1940 Le Blond Regal Backing Plate Installation Instructions

[Shiseiji]

Their would be a risk of movement if the chuck register isn't a tight fit to the back plate I would of thought. Unless you did the "buck chuck" style screws to lock it in place.

If you had no interference fit you would need to indicate it in as you tightened the chuck bolts to the backplate.

Stu

Stu, my apologies, I shouldn't have answered pre-coffee. Yes, my bad for not making it clear that isn't the interface I'm talking about. The backing plate/chuck interface needs to be a press fit of the plate "spigot" into the chuck counterbore or in the words of LaBlond: " . . . rough turn out-side diameter 1/32-inch above diameter of counterbore in chuck. Also counterbore tapped hole at 45 degrees to 1/8-inch across flat; next, take finish cut off face of chuck plate.

Caliper counterbore of chuck and transfer size to outside mikes. Finish turn OD {of the spigot} to fit counter-bore allowing for a slight tap fit."

1/32" into the chuck body counter bore wit h a "tap" fit.

 

[Shiseiji]

I've read one place, un-cited, as most comments are, the "real" purpose of the spindle is to simply guide the chuck as it comes off the threads until it makes contact with the shoulder. Most opinions are that, with the exception of square cut threads, the spindle threads center the backing plate and hold the center until the backing plate makes contact with the spindle shoulder.

Lots of arguments, but also many reports that a backing plate machined for the larger diameter SB register, when the registration interface is lengthened to cover a Logan's longer register, will repeatedly hold the TIR it starts with. Usually better if the back plate/spindle shoulder contact is re-faced as above.

Not trying to argue, just comparing what I've read with the LaBlond instructions.

 

[Shiseiji]

When I've made backplates for my lathe I have held the blank in the three jaw faced bored and threaded then tested with a thread gauge (clone of spindle thread) then threaded the backplate onto spindle (with the three jaw still attached just in case ) then made the register to fit the new chuck.

I have always tried to get it as close as possible to the chucks register step.

Stu

When using a chuck, keeping the backing plate in the chuck is oft given and IMHO smart advice! I've only done one backing plate, for a cheap collet chuck I'm sorry I bought. My 4 jaw is < half the weight of my 3 jaw and while the 3 jaw TIR isn't bad, I figure if I go that route I'll use the 4 jaw just to spare my two bad shoulders

 

[stupoty]

When using a chuck, keeping the backing plate in the chuck is oft given and IMHO smart advice! I've only done one backing plate, for a cheap collet chuck I'm sorry I bought. My 4 jaw is < half the weight of my 3 jaw and while the 3 jaw TIR isn't bad, I figure if I go that route I'll use the 4 jaw just to spare my two bad shoulders

Hello,

No offense taken (or meant) I too was trying to check which register you were talking about

yeah the face and the short part that is not threaded on the spindle nose gives the repeatable mounting.

The chucks getting heavy is a pain for sure I've seen some people on the forum have made wood sleds that put them on center for fitting, definitely looks handy.

Stu

 

[Shiseiji]

And none taken. Been on forums long enough to know I'm often the one guilty of any poor communication. Didn't want to steal other's illustrations, in retrospect I should have waited until I had something I could use. I'll edit the top post when I do in hopes it will help others. My only intent.

I use a chuck "sled" in part to protect the ways from "opps." But am close to mounting some Unistrut as a mono-rail over both the Logan and the Monarch to just lift the things up and away from the lathe. I've had the stuff for too long in my "I'm a gunna." pile.