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What am I doing wrong

azshadeguy

Active Member
Active Member
#1
Okay I know that this little Craftsman Lathe is to small but still.
I have a 3/4 thick x 3-1/2 round disc.
I put the disc in a 4 jaw chuck got it centered and turn it on.The disc is a36 steel
All I had was one 1/4 inch tool steel I shaped it according to something I read.
Any way all its doing is grinding the cutter. Not even scoring the disc.
What am I doing wrong?
 

francist

Active User
H-M Supporter-Premium
#2
A picture would really help here, there are many variables that come into play especially for a first-timer. A few that you could check right away though:

-you say you ground your own cutter. Make sure it is indeed sharp and that you have it set up in the holder so that there is clearance underneath the cutting edge. No clearance there = no cutting there.
- are you turning or facing? I am guessing facing, but not sure. At any rate, is the mill scale still present on the surface you are trying to cut? If so, you need a sharp tool and agressive depth of cut to get through that. It can be challenging, especially for a small machine, and it does make short work of a sharp tool if you just peck at it.
- is your cutter on the centre height of the spindle? Put a centre in your tailstock, bring the cutter up to that, and make sure the two points are lined up. If not, adjust. There are other more fussy ways to get closer, but for starters that should get you into the ballpark of making some form of cut.

-frank
 

mikey

Active User
H-M Supporter-Premium
#6
I agree that a flame cut disc can be quite hard at the edges. A turning cut at the edge to get under the top layer might do it, or you can anneal the entire disc to soften it before cutting. It should face okay, though, at least past the edge.
 

markba633csi

Active Member
Active Member
#7
Is that a good quality tool you are using? Also with a large workpiece the surface feet per minute will be high at the outer edge so use a slow enough
spindle speed and some cutting oil- carbide tools are great for that flame-cut stuff
Mark S.
 

682bear

Active Member
Active Member
#8
What spindle speed are you turning at? A rough surface like that should be turned very slowly until it cleans up... also, being torch cut, it may be a lot harder on the edge than in the center.

It may help to slow it down and, starting at the edge, feed toward the center until it cleans up, back out, move to the left .010 thousandths, then feed back toward the center... repeat.

In other words, rather than feeding across the cut edge, feed into the cut edge... being sure not to cut past your finish diameter of course. When you get the edge cleaned up, it should cut easier.

Also, I can't tell for sure in the pics, but it looks like you may have too much relief below your cutting edge, making the edge weak. For an interrupted cut, you need just enough relief to prevent 'rubbing' the workpiece.

-Bear
 

Hawkeye

Active User
H-M Supporter-Premium
#9
I have one such disk that a file won't cut. It's either all hardened, or, as mentioned above, the flame cutting may have hardened the outer layer. Have you tried scratching it with a file?
 

tq60

Active Member
Active Member
#10
Get the largest brazed carbide that cuts on the left side that you can hold in your tool post.

Adjust so tip of tool is as close as possible to tool post so it has less leverage to it.

Put in back gear and slowest speed and start the cut on the face.

Depth of cut should be such that it is consistent and not interrupted if at all possible.

Use power feed set to smallest available, you may need to manually feed it if the motor stalls.

If motor stalls it may chip the cutter.

Cut until close to chuck then flip it over and do other side.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 

francist

Active User
H-M Supporter-Premium
#11
Paul, you're getting lots of pointers not the least of which is that burned (torch cut) edge. They can be real bothers to get through. Before you even think about taking very heavy cuts though I would take a close look at your compound slide. It's extended quite far out to end of its travel. This is very precarious, and on the 6" lathe like you have the compound slide is not robust to say the least. You really run the risk of breaking it with heavy and/or interrupted cuts when it is extended that far out. Please don't let it to end up like this one...

image.jpeg

-frank
 

GK1918

Active User
Active Member
#12
Yes nasty; I would throw the thing in a charcol pit. the ole Henry Ford Kingsford stuff.
go home tomorrow will be a different day. Then what I do is not chuck it but drive it
between centers with two way tape anything. cover lathe, turn lathe on and lightly
grind the torch cuts, then proceed to turn down. And I say cover lathe beds. I hate any
kind of grinding on any of my lathes but sometimes ya have to ..damp rags work too.
 

neshkoro

H-M Supporter - Premium Content
H-M Supporter-Premium
#13
I agree. The compound is cranked way to much to the left. Crank it back until the tool holder is supported by the gibs/ ways. Carbide is the way to go with that flame cut material. At least until you get past the hardened part. Good luck.


Sent from my iPhone using Tapatalk
 

Wreck™Wreck

Active User
H-M Supporter-Premium
#14
I hate to ask but is the spindle turning in the correct direction for the tool? Last year I set up a lathe job for someone else to run, ran a few while he watched (1400 total parts) then went to another machine.
10-20 minutes go by and he comes over and tells me that the insert broke, I have a look and can't see any reason why, checked the offsets and they were fine so finally asked him to show me what he did and sure enough he turned the spindle on in the wrong direction. I managed to stop it before he hit the start button.

Another guy I know from the local Tavern asked me about his wood lathe problem, said it wouldn't cut, asked him which direction it was turning, he spun a finger in the air, wrong direction of course so I told him it wouldn't cut that way but is surely safer (-:

Turned this lovely beast this past Friday, 500 FPM with a CNMG insert without a problem.
24 1/2" OD at 80 Rpms. .008" IPR feed.
 
Last edited:

azshadeguy

Active Member
Active Member
#15
Disc appears to be torch cut. If so you may need to grind to the heat affects hard edge before attempting to turn.
Good luck.
Dave
.
Yes they are torch cut I will grind them

Is that a good quality tool you are using? Also with a large workpiece the surface feet per minute will be high at the outer edge so use a slow enough
spindle speed and some cutting oil- carbide tools are great for that flame-cut stuff
Mark S.
These are cheap tools off ebay
http://www.ebay.com/itm/5pc-3-16-x-...e=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649
where do you get carbide in a 3/16 cutter?
 

azshadeguy

Active Member
Active Member
#16
What spindle speed are you turning at? A rough surface like that should be turned very slowly until it cleans up... also, being torch cut, it may be a lot harder on the edge than in the center.

It may help to slow it down and, starting at the edge, feed toward the center until it cleans up, back out, move to the left .010 thousandths, then feed back toward the center... repeat.

In other words, rather than feeding across the cut edge, feed into the cut edge... being sure not to cut past your finish diameter of course. When you get the edge cleaned up, it should cut easier.

Also, I can't tell for sure in the pics, but it looks like you may have too much relief below your cutting edge, making the edge weak. For an interrupted cut, you need just enough relief to prevent 'rubbing' the workpiece.

-Bear
I will re grind the tool and slow it down

I agree. The compound is cranked way to much to the left. Crank it back until the tool holder is supported by the gibs/ ways. Carbide is the way to go with that flame cut material. At least until you get past the hardened part. Good luck.
I will pull it in
 

azshadeguy

Active Member
Active Member
#17
I hate to ask but is the spindle turning in the correct direction for the tool? Last year I set up a lathe job for someone else to run, ran a few while he watched (1400 total parts) then went to another machine.
10-20 minutes go by and he comes over and tells me that the insert broke, I have a look and can't see any reason why, checked the offsets and they were fine so finally asked him to show me what he did and sure enough he turned the spindle on in the wrong direction. I managed to stop it before he hit the start button.

Another guy I know from the local Tavern asked me about his wood lathe problem, said it wouldn't cut, asked him which direction it was turning, he spun a finger in the air, wrong direction of course so I told him it wouldn't cut that way but is surely safer (-:
Which way should it be turning? so looking at the part it is going counterclockwise
 

neshkoro

H-M Supporter - Premium Content
H-M Supporter-Premium
#18
If you have a mill you could cut down a 3/8" brazen carbide tool.


Sent from my iPhone using Tapatalk
 

Wreck™Wreck

Active User
H-M Supporter-Premium
#20
Which way should it be turning? so looking at the part it is going counterclockwise
The surface of the part moves towards the cutting side of the tool, CCW when facing the spindle when the cutting face of the tool is facing "up" on the operator side of the part, otherwise known as the front.

It is entirely possible that the tool that you ground is dragging a non cutting surface on the work, this may be caused by the cutting edge being well above the centerline of the spindle. Place a center in the tailstock and run the tool tip to the point of the center, if it is well above the center point this is your problem. Otherwise examine the tool closely as the point of contact with the work will leave a mark on it revealing the problem.
 

Silverbullet

Active Member
Active Member
#21
Well newbie , your learning start watching some YouTube's Mr Pete Tubalcain . Or barrow some shop teaching books and start reading about lathe tool cutters and shaping and sharpening of them. Carbide lathe bits come brazed on strong steel support to fit holders . Insert tools use carbide tips . With many steels when torch cut they harden and some need annealing. I had a job making hold downs for a planer for a shop I worked in . I had a lathe and mill in my garage and a bandsaw to cut stock. The company ordered the steel when I got it it was so hard even grinding was tuff. They sent it back after annealing the steel worked beautifully. I would bet about 1/4" will need to be turned before it's past the hardest edge. You can anneal it yourself usually by heating up in a coal fire then just leave it till all the coals and steel are room temperature. It's kind of a big piece to practise with but we use what we have. Find some aluminum to practise tool sharpening and making. Different metals at times need different angles and shapes.
Good luck and keep turning
 

francist

Active User
H-M Supporter-Premium
#23
If you have a mill you could cut down a 3/8" brazen carbide tool.


Sent from my iPhone using Tapatalk
You can also use up to a 3/8" tool bit directly in the lantern post bypassing the smaller tool holder altogether. Would probably need a shim (another tool bit, or piece of key stock) to bring it up to height, but it can be done and makes for a pretty rigid setup. May not be useful in the O.P. application though as I'm thinking he will need the reach of a tool holder to get to the part. On a smaller diameter though it should be do-able.

-frank
 

ericc

Active User
Active Member
#24
If a file can cut that torch slag, the lathe should be able to kind of cut it. I turned a 4" diameter torch cutout on my Craftsman AA 109 lathe. It was good and hard, and until it got below the torch cut, it was throwing sparks. The belt was loosened so the spindle wouldn't get harmed. The tool had to be sharpened three times, but HSS is cheap. In this case, I just used a broken drill bit, and worked it hard, so it was free. Finally, it was done in back gear with oil, so slow down.
 

MachinistDroid

Swarf
Registered Member
#25
Okay I know that this little Craftsman Lathe is to small but still.
I have a 3/4 thick x 3-1/2 round disc.
I put the disc in a 4 jaw chuck got it centered and turn it on.The disc is a36 steel
All I had was one 1/4 inch tool steel I shaped it according to something I read.
Any way all its doing is grinding the cutter. Not even scoring the disc.
What am I doing wrong?
 

MachinistDroid

Swarf
Registered Member
#26
Sounds like your SFM might be too fast. A36 is pretty soft so it cuts easier at higher RPMs but using a high speed steel tool will limit you. After you get your tool reground try around 25-50max SFM. That's about 25-50 RPMs at 4" diameter. Sounds slow but HSS tools were named "high speed" when most tools were high carbon steel. Some M42 cobalt or carbide will get you up there. (3.82*SFM)/diameter=RPM . RPM depends on the material AND the cutting tool material.
 

mark_f

Global Moderator
Staff member
H-M Supporter-Premium
#27
I got a 8 inch diameter X 2 inch thick steel slug to make a steady rest. It was torch cut and would not cut. I took it to the belt sander and ground most of the torch cut off. I then had to use carbide cutter and run SLOW in back gear and take light cuts to get it to the softer area past the torch cut. Once I had cut about 1/4" off the diameter, it cut fine. Torch cuts are herd to machine.
 

Glenn Brooks

H-M Supporter - Premium Content
H-M Supporter-Premium
#28
Mark, yep, you hit the nail on the head. Flame cut steel hardens up sometimes to the consistency almost of diamond. I ruined a complete set of carbide and HSS 1/2" lathe bits trying to turn one flame cut 6" disk round, earlier this year. Finally figured out the grinding part and easy steven thereon in!

I suppose you could anneal the other parts, if you have a lot of them. I never tried anealing flame cut material, but it seems like it would help - if you anticipate a lot of grinding . Maybe comeone else will comment if this's a good idea or not.

Glad you got it solved.

Glenn
 

GoceKU

Active Member
Active Member
#29
On flame cut steel i usually take the first deep cut to get underneath the hard part fast, my lathe has 11KW motor so i can take 6mm deep cut without the lathe changing sound.
 

Highsider

Active Member
Active Member
#30
I see the disk has been flame cut. To turn the flame cut portion, you must use a depth of cut that will get below the cutting slag on the first pass or it will wipe the tip off your cutting tool.