Proccess of making a new chuck backplate

tarmo120

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So finally I got around to get a new 4-jaw chuck. It came with a backplate that mounts on the chuck.
The lathe I have, has 3 holes diameter 10mm located 120 degrees to eachother.
And a plug or and extruded part that goes inside the backplate.
I measured the spindle and it has about 0.002mm of deviations in x and z.

Now the new backplate does not have the correct size bolt threads to bolt it to the spindle nor has it the right size bore.

My question would be, what would be the correct order of operations to make a new plate from scratch.
And how would one go about measuring the diameter that the spindle holes are located?
Then I could atleast mount the 4-jaw to the machine and get some work done.
About the wrong bore, I think I can just mount the chuck backwards and dial it in.

I have more questions, but let's start with these first.
 
At this time I can only give you guys 3d models/views of the spindle and backplate and how they connect.

I forgot to take pics when I was at the garage and now I wont be there for at least 2 weeks. Too much cnc work in town.
The models I will make tomorrow. But as far as I saw from your thread, my backplate and spindle are similar except for the camlocks.
 
Ok, I made a few rough models. This is just to show what kind pf spindle I have and what kind of measuring device can I use for measuring the backplate.

Left pic is spindle, right is backplate
spindle.jpg backplate.jpg

My question is how to measure that diameter 80 h6 with a micrometer?
It doesnt extrude enough to measure it correctly.
Or do I really have to cut it by triel and error?

I'll try to put up as much info as I can and if there is something missing ask away.
Pictures of the real thing will be up next weekend I hope.

spindle.jpg backplate.jpg
 
Is that plate threaded? Please don't forget to take pictures of the lathe and spindle while you're at it.

This is not ringing any bells and I'm wondering if this is some kind of chuck plate adapter.

What model lathe are you working with?

.... Hang in there, we'll get this all worked out.

EDIT: So the more I look at this, it appears you're working with a threaded-type backplate to an Atlas or older South Bend type machine. -But there's room for error on my guess here. Those spindles are common as water, usually 8 TPI with 1-1/4" or 1-1/2" diameter. How to find out? Count the number of threads (say from crest to crest or, trough to trough) in 1" and measure the diameter which will read a little shy of the dimensions noted above.

If you're intent on making one, it's not hard but you'll need to cut the threads on the lathe and you'll need a reasonable drill press (preferably mill) to drill the holes. You'll need to tap the holes very straight...



Ray
 
Last edited:
Well as far as I saw nothing is threaded except for the pull studs and bolts connecting the backplate to the chuck and the chuck assembly to the spindle.

The lathe I'm working with is this, http://www.koneita.com/metallisorvit/metallisorvi_nova_290VFx700G.htm
That page is in finnish language, but the main info is there.
The four jaw chuck is in the accessories and was supposed to fit directly to this machine, but apparently someone made a small mistake along the way.

The chuck mounts to the machine like so.
From right to left.

Chuck-backplate-spindle
Each part has a register that centers the other part. And connects using bolts and nuts.

Also, I really like this forum, as people here are very helpful no matter what machine you have.
Thanks, guys.
 
Hey Tarmo,

I can't see a pic of the actual spindle or I could help you




Bernie
 
Same here, couldn't find a pic of the chuck or spindle... When you post some pictures, we'll probably get closer to an answer.

Nice looking lathe...


Ray

Hey Tarmo,

I can't see a pic of the actual spindle or I could help you




Bernie
 
I will look into the picture problem in the evening. Right now in my phone I also can't see any pictures. I am not afraid of doing a new plate as I work on cnc milling centers and turning is just a hobby. Later guys
 
This is weird. In my computer using firefox I can see both pictures and can click on them to be magnified.

But I'll give you guys the links.

http://www.upload.ee/image/2987437/spindle.jpg
spindle.jpg

http://www.upload.ee/image/2987445/backplate.jpg
backplate.jpg

The upper picture is called spindle because that is the part where the backplate and chuck mount.
That part comes straight out of the headstock. Maybe the threads are inside the headstock but I highly doubt that. I wouldn't want to mess with removing this part.
All I want is wo know the order of business when machining a new backplate and how to measure it correctly. Mainly because of the small amount of material for measuring.

spindle.jpg backplate.jpg
 
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