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Questions About Lathe Way Scraping

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robotwizard

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#1
Considering scraping the ways and carriage on a 44" long by 7 1/2" wide lathe bed with 2 70 degree V's and 2 flats. Besides the basic hand scraping tools what else would I need to do this? What is used for a reference? Would I need a 4' long straight edge? A 4" granite table? ...or something different yet? I've downloaded the Connelly book and am reading through it...
 

Uglydog

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#2
Sounds like a great project!
Huge fun.
Do you know if she has hardened ways?

Have you scraped before?
You might want to start with a smaller project.
This is very doable. However, if you are like most of us it will take some practice.
You might want to start out with a smaller project with less at stake.
There is a clear learning curve.

I'm by no means an expert scraper. But, I'd be glad to share what I know and introduce you to my rebuilding mentor.
It'd require at least one trip to MN, if not several.

Daryl
MN
 

4gsr

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#3
Me myself, an average at scraping, somewhat knowledgeable at the subject. A lathe bed is not easy by any means to scrape back to true. I know of people that have done it, but they knew what they were doing. Myself, I would not tackle it, scraping back to true geometry.
You're lathe bed only being about 44" long can be easily be re machined on a good precision CNC mill or surface grinder if it has harden ways. Then from this, scrape the freshly machined surfaces, if not hard, to get the bearing spots per square inch. After this, scrape the saddle to fit the new bed.
If the lathe bed has less than .005" wear, checking against a straight edge and feeler gages, this can be be easily scraped in. Any worse than this, the bed should be machined. Just my two bits worth.

Ken
 

astjp2

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#4
Lathe ways are normally planed, then the saddle is scraped flat and true. Just some food for thought. tim
 

robotwizard

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#5
Thanks for replies...I've given up on having it reground as quotes I've gotten are astronomical. Only local place I could find wanted $6800. Others ranged from $850 and $1600 and would involve shipping to and from. MN too far to be practical for me, but thanks for the offer. Would be interested in connecting with the group once you get up and running tho. Trying to figure out what I will need for a reference for lathe bed.... Do I need to get some 70 degree V-blocks? Straight edge?
 

astjp2

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#6
You should get the connley book and read it, it would answer a lot of your questions. its available as a download on here. A straight edge would be used and the saddle would be scraped to match the bed.
 

4gsr

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#7
Need to look for a local shop that has a large CNC mill. Have them quote setting the bed up on their mill and taking off just enough material to get 100% cleanup. Will require carbide endmills ground with the correct angle to match the bed.
 

Woodemp

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#8
How do u know it needs to be scraped if you don't have a tool to check it? Maybe the bed is not the problem.
Does it have Gibs? Is the V's for the Tailstock?
Some lathe's use the flats for the carriage to ride on and gibs to locate it and the V's are for the Tailstock.
You need Prussian Blue to test your fit. Come's in tube's. And a lot of time and patience. I've scraped a few carriage's, crosslide"s, and other
fits with all the tool's I needed and it take's a lot of practice to learn how to read the contact area. Read it wrong and your back to the beginning.
A Milling Machine fit up is real fun.
 
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