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Scraping a mini lathe?

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Sdmf5150

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#1
Probably a silly question, but I was wondering if anyone has scraped in one of the Chinese mini lathes.
I want to learn more about scraping and thought it might be a good project to see how smooth and accurate they could be made.
 

Asm109

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#2
Sure. Why not. You get practice on a practical item and your downside if things go pear shaped is modest.
At a minimum you will learn how to measure and see how accurate your lathe is to start.

Lastly, if everything goes south all you have to do is edit the title of this thread to Scrapping a mini lathe.
 

tertiaryjim

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#3
Scraping in my 13-36 crappy lathe made a world of difference.
Many complain about the mini lathes but I'm certain they can be much improved.
Study it and gather your surface plate and measuring tools first.
Then, you can check to see if it needs scraping before purchasing or making scraping tools.
This will also assure you know how to properly check the component alignments and give you time to
make any jigs or tooling needed.
Don't forget that the surfaces will need to be flaked as well.
Those dovetails are a killer to flake by hand and most of mine look like a steel clawed chicken was grubbing for worms.
On the other hand they retain oil and move smoothly on the mill/drill I'm completing.
The lathe is scraped in but I will need to tear it back down to flake it.
I did the lathe one component at a time so had to tear it down several times.
This was a pain but it worked out as I found just properly spreading the blue and using the surface plate
requires learning. Each time I tore the lathe down I re-checked the compleated components and found they needed
more work as my skills had improved so I was better able to expose and see the flaws I had left.
Gibbs can be a real pain to make, they warp badly during machining, but it's fine to shim the old gibbs if they
were properly made at the factory. Many/Most weren't.
Many cheaper machines were so poorly built that even a crappy scraping job will make a incredible improvement.
 

royesses

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#4
There is a post somewhere on this forum where one of the machinists scraped in a mini lathe for his young son. Try searching mini lathe modifications

Roy
 

fitterman1

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#5
I've scraped my G0602 headstock, crosslide and compound and it made a huge difference to smoothness and accuracy. Haven't touched anything else yet. I know my tailstock is high because I lowered my headstock by about 006". Good thing about doing this is you can control to the nth degree all the geometrical tolerances of your machine, and you know where you stand in that regard. Working out the sequence of how your going to go about it can save you future rework. I suggest if your going to scrape your cross and compound slides and you decide to flake them, flake them a little sparser towards the extremities so those small depressions don't collect the fine particles that will eventually become a grinding paste.
Some serious measuring gear won't go astray either.
cheers
 

Sdmf5150

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#6
Where is a good place to get straight edges? I have seen the ones Richard King sells but I think they ar too big
 

fitterman1

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#7
Dunno, I live in Australia and they're rarer than rocking horse sh_t here. They have to be selfmade here I reckon.
cheers
 

machPete99

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#8
I "scraped" in the saddle and tailstock of my minilathe using needle files.
Also replaced the standard spindle ball bearings with tapered roller bearings (intended for auto wheel bearing use), which ran much smoother.
Shimmed headstock and tailstock so inline with bed and each other.
Its fairly accurate but still very wimpy in terms of size of stock and DOC that it can comfortably handle.
Bought a Clausing and now do most of my work on that.
The minilathe did make the bushings needed to get newer bearings to fit the Clausing, Its also good for small work.
 
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homebrewed

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#9
Home Shop Machinist published a series of 10 articles about scraping small items, including a mini lathe. The first one with the mini lathe info appeared in the September/October 2012 issue and the last one was in the November-December 2012 issue. They do sell reprints. There was enough there to make a book on the subject but that doesn't seem to have happened. The earlier issues include info on how to make your own scrapers and a diamond-charged grinder to shape and sharpen carbide scrapers.

Mark
 
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