• Hi - We're having intermittent forum issues. Posts, alerts, and anything involving email like signing up or password changes are having problems but not for everyone or everywhere. Josh is working on it. No ETA right now. Thanks Josh - BTW this is a volunteer forum so SLA's are just best effort. EDIT -> I manually batch updated about 25 people stuck on the email notification. Try logging in now with your password. EDIT -> May 8/23. I updated another bunch of users stuck on email notifications. Try to login if you are stuck. If you really can't get in contact us on facebook or if you know a forum member get them to ask us.
  • [Ad-Free Experience]
    Register Today, Craft a Post, and Enjoy an No-Advertising Experience.
    Click Here to Register

A small job for larger lathe - must be able to chuck up a 5" backing plate

Perry

Super User
I'm looking for someone in Calgary that has a larger lathe that can chuck up a 5" backing plate.

The backing plate only threads onto my lathe with about 2 1/2 threads. I'm thinking I would need just over 1/8" taken off to make things a little safer.

Thank you DSC_2820.JPG
 

David_R8

Scrapper of metal
Moderator
Premium Member
I'm looking for someone in Calgary that has a larger lathe that can chuck up a 5" backing plate.

The backing plate only threads onto my lathe with about 2 1/2 threads. I'm thinking I would need just over 1/8" taken off to make things a little safer.

Thank youView attachment 11688

Just thread it on your lathe with the spigot facing out and then then face it down to the right depth.


Sent from my iPhone using Tapatalk
 

RobinHood

Ultra Member
What @David_R8 said - should work if you can mount the plate reversed and you can bottom it out onto it’s spindle register. If you can’t bottom it, the spigot face may not be in a plane parallel to the register after machining because the threads are not usually accurate enough to locate the back plate. After you mount it reversed, check the runout of both the chuck mounting face and the spigot. There should be none. Threaded chucks depend heavily in their registers for location.

If David’s method does not work for you, I can machine the plate for you.
 

Tom Kitta

Ultra Member
If you want you can use one of my lathes - both can easily turn 5". Try first to put it backwards on your lathe but measure with indicator that it is indeed flat. Alternatively this can be cut on a lathe or a mill and then ground on a grinder.
 

Perry

Super User
Sorry for the slow reply here guys. I've been reading the responses just haven't had a good time to sit down and reply.

@YotaBota I was looking for that thread. I remembered reading it but could not remember what site I seen it on. Thank you.

@Tom Kitta I have a mill that might be large enough to rig something up to do this, but in the end I figured it would be best done on a lathe. Simpler with a better outcome.

My big concern is my little shop is down in my basement. I have never cut cast before and understand it can be very messy. Most of my work is on small watch parts and pieces. Keeping everything clean is hard enough. This lead me to the conclusion to farm this one out.

@RobinHood I will send you a message.
 

YotaBota

Mike
Premium Member
I have never cut cast before and understand it can be very messy
From what I understand the fine cast dust is very abrasive and everything needs to be cleaned afterward.
When I was parting my backing plate I kept the ways covered and the shop vac sucking up the cuttings, worked out well with very little extra cleanup.
 

Perry

Super User
Just a big thank you for Robinhood for helping me out with this little project. More time involved in setting it up then actually cutting.

Thank you for all the comments and the help.

DSC_2827.JPG
 

PeterT

Ultra Member
Premium Member
Nice work. I've never really understood the mating surfaces of screw on adapters when it comes to seating. Is contact confined to the larger face (green) or does the inner lip (red) also come into play?
 

Attachments

  • 2020-11-22_9-22-58.jpg
    2020-11-22_9-22-58.jpg
    13.9 KB · Views: 31

Dabbler

(John)
@YotaBota cast iron has carbide inclusions in very small crystals. when you cut the material these become parting lines in the matrix, so many of the 'dust' particles have at least one side with a ferrous carbide surface, which is MUCH harder than any lathe bed (or even some grinder wheels). This dust destroys mating surfaces as it is a very effective lapping compound when mixed with any oils.
 

Johnwa

Ultra Member
Nice work. I've never really understood the mating surfaces of screw on adapters when it comes to seating. Is contact confined to the larger face (green) or does the inner lip (red) also come into play?
Both of those plus the threads (they act as a really steep taper). I believe if you want to take the chuck off and then have it go back on exactly right then the red surface is the most important. It’s the most difficult to fit though and unless you bore it yourself tends to be a bit loose. The green surface ensures things are square. It along with the threads will get you pretty close.
 

YotaBota

Mike
Premium Member
Dabbler - thank you sir, I knew I'd read somewhere that cast dust was bad and now we know why. From now on I'm going to cover the ways as well as using the shopvac.
 

TOBARApprentice

Super User
Why not put it in the mill and machine the 1/8 off? If you don’t have a mill then here’s a great way to start the conversation...... Ask the misses “do you want me to be safe?” To which she’ll answer, of course..... to which you reply that you need a mill.... zip, zap, zooey, you have a mill and problem solved!


Sent from my iPhone using Tapatalk
 
Top