Scraping Of Old Lathe Ways

[Micke S]

Here are some food for thoughts regarding renovation of old and worn lathes. This is what I learned yesterday from a Swedish guy who has been travelling all over the world renovating lathe and milling machines. He will now retire and I asked if he could scrape the ways on my old Bahco late to make them like new.

He told me that any renovation of an old lathe starts by grinding the ways to true them. Deep scars must be removed and any sag etc. near the headstock can only be corrected by corrected by grinding the complete ways. There is only one or two companies in Sweden that provides such service these days.

The scraping is just the last measure as he said, to make it more perfect. This ends up in that a full renovation is very expensive (many thousands of dollars), so even big companies hesitates to renovate old machines. He also told me that if I wanted a like new appearance it wouldn't cost me much to get the lathe scraped by him, but it wasn't really meaningful unless the appearance is in priority.

The good news, which were no news to me though, is that some sag on by worn ways often doesn't mean a lot as long as the requirements are not very high. In case the apron drops like e.g. 0.001 inch due to worn ways it doesn't affect the turning diameter nearly as much unless the diameter of the work piece is very small.

It is of course always good to file down any damages that protrudes from the ways to avoid steps on a workpiece.

 

[cathead]

Here are some food for thoughts regarding renovation of old and worn lathes. This is what I learned yesterday from a Swedish guy who has been travelling all over the world renovating lathe and milling machines. He will now retire and I asked if he could scrape the ways on my old Bahco late to make them like new.

He told me that any renovation of an old lathe starts by grinding the ways to true them. Deep scars must be removed and any sag etc. near the headstock can only be corrected by corrected by grinding the complete ways. There is only one or two companies in Sweden that provides such service these days.

The scraping is just the last measure as he said, to make it more perfect. This ends up in that a full renovation is very expensive (many thousands of dollars), so even big companies hesitates to renovate old machines. He also told me that if I wanted a like new appearance it wouldn't cost me much to get the lathe scraped by him, but it wasn't really meaningful unless the appearance is in priority.

The good news, which were no news to me though, is that some sag on by worn ways often doesn't mean a lot as long as the requirements are not very high. In case the apron drops like e.g. 0.001 inch due to worn ways it doesn't affect the turning diameter nearly as much unless the diameter of the work piece is very small.

It is of course always good to file down any damages that protrudes from the ways to avoid steps on a workpiece.

Thanks for the excellent information. I run old lathes and one learns how to operate the machine even though there may be
considerable wear. If you know the inaccuracies, you can effectively compensate for them and still produce good work.
I don't think it would be a practical thing to try to rejuvenate my old machines. It becomes more than setting the dials
and machining away. This was explained to me by an older machinist who ran lots of old equipment and did it very well.
He's gone now but I'm happy to have picked up on some of his amazing skills.

 

[Bob Korves]

Let's put this in perspective. Scraping in a South Bend 9" lathe with a three foot bed, not hardened, that is in moderately worn condition and is owned by a hobbyist, doing the work for a personal and educational project is certainly a worthy and attainable goal. Scraping in a heavily worn Monarch 18 X 120" lathe with hardened ways that is used commercially in a small one or two man shop is quite another thing altogether. It is doable, but you would need to start as a young man and have a plan to get it done before retirement in between other work...

Properly and accurately ground beds and slides do not need to be scraped in. Some high end lathes are scraped in after grinding, either superficially for looks or seriously for ultimate accuracy and damn the cost. Other lathes are scraped after grinding because the old grinder is little more accurate than the clapped out lathe. Scraping a ground surface is a PITA until you get underneath all of the ground surface.

Do not think for a moment that the 40's and 50's South Bend and other lathes that sold for $100-200 were properly scraped in, it was done quick and dirty because that is how the big boys did it, and customers liked the "look."

Scraping is a tedious job, but becomes a Zen sort of a way to help let life's worries aside while getting absorbed into the rhythm of the scraping cycle of plan, inspect, mark, interpret, scrape, debur, repeat, over and over and over, while time and other worries melt away. Paying for real, serious, machine reconditioning scraping, not decorative scraping or flaking to try to make a silk purse out of a sow's ear, is not really an option, especially for a hobbyist. The work is too labor intensive, and time costs money. For a hobbyist, scraping a machine is done because the owner wants a challenge, wants to learn and practice how to do it correctly, does not own a grinder big enough to grind the ways and cannot afford to hire it done, and accepts the considerable time and effort involved in doing the project correctly to a proper end result. To paraphrase JFK, he does not do it because it is quick and easy. He does it because it is difficult and rewarding. It is certainly not something to take lightly, and buying a new machine is probably the best choice if you cannot accept a worn machine, but are not likely to properly learn the skills and invest the time and effort to scrape the machine in properly.

 

[samthedog]

I always thought that grinding the ways and scraping the saddle was the way to go. This way you reduce the amount of scraping needed while achieving a high level of accuracy. This is what I have seen done on a few lathes and they were brought to as good or better than factory spec.

On milling machines this is a different story as many mills didn't have hardened dove tails. On some mills though, like the Schaublin 53 the ways and dovetails were hardened and in some cases blocks of high chrome steel that could be swapped out. This was also employed on the Weiler Primus lathe where the lathe ways were also bolted on blocks that could be swapped out.

Paul.

 

[expressline99]

Let's put this in perspective. Scraping in a South Bend 9" lathe with a three foot bed, not hardened, that is in moderately worn condition and is owned by a hobbyist, doing the work for a personal and educational project is certainly a worthy and attainable goal. Scraping in a heavily worn Monarch 18 X 120" lathe with hardened ways that is used commercially in a small one or two man shop is quite another thing altogether. It is doable, but you would need to start as a young man and have a plan to get it done before retirement in between other work...

Properly and accurately ground beds and slides do not need to be scraped in. Some high end lathes are scraped in after grinding, either superficially for looks or seriously for ultimate accuracy and damn the cost. Other lathes are scraped after grinding because the old grinder is little more accurate than the clapped out lathe. Scraping a ground surface is a PITA until you get underneath all of the ground surface.

Do not think for a moment that the 40's and 50's South Bend and other lathes that sold for $100-200 were properly scraped in, it was done quick and dirty because that is how the big boys did it, and customers liked the "look."

Scraping is a tedious job, but becomes a Zen sort of a way to help let life's worries aside while getting absorbed into the rhythm of the scraping cycle of plan, inspect, mark, interpret, scrape, debur, repeat, over and over and over, while time and other worries melt away. Paying for real, serious, machine reconditioning scraping, not decorative scraping or flaking to try to make a silk purse out of a sow's ear, is not really an option, especially for a hobbyist. The work is too labor intensive, and time costs money. For a hobbyist, scraping a machine is done because the owner wants a challenge, wants to learn and practice how to do it correctly, does not own a grinder big enough to grind the ways and cannot afford to hire it done, and accepts the considerable time and effort involved in doing the project correctly to a proper end result. To paraphrase JFK, he does not do it because it is quick and easy. He does it because it is difficult and rewarding. It is certainly not something to take lightly, and buying a new machine is probably the best choice if you cannot accept a worn machine, but are not likely to properly learn the skills and invest the time and effort to scrape the machine in properly.

This is a perfect description of why I want to do mine. The zen and tediousness is something I seriously require in my life. That and my love of old machines in general.

Paul

 

[Ulma Doctor]

This is a perfect description of why I want to do mine. The zen and tediousness is something I seriously require in my life. That and my love of old machines in general.
Paul

Hi Paul,
with your attitude and a little instruction- you can do what we do....

 

[tertiaryjim]

I have scraped the saddle on my China lathe "Three Times"' before calling it goodnuff and though its now far better than it came from the factory I can't say it's truly correct.
Getting that V shape and the correct alignment rite is tough.
Dovetails are difficult but much easyer.

 

[ewkearns]

Hand scraping is always the way to go... if for no other reason than giving lubrication somewhere to be, other than at some variable thickness trapped [for an indeterminate time and indeterminate thickness] between two finely ground way surfaces. Gage blocks should wring, way surfaces, not so much....

Okuma's opinion.

 

[Bob Korves]

Hand scraping is always the way to go... if for no other reason than giving lubrication somewhere to be, other than at some variable thickness trapped [for an indeterminate time and indeterminate thickness] between two finely ground way surfaces. Gage blocks should wring, way surfaces, not so much....

Okuma's opinion.

I agree, ewkearns. Unfortunately, not many hobby machinists can afford to buy an Okuma. Properly scraped and fitted new machines are jaw dropping expensive, and for those of us who have done some scraping, totally understandable why they cost so much.

The learning curve of doing it properly yourself in your home shop is much higher than than what it seems at first look, but the skills and tools for doing good scraping work are quite attainable and affordable. The real issue that needs to be addressed is the nut behind the scraper -- are you REALLY willing to take the time to fully understand and practice the details of how to approach a scraping job, and then spend LOTS of hours doing careful work to a high standard?

A piece of canvas, some tubes of paint, and a few brushes does not make a Rembrandt... There is only one man teaching the art of scraping as a full time business in the US that I am aware of, and he is getting ready to retire...

 

[projectnut]

Having the ways ground may not be as expensive as some think. I recently purchased a Sheldon MW-56-P lathe with hardened ways. As the name implies it's an M series lathe with a Worthington variable speed drive. It has a 56" bed mounted to a pedestal base. The bed ways carriage and cross slide were reground as part of the refurbishing process.

I am currently out of town, but if my memory serves me correctly it was done by American Grinding and Machining Company based in Chicago.

http://www.americangrinding.com/grinding-services.html

At the time the cost to regrind was $400. 00. That's been a few years ago so I'm sure the cost has gone up somewhat. The final scraping was done by the previous owner. To me the prices seemed reasonable. When I return home I intend to contact the company and get a price for regrinding the bed and cross slide ways on my 60" Seneca Falls Star #20 lathe. If the prices are still reasonable I'll be disassembling it and taking it to their facility.