Lead screw bearings and other things

[PeterE]

Well, now I am slowly enbarking on a longer project on/with my C3 lathe. The project is of the kind that if one wants to do this, then one might just as well do both that and the other

The means that I intend to put the saddle micrometer stop in place, but that requires that I remove the saddle to drill and tap the fastening hole, and to remove the saddle I have to remove the apron and lead screw as well. All in all this amounts to several things to be done in sequence:

 - Strip down the saddle, apron and leadscrew
 - Make a swarf guard for the apron hand-wheel gears
 - Update the hand-wheel like the MEW example but with my own scale ring
 - Fit the saddle micrometer stop
 - Make and fit a saddle lock
 - Fit the saddle and adjust backlash to as little as ever possible
 - add ball bearings to both leadscrew ends
 - Add a dis-engageable hand-wheel to the leadscrew.

So right now I am trying to make all the needed parts in advance while my C3 is still assembled. The first bits produced are the parts for the right hand leadscrew bearing and the leadscrew hand-wheel. The following pic shows the bits:


The black thingy is the housing (sorry for the bad photo angle).The lower row from left to right shows:

 - The extension sleeve that I add because I want to move the whole assembly to the right with about 20 mm to gain extra travel for the saddle and a good position for the leadscrew hand-wheel.
 - left ball bearing which is a 12x28x8 bearing,
 - an inner ring distance and the right ball bearing (same type).
 - Then the leadscrew extension.
 - The lock nut pushing the bearings together to eliminate backlash.
 - Finally a dial that will fit over the hand-wheel and cover the lock nut. The fiducial line will be on the housing. The shown dial will be replaced with one that is a bit wider but it will look the same. This dial will go on the apron hand-wheel instead.

A trial assembly of the parts without the hand-wheel shows that it will be a quite compact assembly in the end.


As you can see, there is no fastening screw on what will be the underside. This is because the bearing has been moved past the "leg" on the right side and there is nothing to put a screw into so there are two screws at the top and two guide pins to fix the bearings position once it is fitted. Adding the hand-wheel, the whole setup will look something like this (but not nipped in the bench vice)

This pic shows more clearly the fastening holes.

I choose to make the extension sleeve slightly conical because then I think/hope that if I run with the leadscrew  clamp closed for left-hand threading for example, the clamps will be forced open when climbing on the sleeve, but whether it works remains to be seen. Anyway it looks nice

BR

/Peter

[andyf]

That looks like it will be effective, Peter, though I think the design of the half-nut engage/disengage mechanism in the apron is such that the cone won't act as an emergency stop. But if you manage to stop in the right place and avoid crashes when the saddle is moving towards the headstock, you will avoid them when turning the other way or LH threading, which probably won't be very often.

How are you going to add a bit of friction to the dial? The easiest way would be to squeeze an O ring between the dial and either the handwheel or the locknut - less likely to fly into a black hole than the bits of spring steel the manufacturers fit to their dials.

One thing you might consider is filing a flat on the extension shaft where the grubscrew in the handwheel will bear on it. Besides giving a more secure fixing, this will avoid the problem of the grubscrew roughing up the cylindrical surface of the shaft, making it difficult to pull the handwheel off.

Andy.

[PeterE]

That looks like it will be effective, Peter, though I think the design of the half-nut engage/disengage mechanism in the apron is such that the cone won't act as an emergency stop. But if you manage to stop in the right place and avoid crashes when the saddle is moving towards the headstock, you will avoid them when turning the other way or LH threading, which probably won't be very often.

How are you going to add a bit of friction to the dial? The easiest way would be to squeeze an O ring between the dial and either the handwheel or the locknut - less likely to fly into a black hole than the bits of spring steel the manufacturers fit to their dials.

One thing you might consider is filing a flat on the extension shaft where the grubscrew in the handwheel will bear on it. Besides giving a more secure fixing, this will avoid the problem of the grubscrew roughing up the cylindrical surface of the shaft, making it difficult to pull the handwheel off.

Andy.

Hi Andy,

Thanks for comments and suggestions!

Whether the cone or slope on the extension sleeve will actually work as an emergency release I really cannot say. It would be useful if it works, but I actually don't think it will because the lock on the engage/disengage mechanism is probably more powerful.

To be honest, I designed the sleeve to look nice and afterwards saw a possible functionality within the design. 

The friction to the dial(s) will be made using O-rings as being the simplest way forward.

To lock the hand-wheel my thought have been to drill a shallow hole suitable for a dog point on the lock screw (thumb screw) that will lock the hand-wheel to the shaft, but as you say, it might be better to just make a flat to lessen the risk of burrs of any kind limiting the movement of the hand-wheel. Thanks, I must think of this some more.

BR

/Peter

[PeterE]

Since this project includes dismantling the apron, removing the leadscrew, and other things, I need to make and fit a saddle lock. This to be able to turn stuff even if the apron is off.

Having searched for ideas I have seen three major solutions, the first is to add a clamp to either the front or rear right or left corner of the saddle, the second is to fit a single lock in the middle right using a tab going in under the saddle, and the third is to fit a locking screw through the right free side of the saddle. Option 3 goes for WIESS or REAL BULL machines, but mine is a SIEG machine so that leaves two variants.

A lot of thinking about goods and bads, I have ended up with this idea.

Fitting a piece of mild steel in the opening to the right and securing it to the saddle using two M4 srews straight into the side. (...and now I can see that the drill wandered at of the holes   )

I choose this way because I only need one locking point at the center. It will not try to skew the saddle under pressure (too much) and it will be fairly easy to fit without having to remove the saddle from the bed. I will be using an ordinary hex-head screw to avoid having to clear the head for a hex key.

Now, before making holes in the machine, I would like to ask the readership for more goods or bads with this way of fitting the stop.

BR

/Peter

[S. Heslop]

This is how I made my saddle stop.



It's perhaps a bit hard to see whats going on because it's just a sketch, but the dashed line going through the two holes is where a bolt goes and the bottom bar's hole is threaded. The thing is just a removable clamp that pulls the saddle down on the ways, and avoids having to drill holes in the saddle.

Thing is that with so many wonderful and elaborate saddle stops out there I feel this is just too simple to work brilliantly, otherwise somebody else would've already thought about it and published the idea. So i'm not too confident in it.

[AdeV]

02sheslop - that's pretty much exactly how my tailstock clamp works, and the tailstock is absolutely nailed down solidly when the clamp is engaged, I'd have no qualms about using a saddle stop based on the same principle (in fact, my saddle stop works differently, and nothing like as effectively).

[andyf]

This is how I made my saddle stop.

[Drawing omitted for brevity]

It's perhaps a bit hard to see whats going on because it's just a sketch, but the dashed line going through the two holes is where a bolt goes and the bottom bar's hole is threaded. The thing is just a removable clamp that pulls the saddle down on the ways, and avoids having to drill holes in the saddle.

Thing is that with so many wonderful and elaborate saddle stops out there I feel this is just too simple to work brilliantly, otherwise somebody else would've already thought about it and published the idea. So i'm not too confident in it.

Nothing wrong with that; in fact, I reckon it would be mechanically sounder than one relying for its strength on two small screws holding it to the saddle. And I think that on Pete's lathe the tailstock base may fit between the "wings" on the saddle (admittedly, that feature wouldn't often be needed), so a screwed-on version might occasionally get in the way.

How about a further refinement? Two short holes, one drilled into the top of each wing, taking two short pegs sticking out of the bottom of the upper component, so the thing would stay loosely in place when not in use. Then it could easily be removed if it ever got in the way, by unscrewing the clamp nut enough to allow the pegs to come out of the holes and the whole thing to be slid down the bed and rotated 90 degrees to lift out between the ways.

Andy

[Stilldrillin]

How about a further refinement? Two short holes, one drilled into the top of each wing, taking two short pegs sticking out of the bottom of the upper component, so the thing would stay loosely in place when not in use. Then it could easily be removed if it ever got in the way, by unscrewing the clamp nut enough to allow the pegs to come out of the holes and the whole thing to be slid down the bed and rotated 90 degrees to lift out between the ways.

Andy

That's a great idea Andy! 

David D

[PeterE]

Thanks both 02sheslop and Ady for very good thoughts and ideas on this!   

It verifies that a central clamping contraption is the best way to go to begin with.
Andy, your idea on using a loose clamp guided by a couple of vertical pegs for positioning is really good!         This was exactly why I decided to ask before drilling!

About my tailstock fitting between the "wings", no it does not. That was why I opted to use that particular space.

I think I can actually take it one step further. If the clamp part on the underside of the bed is shaped in the same way as the clamp part of a Myford type fixed steady, it can be turned and lifted/inserted very easily.

Back to the workshop to make a new version. The old thing goes into the good-to-have-bin (the round archive) as it went bad anyway. 

BR

/Peter

[PeterE]

Well, at least some work has been dine in the past period. There is awful little space to work in as is shown below:

The tailstock comes right up to the saddle but the mid section in the saddle is free and goes free also for stuff mounted in the tailstock.

My interpretation of the drawings and ideas looks like this

A fairly simple bit of steel. I had to make a "track" for the cross slide setting screws which narrowed down the width of the saddle clamp "wings". A wide "Countersink" for the hex-head screw was also included. In place at the tail stock it looks quite OK so far.

Still a bit to go, but I think this will work out alright. The stop block currently rests on the bed, but I will remove a bit from the bottom to make it rest on the saddle to get a firm clamp down which together with the pegs will secure the saddle.

By the way, I will put the pegs in the saddle and keep the holes in the clamp block. Then I don't need to clear out swarf from the holes before attaching the clamp.

BR

/Peter

[andyf]

By the way, I will put the pegs in the saddle and keep the holes in the clamp block. Then I don't need to clear out swarf from the holes before attaching the clamp.
/Peter

Good thinking, Peter. That didn't occur to me when I suggested it.

Andy

[Stilldrillin]

By the way, I will put the pegs in the saddle and keep the holes in the clamp block. Then I don't need to clear out swarf from the holes before attaching the clamp.
/Peter

Good thinking, Peter. That didn't occur to me when I suggested it.

Andy

As I was reading through. I was thinking the holes could be used for lubrication purposes....... 

Didn't give any thought to the swarf! 

David D

[PeterE]

Well, a small update on the saddle lock.

The pegs are in place in the saddle. They are made of old broken drill shanks and should be tough enough  

The bits making up the lock looks as follows.

Three simple parts, the clamp, a screw, and the lock nut. Simple as that. Future will tell me if I should include a washer under the screw head. The clearance milled for the cross slide set screws had to be taken further down to make it possible to drop the clamp onto the pegs. But I kept a good bit as a "foot" thinking it will give better clamping.

The lock nut is designed in the same way as the Myford fixed steady making i possible to drop it right down onto the bed.

Here it is placed on top of the pegs.

Dropping it in place, the lock nut can be turned to bridge the bed gap.


... and finally, the lock is in place and tightened. The saddle does not move at all!


So, another required and useful little accessory made as a detour, but now I can get back to the project I was going to do!

Thanks for great ideas on the way!  

BR

/Peter

[Stilldrillin]

Very nicely shown Peter! 

And, even more nicely done....... 

David D

[andyf]

That'll do nicely, Peter.

One final thought: use pliers to give the end thread on the clamp screw a bit of a squeeze to damage it ever so slightly. When the device isn't in use, vibration might lead to the lower component slowly unscrewing itself, and the damaged thread will stop it finally falling off into the swarf.

Andy.

[PeterE]

Thanks for nice comments David and Andy!   

And Andy, your idea on onching the last thread to avoid the lock nut dropping off is really good! That will be done next time I get into my shop.


BR

/Peter