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Black_Moons
10-31-2009, 10:03 PM
Hi, Recently iv experianced a few dangerious events when facing far away from the chuck, ie the work bending and going crazy, Really ruins my day. usally happens when I go a bit too agressive trying to reduce the length of a peice, often to get the center drill mark out..
Basicly im wondering how to go about reduceing the chance and danger of that when reduceing length of a peice, Should I turn the diamiter insted insted of facing multiple times? Or just take finer facing cuts at a more sane feed rate? Or should I take deep facing cuts but at a very low feed rate?

Evan
10-31-2009, 10:10 PM
Use a 4 jaw chuck. If you are taking facing cuts you are putting a lot of side load on the work and a 3 jaw isn't good at handling a lot of side load. With a 4 jaw it has much better grip and if facing precise centering isn't required.

Glenn Wegman
10-31-2009, 10:12 PM
Use a steady rest if the part will not fit into the chuck far enough! More than three times the diameter hanging out of the chuck may be pushing your luck in most cases.

J Tiers
10-31-2009, 10:13 PM
Don't face a long thin piece.

Don't face a piece that isn't held very deeply in the chuck. With a bit of mechanical instinct, you can look at a setup and decide if it's a bad idea.

If you DO have to face long work sticking out, use the steady as a support.

BobWarfield
10-31-2009, 10:18 PM
Glen has it right. Use the steady rest.

But even before that, make sure you get fairly close just by sawing to length. You should be within 0.1-0.2".

Best,

BW

tattoomike68
10-31-2009, 11:02 PM
If the part is short face it, if its long turn the extra off.

simple rules like that are easy. if its round it goes in the lathe if its flat and square it goes in a mill.

boslab
10-31-2009, 11:41 PM
i sort of work on 3 X diameter protruding for facing, you can go more but i found i enter the mess up zone above this with bars climbing over the top and suchlike, like to use the same roule of thumb for parting too.
i dont think i do any real precision stuff anyway, it all seems to be rip an tear these days, surface finish comparison blocks replaced with a chesegrater!
mark

Black_Moons
11-01-2009, 02:26 AM
I was using a 4 jaw, my problem wasent the material leaveing the chuck jaws, it was it actualy bending -_-; One thing I made I had to hammer back straight on my bench after a screwup (thankfuly straightness wasent a requirement)

Forrest Addy
11-01-2009, 02:31 AM
Long skinny work has to be supported. If not with a center then with a steady rest. Period.

If the work has to be faced on the end all the way to the center first see if the spindle will "swallow" it; that is slip inside the spindle so only a short bit extends beyond the jaws for facing. Otherwise a steady rest is your best friend.

Black_Moons
11-01-2009, 05:02 AM
I guess I should get my steady rest off the shelf and clean/oil it and stick it on my lathe then. Its around here.. somewhere. :)

Forrest Addy
11-01-2009, 08:13 AM
I guess I should get my steady rest off the shelf and clean/oil it and stick it on my lathe then. Its around here.. somewhere. :)

Yup. All that stuff that's painted to match your machine has a function.

Black_Moons
11-01-2009, 09:06 AM
Ah, that explains why I ended up taking off the splash guard then. Or maybe it was because it got in the way of taking off my cross slide..

beanbag
11-02-2009, 04:22 AM
Keep in mind that the angle of the cutter edge to the work affects the cutting forces. If you have a cutting edge parallel to the axis and plunge it straight in, all the force is directed radially and perpendicular to the axis (i.e. tries to bend the rod out). If the cutting edge is at an angle, the forces are shared radially and axially (partially tries to push it into the chuck).

Black_Moons
11-02-2009, 05:47 AM
ahh, so thats why facing requires much lighter cuts then turning.

gwilson
11-02-2009, 08:15 AM
You will be lucky if you haven't yet sprung your chuck jaws by now. Bending metal clamped in them is a terrible thing to do. Do you have a "How To Run a Lathe" manual?

Doozer
11-02-2009, 08:20 AM
Yes, you should always consider a 3 jaw lathe chuck as somewhat fragile, that does not grip very tight (compared to a 4 jaw).
A 6 jaw is downright delicate.

--Doozer

JMS6449
11-02-2009, 08:58 AM
To much BS just listen to the simple answer from Forest - Steadyrest.

Though even before that, use common sense.

jstinem
11-02-2009, 09:49 AM
I use one of these that made from an extra dead center:
http://www.lathemaster.com/HALFNOTCHCENTERMT.htm
It works perfectly for any thing that can have the center hole left in the end. You have to have a steady for things that can't have the hole.

Doozer
11-02-2009, 11:00 AM
JMS6449- Go over to PM and play with Don Thomas. I bet you will have lots in common.

-Doozer

Carld
11-02-2009, 11:37 AM
The answer is quite simple. If the work will fit through the spindle bore slide it in and face the end. If the work will not fit in the bore then you must use a steady rest.

camdigger
11-02-2009, 12:28 PM
The answer is quite simple. If the work will fit through the spindle bore slide it in and face the end. If the work will not fit in the bore then you must use a steady rest.

Ummm. Yes, the work needs to be supported. Rules of thumb vary as to what ratio of diameter to "stickout" is the limit - I've heard anywhere from 1 1/2 to 3 diameters is the maximum. Support can be from Steady rests or follower rests (if turning), but don't discount the center in the tailstock. It's a handy item for supporting the end of a bulky item or one without a circular crossection - like a square shaft, splined shaft, Etc....

JMS6449
11-02-2009, 01:46 PM
JMS6449- Go over to PM and play with Don Thomas. I bet you will have lots in common.

-Doozer

Some people just hate cutting to the chase!

Black_Moons
11-02-2009, 04:54 PM
camdigger:I recall theres something called a 'cats eye' or somesuch thing that allows you to use steady rests on non round things. (Basicly its just a chunk of pipe with some setscrews in it. slide over work, tighten set screws, presto, square thing now has round surface)


gwilson: I have read a few books, Not one of them told me don't face the end of long bars. And I bet no book tells me exactly how long each material could be and what depth of cut/etc I could get away with.

One of my 'bent' objects was UHMW and it was only exiting the chuck by 3 or 4 diamiters and it was 1.5" thick!

Another was 1/2" mild steel that was protrudeing maybe 20 of the smallest diamiters (about 3/8" smallest diamiter) along the part (it bent at that diamiter..), it was going fine untill I faced just a little to agressively (Ok extremely agressively) Im kinda used to fast feeds on the facing since when everythings setup my lathe often handles it nicely, even leaves good finish at higher feed rates.

Material and experiance play a GIANT roll. How can you tell someone never to bend something if they don't know how much cutting force bends things? Do you expect all HSM's to only take 0.01" DOC and widdle away at bars all day getting them to size just to 'stay safe' because they don't know what happens at 0.05" DOC? or 0.1"?

camdigger
11-02-2009, 05:35 PM
camdigger:I recall theres something called a 'cats eye' or somesuch thing that allows you to use steady rests on non round things. (Basicly its just a chunk of pipe with some setscrews in it. slide over work, tighten set screws, presto, square thing now has round surface).



IIRC, that's a catspaw. It has the same issue as the spindle bore... the material has to fit through it, then the catspaw has to fit through the steady, then the material has to run true to the lathe axis by adjustment of the catspaw screws relative to the steady, and the catspaw has to run centered on the lathe axis for accurate work.....
Sounds worse than it is in practice, I'm sure. IIRC, the steady on my 1440 will only pass +/- 3 1/2" can't tell from here at the moment, it's over 100 km away at the moment...

BTW, here's a turning I did a while ago... faced the outer end.
http://i766.photobucket.com/albums/xx301/camdigger/camtrac008s.jpg

quasi
11-02-2009, 05:44 PM
I think you mean a "cats head" ?

camdigger
11-02-2009, 08:52 PM
I think you mean a "cats head" ?

I was taught early on a cathead was sumpin' like the doohickey on the side of this winch...

http://i766.photobucket.com/albums/xx301/camdigger/Irricana2006006.jpg

J Tiers
11-02-2009, 09:24 PM
A cathead is also a gunsmith's tool which has 8 screws and a smooth area for the steady to run on. I have no picture, I gave my cathead to my father-in-law.

The screws allow an uneven or tapered part to run in the steady.


I assume the name is because the tool has "whiskers" sticking out all over it.

The shipboard cathead is a beam that carries the anchor and cable out over the bow, typically on a sail ship. Normally there are two.

The thing you show has a different name, which I won't repeat here, as it is a "tad" offensive. Although I have heard it called a cathead also....dunno why.

motorcyclemac
11-02-2009, 09:40 PM
A cathead is also a gunsmith's tool which has 8 screws and a smooth area for the steady to run on. I have no picture, I gave my cathead to my father-in-law.


The thing you show has a different name, which I won't repeat here, as it is a "tad" offensive. Although I have heard it called a cathead also....dunno why.


I use a cathead for barrels quite often.. When I turn crowns I use it.. I also have a sort of cathead that I attach to the spindle on the outboard end. It has 8 allen screws in it to align barrels thru the spindle.

J.. I nearly laughed my arse off at your comment about the .....uh...yeah....winch drum. I KNOW what you were going to call it... That is what I call them.

Cheers
Mac.

darryl
11-02-2009, 10:28 PM
I can see a project coming- a single ball bearing race with a large id, set into a steady. Then a couple different sized inserts, one to cater to the smaller diameters of shaft, and one for the larger. Set up like a cathead to grip the work.

I've made a similar thing but using two bearings and a bit of length of pipe between them. There are enough tapped holes around the pipe at both ends to center and hold the workpiece. It's good to hold up to about 3 inches diameter. I have to select the length of bolts I use so they don't extend so far out that they interfere with things.

One advantage of this one is that larger diameter, and especially irregular shaped workpieces can be securely held and centered, and the lathe used to either drive the pipe, or the workpiece via a center and lathe dog of some kind.

The single bearing model would be the most used probably, and you have the potential to make the insert cone shaped so the gripping end sticks out away from the structure to leave it out of the way moreso than the standard steady.

deltaenterprizes
11-02-2009, 10:49 PM
The cats head is also called a spyder.

Doozer
11-03-2009, 07:59 AM
I thought a spider had 8 screws and a cat head has 4 screws.
Seems right, but I might have it backwards.
Pretty sure that they are two different items.

--Doozer

JCHannum
11-03-2009, 09:37 AM
Cat head and spider are two terms for the same thing when used on a lathe. It can either be an outboard support to hold long stock passed through the headstock, or a surface for the steady rest fingers to run on when turning an odd shaped part that needs the support.

Doozer
11-03-2009, 02:00 PM
Surfing some patents, it seems a spider is most used at the left end of the lathe spindle to center a bar or a gun barrel. 4 bolts.
A cathead is used with a steady rest, and has 8 bolts.
Funny real spiders having 8 legs, a lathe spider has 4 bolts, not 8, kinda strange.
Could "cat" be short for "catch" in cathead, as in it catches the piece of stock?
I knew I saw more about catheads and spiders in a book, so I could cite a proper reference, but I have been looking in my library and can't find where I saw what I remember seeing. Hummm.
Back on topic, the first time I used a steady rest, was when I had one for an 11" Rockwell lathe and I milled the base to fit my 10" Atlas. Now I think steady rests are a great tool.

http://i72.photobucket.com/albums/i169/kooldoozer/IMG_0257.jpg

--Doozer

Evan
11-03-2009, 03:19 PM
I was taught early on a cathead was sumpin' like the doohickey on the side of this winch...




I agree. That is what I maintained as well in a thread some time ago. Strenuous efforts were made by several members to deny any connection to that device you show.

The example I gave was this one:

http://metalshopborealis.ca/pics/cathead.jpg

It was and is my contention that the catshead was the inspiration for the name of a tailstock mounted chuck because of the strong similarity in appearance and even function.

JCHannum
11-03-2009, 03:48 PM
I agree. That is what I maintained as well in a thread some time ago. Strenuous efforts were made by several members to deny any connection to that device you show.

The example I gave was this one:

http://metalshopborealis.ca/pics/cathead.jpg

It was and is my contention that the catshead was the inspiration for the name of a tailstock mounted chuck because of the strong similarity in appearance and even function.

Which, in fact, was the historic thread in which you conceded that Sir John was correct.

http://bbs.homeshopmachinist.net/showthread.php?t=23089&highlight=cathead

Evan
11-03-2009, 03:51 PM
That's impossible according to you and others. Somebody must have hacked the BBS.

The Artful Bodger
11-03-2009, 04:32 PM
I agree. That is what I maintained as well in a thread some time ago. Strenuous efforts were made by several members to deny any connection to that device you show.

The example I gave was this one:

http://metalshopborealis.ca/pics/cathead.jpg

It was and is my contention that the catshead was the inspiration for the name of a tailstock mounted chuck because of the strong similarity in appearance and even function.


Except that this particular winch does not have a catshead which was the socketed part of the winch or capstain into which the bars were inserted to give leverage to turn the device.

I would be more sympathetic to your theory regarding the name being given to tailstock mounted chucks if you were to show early (?) lathes with a 'catshead' to stop the chuck rotating.

Evan
11-03-2009, 05:04 PM
The device I show is a friction cathead according to OSHA.


http://www.osha.gov/SLTC/etools/oilandgas/illustrated_glossary/cathead.html

The Artful Bodger
11-03-2009, 05:34 PM
Deleted by me.

darryl
11-03-2009, 08:39 PM
There was a cathead around here some time ago. Came with a body and four legs, drank some milk, ate some food, hasn't been seen since.