noticing still chattering, I threw a bit of weight on the end (with the tool rest up pretty close), and noticed a distinct movement (from centre).

From which I'd definitely say that there's movement in the headstock. :~

Now ... short of buying a new lathe (I so wish), is there another way to remedy this. ie will a steady do the job or not?
Or should I just go and use my mates Vicmarc 175???

thanks again in advance
TT

tea lady
1st Jun 2010, 12:19 AM
From which I'd definitely say that there's movement in the headstock. :~

Now ... short of buying a new lathe (I so wish), is there another way to remedy this. ie will a steady do the job or not?
Or should I just go and use my mates Vicmarc 175???

thanks again in advance
TTI was able to reinforce the head stock of my lathe so it didn't noticeably flex. :shrug: Do you have a "mate" that could check out whether its a bearings prob or a flexible head stock?

Maybe go and use your mate Vicmark just to know you can do it normally. :cool::D

tea lady
1st Jun 2010, 12:24 AM
What "tool" are you using? A bowl gouge? Or a spindle gouge? :think: And how deep are you? And how far off the rest is the tip of the tool? :think:

John Lucas
1st Jun 2010, 06:06 AM
Try a short fat piece. If you still have the chatter then it's probably the lathe, tool extended too far, cutting technique, or all of the above. Don't forget the tool rest. Shopsmith for example has a very flimsy tool rest and you get vibration just from that even though the headstock is stable and the tool is good, sharp, and not extended over the rest.

rsser
1st Jun 2010, 03:27 PM
If the bearings are clapped out normally you'd hear it.

thumb trimmer
1st Jun 2010, 05:32 PM
tea lady - do you have photo's of the work that you did to reinforce your headstock?

Also, I've been using a (1/4" - I think) spindle gouge with a fairly 'pointy' grind to do the hollowing. NB: though I did take to it with my 1/2" bowl gouge when it first started chattering, to see if that would also chatter ... and guess what ... it did.
in both the pine and myrtle, I've only got in about 5mm(ish) with torn grain, and a 'lovely' wavey pattern in the myrtle ...:~ ... my tool rest is set 2-4mm away from the end of the work piece (ie. as close as possible).

John Lucas - I've got the very thing. A short section I cut off theend of the myrtle blank (approx 2" long). I'll stick that in the G3, and see how it goes.

I also don't expect the tool to be too far in or hanging too far over the rest, as I've got the rest as close as possible, and have only cut approx 5mm into the endgrain.

There is always the possibilty that there is some vibration in the tool rest, however as I mentioned earleir, when I pulled/pushed on the end of the blank, I could see it 'move' off centre.

Not sure about the bearings, but there is no distinct 'bearings' noise.

Thanks again
TT

thumb trimmer
1st Jun 2010, 05:45 PM
below are to photo's of the lathe in question

http://www.woodworkforums.com/members/30814-thumb-trimmer/albums/other-stuff/4422-turning-lump-unknown-timber.jpg

http://www.woodworkforums.com/members/30814-thumb-trimmer/albums/other-stuff/4423-3rd-bowl-progress.jpg
PS - doesn't chatter when cutting across the grain

issatree
1st Jun 2010, 09:39 PM
Hi Thumb Trimmer,
I haven't read all of the replies, but I think it is the Lathe that is the problem.
Those particular Lathes, Bounce Like Corks.
Now, that is my experience with them.
The only other point is, Does your Flute on the Bowl Gouge Face you or away from you,
as it should be.
Regards,
issatree.
<input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden"><input id="gwProxy" type="hidden"><!--Session data--><input onclick="jsCall();" id="jsProxy" type="hidden">

thumb trimmer
1st Jun 2010, 10:35 PM
Hi issatree,

When hollowing a bowl, the flute faces away from me.
When I was trying to hollow the 'bowl' of the goblet, using R.Raffans technique, I had the flute facing me.

TT

cultana
2nd Jun 2010, 01:01 AM
I presume that the lathe has a metal base that the head stock housing is mounted on and the tail of the bed is attached to. Also the lathe bed is only held to the headstock body by a bracket and 2 bolts similar at the tail end of the bed to the base.

There would be sufficient flex in such an arrangement to get that off centre movement you mentioned.

It may pay to make a steel bracket that links the lathe bed to the base and to the head stock body.

Just a passing thought.

Sturdee
2nd Jun 2010, 02:52 PM
That's the same as my old lathe. One thing is to bolt it onto the bench, this will alleviate it, but it still is really only good for converting it into a sander.


Peter.

thumb trimmer
2nd Jun 2010, 09:58 PM
Sturdee - You probably can't see it in the photo's, but it is bolted down in three places (either side) along its length.

Cultana - I think I understand what you're getting at, but don't see how that would stiffen up the headstock???

regards
TT

thumb trimmer
2nd Jun 2010, 10:00 PM
For those who have owned one of these style lathes; when you upgraded, what did you upgrade to?
Given my tight financial controller, I was thinking of getting a MC900.
What say you?

thanks in advance
TT

thefixer
2nd Jun 2010, 10:40 PM
G'day TT

Yep, I started with the same lathe and had the same problems. Flex in the bed is the major problem. Easily demonstrated by tightening up the tailstock and watching the end of your piece of timber raise up from the bed as the tailstock tilts back:(( A quick demo to SWMBO should help your cause toward a new lathe:wink:

I upgraded to the MC1100 and never looked back. Having said that, I have done a lot of work in tuning up the lathe by removing sideways travel in tailstock and alignment of head and tail.http://www.woodworkforums.com/f8/mc100-tailstock-woes-93750/, All in all, a great entry level lathe at an affordable price and easy to obtain extras for. Or make them yourself as the case may be.

TTIT
2nd Jun 2010, 11:22 PM
For those who have owned one of these style lathes; when you upgraded, what did you upgrade to?
Given my tight financial controller, I was thinking of getting a MC900.
What say you?

thanks in advance
TTMy 1st lathe was a home-made job powered by a washing machine motor and it was even more flexible than what you have. I went to an MC900 from there and thought it was the bees-knees until it's shortcomings started to hinder my progress so I ended up stepping up to my Stubby only a year or two later. My advice - If you are already hooked on turning, don't beat around the bush, get something that's going to see you out. Explain to the financial controller that if you had a hobby like car racing, marlin fishing or aerobatic flying, it would cost many times more - a good quality lathe is an absolute bargain in comparison - and what financial controller can resist a bargain! :;:U

cultana
2nd Jun 2010, 11:43 PM
Sturdee - You probably can't see it in the photo's, but it is bolted down in three places (either side) along its length.

Cultana - I think I understand what you're getting at, but don't see how that would stiffen up the headstock???

regards
TT

First it will lock the head stock, the lathe bed and the base at one place and should thus reduce the flex you indicate. The current arrangement allows this flex as it is not at the same place and cross bolted.

Also if possible you should add extra bolts through the lathe bed in the head stock housing to the table base you have. It is only bolted along the length of the base under the lathe bed and tail end of that bed.

cultana
2nd Jun 2010, 11:51 PM
Well if you want to travel the MC900 way I would suggest go the MC1100 way. Just a longer bed but better having the extra length for that occasional situation.

As thefixer said the MC collection can have their problems. I got an MC1100 and possibly by luck and after much measurement and cross checking don't have the same problems as thefixer had with his tail stock. Others have had head stock issues. Seems I have avoided theses so far as well.

But I did have to throw away the live centre that came with the lathe as the bearing went within a month of use. I was going to get a new live centre anyway so it was no big deal.

All I can say is if you go the MC path do all necessary checks ie floppy tailstock head stock etc ASAP and if not suitable get the dealer to do the replacement. You should be able to check head stock and tail stock flex etc in the shop anyway.

thumb trimmer
2nd Jun 2010, 11:52 PM
Cultana - I'll have a look at that ... hmmmm :roll: ... but probably not tonight, might be a weekender job.

TTIT - my financial controller was never and still is not a shopper (one of the reasons I married her), so the bargain bit won't likely work.:doh: ... And it was my b'day the end of last month, and I 'suggested' that she buy me a new lathe, which was strongly rebutted. :~

oh well ... I'll give the bolt it down more things a go, and see if that improves it some.

regards
TT

tea lady
3rd Jun 2010, 12:02 AM
Hi issatree,

When hollowing a bowl, the flute faces away from me.
When I was trying to hollow the 'bowl' of the goblet, using R.Raffans technique, I had the flute facing me.

TTThat is right. :cool: A "normal" bowl that has the grain running perpendicular to the shaft you can actually hollow either way, cos the grain will always by backwards half the time anyway. But an "end grain" bowl of the type that is part of a goblet is hollowed from the center to the edge (Ie: down the grain:cool: ), with the flute facing you. :2tsup: You can use a spindle gouge or a detail gouge too. I find they actually work better that a bowl gouge in this situation cos the "wings" aren't in so much danger of digging in as you come near the walls of the bowl. :)

Sturdee
3rd Jun 2010, 12:43 AM
Sturdee - You probably can't see it in the photo's, but it is bolted down in three places (either side) along its length.


regards
TT

Can't see the bottom properly but I presume its a thin pressed steel plate with U shaped sides like mine was. Whilst appearing to be solid it had flexed when bolted to a bench (especially as the bench is not dead level.:- ).

I was toying with the idea of getting a steel plate made that I could slide along its length inside the U shape to stiffen it and then bolt it to the bench but instead upgraded to a MC900 from H&F.

Peter.

thumb trimmer
5th Jun 2010, 08:04 PM
I've just tried a much shorter (approx 3" long) length of myrtle.

The blank seemed not to move anywhere near as much as the longer blanks, and the chatter was minimised, particularly when I concentrated on taking 'light' cuts only. I still had a fair amount of tear out, so I'll sharpen the spindle gouge a bit and give it another crack.

Failing this, I might just go back to turning pens and bowls.

Thanks to all who commented and provided feedback.

Regards
TT

Sturdee
6th Jun 2010, 02:22 AM
I was watching a Mike Darlow DVD the other night (filmed at the time when your lathe was common ) and he mentioned that if you poured concrete into the hollow square tubes on which the toolrest and tailstock slides it will stiffen up the whole lathe.

Might be worth doing.


Peter.