Myford carriage binds going away from chuck??

In message , Len S writes

Len, One thing that might be worth checking is the depth of engagement of the half nuts onto the Leadscrew. There is an adjustment screw to set the depth under the bottom half nut.

Also, strip out the front of the carriage and check for swarf embedded in the half nuts - they are made of soft alloy and pick up swarf quite easily. Worn half nuts might also cause the problem, especially if the power feed had been used predominantly in one direction.

Regards,

Do you a Thread Dial Indicator fitted? If so swarf can get into the little gear that engages with the leadscrew and that often makes it tight in the reverse direction. Solution is simple.... just loosen the nut holding the TDI swing clear and clean gear.

Otherwise I would go with the previous post as a possible cause.

Alan

No, the dial indicator is clear. I started to pull the front of the apron off. I can't open the half nuts enough to get them clear of the screw. It's close but I don't want to pull hard on anything. Do I need to run the saddle off the tail end and remove the support for the lead screw at that end? Seems like it shouldn't be that complicated. Is there a way to pull the apron off perpendicular to the screw?

In message , Len S writes

Len, Remove the half-nut operating handle from the front of the apron - one nut and a couple of washers I think...

Then you should see two screws behind the handle which engage in the slots in the handle and operate the half-nuts. (They look like steel pins with a slot in the head for a screwdriver)

Remove those and the half- nut "halves" will separate enough to pull off the front of the apron over the leadscrew - assuming you have removed all the socket screws that go through the saddle from the top that is.

The half-nuts run in V grooves which are adjustable by a gib strip, the adjusting screws of which go through the apron from the left hand end. It may help in separating the screws if you slacken the gib adjustment a little.

Regards,

On my Super7 there was a set screw in the left hand side of the apron that located the cam and half nut operating handle assembly. Loosen the screw and the whole lot pulls out revealing the pins in the half nuts. The rest of the description is correct.

Len - refer to pages 44 & 45 of the manual. If you haven't got one download from my site, link on the following page:

OK. I got the manual and drawings - great help. I can now have a deeper look. Thanks very much.

Is there any chance that the gib strips are actually sloppy and acting as one-way clutches? This sort of behaviour can happen in lots of devices with sliding contact - works ok one way, but jams the other.

Dave.

Mme too. I note that the gear inside the apronhas an awful lot of play. I have been recommended to get a set of bushes from Myford and perhaps the gear itself. Taking the saddle away from the chuck end seems to lift that gear, so it binds on the rack. If I disconnect this gear from the rack or remove the rack entirely (lots of screws along the under side of the bed), the saddle is a smooth as silk. when all is reassembled it crunches or is very stiff, mainly on moving away from the chuck end like you. Has anyone any comments? G.H.Ireland.

Good point! Turning the handwheel clockwise to move the saddle away from the headstock will cause the gear that meshes with the rack to rise up and possibly bind if its shaft or bushings are severely worn.

Having had to replace them on my ML7, I can add two comments. First is that the journal and bushes will both wear and if you need to replace one you need to replace the lot (they aren't expensive). The second is the one that the previous owner of my lathe had missed... After pressing the bushes in, drill holes through them down through the oil ways, Otherwise they don't last very well at all :-|

Mark Rand RTFM

OK. I finally got a good look at the half nuts. They had a lot of swarf in them. I cleaned them and at first glance they look OK. But nothing worked better when I put it back together. I pulled off the apron again and looked more closely. I noticed that one side of the half nut threads where pretty square while the side that drives away from the headstock was worn so it looked like a normal screw thread (rather than acme). It seems pretty certain that it is the half nut that's binding since I can move the carriage nicely both ways with the rack. Also, the binding has no connection to position on the bed. it just starts after a few cranks on the leadscrew no matter where the carriage is.

I just posted separately under "Does Myford answer email?" because when I emailed them to get new half nuts and some other parts, I got no reply after 5 days. Is this normal for them?

I had a Drummond M type (same bed design) many years ago with the same problem. It was down to wear on the inner bed face near the chuck (where most of the wear occurs). I ended up having it reground, which might be an option from Myford?

Mind you I would be surprised if that was the case, mine had had some pretty extensive use before it got to that stage.

In message , Len S writes