Milling Machine Gib Locks

[Darren]

Another mini project for me tonight. Nothing much, but sure is a pain not having any. Esp when plunge milling.

That's Gib Locks to clamp the table on the X axis.

I knocked up these bits. Free cutting steel for the main body with 1/4" 26 threads, or 1/4" bsf if you prefer. (threads are good, just covered in oil & muck)
The brass bars are to be the levers.

Threaded 1/4 26 and tapered the shafts. Tried several angles of 2,3 & 5 Deg to create different lengths. (just trying not to have a straight bar for the fun of it)



Cut the bars and rounded the ends with a file. I lost one, snapped the threaded end off.   At least it can be salvaged later.  



Didn't finish the Gib locks, but I did use one of the levers for my QCTP. Finally it has a proper handle instead of a bolt  

[bogstandard]

Very nice job Darren.

If you don't mind a slight criticism.

If you look at this C-o-C, it shows that with just a little more work you can help prevent the handle snapping off under high stress manoeuvres.
Where the thread joins the handle, is a very weak spot and it is liable to break in that area due to the bending forces involved.

By moving the bending force away from the thread and putting it into tension by use of the the two flat faces, it will tend not to snap off or bend as easily.




John

[dsquire]

John

That is a very neat little trick. I would never have thought of it but I can see where it would make an big improvement.

Darren

How could you lose something so big so quick? 

Cheers 

Don

[Darren]

Thanks for the tip John, If you look at the QCTP you can see that I have done as you suggested.

It's not screwed in fully yet as I need to shorten the thread a touch. It was late so I left it at that for the night 


I lost the other piece in the lathe while rounding the end. I made a boss with a thread to hold the lever whilst rounding the end. Sticking out so far at 3,00rpm and attacking it with a file was a bit too much to ask.

Lets just say another lesson learnt giving a touch more wisdom to be locked away 

[Darren]

Preparing the main body, set at 5 deg and milled a flat.



Drilled and tapped 1/4" bsf and fitted the brass levers



Due to the fact that the holes in the machine are not threaded right through some spacer pins were required



The front end of the pin was machined (bench grinder & file) to 60 deg to match the Gibs.
It occurred to me that if there was ever a need to retrieve them from the holes it would be rather difficult. Say the tapered end didn't line up or something, or they became worn short later etc.
So I drilled a 2.5mm hole in the end so a tapered scribe could be pressed into the backs to grab them.
Worked rather well   



All in place, here they are locked



And here un-locked. I will be able to see at a glance if they are locked or not without touching them 




I'm happy to say they work rather well and that's one step closer to making this mill further complete.
There should be some to lock the knee as well, not sure how much these would get used ? Comments anyone. So far I have not noticed a problem in not having any. Comments anyone.

And I can't see anywhere they could be fitted to the Y axis 

[AdeV]

Nice work, those handles look really good   

I'm fortunate in having the room & electrickery to be able to run a Bridgeport: The Y-axis gib lock on that is a couple of inches back on the saddle under the table; if you had one on yours you'd see it roughly where that knobbly black pipe can be seen disappearing behind the table.

As for Z-axis: I read somewhere (HMEM or here) that you should tram your head in with the Z-axis locked (which I did); I notice there's at least a couple of thou of droop along the Z-axis if I mill with it unlocked. So if you're trying to hold tight tolerances, a Z-axis gib lock would seem to be necessary. Or just tram in with it unlocked & use it as is, I guess? So perhaps not after all...

[bogstandard]

I think you have told us before Darren, that your Y axis gibs don't use gib strips.

You have most probably already thought of this, but I have done a C-o-C. It is based on the same idea I used for the saddle lock on your mini  lathe.


Bogs

[Davo J]

Hi Darren,
I will pass on a tip I picked up. In between the gib locks and the spacers put a ball bearing in there ( I just used crank bearings out of a pushbike) It makes it easier to do up and you get alot more presure for the amount of effort put in to lock the axis. I have just done this to my X,Y and Z axis of my mill. What I did was to drill partly into the end of the thread of the gib lock and the spacer for the ball to sit in and stay in the middle, the one I saw didn't have this. You already have the hole in the spacer so you would only have to do the thread.

I would recomend this to anybody having trouble with strenth in their hands also.

Dave

[Darren]

Hi John,

If you have a look at my last picture in this thread you can see the Gib in the centre of the saddle, in this case it's a square block and not a taper.

I had a study of the manual last night and although it's not clear there seems to be a gib lock that pressed against this gib.
Having said that there is hardly any room so your idea might be a much better solution all round. Only concern are the thickness of the bar I made to take a thread and flexing of same said bar.

I will have another look at the machine think on it...

[Darren]

Davo, handy little things those balls,

Where would we be if that bright spark from long ago never discovered what a round thing could do ..... 

[bogstandard]

I notice it now Darren.

The way I have suggested still seems the logical easy method. The slug on the end only has to be about 2mm long, or even less if you incorporate it into the clamp bolt itself, it is only to prevent damage, so you still might be able to get one in there.

If you are going to try to clamp the gib strip, it seems an awfully long way from the outer edge to put a bolt down.


John