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[4]

Proccess of making a new chuck backplate

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tarmo120

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#1
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.
 

Ray C

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#2

tarmo120

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#3
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.
 

tarmo120

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#4
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
 

Ray C

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#5
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
 
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tarmo120

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#6
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.
 

itsme_Bernie

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#7
Hey Tarmo,

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




Bernie
 

Ray C

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#8
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
 

tarmo120

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#9
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
 

tarmo120

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#10
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
 

darkzero

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#11
That lathe looks identical to a PM1127VF. I had originally ordered one these before changing my mind to get the 1236. Assuming that lathe is built to spec similar to the PM version, before the large bore model was available, the PM1127VF had a DIN 55021 spindle mount. This lathe does not have a cam lock or threaded spindle. It's basically the same type of spindle found on most mini lathes except the the DIN 55021 has a nose taper instead of a raised boss. Either the chuck adapter bolts onto the spindle using SHCS from behind the spindle or the chuck adapter has studs installed which again mounts on the back of the spindle with nuts. More details on chuck mounting with these types of spindle here.


Here's a photo of the spindle on my old mini lathe which is similar:
Img_0622.jpg



I hated changing chucks on that lathe. The back of the spindle has counterbores for the SHCS to sit in. Space was tight & it required a shortened hex key to loosen the SHCSs, it was a slow process.

PM's site no longer lists the spindle as a DIN 55021. I assume it has to do with when the large bore model was released. I hear the PM1127VF no longer uses the DIN 55021 spindle but mounting is still essentially the same, just doesn't have a taper for the nose anymore. I think someone called it a C3 mount like on their 10x models but I'm not sure if that's actually true. I can't find any specs on a C3 type spindle.

In relation to the OP's question, if your spindle is similar, the mounting bolt pattern is not critical as the boss/register (or if you have a nose taper) is what you would rely on to locate the chuck adapter. The bolts just keep it attached to the spindle. You could make a short transfer puch & try to get enough of a mark on the adapter you make to indicate the holes. When I made an adapter for my mini lathe I ran into the same issue & did not have a mill. There was so little room I improvised my putting double sided tape on the spindle holes & pressed the adapter on to it to leave an impression of the holes. It managed to work out fine for me. Photo
 

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tarmo120

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#12
That is excactly the kind of spindle I have. I managed to get a few photos along the weekend.

DSC_0106.JPG
DSC_0113.JPG
DSC_0117.JPG

This is the original 3-jaw
DSC_0109.JPG


This is the new chuck next to the original.
DSC_0129.JPG

For starters I can use the 4-jaw chuck and rough the backplate out.
Oh and as far as I can see, there seems to be no taper to any part of the spindle.

DSC_0106.JPG DSC_0113.JPG DSC_0117.JPG DSC_0109.JPG DSC_0129.JPG
 

Ray C

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#13
I sure am glad Will (darkzero) came to the rescue on this as I sure was stumped. I've never seen this type of setup...

Sounds like you're on your way now...


Ray
 

tarmo120

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#14
Now I just have two more question.
Does the thickness of the backplate matter much?
I mean I could get same thickness material or slightly thicker.

And secondly is there some kind of way to smooth the start of the machine?
It has a belt driven pulley system and no clutch. Also no variator.
I just want that the starting of the machine would put less stress on the motor and household powergrid.
 

Ray C

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#15
Within reason, thickness of the plate should not matter. If the bolts have enough stock to thread into that is all you're concerned with.

What is the power service in your home (i.e. 120 or 220, 50 or 60 Hz) and what are the electrical specifications of the motor? I am assuming it is a single phase and not 3 phase motor.

Depending on your household power service in your home and depending on the motor, you might be able to rewire the motor (assuming you're not already on 220 volt system).

There is no good way (that I know of) to give a single phase motor a "soft-start" or "ramp-start" capability that is economical/practical.

Ray



Now I just have two more question.
Does the thickness of the backplate matter much?
I mean I could get same thickness material or slightly thicker.

And secondly is there some kind of way to smooth the start of the machine?
It has a belt driven pulley system and no clutch. Also no variator.
I just want that the starting of the machine would put less stress on the motor and household powergrid.
 

tarmo120

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#16
Most of Europe is on 220 volt. So am I. The machine has a 220v motor and power rating is 1.1kW.
I don't know if it is 50 or 60Hz. At home I know that I've got max of 16A relays for 220v and 20A relays for the industrial 380v.
The industrial grid is 3 phase. That is pretty much everything I know about electrics at home.
 

Ray C

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#17
OK...

My guess is that the motor is already wired for 220v and thus, it will draw the least amount of Amps already. What problem do you have with the motor? Is it blowing-out the circuit breakers or making the lights in the rest of the house flicker?

Your motor should only be drawing 5 amps so, a 16A breaker should be fine unless there are many other things connected to that circuit or, if the wire is not a heavy gauge.



Most of Europe is on 220 volt. So am I. The machine has a 220v motor and power rating is 1.1kW.
I don't know if it is 50 or 60Hz. At home I know that I've got max of 16A relays for 220v and 20A relays for the industrial 380v.
The industrial grid is 3 phase. That is pretty much everything I know about electrics at home.
 

tarmo120

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#18
No problems. I just wanted to make sure I wasn't overloading the motor due to toe bigger chuck and possibly a thicker backplate.
The original is 160mm and new 4-jaw is 200mm.
I don't want to mess the motor up.
 

Ray C

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#19
Ah, there will be no problem with that. The extra mass of larger chuck is a theoretical nuisance but not a significant practical one. If that were not the case, imagine the problems we would have every time we worked on a 0.75 meter shaft of 10-12cm diameter... The world would end -but it doesn't.


Ray


No problems. I just wanted to make sure I wasn't overloading the motor due to toe bigger chuck and possibly a thicker backplate.
The original is 160mm and new 4-jaw is 200mm.
I don't want to mess the motor up.
 

tarmo120

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#20
Ok. Thanks for the info.
If I have any other questions about making the plate, I'll ask.
But I wont have enough free time to make it or get the material.
We'll see what next month brings.
 

worm2trn

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#21
What was the bolt pattern? Wanting to make a back plate for a CDCO chuck, think I have the same lathe.
James.
 

British Steel

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#22
The bolt circle can vary, best method is to machine the backplate to a snug fit on the register, then make a set of three transfer punches- bushes to fit the bolt holes in the spindle flange with flanges to locate against the spindle face with 60-degree points (look like umbrellas with fat handles), short enough to slide the backplate on the.register, then a tap with a mallet will give three neat punch-marks on the bolt centres.

Or you could put pins in the holes, measure one pin with a digital caliper *then zero it without closing up* then measuring across two pins will give the spacing, jommetry [1] will give the circle radius/diameter.

Transfer punches are easier, though, and you'll have them next time you need to make a backplate...

[1] spacing/2 = r sin(60), rearranged gives
r = Spacing/2 sin(60)
r = spacing/root(3)

Just like star-delta three-phase...
 
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