Lathe restoration SN20

[TexBuxer]

I made folder to google pics, I have problems with postimage.org https://photos.app.goo.gl/HEhxoY152FhQqShB9
Wormgear has made room for itself in casting.
I found what is wrong in feed lever, guide piece was worn, I welded and grinded to original shape.

[Toolmaker51]

Well, it's not cut and dry easy; just worthwhile. It's a stout machine, visible in proportions of headstock. TOS isn't common here, I've run their mills and they are astounding.
You are learning [and doing] things millions have no clue exist. It's OK with thousands of us looking over your shoulder.

[TexBuxer]

I've been thinkin that I make diy grinder for bedways. There would be rigid frame that rolls over bearings in unworn grooves, and takes guidance from outside and underside surfaces. Frame would be 300-400 mm long, both ends on bearings. Side and under bearings slightly loaded so frame has no freeplay. Adjustable stand that carries small bench grinder with cup wheel. Stand can be mounted in each end of frame so bedways can be grinded fully. Also there could be stand for mm dial clock to monitor how much material is removed.

Ive been looking for pictures from ready devices but I could find. Some youtube videos has those. If you have suggestions, please tell.

[Frank S]

I for one am not in favor of grinding the bedways let alone trying to build some portable grinding device capable of maintaining all of the many flat angled and vertical surfaces in true precision parallelism and angularity. Before such a method is even considered other options should be investigated.
In all cases you will need a couple pairs of matched V blocks, 123 blocks long precision machinist straight edges and shorted ones , a set of parallels dial indicators depth gacues and other precision measuring equipment like a precision machinist protractor machinist squares verniers or digital calipers all of these are required to determine which surfaces are the ones worn most of all a good pencil and note pad and some marking agent such as dykem (Prussian blue).
You may find that using such devices as block sanding/ or scraping planes or a large machinist file, hand scrapers and or power scrapers will be the better choice for truing your ways. You may also find that just a good cleaning and oiling then adjusting the carriage will be good enough even if there is some slight deviation in tightness throught eh length of the travel you will need to check the concentric alignment of the spindle to the tail stock and run out.
But to try and DIY some form of grinder to do this for a 1 off would be quite an undertaking in itself. Even if the bedways were ground to shape the likehood that they will require scraping afterwards is high on the scale
That's just my opinion

[Toolmaker51]

I agree with Frank S. Feeler gauges alone do not prove a lathe carriage cannot maintain a cylinder over available transit of ways.

The depth of tooling to just build a 100% accurate way grinder is steep. That said, portable way grinding isn't unheard of. The first issue is if SN20 ways are hardened. If so, that further complicates getting a proper sliding finish. That texture is called 'lay marks'. Like scraping, even though small, retain lubricant. A cup wheel has the wrong contact orientation. I'd question bench grinders have suitable concentricity of bearings and wheel mounting to generate flatness. Another issue of grinding in place is getting all of the length in plane head stock to tail of bed. There are not less than two measures of this flatness, not just end to end plane, but peaks demonstrated by a profilometer.
Most of the challenge hangs on attaining a guiding footprint on dependable surfaces that will re-establish continuity to worn areas. If I was there 'selling' to you, my task be illustrating carriage falls into a pair of depressed areas simultaneously.
Lets say you are set on restoring the ways. Remove the carriage, rent a full length cast iron straight edge [or optics] determining how far out it really is. A simple google search will locate machinery rebuilders that will estimate or quote cost to accomplish what is needed.
That will either dissuade or initiate building a DIY way grinding machine.

[TexBuxer]

I have minimal budjet in this project. My car is very greedy I know what it will cost if repair is done by professional, I could get decent lathe with that money. I paid this lathe with work, and I like to diy my stuff. Lathe is only supporting tool for my car projects.

[Frank S]

I have minimal budjet in this project.I know what it will cost if repair is done by professional, I could get decent lathe with that money. I like to diy my stuff. Lathe is only supporting tool for my car projects.

All's more the reason to shy away from an attempt to build a grinder set up.

[TexBuxer]

Bedways are now grinded with homemade grinder. Now I have to rise saddle to correct wear, I was thinking to get suitable metal rulers and tackweld them in to saddle bottom to rise it. Hope there isn't too much friction. Scrapers must be fixed too.

[Frank S]

How were you able to maintain flatness, parallel square straight and true to all surfaces using a grinder set up running on the ways themselves?
And why would you need to raise the saddle? if you took so much off that the rack and pinion no longer have proper mesh then shim the rack down to meet the pinion.
the Head stock and the tail stock alignment are the 2 most critical items. I can't see the height of the saddle being that critical unless you too lots of material off of the ways

[TexBuxer]

I had to grind so much that lead screw is not in correct line. Frame of the grinder is longer than saddle and it slides in surfaces that doesn't wear, I made frame so rigid that it won't vibrate and took small amount at a time. There is more pictures in shared gallery. https://photos.app.goo.gl/HEhxoY152FhQqShB9