I really want a beginner scraping project!!!

Saw this thread on the latest posts...

Hope this is not hi-jacking to much... however... had this idea...

For the purpose of 'true-ing' the ways of a lathe or mill... would it be possible (reasonable) to consider mounting a grinder on the spindle of a Bridgeport style mill, then mount the parts to be 'trued' on the table... and grind them?

This was/is an idea I had a while back... thought I would run it by folks and see how many holes there are in the idea.

THX for any replies.

John/GA
 
NO, grinding is not the correct surface for machine ways....or a mill table or lathe bed unless its specifically designed for turcite and then it is scraped. Tim
GA said:
Saw this thread on the latest posts...

Hope this is not hi-jacking to much... however... had this idea...

For the purpose of 'true-ing' the ways of a lathe or mill... would it be possible (reasonable) to consider mounting a grinder on the spindle of a Bridgeport style mill, then mount the parts to be 'trued' on the table... and grind them?

This was/is an idea I had a while back... thought I would run it by folks and see how many holes there are in the idea.

THX for any replies.

John/GA
Click to expand...
 
You would maybe grind it or mill it before you scrap it if you have a lot of variation to remove. Take you for ever to scrap .025 off the last 3in of the ways to get to the sag. At least in my head anyways, no experience.
 
astjp2 said:
NO, grinding is not the correct surface for machine ways....or a mill table or lathe bed unless its specifically designed for turcite and then it is scraped. Tim
Click to expand...

Hmmm...

Now you have my curiosity up...
Is grinding too smooth to hold oil?

Curious as to the 'why' on this...
And why Turcite is different?

THX
 
GA said:
Hmmm...

Now you have my curiosity up...
Is grinding too smooth to hold oil?

Curious as to the 'why' on this...
And why Turcite is different?

THX
Click to expand...

Short answer: friction.

Ground surfaces are too flat. Have you ever wrung gauge blocks together? Ground surfaces (although no where near as flat as gauge blocks) create too much drag. You are correct in that they don't hold oil but they also don't play well with foreign objects that get caught between them, especially if the object is a steel chip that is harder than the ground cast iron.
 
In machine tool building and rebuilding, commonly the bed or table ways are ground, for a smooth true surface; then the matching surfaces, I.E. the saddle of a lathe or the saddle of a mill is scraped to fit the ground ways, whether on the original surface or the Turcite that has been applied to the worn member if necessary; this presents a surface that may be flaked to hold oil to the ground surface. The ground surface, or scraped if that is the mode of the rebuild, should never be flaked due to the possibility of dirt or small chips may be dragged into the interface and cause wear. This mode is seen all too often for decorative purposes --- This is one lesson learned in Rich King's scraping classes.
 
This is dependent on what types of ways the machine has. Box ways will be ground due to ease of manufacture, dovetails will largely be scraped. Read the Connelly book, it gives the best explanation. Turcite is a plastic that has metal like brass imbedded in it that is scraped to hold and channel the way lube and becomes the wear surface over the hardened ways. Tim


benmychree said:
In machine tool building and rebuilding, commonly the bed or table ways are ground, for a smooth true surface; then the matching surfaces, I.E. the saddle of a lathe or the saddle of a mill is scraped to fit the ground ways, whether on the original surface or the Turcite that has been applied to the worn member if necessary; this presents a surface that may be flaked to hold oil to the ground surface. The ground surface, or scraped if that is the mode of the rebuild, should never be flaked due to the possibility of dirt or small chips may be dragged into the interface and cause wear. This mode is seen all too often for decorative purposes --- This is one lesson learned in Rich King's scraping classes.
Click to expand...
 
astjp2 said:
This is dependent on what types of ways the machine has. Box ways will be ground due to ease of manufacture, dovetails will largely be scraped. Read the Connelly book, it gives the best explanation. Turcite is a plastic that has metal like brass imbedded in it that is scraped to hold and channel the way lube and becomes the wear surface over the hardened ways. Tim
Click to expand...

When I was researching scraping and oil retention the the only peer-reviewed paper I found on the subject concluded that the optimum surface had .1" dia by .001" deep round-bottomed dimples burnished into it so as to cover 25% of the area. This resulted in a 25% reduction in wear compared to a ground surface. Thus the best thing to do is to go over your ways with a ball-peen hammer and then stone out the ridges.

I'm not about to try it.
 
in Richard King's scraping class we were shooting for 20-25 DPI, .0005" to .001" deep , oil flaking was .002"-.004" deep.
 
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