Restoring Presto 8N

[marchingband]

Heya Trolls.
I started working on a new (to me) lathe today, a Presto 8N.
The first problem to come up is a missing element to the bearing and TT shaft assembly, and I am stumped because I cannot seem to locate an exploded diagram of the assembly, or any info online about this part.

At the base of the TT shaft, a single ballbearing is nested into the end.
The TT shaft mates with a housing, which in my case, has the TT shaft end mating with a concave race (or what looks like it could be a race), but the ballbearing doesn't even reach the race. I think I am missing a part.
Does anyone know how this part of the assembly is supposed to work? Is there a thrust bearing in the 8N? if so, why the nested ballbearing at the end of the TT shaft!?
Does anyone have an exploded diagram of this assembly? The 6N manual (I can't find the 8N manual) has no helpful info.
thanks!!!!

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[MEGAMIKE]

hi
there is a loose ball bearing that sits in between the mounted ball bearing and the bottom plate..

i love my 8n hahah

when i go to studio tonite i will measure the ball

[marchingband]

Thank you Megamike!
Please do let me know the size of the ballbearing when you get a chance!
cheers!

[tragwag]

seconded - yes there's a loose bearing in there too.
I can't get it out to measure, but it looks about 3/16" maybe?
I got a replacement at a regular hardware store, no issue

[marchingband]

Thanks Tragwag, 3/16" worked well.
Here are a few photos of this project.
As you can see, this machine is missing the feedscrew.

Has anyone had feedscrews machined? 3D printed?

Does anyone have one for sale?

Does anyone have a creative solution to advancing the carriage in the absence of a feedscrew?

Thank you!

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[Soulbear]

Hi marchingband,

Does anyone have a creative solution to advancing the carriage in the absence of a feedscrew?

This :-

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Driving This :-

24 Volt Gearmotor Lathe Leadscrew Motor2.jpg

Driving This :-

Stainless Leadscrew.jpg

A Further Toothed Pulley Machined to fit the Stainless Steel Studding "Leadscrew" and with the 24V DC 160RPM Gearmotor (Guessing here, because I don't know the Ratio of "Platter Rev's to Leadscrew R.P.M.) combined with the Pulse Width Modulation Speed Controller and Digital Display, you'd have a Infinitely Variable Range of L.P.I. whilst Cutting.

BSR DR33C Restoration-39.jpg

I've not yet done any Cutting with my BSR DR33C "Lazarus Lathe Project" but the "Omens" are looking "Pretty Good" following a similar Modification to that particular Lathe. Check out the Thread to see how whilst using this Set Up, I've also acheived "Semi-Automated" Cutting of Lead-In and Run-Outs at the press of a Button. Just a few Hopefully Helpful Suggestions as an Alternative to Sourcing the Missing Presto Leadscrew.
Regards Soulbear

[rsimms3]

The good thing about the 8N is that it uses the same feedscrews as the 6N which a lot of folks use so finding a feedscrew will be a little easier than say finding one for a 6D or other earlier model. I know piaptk had some made at one point and I think ROLANDJAYS either made some or had some made (don't quote me on that). Hopefully if others have had some made they can speak to recommendations for machinists.

There have been a couple thread about feedscrews through the years. Markrob actually created a diagram that could be used as a basis to have screws made, the picture is in the Wiki here: http://lathetrolls.pbworks.com/w/page/53979308/Feedscrews


The diagram doesn't explicitly say it but you need a keyway cut in both ends of the feedscrew. On the spindle end you need it to drive the feedscrew from the "ratchet" as it's described in the manual and the other end for the hand crank to advance the overhead for lead in/out and between tracks.

[marchingband]

Thanks soulbear and rsimms3 !
hopefully piaptk or ROLANDJAYS can advise.
I prefer to use the original feedscrew method, if possible, though the potential for automation seems tempting.

[marchingband]

I have found a company that can provide a generic acme feedscrew, 3/4", left handed thread, at a pitch that would provide about 140 LPI.
They are also able to machine the end holes.
The cost is very low, about $40 for stainless, and half that for normal steel.
Has anyone tried using a generic feedscrew for this purpose?
thanks!

[markrob]

Hi,

I don't think acme threads will work. The overhead uses a replaceable knife edge rather than a half nut. The butress style thread is better suited to work with the lathe.

Mark

[marchingband]

Oh ya I see that, Thanks Mark. I was looking at my 8DG which has the threaded 1/2 nut type feed finger, and the thread profile on the feedscrew looks like acme.
thanks for clearing that up. Too bad really...thought I had found a cheap solution.