# scraping my mini-mill, need advice



## Anko (Feb 1, 2011)

hi to all!

time as come to correct the poor´s dovetails of my mini mill, how i know that they are poor? when i disarm the table for cleanup and lub i notice that just a tiny line of the contact surface shows wear of use, then i check with my surface "porcelanate" plate if the middle piece of the table (the one that have the x and y dovetails) was flat, and it was no good, only two point of contact at the extreme, if i touch the piece a little i can feel and hear the click click of the metalic sound of the other two points balancing.

(and with the screwless vice, parales and all the stuff i still cant cut a 90 square corner ajja)

i research on the internet how to scrap metal, made a scraping tool out of a old file just as everybody recomend, that work good

but i have a little trouble whit my dye, im currenly using blue chinese ink, that cheap ink for drawing, i cant get those metal ink that everybody use, here in Chile i dont know if are abiale some of that, at least i have not find yet .

two problems: 1- the ink dry too fast (here is summer) and i have to remove the dry ink for every pass on the plate

2- the resulting marking on the workpiece is not like i see in the pictures and tutorials i have for reference

i show you some pictures:

the tool:







the piece:






the surface plate and ink:






the ink rare spotting point:






the point scraped:






afther a few passes:






as you can see, the ink spotting point is not like the references:






that keep my concern, and more the fact that that the ink not paint the wear lines, in this case this comes to my mind:






this is getting a little weird, if my mill is so bad, i start thinking better to let the thing like they are now, i do not have experience with scraping, and i do not want to ruin my mill!!

please
need advise to carry on this process, any help i will apreciate much!!

saludos


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## Tin Falcon (Feb 1, 2011)

check the gibs on that . I thought the ways were off on my mini mill made a new brass gib made a world of difference check the simple stuff first bud.
Tin


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## Maryak (Feb 1, 2011)

You could try adding a very small amount of heavy oil/grease to your ink. It may stop it from drying out and giving you a false reading.

Best Regards
Bob


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## Anko (Feb 1, 2011)

i have checked the gibs a lot, also made a brass one for the y axis a long time ago, they shows a tiny line of contact too, like this:






to solve that i have made a new one on brass, sanding, replasing the set screws, adjust a lot and all the times is the same result.

how i cant comprobate that the problems are the gibs?? i have trying to adjust rigth a tons of times

thanks for the quick responce tin falcon!

saluods


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## steamer (Feb 1, 2011)

Anko,

Send me a PM....we'll see about the ink.

I am trying to figure out a way to qualify your "surface plate"....but I havn't yet ...I'll keep thinking

Dave


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## steamer (Feb 1, 2011)

Hi Anko,

To accomplish what you have set out to do, you will need a surface plate and a master straight edge.

You can create the straight edge if you have a good surface plate...but if you don't, then you have two choices

Buy a surface plate from somewhere

Or 

Make three by one of the binary methods.

I would suggest you get a surface plate, or at least a very thick piece of polished granite floor tile.'

I am afraid your glass "reference" is too thin and will distort during your marking.

If the glass is all you have, I would stop where you are until you can get something a bit more suitable.

A 300mm x 450mm plate would be more than suitable...if you can get a mini mill, you should be able to get a plate.

If you can't trust the plate you have, I am afraid you will be chasing a ghost and slowly destroying your mill.

Let's start with a decent plate....see if you can find a chinese one in your area....that should be a start.

Then we can talk about straight edge construction.....I have some recent experience here.

Dave


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## steamer (Feb 1, 2011)

oh and some very good reading and video


http://www.machinerepair.com/

the video is worth it!

Dave


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## Tin Falcon (Feb 2, 2011)

there should not be a tiny line of contact like the photo shows. that was my problem.
I made my gib a bit oversize to better fill the space and prevent twisting. fignoggle is now recommending acetal gibs that may be worth a try as well. 
Tin


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## TroyO (Feb 2, 2011)

I had a similar problem with my mill.
I think it was made by Pringles, I'm pretty sure using the same mold they use for chips!

So, figuring a replacement table would be the fix I went ahead and tried my hand at "scraping" the ways. Nothing to lose, if I horked it would still have to buy a table! Even with my limited knowledge and total lack of skill I was able to make it a LOT better.

Instead of marking on a flat surface I simply ran over all the ways and dovetails with a magic marker and then assembled it and ran it back and forth a few times. Then I would "scrape" (I'm using the term loosely) the areas that the ink had rubbed off using the ground down file method. After several evenings of this I got to where it was rubbing the ink off over about 60% of the mating surfaces. Once I got that done I use valve grinding compound for a few hours (Messy) and finally got it to where it worked pretty well and evenly over the whole travel. THEN I made and installed brass gibs.

It is by no means perfect, but it is worlds better than it was. I went from having to keep the gibs so loose the table would visibly rock in the center and bind at either end of the travel to a smooth even travel all the way acoss with NO binding, and gibs that are touchy to adjust because the lock/no lock point is just a small fraction of a turn.

On the down side... "lock" is not as locked as it was before. The gibs slide smooth enough now that the hand wheels CAN overcome the "locked" gib which wasn't the case before.

I do however think I got "lucky" in some ways. I checked the table over it's travel and have less than .0004" difference. I tried to randomize my efforts so my accumulated errors would average out, LOL. overall, it turned out pretty well considering I was flying blind and just trying to make it work.

I guess the point of my rambling is... when your starting point is non-functional, it's kind of hard to go anywhere but up... and it may turn out better than you think.


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## Anko (Feb 2, 2011)

thanks for all the responses!

Steamer:

thanks for the advice! i stop scraping the mill to revaluate the situation

my porcelanate plate is a experiment, i was trying to find a economic replace for a granite plate, here i find a 40x60 granite plate (the same thats sold grizzly) but overpriced alot, because of that i was searching for a economic substitute

the porcelanate sure is fat, but as you said, it flex because is too thin

i will follow your advice, and go for the 60x40 granite plate!

thanks for the video links too!

Tin Falcon:

seem that the picture is not the correct to describe my problem, i will to try to explain better: :






that happens will my normal gibs and the one i made with brass too

the uper and bottom edge do no contact the surface, just te gib is not making a full contact

i think that the set screws heigth are not well, or that i conclude when my brass gib not solve the problem jajaj just frustrated

any advice?? i will apreciate!

TroyO:

at the final i was doing the same that you describe! with marker i was spoting the contact points and scraping






just i do not have the same trust that you, because i cant affort a new mill table, here all are super priced, and the tables are the same china made stuff that probably came with the same problem, if just the tables that shows grizzly catalog were here, and with that price probably i will have the same situation that you



i not have the trust to scrap the pieces too far, just a little passes and sand, but the mill showed improvement, not critical but good

i will save money to get the surface plate and continue with this process!

this is a little tool i made with a mt3 drill arbor and scrap plate to set the spinde true to the table movement, i made a 0.01 mm of terror at the extreme of the diameter in all directions






hope with this i will made a decrease in the tool marks!

thanks for the help!

saludos!


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## steamer (Feb 3, 2011)

Good, glad to hear Anko.

Like Tin Said, lets try the simple stuff first. Make up a new gib that fits properly.  If it doesn't work, you only lose the work on the new gib and you can put your old one back in.

Additionally, you should try your local library and find some books on the subject of scraping.  You will need to invest in your education too if your going to scrape your mill in.  

Connelly's book " Machine tool reconditioning" is a very good text on the procedures.

The book from my last post is a good scraping "how to do" book, and also worth investing in.

Be careful what you wish for my friend.  This is not a small task and will be a lot of work!

Dave


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## TroyO (Feb 3, 2011)

I think I recognize that picture....There are a couple of fixes I tried... 

Your gib locking screws are probably square on the end. That means the top of the square edge is contacting the gib above the centerline of the gib. That pushes the jib out of line like pictured. I put my gib screws in the lathe and put a rounded 45^ angle on the ends. That helped some. (Edit... ignore this bit, LOL.. I missed where you mentioned you had already made new gibs.) If/when you make brass gibs you can also change and correct the location of the pips. 

There is probably a better way than what I did, but when I made my brass gib I put the gib in place and aligned it where I wanted then tightened the gib screws to lock it in place. Then I found a drill bit that was a slip fit in the gib screw holes and removed one at a time and used a hand drill to drill the "pips" so they were aligned. Since the gib was in position at the time it also drilled the "pips" at the correct angle in relation to the gib.

Proper proceedure would probably be something like marking each "pip" with a transfer punch, then mounting it in a drill or mill at an angle matching the angle of the dovetail and drilling each one to matching depth. My way did work though, LOL. A happy medium would probably be something made like a spotting drill that just fits the screw hole?


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## TroyO (Feb 3, 2011)

Ohh, and another thought... I saw this somewhere although I don't recall where? Anyway... this one is a groove across the entire gib, you leave your set screws square. You may (?) have to still drill a flat bottomed hole to keep the gib from shifting around. I saw a diagram of it once and filed it away in the "Hey, good idea!" section of my brain.


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## Tin Falcon (Feb 3, 2011)

> Tin Falcon:
> 
> seem that the picture is not the correct to describe my problem, i will to try to explain better: Roll Eyes


You communicated well and I understand . where and how the back side of the gib hits is not important . the problem I had and I believe you have is the sharp edge of the gib is riding on the mating surface . Make the gib bigger so there is not all that extra space to twist out of position. fill that space. Do not make it tight that is what the adjusting screws are for. You want the flat of the gib bearing against the flat (s) of the dovetail. Also as others have said drilling or milling a flat for the screw to bear on is also important. 
Tin


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## bambuko (Feb 3, 2011)

It's always a dodgy thing to contradict the administrator and senior member , but I am sure he will not mind? (too much).

To "...Make the gib bigger so there is not all that extra space to twist out of position..." doesn't solve the problem, if anything, it might make things worse by gib lifting the things away from the dovetail. You are of course correct, when you say that we are to prevent "...twist out of position...".
Best way to do it, (apart from making new gib) is to do what TroyO has suggested (ie the groove) or make sure you gib screws have tapered ends. They should never be flat!
This is shown very well in this extract, form very excellent report on mods to 9x20 lathe, comparing asian modified gibs with original that inspired them:




You never want to make a gib so big, as to allow it to touch moving part - it should work against the dovetail pulling the moving part down.
Better still - make tapered gibs and never look back ;D

Chris

ps gib drawing is taken from:
9x20 lathe rebuild manual


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