Grafting feedscrew (Q from a new guy)

[Dr Stan]

(04-28-2015, 05:58 PM)DaveH Wrote: This will get me into a lot of trouble.
Your lathe was designed by engineers made by machinists.

DaveH

Yep, just when you think it's all blown over the anvil will drop. 

[TomG]

(04-28-2015, 09:20 PM)Pete O Wrote: Is crashing as much an issue with the crossfeed as with the longitudinal feed? The drive gear on the leadscrew of my lathe is a slip fit with a tapered pin, so the drive is only transmitted by the pin. However if I introduce a clearance fit into the middle of the crossfeed screw, as it is only supported at either end, I think it would cause problems with sagging in the middle (like me).
I'm not sure I have the confidence to produce a tapered fit, I'm only going to get one chance at this (unlike the threading of the new nut, thankfully) and don't want to risk destroying the driven section of the shaft.

Oops. I was thinking you were joining the leadscrew. The cross feed screw does not need a shear pin because it is driven by the leadscrew.

Nevermind.

Tom

[f350ca]

(04-28-2015, 05:58 PM)DaveH Wrote:

(04-28-2015, 04:15 PM)EdK Wrote: I guess I misspoke. My lead screw is pinned but not with a shear pin. It's pinned with a 3/16" spring pin with a breaking strength of about 4100lbs.  

Ed

This will get me into a lot of trouble.
Your lathe was designed by engineers made by machinists.

DaveH

And then for poetic justice, some of us engineers have to build our own designs.

One of the kids and I were making a cross country trip when he was about 3. Stopped at a dinner and got chatting with one of the locals, he asked what I did, told him I was an engineer, Charlie looks up at me and say's no your not, you don't drive a train.

[EdK]

(04-28-2015, 10:53 PM)Dr Stan Wrote: sounds like someone replaced the shear pin with a spring pin.  Not too difficult to correct.

Nope, came right from the manufacturer that way.

Ed

[DaveH]

It seems to happen all the time, one part is replaced with another part just to save 0.5 cent with little or no thought.

I also thought we were talking about the main lead screw   I think I have lead screws on the brain  
 
DaveH

[Sunset Machine]

Did somebody say "Logan"? The leadscrew gear on mine has a bunch of spring loaded detent balls between the gear and the hub. I left a board on top of the chip tray a while back and heard the gear let loose when the board caught the carriage. I don't remember the sound it made but it sure got my attention.

Mumble, grumble.. Can't turn a taper.. Wish I had your lathe. Both of mine turn tapers all by themselves.

[Vinny]

It's called a Safety Gear. Unfortunately mine doesn't have one. It was an option that's no longer available and I haven't seen one on ebay (yet).

[Dr Stan]

(04-29-2015, 04:54 AM)EdK Wrote:

(04-28-2015, 10:53 PM)Dr Stan Wrote: sounds like someone replaced the shear pin with a spring pin.  Not too difficult to correct.

Nope, came right from the manufacturer that way.

Ed

Still does not sound right.  The spring pins could have been installed by an error at the factory.  IMHO I'd replace it with a very soft steel or even aluminum pin just to protect the more expensive parts of the lathe.

[Highpower]

Mine has a spring pin too (lead screw to gearbox) from the factory. Bought the lathe new in the crate.

[EdK]

(04-29-2015, 10:54 PM)Dr Stan Wrote: Still does not sound right.  The spring pins could have been installed by an error at the factory.  IMHO I'd replace it with a very soft steel or even aluminum pin just to protect the more expensive parts of the lathe.

Not likely a factory error, more likely a design error.

How would one go about figuring out the correct diameter and material to use to replace the spring pins with shear pins?

Ed