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

[Perry]

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

 

[David]

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.


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[RobinHood]

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]

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.

 

[YotaBota]

I had the same problem with a 3 jaw. I mounted my faceplate on the lathe, took off a skim to make sure it was flat then mounted the adapter to the faceplate and parted off about .375 of the register.
https://canadianhobbymetalworkers.com/threads/1-1-2-8tpi-3-and-4-jaw-threaded-chucks.1833/post-19238

 

[Johnwa]

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

In addition make a spacer that fits over the spindle register.. It will keep thing a bit more true than the threads by themselves.

 

[Perry]

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]

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]

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.

 

[PeterT]

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?

 

[Dabbler]

@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]

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]

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]

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!


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[Dabbler]

@Perry, you can come over and machine it here..

 

[Perry]

This was completed back in November. Robinhood came to the rescue. Thank you again R.


@Dabbler, thank you for the offer.
@TOBARApprentice ...not so loud....... they might hear us.