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9c to 9a conversion

elugosch

Plastic
Joined
Feb 16, 2018
Hi,
new to the forum. I have a S-B 9C lathe made (near as I can tell) in 1916. I would like to convert the apron to a 9A so I can get the power cross feed. I don't care about the quick change gears. I can change them as necessary with no trouble. My question is: can I just change the apron or do I need to also change or modify the carriage?
 
From your comment about the gearbox I believe you are trending toward a 9B, as I am currently doing. What I have found out:

You will need a differend leadscrew and crossfeed screw. The leadscrew for the B model has a keyway along the length. The B model crossfeed screw has gear teeth that mate with the drive gear in the B model apron.

The crossfeed screw drive gear on the apron comes in 3 "sizes" It will be marked S, M10, or P10 meaning standard, undersize and oversize. The gear is selected to mate correctly with the gear teeth on the particular crossfeed screw. Different gears are available.

Post a picture of the underside of the saddle. Some have the configuration to accept the geared screw and some don't.

Being new to lathes I am really not this knowledgeable. But after embarking on the same journey I was lucky enough to contact "latheman" who kindly steered me in the right direction.

Thank you,
Mr.Smith
 
In general, you need a cross feed screw with a gear on it, and some saddles are not clearanced for that gear.

However, the 9 A/B/C lathes were not made in 1916. You really need to show us pictures.

allan
 
Here are all the pics. I hope they all downloaded.

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That machine was not made in 1916. Your date should be more like 1943 or later. Give us the serial number, it is located on the right end of the bed between the tailstock in the front way.

From what I can see in the pictures, you should have no trouble converting it to a 9B. It is hard to tell in those pictures but I believe the bed has been modified from the factory to accept the power feed apron. You will need a new leads crew, an apron, and a crossfeed screw. You should not have to change the saddle, which is not recommended anyway. The major concern is the alignment of the lead screw. Worst case scenario, you melt out the Babbitt In the two bearings, reposition your lead screw properly and re-poor the Babbitt. The best case scenario, you don't have to do anything. Everything lines up properly.

Stay safe and have fun.

Joe.
 
I may have some of the parts you need. What length is your bed? I have a lead screw that might work, some other stuff you may be interested in as well. Send me a PM if you're interested.
 
I can understand the finish bore on the apron but not the lead screw. What is different about that and why . Also couldn't one bore out the apron to accept the cross feed screw?
he may need a saddle too...9" model C is not finish bored for the crossfeed gear on all the ones I have seen.
 
That machine was not made in 1916. Your date should be more like 1943 or later. Give us the serial number, it is located on the right end of the bed between the tailstock in the front way.

From what I can see in the pictures, you should have no trouble converting it to a 9B. It is hard to tell in those pictures but I believe the bed has been modified from the factory to accept the power feed apron. You will need a new leads crew, an apron, and a crossfeed screw. You should not have to change the saddle, which is not recommended anyway. The major concern is the alignment of the lead screw. Worst case scenario, you melt out the Babbitt In the two bearings, reposition your lead screw properly and re-poor the Babbitt. The best case scenario, you don't have to do anything. Everything lines up properly.

Stay safe and have fun.

Joe.

Yes, it was made early to mid 1947. I don't get the new lead screw. I'm not changing to a quick gear change. I have seen cross feed screw gears and wouldn't that answer the cross feed screw problem?
 
Your leadscrew does not have a key way in it to drive the power feed apron.

To see if your saddle will accept the geared cross feed screw,unscrew the cross feed and measure the part of where the gear would be. The diameter of the cross feed gear is ~.687"...if it is more than a few thou smaller turn a piece of scrap to .690" and see if it will fit all the way in.
You might be ok there.
 
Last edited:
iwananew10K, Is correct about the lead screw.

But you will need to replace the apron. I believe he was thinking of the saddle. If the picture you took, Is of your saddle, You should be fine.

The problem arises if you have a 9C made before approximately 1943. The original 9A, B and C, designation did not start until about approximately 1940. Apparently they had a lot of old beds and saddle castings that they had to use up. The old bed castings would not accept the new apron, there was a clearance.problem. And the Saddle did not have an opening for the crossfeed gear. Sometime after 1943 they used up all the old stock, and everything was being made with the new castings.

The parts you will need,

1: a new lead screw, With a keyway group cut into the acne threads. The same length as the original lead screw.

2: a new crossfeed screw, with a gear. The gear is located just before the Acme threads start. All one piece.

3: a new apron. The new apron must have the gear shift selector and a clutch knob.

If the machine you're trying to convert was made in 1947, you should not have any other problems. Just check the alignment of the lead screw when you put it all together.

Stay safe and have fun.

Joe.
 
Well Ok! looks like I can do this. I think I can get all the parts. Have an apron on ebay, crossed should be avail there also. I haven't seen a lead screw for a 3 ft bed 9B but I'll keep looking Thanks for the information.
Emile




iwananew10K, Is correct about the lead screw.

But you will need to replace the apron. I believe he was thinking of the saddle. If the picture you took, Is of your saddle, You should be fine.

The problem arises if you have a 9C made before approximately 1943. The original 9A, B and C, designation did not start until about approximately 1940. Apparently they had a lot of old beds and saddle castings that they had to use up. The old bed castings would not accept the new apron, there was a clearance.problem. And the Saddle did not have an opening for the crossfeed gear. Sometime after 1943 they used up all the old stock, and everything was being made with the new castings.

The parts you will need,

1: a new lead screw, With a keyway group cut into the acne threads. The same length as the original lead screw.

2: a new crossfeed screw, with a gear. The gear is located just before the Acme threads start. All one piece.

3: a new apron. The new apron must have the gear shift selector and a clutch knob.

If the machine you're trying to convert was made in 1947, you should not have any other problems. Just check the alignment of the lead screw when you put it all together.

Stay safe and have fun.

Joe.
 
Yes, meant to say saddle...edited now,thanks for the check

Unscrew that cross feed and measure the diameter and check the bore in the saddle before you start dumping money into parts....if it's a case that the cross feed screw is the same dimensionally but simply doesn't have teeth,you could just cut the 12 teeth in and use the original part....you can do it on the lathe without even being plugged in....hint-the spindle gear is 24 teeth...there's your indexer(and your guide to grind a tool since it's Also 20DP-same as the cross feed gear)....the cross feed gear does not need to be a "precision" gear.

Use the lathe like a shaper, it does not take long to cut 12 teeth a few thou at a time...IIRC it took me about 1/2 hour.

you can even cut the key way in the lead screw too this way.

Think it though and practice on some scrap....not only will you minimize costs that you can then spend on tooling, you will have gained some very valuable skill in the process.
 
Like I said earlier, I have some stuff you may be interested in. I have a lead screw for a 9b. It's for a slightly longer bed, but could easily be cut down. I also have a QCGB, lead screw, banjo,and hardware if you want to convert it to a 9A. QCGB saves a lot of time when doing a job, if you're going through the trouble of changing it to a 9B, might as well go all the way and have a 9A.
I also have a cross slide screw with the power feed gear. The screw is worn but the gear is good. Could be modified to work with what you have.
If the OP or anyone else is interested, let me know what you need.
 








 
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