I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

"chuck" wrote in message
...
I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

If I had to do it I'd try the following:

1. Oxy cut the circle oversize.
2. Drill & bore the 1" hole in the center.
3. Mount the plate on a mandrel of some sort and turn the od to size.

I'm sure our guru's here will have lots of better ideas!

On Fri, 23 Jan 2009 03:33:35 -0800 (PST), chuck
wrote:

I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

Torch, saw, whatever, close to a circle but a bit oversize. Drill hole
in center. Bolt with a 1" bolt. Put several nuts on the bolt and line
them up. Now you have an arbor to turn plates to size.

karl

On Jan 23, 6:33*am, chuck wrote:
I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

I don't know 'best' or even good & fast, but some slow, tedious ways
to cut one on an old 10" belt-drive lathe are

Large hole saw
Trepanning tool, like a cutoff bit but ground to the curvature
Cut off the corners with a bandsaw
Rough it out with a torch or plasma.

I saw the corners and then round the blank because the hole saw and
trepanning tool are likely to jam, and heat may harden the cut line.
YMMV on a larger machine. The vise on my 4x6" bandsaw won't hold large
squares securely at an angle either horizontally or vertically so I C-
clamp them flat on the table.

After sawing the corners you could rough quite close to the line by
clamping the drilled blank(s) upright in a mill vise on a rod or bolt
shank that rests on the vise jaws. Mill off the top, loosen and rotate
a little, mill off the next corner, etc, all by eye without
measurement. Cut crosswise, chips flying toward the column, otherwise
the blanks may shift. If you rough to within ~1/8" then the light cuts
necessary when the work is on a mandrel or stub arbor won't take too
long. I've had the best luck and fewest jams with a narrow bit such as
a TPx insert or the HSS equivalent, mounted point-in like a threading
tool. It's much easier if you can drill extra holes and bolt the blank
to a face plate.

Jim Wilkins
amateur machinist

--Find a pal with a mill?

--
"Steamboat Ed" Haas : Do us a favor and rescue
Hacking the Trailing Edge! : a doggie or three...
www.nmpproducts.com
---Decks a-wash in a sea of words---

chuck wrote:

I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.


It all depends on what equipment you have to work with. With a good
lathe I would just chuck the piece using stops in a four jaw chuck and
cut them round, half a side at a time, then drill and bore your hole.

By stops I mean hex bolts set into tee slots of the chuck the heights
of each bolt set so that half the thickness of the plate extends beyond
the jaws of the chuck so you can cut it. Remove the jaws and cut the
tops of the bolts so they are even and you can bank each plate against
them. Put the jaws back and chuck up the piece using a scale to get the
piece centered in the chuck by measuring from the outside of the chuck
to the four sides.

With a solid lathe you will have no trouble with the interruped cut. If
you lathe is not that sturdy, waterjet would be another way to go. Steel
suppliers will usually cut the plates for you at a nominal charge if
they are supplying the material. Cutting through burned out material
can be a minor problem. Grind off the slag before you put it into your
lathe.


John

"chuck" wrote in message
...
I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

I bought a bunch of 5" x 1/4" disks and I think they have them up to 3/8".
If you need the full 1/2", could you bond two of the 1/4" together? Sure
would save a lot of time!

On Jan 23, 8:12*pm, "Buerste" wrote:
"chuck" wrote in message

...

I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

I bought a bunch of 5" x 1/4" disks and I think they have them up to 3/8"..
If you need the full 1/2", could you bond two of the 1/4" together? *Sure
would save a lot of time!

Thanks all for your ideas. I have a SB10K lathe, I don't think it
could handle interupted cuts. I'll use a torch to rough cut then the
lathe.

"chuck" wrote in message
...
On Jan 23, 8:12 pm, "Buerste" wrote:
"chuck" wrote in message

...

I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

I bought a bunch of 5" x 1/4" disks and I think they have them up to 3/8".
If you need the full 1/2", could you bond two of the 1/4" together? Sure
would save a lot of time!

Thanks all for your ideas. I have a SB10K lathe, I don't think it
could handle interupted cuts. I'll use a torch to rough cut then the
lathe.
================================

O/A can leave very very hard edges/slag that is tough on tooling.

My buddy made thousands of circles about this size, but from 1/8 material.
Cut in squares, drilled, mounted on an arbor with staggered corners, and
let'er rip -- metal flying all over the place.

Mebbe you can do the first two steps, and bring them to someone with a
heftier lathe (15"), to do the rough turning, which goes pretty quick. May
not cost much. Depends on how many you have to do.

They make rigid hole saws (even carbide) that will do this, as well. Will
likely need a bridgeport or equiv, can finish on a lathe.
--

Mr. PV'd

Mae West (yer fav Congressman) to the Gangster (yer fav Lobbyist):
Hey, Big Boy, is that a wad (of cash) in yer pocket, or are you just
glad to see me??

On Jan 23, 9:15*pm, chuck wrote:

Thanks all for your ideas. I have a SB10K lathe, I don't think it
could handle interupted cuts. I'll use a torch to rough cut then the
lathe.

My 10L handles interrupted cuts well. The only real problem is slip
when driving the disk from a small diameter shaft.

jw

Thanks all for your ideas. I have a SB10K lathe, I don't think it
could handle interupted cuts. I'll use a torch to rough cut then the
lathe.

I do this often. first, grind off any slag. In the lathe, I've had
much better luck with an extremely deep cut and a very light hand
feed. You get almost no interuption this way. If you use HSS it will
dull quickly. You can either resharp often or use brazed carbide.

Karl

On Jan 23, 6:33*am, chuck wrote:
I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

Chuck a 5-1/2" hole saw in your lathe. Hold the plate against a pad
center in the tailstock ram. Feed the tailstock ram to cut out a
disk.

Chuck a disk and bore out the center to 1".

Mount one or multiple disks on an arbor and turn the OD to 5".

No bandsawing. No water jet or plasma cutting. No torch cutting. No
interrupted cuts. All done on the lathe, as you asked.

John Martin

chuck wrote:
On Jan 23, 8:12 pm, "Buerste" wrote:

"chuck" wrote in message

...


I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

I bought a bunch of 5" x 1/4" disks and I think they have them up to 3/8".
If you need the full 1/2", could you bond two of the 1/4" together? Sure
would save a lot of time!


Thanks all for your ideas. I have a SB10K lathe, I don't think it
could handle interupted cuts. I'll use a torch to rough cut then the
lathe.


The other thing you could do is have your metal supplier cut them off a
5 inch round bar. Then just face and bore them.

John

On Sat, 24 Jan 2009 17:37:45 -0500, john
wrote:



chuck wrote:
On Jan 23, 8:12 pm, "Buerste" wrote:

"chuck" wrote in message

...


I need to cut 5" circles out of 1/2" steel square plate. I will have
to bore a 1" hole in the center.
Whats the best way to do this with a lathe.

I bought a bunch of 5" x 1/4" disks and I think they have them up to 3/8".
If you need the full 1/2", could you bond two of the 1/4" together? Sure
would save a lot of time!


Thanks all for your ideas. I have a SB10K lathe, I don't think it
could handle interupted cuts. I'll use a torch to rough cut then the
lathe.


The other thing you could do is have your metal supplier cut them off a
5 inch round bar. Then just face and bore them.

John


that is a much easier lateral thinking approach.
bandsaws these days do pretty accurate slicing work.
Stealth Pilot