Mellor lathe.

[God mode restorations]

Morning guys.
Been experimenting with the lathe. Just getting used to it and adjustments where needed. The small problem I have is when I disengage the power feed I am getting a small dip at the end .everything is running nice and all gibs are good with no movement. It's got me puzzled as I have checked everything.

 

[gaz1]

from my understanding of what your doing is your finish except for using a tool to go to the right

so you need a left cut tool and then move away from the part being lathed

 

[Richard.]

That finish is awful spencer. Almost looks like a very fine thread. I’m not an expert but I’d look at changing a lot of stuff to improve that.
Your feed to rpm ratio seems to be traveling too quickly.
Get that set up to feed slower
I’d be looking at a high rake tool
Slow things down and take a proper cut.
Obvious things to check
Tool on centre
Minimum over hang of the tool and job or support the job with steady or tail stock.

 

[God mode restorations]

That finish is awful spencer. Almost looks like a very fine thread. I’m not an expert but I’d look at changing a lot of stuff to improve that.
Your feed to rpm ratio seems to be traveling too quickly.
Get that set up to feed slower
I’d be looking at a high rake tool
Slow things down and take a proper cut.
Obvious things to check
Tool on centre
Minimum over hang of the tool and job or support the job with steady or tail stock.

It's not finished yet just rough turning. I have a finishing tool .still sussing things out and my tooling isn't the best.

 

[Richard.]

It's not finished yet just rough turning. I have a finishing tool .still sussing things out and my tooling isn't the best.

That’s not a roughing cut.
I’d look at getting the set up sorted with some carbide inserts. Eliminate the tooling for the time being and get the feeds/speeds/rigidity sorted. Once your finish is coming off nice with the inserts you know then all you’ve got to address is your tool making skills.

 

[God mode restorations]

After some examination I have a cross slide issue to sort. Some shiming needed .A lot of movement in the screw. And the screw nut is loose in its seat. Always faffing something.

 

[God mode restorations]

That’s not a roughing cut.
I’d look at getting the set up sorted with some carbide inserts. Eliminate the tooling for the time being and get the feeds/speeds/rigidity sorted. Once your finish is coming off nice with the inserts you know then all you’ve got to address is your tool making skills.

Yer . Still sorting bits out and doing repairs where needed. Gets time consuming and frustrating

 

[zx9]

After some examination I have a cross slide issue to sort. Some shiming needed .A lot of movement in the screw. And the screw nut is loose in its seat. Always faffing something. View attachment 137041 View attachment 137042

I can or think I can see the ghost of a missing fitting in that last photo, kind of a round baring housing around the screw with a lobe each side to locate on the two pins.
Though that could be just my imagination.

However the rough finish does look like there is play in some of the slides / gibs, from doing the rounds sorting out the Drummond I found a better cut under power as everything was under a constant force. Could the saddle gibs be too tight causing the power feed to stutter as it overcomes the resistance? ( that last bit was thinking out loud rather than talking from my very limited experience)

 

[zx9]

Another thought, how far is that bar sticking out of the chuck? And have you tried it with a centre in the tail stock?

 

[God mode restorations]

I can or think I can see the ghost of a missing fitting in that last photo, kind of a round baring housing around the screw with a lobe each side to locate on the two pins.
Though that could be just my imagination.

However the rough finish does look like there is play in some of the slides / gibs, from doing the rounds sorting out the Drummond I found a better cut under power as everything was under a constant force. Could the saddle gibs be too tight causing the power feed to stutter as it overcomes the resistance? ( that last bit was thinking out loud rather than talking from my very limited experience)

Yes there is a large housing that I have. I removed it to see what was going on. The problem is a very worn cross slide screw. So worn in the middle it's caused the screw nut to come loose in its seat. Plus with the movement it's made an oval of the casting. I thinks it's off to a machine shop for a new screw and nut.its a 5/8 5tpi left hand square thread form. What ever that means.

 

[zx9]

I thinks it's off to a machine shop for a new screw and nut.its a 5/8 5tpi left hand square thread form. What ever that means.

it probably means expensive.
There is a slight bend in my lead screw which I only noticed when I trial fitted the thread dial indicator bracket I am making, we will see how that pans out.

 

[God mode restorations]

it probably means expensive.
There is a slight bend in my lead screw which I only noticed when I trial fitted the thread dial indicator bracket I am making, we will see how that pans out.

Yes. I appreciate the fact that old machinery will need work. It does naff you off thoe at times.

 

[addjunkie]

Before you rush to spend big, usually one piece is sacrificial...if you had a new nut made, and reamed the slide hole for a bush. Might not be perfect but would be a big improvment. Then again to a man good on a cnc lathe will make the bits without too much trouble

 

[Seadog]

Before you rush to spend big, usually one piece is sacrificial...if you had a new nut made, and reamed the slide hole for a bush. Might not be perfect but would be a big improvment. Then again to a man good on a cnc lathe will make the bits without too much trouble

I doubt it. Compare the thread form at the end to that in the middle, it's around a third smaller. You need both parts Spencer. I'm tempted to have a crack at it, but it could take me a little while to do. I've only ever cut standard V form threads and one ACME/ Brown and Sharpe, all right handed, so it would be an interesting challenge.

 

[God mode restorations]

I doubt it. Compare the thread form at the end to that in the middle, it's around a third smaller. You need both parts Spencer. I'm tempted to have a crack at it, but it could take me a little while to do. I've only ever cut standard V form threads and one ACME/ Brown and Sharpe, all right handed, so it would be an interesting challenge.

Yes it needs both parts. But I got it covered. I appreciate the offer seadog.

 

[Bill Edwards]

Cutting a left handed thread is no different than cutting a right hand.

Instead of the carriage advancing towards the chuck it's simply reversed, so the tool starts from the chuck end and moves in the direction of the tailstock.

Arguably it's actually easier than a RH thread because you can work away from a shoulder rather than advancing towards it, which frightens some people.

 

[Pete.]

New screw is made, nut nearly finished. I cut a 10tpi thread instead of 5tpi so the dial is now diameter-reading. I'll finish the nut over the weekend, it's going to take some figuring out because the spigot is not over the screw centre-line. The screw and the hole in the cross slide were both badly worn so we incrased the screw diameter to 1/2" and stuffed a 1/2" reamer through the hole to straighten it up.

 

[Hood]

Nice work Pete

Bit confused about increasing the Dia to !/2", thought the original was 5/8"

 

[Pete.]

The screw is 5/8" but diameter at the dial end reduced to 7/16" but there was no bush so the mild steel screw running on the plain cast iron had worn both badly.

 

[Hood]

Ah sorry Pete, read that wrong.
Once again, beautiful job