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View Full Version : Evan, other SB gurus, quick weight reduction



nheng
10-07-2005, 09:40 PM
I need to help a friend break down a long bed Model A for our aging backs to handle.

I see two screws that hold the right support bearing for the leadscrew. Will the carriage and apron slide off once the support is removed? How about the leadscrew? What secures the left end?

Can the headstock be removed easily? Any estimate of the weight of a 52" bed?

And one operational question ... is it normal for the carriage to move slightly to the left as the feed lever (not the clutch) is engaged?

Lots of questions so thanks in advance for any advice you can offer on breaking it down.

Den

[This message has been edited by nheng (edited 10-07-2005).]

Evan
10-08-2005, 04:25 AM
The headstock comes off by removing the two clamp bolts on the underside. Piece of cake. Alignment is not a problem as it is scraped in to the vee ways. Mark the exact position it was at and put it back there. Yes, if you remove the right support for the lead screw the carriage will run off the bed to the right, also simple. Support the lead screw while you do this, don't just let it hang from the left bearing/box. You can remove the entire lead screw by just removing the gearbox with a couple of screws in the bed above the box but you won't save that much weight.

I don't recall how much mine weighed last time I moved it. Even with a 52 inch bed it shouldn't be that heavy with the carriage, headstock and tailstock off.

"is it normal for the carriage to move slightly to the left as the feed lever (not the clutch) is engaged?"

I presume you mean the half nuts? If so then if the lead screw and the half nuts are not exactly aligned then it will move slightly when engaged. If it is always moving left I suspect some wear on the halfnut threads. Since the right side of the halfnut threads is the side that the force is usually applied that side will take the most wear and the thread profile of the halfnut will be somewhat "sloped" on that flank.

Does the halfnut engagement handle tend to pop out slightly under load? Also look for wear on the leadscrew threads on the left side of the thread flank.

nheng
10-08-2005, 12:02 PM
The machine has very little wear but is a bit stuck up (old oil / dust) at the moment. The half nut lever cannot be engaged (should swing down??) when I have the feed change lever in neutral.

The movement (shift) I'm referring to is when the feed change lever is swung into the longitudinal position. Would that be normal or maybe related to the general need to be de-gunked?

It does the same for the cross feed ... the cross feed dial will turn with/as the feed lever is swung into cross feed position.

Back to the half nuts. Is there a lockout mechanism that may be stuck since long. and cross feeds work ok?

I guess it's time to break out an apron breakdown http://bbs.homeshopmachinist.net//wink.gif

Evan
10-08-2005, 01:11 PM
It sounds like time for a clean up and lube of the apron. It's been so long since I used a model A I don't recall if it has a lockout for the half nuts but that does sound vaguely familiar. As I think on it I'm pretty sure it does. Seems to me that there is a cam behind the apron that stops the half nuts engaging except in longitudinal feed.

Mike Burdick
10-08-2005, 01:14 PM
Den,

You may already have the parts breakdown but if not here it is.

http://www.bbssystem.com/viewtopic.php?t=68

shapeaholic
10-08-2005, 02:25 PM
Den:
Yes there is a lockout for the halfnuts. It is a pin moved by a cam on the long/cross feed selector.
If as you say it's got dried oil "stuff" I wouldn't be supprised if the pin is stuck.

Regarding the weight. There aren't any parts of the 9x36 southbend that can't be carried by two reasonably healty people.

Headstock removal is two bolts from underneath.
Carriage can be easily removed by a) removing the gib on the bottom of the back way, b)removing the two large slotted screws that secure the carriage to the apron. lift straight up. c) support the apron and remove the rh support for the leadscrew. slide the apron off the screw and then put the support back on. You won't gain much by removing the qc as it only wieghs about 20 lbs.

Watch your back ;-))

Pete

nheng
10-08-2005, 05:20 PM
Thanks guys! It looks like we'll have a chance to loosen it up while the apron and carriage are off.

The lathe was supposed to go into my shop but instead a friend is buying it from me. My wife, far wiser than I, thinks that 4 lathes (5 counting wood) are my limit. The machine is in nice shape, bought in 1948 with ALL accessories, including the taper attachment.