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Faceplate Question

Padrig

Plastic
Joined
Feb 18, 2005
Location
Canada
I have a couple of faceplate for my SB9 lathe and I was wondering if it is normal that when I screw them on, they don’t go very far, nothing close to the shoulder. The thread seems the same and they came with the lathe so I assume that the prior owner used them with it.

Pad
 
Padrig, They definitely should go on all the way. That does seem really strange. Normally I would use valve grinding compound on the threads and just keep working them until it would go but in this instance I don't think You would want to do this to your lathe spindle. If you could find a 1&1/2 X 8 tap to chase the threads in the face plates would be best. Kenny
 
Just to make it real clear, I'm going to say
it differently:

NO

VALVE

COMPOUND

ON THE

SPINDLE

That's not done. If the faceplate has been
fitted to the machine before, then there's
a chip or something in the threads. If
they never did come up all the way, then
the register diameter (the *un*threaded portion
of the spindle at the innermost part) of
the lathe's spindle may be larger than the
counterbore in the faceplate that is designed to
accept the register diameter.

The do have counterbores at the bottom of the
threads, right?

Jim
 
Ok, please bear with me as English is not my first language and I am too new to this to understand all the terms. I think I got a pretty good idea of what you meant but in case I don’t be gentle. ;)

I don’t think it is a shoulder problem as it is not even getting close to the shoulder. It only engages for a maybe 1 turn if that. One thing I don’t know if it matters but the pointy ridges of the threading (sorry don’t know how to describe it better) is pointy on the spindle but has a little flat part on the faceplate threading. And as you can see in the pics, for the bigger plate, even if it could go all the way to the shoulder, it would bump into the belt tension lever.

Both plates screw about as far and are clean.

Thanks for your help

Pat

faceplate1.jpg

faceplate2.jpg

faceplate3.jpg
 
Interesting. It's painted the same color as
the lathe, which implies that it has
been formerly used on the machine. The
condition does seeme to be quite pristine
however which means maybe it was never
actually put in use - because it never fit
right.

At any rate you need to determine exactly
where the threads are hanging up. Take
a blue sharpie (permanent marker) and
put marking all over the end of the spindle.

Then attempt to screw the faceplate on and
see where the interference actually occurs.
Some folks use lipstick, I like the marker.

It may be that the interference is at the peaks
of the faceplate threads (that is, at the root
of the spindle threads) in which case you could
open up the minor diameter of the faceplate a
bit and it will work.

If the reverse is true (interference is at the
peaks of the spindle threads, against the
major diameter of the faceplate threads) then
you will have to pick up the threads and single
point them a bit larger.

The same will be needed if the interference is
on the flanks of the threads.

This is something that is tricky but not
impossible. But don't do any cutting until
you find out exactly where the binding is
happening.

Jim
 
Hi There,

I agree with Jim. If someone went to the trouble of painting the faceplate to match the lathe, you would think it should fit.

Check the threads on the spindle for any dings or damage. Jim's Sharpie (marking pen) technique or Dykem layout fluid painted on the threads will help to locate the interference.

Double check for junk deep in the root of the threads; especially in the faceplate's threads. This is usually the problem. But a dinged-up spindle (or faceplate thread) can cause the same symptoms.

One last thing. You are sure the faceplate and the spindle have the same thread pitch?

Good Luck!
-Blue Chips-
Webb
 
If the bigger plate would hit the tension lever the rim is to thick, or the tension lever is maybe bent. I always use a small wire brush to clean the internal threads to remove all the fine chips and dirt. Like everyone else said check the spindle threads for flat spots or wear and even check the plates for damaged threads. I also agree with Jim it might have never fit right. It may have been cut and tested on a lathe with a couple thousands smaller spindle. If i cut a plate to fit my 9" it will not fit my 10K, it looks exactly like your problem. My 10K spindle measures .006 bigger than my 9" measured over thread wires...Bob
 
This may be a stupid question but how do you measure pitch?

Thanks for all the help.

"Stupid" Pad
 
Pad,
Your not stupid! your're learning. Pitch is the thread lead or how many threads per inch. The easiest method to check the thread pitch is with a thread pitch gage. It's a leaf style gage with the thread form cut on each blade, with progressive increasing numbers. For example 7 tpi, next 8 tpi (tpi = threads per inch = pitch) and so on and so forth. For the problem you've encountered though, the pitch diameter is more at issue.
Ed

Check this link out, it has illustrations.

http://www.roton.com/web/identifying.jsp
 
Thanks a lot Ed, that's a very good site for me to learn.


I have pitch gauge that came with the lathe. They are both 8 TPI so it must be in the diameter as you say.

The big plate is stamped SouthBend and LFP100N. It is 7 5/8 diameter and has a 1 5/8 diameter thread. I know the thread on the spindle is 1 ½. The smaller plate has no markings and is 5 1/8 diameter and 1 ½ diameter thread.

So I imagine that the bigger thread on the bigger plate automatically rules out that one but the smaller is the same diameter.

Guess I’ll just have to keep an eye on ebay.

But since I am just starting out, the chucks will keep me occupied for a while

Thanks again to all for your help.

Pad
 
I bought a new old stock faceplate (South Bend) for my SB 9 a year or so ago and encountered the same problem. I fixed it by carefully hand scraping out the thread in the face plate with a threading tool mounted in a boring bar. The shoulder diameter was right. The problem was the internal thread flanks were too tight.

Stu Miller
 
Hi Pad,

The big plate is stamped SouthBend and LFP100N.
That is a genuine South Bend Lathe faceplate for the nine inch lathe.


It is 7 5/8 diameter and has a 1 5/8 diameter thread. I know the thread on the spindle is 1 ½.
This is weird. The faceplate should have a 1-1/2 x 8 thread. Maybe someone changed it? But if the faceplate has a 1-5/8 x 8 thread and the spindle has 1-1/2 x 8 thread, it should thread on (and be very loose too). Something just doesn't sound right here.

Good Luck!
-Blue Chips-
Webb
 
Whoa! Keep in mind, some South Bend 11" lathes had a 1 5/8 - 8tpi spindle threads! Some very early 9" South Bends had 1 3/8 - 10 spindles. There's a lot of not so common South Bend parts floating around out there.
Ed
 
Hi Ed,

What you say is quite true but unit code number: LFP-100N is the unit code of a faceplate for a nine inch with a 1-1/2 x 8 spindle.

Good Luck!
-Blue Chips-
Webb
 
Webb, everything sounds weird to me so I feel right at home. ;)

Thanks for the info on the part number. I measured the 1 5/8 thread diameter on the face of the plate as I dont have anything to measure the on the inside. I don't know if this is why it is not 1 1/2.

As I get a little more experience, I may be able to troubloeshoot this better or eventually rework the plates myself.

Thanks again.

Pad
 
I have two 9As ,one 10L, and one 13 South Bend lathe. I have found in getting replacement spindle thread stuff like faceplates that they usually screw on easily. Unfortunately the register dia. is often oversize so for most machining its OK but there is a chance the concentricity can shift a bit. When I machine my own thread stuff I first make an exact duplicate of my spindle and use that to test the fit of a new faceplate for thread fit and most importently the register dia. to get fit to .0005".
I have had like this case once in a while got one that will not screw on all the way asuming I have already checked the pitch and dia. I then mount the non fitting faceplate on a good faceplate and indicate the register very well. Then catch the thread and take a half thou cut and try the duplicate headstock thread for fit and then rebore the register it is not already oversize. Works for me.
Walt
 
Ok, things are getting worst. Get this, I hadn't tried the 4Jaw chuck but it turns out I have the same problem with it. It won't thread more than 1 turn if that. So the only one that fits is the 3 jaw and by looking at it today it looks like there is a wobble in it for lack of a better term. I have ordered some measuring devices so I should be able to give you exact measurements of the "wobble".

This is suppose to be fun? :(

Pad
 
Pad,
This is getting a little beyond weird! I vaguely remember an episode like this on the Twilight Zone. Please keep us in the loop, I'm dying to hear the ending.
Ed

PS Yes, this is fun! :D
 
Pad,

You are not alone! I'm having the same problem with a driver plate for my 9A. In my case, the diameter of the driver plate thread is smaller than the spindle thread by about .008. So I'm following this discussion closely.

Jeff Greenblatt
 








 
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