Lathe broaching a keyslot

[vtcnc]

There is this option as well:

Punch Broaching

 

[stomp10]

vtcnc,
Awesome! I've been trying to work out a way to do octagon cuts on the lathe in my head.
This is def a possibility.
Thanks for sharing that!

And thinking about other possibilities.... WooHoo!

 

[Cobra]

if it's any help, this link shows the broaching of some pulleys for a project.
The holder is from O1 steel and the cutting tool is ground from a broken endmill.

Tool Post Grinder

I have been building some small engine models and particularly when doing the pistons and cylinders thought it would be great to have a tool post grinder. Well, I didn't like the price for one so decided that it would make a good project. Using one of the Wrokshop series of books on spindles...

www.hobby-machinist.com

 

[stomp10]

Great write up, Cobra. You do some nice work!
In your shots it looks like that broach face is 90 deg to the cut with a little bit of relief ground on the contact face? Is there a rule of thumb for grinding these?
I have ground mine at about 7 deg. I haven't yet made the cut. Maybe later this afternoon if I have time.
I hope it works as well as yours did....
I also have only about an hour a day most days to devote to my hobby, so my learning process is pretty slow at this time....

 

[Cobra]

Great write up, Cobra. You do some nice work!
In your shots it looks like that broach face is 90 deg to the cut with a little bit of relief ground on the contact face? Is there a rule of thumb for grinding these?
I have ground mine at about 7 deg. I haven't yet made the cut. Maybe later this afternoon if I have time.
I hope it works as well as yours did....
I also have only about an hour a day most days to devote to my hobby, so my learning process is pretty slow at this time....

Hi Stomp10.
I don't know if there is a proper rule for the relief but I ground the endmill shank to 5 degree relief on both the face and the sides of the tool.
As I said, it worked OK if you take LITTLE bites. The first try just bounced off the pulley! Once I reduced the bite to about a thou or two, it went much better. The tool is ground to give a finished 0.125 keyway from the initial set up. I didn't want to attempt to re-set the height up and down to get the finished size on the keyway.
If I can provide any more help, just give me a PM. I am certainly no expert but would help where I can.
Jim

 

[stomp10]

Thank you Jim, I really appreciate that.

This slotting project worked out really good in the end.
Got the tool ground, set up in the lathe, set a first depth of cut, ran the saddle into the cut and got scrapings from 2 sides of the arc.
So far so good. Took a few more cuts and the cutter never seemed to get past the arc. Wanting a result i advanced it to what I knew would be too deep of a cut and put some torque on the saddle wheel. Discovered all kinds of places from the saddle to the toolpost where movement is evident.
Gonna have to run them all down eventually.
Right now I need a slot, and sure glad I used tool steel for this. I went caveman on the rest of the cut. I cant see HSS surviving what I just did to that poor cutter. But now I have a straight, tight slot in my pulley with no slop. And it still slides on the shaft. Got the motor mounted and running again in no time at all.


Totally thrilled today!
Thank you everyone for sharing!
Brad

 

[gwelo1962]

A friend of mine has done a bit of this. His advice was if your lathe is small/light(9"SB) "pull" the cutter out, not pushed in towards the headstock.

 

[benmychree]

Ben, the boring bar method is actually my plan B with a single tooth cutter, as to me grinding the cutter seems an easier solution based on my meager shop. Until I get the drill\mill thing running again I am quite challenged in drilling holes for a boring bar. I am hoping to change that soon though.

I'll have to take your word on what you just said as understanding the modulus of elasticity is way outside of my wheelhouse.

Its hard to believe that HSS and tool steel have the same flexability cuz in my hand tool steel just feels harder\stiffer. I realize that isn't any reliable test, but just my feel for it.
I'll gladly soak up any shreds of wisdom anyone wants to share though.
Is there a way to briefly describe what that is for me?

There is a demonstration of it in the book "Tool Steel Simplified", they have heat treated and soft steel clamped on one end, and hang equal weights on both, and they deflect equally until the elastic limit is reached, and the soft steel takes a permanent set (bent). This is why a hard boring bar is no stiffer than a soft one.

 

[stomp10]

Thanks Ben, that actually makes sense to me now.

Gwelo, I have taken some time to eliminate as much flex in the cross slide as possible and working on finishing up mounting a nice new Bostar wedgie tool post on the crosslide. I figure this is the best way to go for the sake of ridgidity.
I'll do a donut mount for the crosslide and keep it around and use it for taper cuts.
And it is indeed an Asian cheapie lathe, I am enjoying the process of making it better than it was though, and seeing what I can make it do. (It was posted in my signature, but for some reason that isn't displaying-something else to figure out. lol)

I have another pulley I need to make, so I will def try dragging the cutter through the slot. I'm expecting much better results this go around. I'll post my results once I get that far. May be a while, life does get in the way....

I appreciate everyone's help, suggestions and explanations though... Very much so! You guys have all helped me out in many different ways!

 

[SnakeyJ]

I was keying some 1/8" internal slots on some 5/8" collars last week - I used an HSS parting tool blank, but I did break it twice keying three collars.

A friend of mine has done a bit of this. His advice was if your lathe is small/light(9"SB) "pull" the cutter out, not pushed in towards the headstock.

^ Definitely good advice here, though much easier for keying external slots. You might need to spend a little time at the grinder to make a tool for internal slotting on small bores.