Chuck critical mounting surfaces

[Vernonv]

Hi All,
I'm trying to figure out how best to machine a chuck mounting for the spindle on my Nuttall lathe. The spindle has a threaded section (2.5" x 6 TPI I believe) about 3/4" long and then a shoulder which measures 64.9mm in diameter. Now from my existing chucks they appear to have the shoulder bore machined at around 65.0 to 65.1mm at the opening, however I can't tell if the bore if parallel or slightly tapered.

Now what I need to know is what is normally the critical mounting surface:

1. The threaded section (I'm doubtful about this).
2. The shoulder being a parallel mating surface where the bore is 0.1 to 0.2mm larger than the spindle.
3. The shoulder being slightly tapered so that the bore diameter mates with the spindle shoulder.

Any help/insight greatly appreciated.

[.RC.]

You could ask the Nuttall dealer... He may have the drawings for the old threaded spindle models.

B & D Machining Pty Ltd: Nuttall Lathe Parts (http://www.bdmachining.com.au/nuttall-lathe-parts/)

[Vernonv]

Thanks RC. I've tried contacting them a number of times without success, regarding manuals and change gears :(. Might have to try again.

The spindle itself isn't a great mystery as I can easily measure it, but I can't accurately measure deep inside the chucks and I just figured that there would be a "standard" for this type of chuck mounting.

[pipeclay]

The Thread not critical in my opinion.

The Register on the Mounting plate is and should be square to the Bore and Thread.

The bore Clearance for the Mounting register is also in my opinion not that critical ( Neither the thread or bore can be like a cock in a sock but +.010" would be ok.)

All of the Alignment is made through the Register Faces.

In all the Screwed thread Backing or Mounting plates that I have made for the 260 and 9" Hercus Spindles there is allways more Clearance than original on the Threads,also slightly more on the Register Bore as I machine this section to remove all the Thread.

I have done numerous checks for Runout with the Plates I make and I find I allways have the same result (Repeatability).

[Vernonv]

The Thread not critical in my opinion.That was my thinking also.


The Register on the Mounting plate is and should be square to the Bore and Thread.

The bore Clearance for the Mounting register is also in my opinion not that critical ( Neither the thread or bore can be like a cock in a sock but +.010" would be ok.)

All of the Alignment is made through the Register Faces.

In all the Screwed thread Backing or Mounting plates that I have made for the 260 and 9" Hercus Spindles there is allways more Clearance than original on the Threads,also slightly more on the Register Bore as I machine this section to remove all the Thread.

I have done numerous checks for Runout with the Plates I make and I find I allways have the same result (Repeatability).I'm not 100% sure what you mean by "mounting register". Are you referring to the chuck registering against A or B on spindle in the attached drawing (or am I way off)?

[Vernonv]

Just to expand a bit - I originally thought I would register the chuck to the spindle using face B, however when I was looking at how one particular faceplate I have, mounted on the spindle it does not even have a face that mates against B i.e. it is threaded through to the front face and there is no step, etc to mate against face B. It appears to mate/register against the OD of the spindle.

That is what prompted me to ask this question.

[rogerbaker]

Hi Vernon
On the two that I have done I have registered against "A" and both have been OK.

Roger

[pipeclay]

All of the mountings whether for Chucks,Faceplates or different attachments that I make mount against Part A.( The Face ).

[Vernonv]

Ok, I spent a bit more time looking at how the different chucks/faceplates that I currently have mount on the spindle and I think I've figured out the actual mating face. There is another shoulder on the spindle that is only just proud of the gearhead (missed it the first time I looked, probably cause I was focusing on the spindle end, thread and main spindle body :B) and I think thats where all the chucks are registering against (see C in the attached drawing).

Does that seem like a reasonable possibility?

EDIT: re-reading the above posts, I have a suspicion that you guys thought that A was actually C ... sorry my crappy drawing ... a photo might have been better.

[rogerbaker]

EDIT: re-reading the above posts, I have a suspicion that you guys thought that A was actually C ... sorry my crappy drawing ... a photo might have been better.


Hi Vernon

Correct

Roger

[franco]

Vernon,

If you go to the HSM website to a thread by davidh entitled "Am I expecting too much from my Bison"

http://bbs.homeshopmachinist.net/showthread.php?t=31148&highlight=threaded+backplates

there is quite a bit of discussion about this. In particular post #30 by Forrest Addy explains how threaded chuck backplates and faceplates centre themselves radially on threaded spindles via the flank angles of the threads when they seat against the spindle nose flange (C in your last sketch).

Provided the spindle nose is running true, its threads are in good condition, the face of the flange C in your last sketch runs true and the backplate threads are in good condition, the backplate should centre itself very consistently even if there is some looseness in the threads.

There has been argument in the past on some of the American Boards that the counterbore in the backplate should be a tight fit on the register, i.e the unthreaded parallel part of the spindle nose between A and C in your last sketch, to ensure the correct alignment of the backplate. This does not appear to be correct. On my Brackenbury and Austin lathe which has been in the family since new in 1948 there is, from memory, about 0.004 - 0.006 in. clearance between the counterbore in the original backplate and faceplate supplied with the lathe, and the register. The two clearances are different, so precision here is apparently not essential. Over the years I have made several more backplates, a catch plate and a spindle nose ER32 collet chuck using the above clearances, and they all centre themselves very consistently. The register does make it easy to start the backplate thread square when installing a chuck or faceplate though.

Frank

[Dave J]

Hi Frank,
Not sure what troubles your having posting a link, but the confusion earlier this year about links was cleared up in a thread from RC back in the August, thanks RC.:2tsup:
On the last page a posting from Neil says, if it's relevant to the thread it's OK to post one up, but not to farm members to other forums.
http://www.woodworkforums.com/f36/absurd-secret-rules-121942/index3.html
I have been posting links to other sites, as well as posting links on other sites to this one with no problems at all. I only do it to direct people to some useful information instead of having to copy it, or repeat it.

Vernon,
With the Nuttall dealer, like I said a long time ago, I bought my Douglas shaper off him and he lives in the next suburb. When I am passing next time I will call in and ask him what's going on for you. It is not a very big shop but he had loads of spares their, maybe thats because no one can get through to him to buy them.:~

Dave

[franco]

Hi Dave,

Thanks for that - I have amended my original post to include the relevant link.

Last time I included a link to a very relevant thread on another machining forum which answered a poster's query here it was very promptly removed. It was a while ago though - will see what happens this time.

Frank.

[Vernonv]

Thanks Frank, I will have a read through that link.


With the Nuttall dealer ....During the last year I've sent him a number of queries (3 if I recall correctly) via his web site and have not got a single response. I should probably call him, but when looking to purchase stuff I like to deal with it in writing.

[electrosteam]

Vernov,
I have a 4-jaw mounted on a plate with a 2 1/4" x 8 tpi register and 126.6 mm OD.
(Sorry, cannot remember if you have already sorted out the size you need)

Additional details and a photo of the plate can be supplied if it could be of use to you.

The plate is otherwise destined to be either scrap-binned or modified ( unlikely ) to a D1-3 mount to fit the chuck to my Bantam.

John.

[Vernonv]

Thanks for the offer John but I've got all the specs/info I need now.

Now I just need to get in and start building my collet chuck.