Scraping Of Old Lathe Ways

The issue with grinding precision surfaces is that it is not easy to achieve, and not easy for the customer to know the difference. I am finding this out personally in learning to use my surface grinder. Shiny does not mean flat! Gleaming does not mean accurate! Ground both sides does not mean parallel! A lot of grinding is done on old worn out machines that are not capable of doing good work, especially without a good operator who really knows and cares how to make the grinder do the best work it is capable of. If you have machine components ground for accuracy, make sure they are properly inspected for parallel, flat, and tolerance to your satisfaction before accepting the work and paying the bill -- unless you only want it to look pretty...

"The issue with grinding precision surfaces is that it is not easy to achieve, and not easy for the customer to know the difference. I am finding this out personally in learning to use my surface grinder. Shiny does not mean flat! Gleaming does not mean accurate! Ground both sides does not mean parallel! A lot of grinding is done on old worn out machines that are not capable of doing good work, especially without a good operator who really knows and cares how to make the grinder do the best work it is capable of. If you have machine components ground for accuracy, make sure they are properly inspected for parallel, flat, and tolerance to your satisfaction before accepting the work and paying the bill -- unless you only want it to look pretty..."

American grinding is family owned and has been in business since the early 1940's. One of their specialties is regrinding lathe bed and cross slide ways. Their major customers are job shops and other commercial machining businesses. I doubt they could stay in business 65+ years if they didn't do quality work at reasonable prices.

I didn't personally inspect their work, but the previous owner was more than satisfied with their work and he is a perfectionist to the highest degree. When I inspected the machine I was accompanied by 2 machinists that each worked over 30 years in our shop. They were both impressed with the quality of work of the grinding company and the previous owner. One of the guys even took several test cuts and was more than satisfied with the results.

I do agree that learning the complexities of grinding can be time consuming and frustrating. Over the years I've used at least half a dozen different brands and styles of surface grinders. Each has it's own personality and quirks.

The most frustrating experience was with the machine I purchased for my shop several years ago. It seemed that as hard as I tried my parts were always slightly oversized. It took over a week of serious inspection of the machine before I found the reason. Apparently the previous owner had changed the gear ratio on the wheel downfeed. The original gear set had a 3 to 1 ratio. The replacement set had a 4 to 1 ratio. So for every .0005 thought I was removing I was actually only removing .00041

Bob Korves said:

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...

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Yeah, didn't mean to imply that everybody was as rich as Croesus, only that Okuma explained the benefits of hand scraping very well. Most of us old timers were expected to learn hand scraping as part of our job. I was pouring and scraping bearings up until NAFTA hit and before that, hand scraping was a way of life on the assembly floor..... Surely, there are plenty of folks out there that could teach other folks how. I'm betting there are a lot of competent teachers from the rust belt (out of work) that could make a healthy living...

Bob Korves said:

The issue with grinding precision surfaces is that it is not easy to achieve, and not easy for the customer to know the difference. I am finding this out personally in learning to use my surface grinder. Shiny does not mean flat! Gleaming does not mean accurate! Ground both sides does not mean parallel! A lot of grinding is done on old worn out machines that are not capable of doing good work, especially without a good operator who really knows and cares how to make the grinder do the best work it is capable of. If you have machine components ground for accuracy, make sure they are properly inspected for parallel, flat, and tolerance to your satisfaction before accepting the work and paying the bill -- unless you only want it to look pretty...

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What Bob says is true. However, I don't believe these concerns apply if you go to a shop who specializes in grinding lathes with CNC controlled grinders. These shops do make it easy and have all the equipment to set up and measure sub tenths precision on their surfaces. The method these shops have told me, is that they first mount the bed on a fixture to measure wear, then flip the bed over to grind the reference surface on the underneath of the ways that the rear gib bears on. THen, Once the reference surface is established they rotate over again and use that surface to measure and precisely grind the V's and flats. No problem they do it every day. Cost estimates for grinding my big iron 12 x48 Utilathe were all around $800.

Ands It's true you don't need to scrape these CNC ground surfaces- they are plenty accurate. however they should be flaked for oil retention or you will get accelerated wear and be back in the same boat as before.

AND, what most people don't think about - you probably should scrape the built up surfaces on the compound, apron, and tailstock bearing surfaces so these components sit flat on the newly ground ways. Otherwise they will rock to and fro like a hobby horse, giving you worse precision than you started with. Hence the $5000 rebuild costs for most lathes. 500 to 800 for grinding. 4500 for all the detail work to rebuild and scrape all the other components - not including coat of new gears in the headstock!

Alas, I opted to go find another used lathe, rather than rebuild. The cost to rebuild simply was more than even a new machine.

Glenn

Glenn Brooks said:

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Ands It's true you don't need to scrape these CNC ground surfaces- they are plenty accurate. however they should be flaked for oil retention or you will get accelerated wear and be back in the same boat as before.
Glenn

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Do Not Flake the bed ways. This is how we used to do it. Doing so, allows particles of grit to get trapped in the flaked areas and when the saddle passes over the bed, the saddle collects these pieces of crud and the wear process is accelerated to the point you have a worn out bed sooner than if you left the flaking off. Way wipers do not do a good job of wiping when it has to pass over flaking.

Now what you do is flake the underside of the ways of the saddle for oil retention. I remember the days of flaking unharden bed ways, some were over 6" wide, and those old machines had worn out beds in less than 3 years from daily continuous operation. And yes, they were lubricated with one-shot lubricators that were pumped once a day. You could see the "black crud" mixed in with the oil as the slides moved over the bed ways.

Ken

Ken, very good information to know! Thanks for clarifying.

Glenn

To flake or not to flake ?

Monarch 10EE bed ways that I've seen weren't flaked from the factory. The beds are hardened and ground.

A couple of guys had their 10EE beds ground by a grinding co. in Dallas ? and they were with .0005 ( I can't remember if .0005 per foot or over the 20" bed length) as close as they could measure.

The carriages, crossfeed and tailstocks were hand fitted to each machine.
Both the carriage and the tailstock have a oil system that oils between the carriage/tailstock and the ways they ride on.

Hal

Up until the early 1960's nobody out there flaked their bed ways. Somewhere in the 1970's when I started noticing it on rebuilds we were getting rebuilt in Dallas, they flaked the ways for oil retention was their comment. I think it was their way to get to rebuild the machine again sooner. I recall seeing flaking on just about everything back then. But after newer machines with harden ways started showing up, the older machines with un-harden bed ways were being scrapped out and replaced.

EDIT:
Machinery dealers were flaking ways on worn machines to hide wear as far back as I can remember! May still do it!

Ken

I'm not sure when Monarch started Flame Harding their lathe beds. Some in the 40's were hardened.
That why they are still running.
Monarch started harding their lathe beds in 1936 .

Hal

4gsr said:

(snip)Machinery dealers were flaking ways on worn machines to hide wear as far back as I can remember! May still do it!

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I think a lot of flaking is done for the sole intention of making a less than proper job look better, to pretty it up. Of course, some flaking is desired for oil retention, so I am certainly not saying that flaking is a scam, far from it...