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View Full Version : Parting Off Large Diameter stock - 6"



bill4227
03-24-2011, 03:40 PM
I have a piece of 6" diameter brass round that I need to part off about 0.5" to make a smokebox front on a locomotive. The piece that I have is about 1.25" and will fit in my chuck.

What is the best way to slice thru it?

Bill

Black Forest
03-24-2011, 04:06 PM
I would use a bandsaw!

form_change
03-24-2011, 04:07 PM
Personally for that size I'd find someone with a bandsaw. A parting tool sticking out 76mm/ 3" is not going to be a pretty thing.
You may know this stuff already but if you really want to part it on your lathe I'd suggest plunging in for say 3/4" backing out, moving along say 20 to 40 thou, plunging in again. Alternate like that so that the tool does not bind up in the slot. Use the deepest parting blade you can find (stiffer). If you have a good slow power cross feed think about using that rather than feeding my hand. Make sure your parting blade is sharp and set on centre (never above) or slightly below. The tip of the blade will need to be square other wise it may tend to pull the cut to one side. Check the alignment of the parting tool to the lathe axis. It must be perpendicular. Easiest way to do that is make it parallel to the front surface of a chuck or face plate.

Michael

Jaakko Fagerlund
03-24-2011, 04:17 PM
It is either bandsaw or just reduce the whole thing to chips if you really want to have that part made from that exact piece.

brian Rupnow
03-24-2011, 04:19 PM
Hate to suggest something wastefull, but if it was me I'd set it up in the chuck, tap it back into good firm contact with the 3 chuck jaws, and face it down to the required thickness.

madwilliamflint
03-24-2011, 04:20 PM
Am I gonna get shot for suggesting turning the lathe on reverse and holding a hacksaw to it?

- n00b

airsmith282
03-24-2011, 04:42 PM
something that big id band saw it for sure

Fasttrack
03-24-2011, 04:48 PM
Am I gonna get shot for suggesting turning the lathe on reverse and holding a hacksaw to it?

- n00b

I'll admit I did that a time or two before I got my bandsaw. However, I would never recommend it to anyone.


If you don't have a bandsaw, try running it in the lathe and put a 1" deep groove in it using your parting tool. Then shut the machine off and hack saw the rest by hand. It will take you a little while, but it can be done. Just watch the saw and keep it in the groove so you cut straight. Make sure you have a coarse blade, too.

Dr Stan
03-24-2011, 05:03 PM
A vertical bandsaw is also my recommendation. Lay out a line all away around the piece and hold it with a C clamp, bar clamp, or other means to keep it from spinning on you.

To me 3" of parting blade sticking out is just asking for trouble.

BTW, if you're going to use the hacksaw with the lathe running backwards "trick", just make sure you're wearing an unrestrained tie, gloves, you have on long shirt sleeves that are rolled down and unbuttoned, and your shirt tail is hanging out. :rolleyes:

(I do hope you know I'm being very sarcastic).

jack3140
03-24-2011, 05:37 PM
Am I gonna get shot for suggesting turning the lathe on reverse and holding a hacksaw to it?

- n00b
hack saws dont cut very well that way i fear ps i would,nt shoot you for that lol

Mcgyver
03-24-2011, 05:50 PM
hack saws dont cut very well that way i fear ps i would,nt shoot you for that lol

right you are, it just passes more material over al already full tooth.

This is quick work for a horizontal bandsaw. Given the width, you can really 'dig a trench' so you'd be parting in one cut.....you are a better machinist than i if you part off 6" material in one cut :eek:

David Powell
03-24-2011, 06:30 PM
The late Bob Bastow ( teenut) ran a machine shop in southern Ontario. He had a very good apprentice. One day he came in from an errand to find no one in sight, the manual lathe happily parting off a piece of aluminium about 6" dia. The apprentice was confident enough that he had gone to the bathroom leaving the job running. Even Bob was a little surprised! Regards David Powell.

Bob Fisher
03-24-2011, 06:43 PM
I would order a 6in square of 1/2 in plate from McMaster Carr and save the other chunk for something more worthy. Bob Fisher.

lynnl
03-24-2011, 07:17 PM
One of my first parting off efforts was on a piece of steel about 6" dia. ...I didn't know any better at the time. Eventually I got it done, by using the hacksaw through the last inch or so, but it was not a happy experience.

I guess that's why I hate parting off to this day. :D

sasquatch
03-24-2011, 07:49 PM
Geez, a 6inch diameter bar of brass, gotta be worth a few bucks to purchase that by the foot. Any price costs on that per ft. or inch????

RussZHC
03-24-2011, 08:11 PM
...just throwing the idea out there...could one make up a sort of guillotine frame and use one of those carbide grit rod saws?

Not just for this but large parting in general...I know, I know, musing.

2ManyHobbies
03-24-2011, 08:16 PM
It is only brass. Get a stick of wax and toss it up on the table saw in some V-blocks. Rotate and push back through as needed.

Dr Stan
03-24-2011, 08:17 PM
I have a piece of 6" diameter brass round that I need to part off about 0.5" to make a smokebox front on a locomotive. The piece that I have is about 1.25" and will fit in my chuck.Bill

Is this a functional or display locomotive? If the latter I like Bob Fisher's idea. Just use some CRS 1/2" plate and have it brass or chrome plated.

Boucher
03-24-2011, 08:45 PM
I recently parted off some 5 9/16 OD pipe with about 3/8 wall. I think that I could have made it to a depth of 1/2" but I sure would not have wanted to go much more than that. I used a Kennametal insert tool that will cut a little more than an inch. This was done to get away from the torch cut zone. Parting was easier than facing thru the rough cut heat affected zone. Getting the speed and feed right was kind of interesting. It was obvious when you were right. There was a significant difference in dark cutting oil brushed on and the flood coolant with water soluable oil. The dark oil was much better. A good horizontal band saw is now near the top of the want list.

sasquatch
03-24-2011, 08:52 PM
I agree the bandsaw would be my choice.

Carld
03-24-2011, 08:54 PM
David Powell, that novice apprentice was inexperienced, fearless, and foolish. No one that has done a lot of parting would ever do something like that. He was extremely lucky to not have the parting tool hang up or break with the cross feed still going while he was in the bathroom. Bob Bastow should have chewed him up one side and down the other for leaving a lathe running in a cut while he wandered off the the bath room. Not to mention trying to part off something that big and aluminum at that. Aluminum likes to wad up in a parting groove.

bob ward
03-24-2011, 09:29 PM
I think I'd be trying to find a small piece of 1/2" brass plate before I tackled parting and/or sawing that 6" round. Realistically you would consume 3/4" of your round to obtain a finished 1/2" thickness, but starting with 1/2" plate you could at least jigsaw it roughly to shape and have the corners to use for something else.

lakeside53
03-24-2011, 09:30 PM
I do it both ways....

Part as far as reasonable, then with the work still in the chuck, use my handy portable bandsaw for the rest. The parted groove guides the bandsaw blade.

SGW
03-24-2011, 09:57 PM
I tend to agree that the only sane way to cut something that big is with a bandsaw, but I like Bob Ward's solution: get a square piece of brass plate the correct thickness and save the 6" round for something else.

Of course, a 6" square of 353 brass from McMaster-Carr is $148.99, and you've already got the 6" round.

If you have a milling machine and a rotary table and you can stand to have a few tapped holes in your piece of brass, here's an idea for you. Attach the 6" round to a flat plate with flathead screws going through the plate into tapped holes in the 6" round. Clamp the plate to your rotary table so the 6" round is centered. Set up a slitting saw in the mill and, using the mill table to advance the feed, rotate the 6" round to cut a groove at the proper height to give you your 1/2" thick disk. The diameter of the slitting saw will determine your maximum depth of cut. You most likely won't be able to get all the way through, but it would be a start.

David Powell
03-24-2011, 10:16 PM
Even Bob Bastow was a little surprised. I certainly would not try that on any of my machines. It was worrisome enough to be running two lathes simultaneously commercially, even though they were facing each other. It is so easy to get involved with a problem or adjustment with one and then have the other get into problems through neglect or bad timing. I was lucky, never did any damage to the machines, occasionally ruined a part I was trying to make.There is a lot of difference between being a Home Shop Machinist and an employee of a dying and desperate firm trying to save the firm----- at home you never get to leave.!!! Regards David Powell.

darryl
03-24-2011, 10:37 PM
Table saw. Put a fresh skilsaw blade on it, one of the cheap ones. Build a box on top of some scrap plywood to nest the brass blank into, and use a clamp across the diameter at center height of the blank. Run this assembly through the blade, taking a decent bite but not too much at a time. Turn the blank after every pass until you get all around, then increase the blade height and go again. When you reach the limit of the height adjustment, you'll probably have an inch or a bit more left to cut with a hacksaw.

It will work with a larger blade, but they are more expensive, and you run the risk of cutting too far towards the center, in which case the clamping could start to pinch the blade. You don't want that to happen. Leave a good inch or so diameter in the center to cut by hand.

I cut a good sized chunk of cast iron on my table saw once. Used a carbide skilsaw blade, and limited myself to 30 seconds of cutting with at least 5 minutes of cooldown between passes.

firbikrhd1
03-25-2011, 10:39 AM
If I had a chuck big enough to accept a 6" diameter piece I would clamp it in my power hacksaw and use that. Power hacksaws cut straight and have about as much kerf as a parting blade.

roundrocktom
03-25-2011, 11:04 AM
Even Bob Bastow was a little surprised. I certainly would not try that on any of my machines. It was worrisome enough to be running two lathes simultaneously commercially, even though they were facing each other.

I'll run the lathe, mill, and drill press. The mill has a power feed, and will trip.

Lathe I have to keep an eye on, but with a fine feed, easy to watch.

Drill Press is hand operation only.

Parting tool... I don't even like parting 1" stock.... 1/2" sticking out there spooks me... I've done some foolish stuff, but need a nice big metal bandsaw with a sled to keep from doing something stupid when it doesn't fit into the 4" x 6" small band saw. :) (I have some 8" diameter 2024 that I need to cut... job keeps getting put off!)

Carld
03-25-2011, 11:12 AM
Yep, I have had a few cutoff blades snap in the groove and you sure find out how fast your reflexes are and how fast you can move.:eek: I can tell you I HATE using the lantern style parting tools, they can hang and shift faster than you can even see it happen.

Having the blade hang out more than one inch makes me real cautious and especially cutting to the center.

Frank Ford
03-25-2011, 11:16 AM
I made up a little sled for cutting large rounds on my old Delta 14" vertical band saw:

http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/sixinchbandsaw01.jpg

I had to remove the upper blade guide to manage a full 6" thick cut because of the thickness of the sled. (I'll have to mill out the center some time, I guess.)

Here it is in action cutting a 1/2" slice from a 1-3/8" long piece of steel, with a lead shot bag to stabilize the sled.

http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/sixinchbandsaw05.jpg

I use a gravity powered feed:

http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/bandsawfeed02.jpg

All about that here: http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/bandsawfeed.html

Cut went slowly and safely, and came out really nice:


http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/sixinchbandsaw07.jpg

rklopp
03-25-2011, 11:20 AM
Nobody asked the OP how big his lathe was. If he's got a 24" Monarch, Sydney, American, etc., a 6" parting cut is no problem with the proper tool. So, OP, what size is your lathe?

firbikrhd1
03-25-2011, 11:27 AM
I made up a little sled for cutting large rounds on my old Delta 14" vertical band saw:

http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/sixinchbandsaw01.jpg

I had to remove the upper blade guide to manage a full 6" thick cut because of the thickness of the sled. (I'll have to mill out the center some time, I guess.)

Here it is in action cutting a 1/2" slice from a 1-3/8" long piece of steel, with a lead shot bag to stabilize the sled.

http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/sixinchbandsaw05.jpg

I use a gravity powered feed:

http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/bandsawfeed02.jpg

All about that here: http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/bandsawfeed.html

Cut went slowly and safely, and came out really nice:


http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/sixinchbandsaw07.jpg

That is awesome! I have that same saw and it never occurred to me to do anything like that. I'll file your idea away for future use. Thanks!
Steve

Carld
03-25-2011, 11:31 AM
rklopp, it's not the size of the lathe but the length of your tool :eek: .

Opps, what I mean is you could have a 48" throw lathe but having the blade of a cutoff tool sticking out 3" is a serious issue and subject to failure no matter what the throw is of the lathe.

Dr Stan
03-25-2011, 11:54 AM
Frank,

That's a very nice design/set up. You should add it to the Shop Made Tools thread.

Stan

madwilliamflint
03-25-2011, 12:17 PM
Frank,

That's a very nice design/set up. You should add it to the Shop Made Tools thread.

Stan

Seconded.

Very nice indeed. That's an awfully pretty cut.

Al Messer
03-25-2011, 12:22 PM
rklopp, it's not the size of the lathe but the length of your tool :eek: .

Opps, what I mean is you could have a 48" throw lathe but having the blade of a cutoff tool sticking out 3" is a serious issue and subject to failure no matter what the throw is of the lathe.


Well, I don't pull the blade out to its full length at first. I extend its length in increments of about 1/2 inch at a time. Yeah, I know it takes longer, but I'm in no hurry at my age!

Al

philbur
03-25-2011, 12:52 PM
It depends on the depth of the tool, everything is scaleable, that's why big machine tools can produce chips the size of your toolpost. Rigid machine tools require rigid tools.

Phil:)


rklopp, it's not the size of the lathe but the length of your tool :eek: .

Opps, what I mean is you could have a 48" throw lathe but having the blade of a cutoff tool sticking out 3" is a serious issue and subject to failure no matter what the throw is of the lathe.

Paul Alciatore
03-25-2011, 01:31 PM
If you are going to try parting it in the lathe or at least starting the cut that way, I would suggest that you get a wide parting blade, perhaps 1/8" or wider.

I haven't done this and it may not be of any value, but I would experiment with the cutoff blade. If you sharpen one end square and the other end with a symmetric Vee point, it may be easier to make the cut. Start with the Vee and when it reaches full depth, reverse the blade and use the square end to remove the sides or the Vee notch. Then repeat until the cut is complete. As I said, I haven't tried this, but it sounds like a good idea to me. Check for sharpness at every change: yea, I know it is brass, but check anyway.

The use of a hack saw in the lathe has been questioned because you would be using the same teeth and they would quickly clog. If I were doing this I would move the saw back and forth as you would in manual sawing. This would certainly help clear the chips. Oh, and use a long hack saw blade to facilitate this.

Paul Alciatore
03-25-2011, 01:37 PM
This is super nice. Why haven't you shown it off before? The gravity feed is the crowning touch.

I wonder if I could make one for a 4X6. I would probably need a better table first.



I made up a little sled for cutting large rounds on my old Delta 14" vertical band saw:

http://www.frets.com/HomeShopTech/Tooling/BandSawFeed/sixinchbandsaw01.jpg

I had to remove .....

Cheeseking
03-25-2011, 01:53 PM
Frank that's a nice little fixture. I just so happen to have a need to cut 1" thick slices of 7-1/8" dia aluminum timing pulley stock from an 8" long pc. I need 4 pc's and was debating how to cut them. Parting on the lathe crossed my mind for about 2 seconds and nixed. I was thinking about an inverted pc of 3-4" angle iron welded to a flat plate and a large hose clamp or 2.

Mcgyver
03-25-2011, 04:29 PM
here's one way to do it in the horizontal bandsaw, just drill & tap and bolt to a tool makers block, no special tooling required

http://i785.photobucket.com/albums/yy132/michael01000/DSC_8172-large.jpg