Toolpost lock nut

[schor]

I've been watching John (doubleboost) for a while on youtube and finally got around to making a toolpost locknut like his.

I started out thinking I could just use a shoulder bolt I had kicking around for the handle but after using it a couple times I turned a stainless and brass handle.



Here's a vid of me making it.

[PixMan]

I might consider making one for my Dorian CA size toolpost, but concerned that I'd need a very long handle to apply the forces I've needed to hold it from rotating around.

My lathe can take some fairly heavy cuts, and I've had it move when trying to use the No.4 boring bar holder with a 1" shank 1-1/2" insert drill. When I need to use those insert drills I have a 24" adjustable wrench I use to snug the toolpost.

Have any of you that use a handle like that ever had to tighten it more using the hex?

[schor]

(08-19-2014, 09:55 PM)PixMan Wrote: I might consider making one for my Dorian CA size toolpost, but concerned that I'd need a very long handle to apply the forces I've needed to hold it from rotating around.

My lathe can take some fairly heavy cuts, and I've had it move when trying to use the No.4 boring bar holder with a 1" shank 1-1/2" insert drill. When I need to use those insert drills I have a 24" adjustable wrench I use to snug the toolpost.

Have any of you that use a handle like that ever had to tighten it more using the hex?

I purposely used the hex to be able to crank it if needed. You could also use a pipe extension.

[DaveH]

(08-19-2014, 09:55 PM)PixMan Wrote: I might consider making one for my Dorian CA size toolpost, but concerned that I'd need a very long handle to apply the forces I've needed to hold it from rotating around

You could use a thrust washer Ken, that will increase the force
Here's a pic http://www.metalworkingfun.com/showthrea...37#pid1037

DaveH

[schor]

(08-19-2014, 11:12 PM)DaveH Wrote:

(08-19-2014, 09:55 PM)PixMan Wrote: I might consider making one for my Dorian CA size toolpost, but concerned that I'd need a very long handle to apply the forces I've needed to hold it from rotating around

You could use a thrust washer Ken, that will increase the force
Here's a pic http://www.metalworkingfun.com/showthrea...37#pid1037

DaveH

That's a great idea Dave.

[PixMan]

I don't see the advantage of the thrust washers. It seems you would have just as much force, but easier to move as the bearing gives up "grip".

Educate me please. I suck at physics.

[Mayhem]

Nice little video Steve and a nicely made part as well.  I like the handle better than the shoulder bolt.  That bolt reminded me too much of the bodged repairs to my mill that the previous owners abusers made to my mill.

[stevec]

(08-20-2014, 06:30 AM)PixMan Wrote: I don't see the advantage of the thrust washers. It seems you would have just as much force, but easier to move as the bearing gives up "grip".

Educate me please. I suck at physics.

The way I see it, the clamping force is not diminished by the thrust bearing but it allows a tighter "clamping" because drag is reduced.
The clamping action is not achieved by the drag of the "nut" against the turret but the drag of the turret against the base (compound).
A ball screw although impractical in this application would be capable of even more "clamping action".
Admittedly one couldn't build a ball screw & nut of a fine enough pitch to resist "unscrewing.

[DaveH]

What is happening is, we are translating torque force (turning on a screw ) into a downward force and into frictional force. It is the frictional force that stops the tool post from moving (rotating). This frictional force needs to be high (obviously) to stop any movement and best positioned at the bottom between the toolpost (block) and the base plate.
Now like Ken has said we only have so much force (W) we cannot magic up any more, we are stuck with the amount W. This force W is distributed between the lower friction (which we need to stop the movement) and the upper friction (which stops us turning the nut).
So we have W = Lower friction + Upper friction.
If the upper friction is 0 (zero) then W = lower friction, which means all the force W is distributed to the lower friction which is where we want it to be.

A thrust bearing can be considered to have zero friction. (In this case)


There is a mathematical (a bit heavy going) proof here http://www.roymech.co.uk/Useful_Tables/C...ews_1.html

Best I can do

DaveH

[DaveH]

Wow Steve, for some one who does not have a degree in physics that is a pretty good explanation

DaveH