rob_b's Little Lathe Rebuild

[rob_b]

Well I finally broke down and bought a mini-lathe. It's been a long time coming but for the past couple years every time I had the money I would end up building a new r/c car. Briefly entertained buying a used machine but in the end I prefer tinkering with new stuff.

There are a million places to pick these machines up but I decided on the Grizzly 7x12. What I like about Grizzly is that they stock all of the parts if something needs replaced.




They come slopped with a heavy coating of grease so the first thing you have to do is disassemble the machine and give it a thorough cleaning. Some people see this as a bad thing but really its not, you get to see how everything works and in my case make some modifications.

Here is the cute little bastard broken down and cleaned up.




On the main unit I have already cleaned up the gearbox and adjusted all of the gear mesh'es (the gears came set with zero backlash and were literally all jammed together). Not sure if I just got lucky or not but the OD of the spindle has approx .0001" runout and the ID taper has about .0003". I have not indicated the chuck yet.

While it was torn down for cleaning I am lapping all of the sliding surfaces to improve the overall quality of the machine and reduce chatter. Lapping is a process where you use an abrasive compound to wear two surfaces against each other to remove the high points and increase contact area. Here you can see some of the parts broken down, cleaned and lapped.




It's hard to show but in the large flat area you can see the rotary machining marks vs. the long straight "grain" of the angled area that has been lapped.




So as of now the compound and cross slide have been lapped and are offering a very smooth motion. Next up is lapping the main ways. First though you have to set the height of the carriage strips. It is recommended to set the strips to a .040" clearance with the carriage, test fit and reduce the clearance between carriage and the ways to .001".

Here I have a .010" and .030" feeler gauge pre-setting the height of the saddle strips.




Installed the carriage on the ways and set-up my new best friend, the .0005" Test Indicator.






First I zero'ed the dial.




Then pushed down on the carriage to see how much it moved. On this side it was just shy of .012" so I need to reduce the strip clearance by .011".




Now zero the other side.




Press down and the dial reads .013" meaning I need to reduce clearance on that side by .012" to get to my .001".




So I guess, I was slightly off setting the height of the strip or something else is up. I'm not sure yet. Just for reference a human hair is roughly .001" in width.



Maybe more tomorrow night, I am really enjoying this so far

[travis c.]

I did all of the same stuff to Chump's lathe when I got it home.




































Yeah right!

[rob_b]

Wouldn't expect any less from you King Travis

[travis c.]

Originally Posted by rob_b

Wouldn't expect any less from you King Travis

ZZZZZZZZZZIIIINNNNNGGGGGGGGGG!

[MTHead]

Sweet, once you get it all dialed in you can come over and do mine...

[jeepman128]

The Goal has shown itself once again

[rob_b]

What lathe do you have John and more importantly does your garage have a/c?


True story Kolby, I'm a believer

[Erik D_lux]

Cool thread rob!

I have one of these sitting in the corner not getting used because I just dont want to mess with it. I will be keeping an eye on this thread for some more good tips.

[DwaneO]

Holly Cow , looks like you spent more on measuring devices than you did on the lathe.......
.0005".....really????

WOW


OK , hurry up and make something already.
Send me a link to the 4 jaw you want too.

[losikid]

Originally Posted by DwaneO

Holly Cow , looks like you spent more on measuring devices than you did on the lathe.......
.0005".....really????

WOW


OK , hurry up and make something already.
Send me a link to the 4 jaw you want too.

I don't have one...but when i was setting the machines up in my mach class at the cc i was using a dial indicator that was down .0001 little ticky's, went to +/- .001. The project i had to use that fine guy, i was milling a 6" stretch and had to be within .0005" on the height from one side to the other (i can't remember the term used for). So that milling head had to be dead on perfect square with the part/table.

I think the .0005 indicator he has is pretty standard...we had like 15 of them, which is pretty good considering we only had 10 edge finders

[sloppy]

Getting the saddle set right is the worst part on these things..

[rob_b]

Thanks Erik, it's been a fun project so far.

Dwane, losikid is correct, it's a standard test indicator .030" travel with .0005" divisions. The really preceice ones have .008" travel with .0001" divisions. I ended up buying three cheaper indicator's because the best ones would have exceeded the cost of the lathe itself. As it stands I have roughly the same value wrapped up in tooling just to get started. Trust me, I want to make some parts NOW but it will be worth it to get the little guy tuned in.

Yeah, setting those strips will take a bit of patience since none of the screws are very accessible while it's mounted.

[MTHead]

Originally Posted by rob_b

What lathe do you have John and more importantly does your garage have a/c?

It's a typical China copy, I picked it up locally for $500.00. They were imported by "Big Dogs" on the bay. Only difference is it has a digital RPM meter..

and NO!!! I'm freaking DYING out there this time of year

BTW,
http://littlemachineshop.com/product...ory=1963256898

Worth every penny..

[sloppy]

Originally Posted by MTHead

It's a typical China copy, I picked it up locally for $500.00. They were imported by "Big Dogs" on the bay. Only difference is it has a digital RPM meter..

and NO!!! I'm freaking DYING out there this time of year

BTW,
http://littlemachineshop.com/product...ory=1963256898

Worth every penny..

Thats the one I have to.. I think if I had it to do again I would get a wedge type.. not to mention the tapers on the tool holders are just terrible, Could just be QC on that brand and yours is good but mine sucks..

[rob_b]

Sounds like you can make two of the covers we were talking about then It's to keep the swarf out of the carriage gears.

Yep that's the QCTP I bought too...

If it is a total failure I'll probably get this setup. Wish I would have seen it before I ordered

[Robbob]

Make anything yet

[sloppy]

Originally Posted by rob_b

Sounds like you can make two of the covers we were talking about then It's to keep the swarf out of the carriage gears.

Yep that's the QCTP I bought too...

If it is a total failure I'll probably get this setup. Wish I would have seen it before I ordered

That is the one I wish I would have went with. And I probably will switch to it or something similar.. The wedge type seem to be a little better..

[rob_b]

If nothing else the wedge style should give you a more repeatable tool position.

Originally Posted by Robbob

Make anything yet

Send your gears!

[travis c.]

The title of this thread makes it sound like a fairy tale.

Especially if you say your name as it looks..............Robbie

[rob_b]

Are you the hookah smoking caterpillar?