Mini Lathe Upgrades

[John Rudd]

oooo. I like that! I will add that to the list!

Where will this end..? The list is growing...

How about a cam lock for your tail stock? Dead easy to make from few scraps, the mini lathe I sold recently was modded in this way to make it a more attractive proposition....

[Brass_Machine]

I got into the shop for a short time this weekend. Didn't have a lot of time, I ended up forgetting to take pictures as I went. I got the leadscrew mounted up. Was fairly easy, just a little time consuming.

It went like this:

1. Mock up
2. Test
3. Test again
4. Spot drill one hole
5. Remove everything
6. Drill the correct hole for the tap
7. Tap
8. Go to step 1 (repeat for all 4 holes)

This was step 7 on the last hole to be tapped.



Finally got it all assembled:



You can't see it, but I have my cordless drill chucked up on the leadscrew off to the left. I ran the saddle up and down the bed a few times to ensure there was no binding. I am happy to report that all looks good. Still a little early but the motion seems much smoother than before.

Just waiting on the new motor mount to arrive now.

I may not be able to work on it in the next few days as I am studying for a test at work...

Still deciding what color to paint it.

Eric

[vtsteam]

That looks great! 

[Stilldrillin]

That's a nice long bed, Eric!   

Don't forget the leadscrew handwheel......... 

David D

[Rob.Wilson]

Looking good Eric 


New bed looks a canny bit longer , which will come in handy with the CNC build 


Rob

PS Hope the test went well.

[Brass_Machine]

Yup. Test went well...

Now going back to the build. I got the motor mount in from LMS. It fits the motor just fine, however, it does not fit in the space for the motor in the lathe bed. Debating on the solution while I am at work today and hope to get something fixed by tonight when i get home.

Eric

[Brass_Machine]

So the motor mount doesn't quite fit.



It fits the motor just fine. I debated cutting it down and making it work, but in the interest in time (I have some work to do) I decided to go with using the original mount. Which is basically cutting some slots and tapping two holes.

I measured and re measured. Then I mounted the bed on the lathe.



I proceeded to try to get the lathe all dialed in and 20 minutes later I started the first cut. A few tense moments later I had the first slot done.



Shortly there after, I got the second slot done. Finally drilled and tapped the two holes.



As you can see, I ended up nicking one of the holes for the high torque motor mount. I did cut the slots the same as the ones on the 10" bed... I don't believe it will matter much. If you look very carefully, you can see where the first cut of the second slot went off track a little. I didn't tighten it down enough and the lathe moved. I am very surprised I got through the first slot without it happening...

Again, not too much of a big deal. It will never be seen.

Eric

[sparky961]

<snip>
Again, not too much of a big deal. It will never be seen.

I see it.... :P


Sorry, couldn't resist.

[No1_sonuk]

Are you going to be adding DRO and/or CNC capability while you've got it in so many pieces?

[Brass_Machine]

So I ran into an issue tonight. I get it all back together and wired up. Turn it on and... nothing. Lights come on but the motor doesn't turn. So I take it apart and start trouble shooting. I have variable power going to the motor. So that part is good. I pop the the motor brushes out. Those look good.

Frustrated I pull the bell housing off the back and check the voltage at the brushes. Nothing. I check the voltage at the brass pieces that surround the brushes. Nothing. Hmmm a closer look shows one of the springs that connects the leads to the brass pieces is busted and not making contact.



Knowing what I have to do, I look at LMS to see if they have replacement leads. NOPE... they do have replacement bell housings at LMS though. $17 a pop. Not sure I want to spend that much. Can I just solder the leads directly on to the brass pieces?

Eric

[Stilldrillin]

 Can I just solder the leads directly on to the brass pieces?

Eric

I'd have a go, Eric! 

Don't go using too much heat, and loosen the fit in the plastic bell..... 

David D

[RussellT]

Can I just solder the leads directly on to the brass pieces?

I don't see why not but I'd think about trying to fix the spring too.  Ideas that spring to mind are tying the ends together with a small piece of wire or hooking the broken ends together, and then locking with a dab of solder.  If the spring is copper you could try winding a new one.  If it doesn't work you have lost nothing.

Russell

[andyf]

I don't know the internal diameter of the spring, but maybe you could pass a length of wire into it at the break, round the spring and then out again at the other side of the break. Put the spring on the brush holder, and then twist the ends of the wire together to tighten it up like a tourniquet.

If that's impractical, cut the spring off the lead, and in its place solder on a length of copper wire so you have a T shape, bend the arms of the T round the brush holder and twist the free ends together to tighten up. I'm not sure how hot it gets inside these motors, but hard solder rather than soft might be better.

Andy

[PekkaNF]

Usually nothing inside of the good quality heavy duty electic motor is soldered, because they can get very hot. Specially the brushes. They easily exceed soft solder meltting temperature...it's not very ideal to have blop of solder bouncing around commutator and brushes. Another reason is repeated thermal shock, usually grimp joint responds better than a solder. Then again: the end bell looks plastic, maybe that motor should not be run hot?

Most usual joint construction is: BRUSH - flat copper braid - then grimp connector or disco connector for lead.
http://www.healystool.co.uk/productimage.html?imageid=18624&size=large
or this type flying lead and spade (sorry for the lamp):
https://www.interlight.biz/itemimages/64382.JPG

Is there any good electric motor shop nearby? They should have something to replace and iprove it. You need to specify voltage (has an effect on brush material), motor type and mechanical dimenssions. We have one oldtimer here...he has retired least 15 years ago and still has his shop on a garage.

Pekka

[Brass_Machine]

Fixed the spring issue on lunch today. BTW Thanks Andy for the idea!!

The broken spring:



I took apart a twist tie for the metal 'string' inside.





Then I threaded it into the spring and tightened it up on the post.





Yes, I trimmed the tie before I put it together again.

[Stilldrillin]

Nicely/ neatly done Eric! 

David D

[Brass_Machine]

Put the motor back together, made sure it spun freely and ran back downstairs to test it out.

The motor started to spin and POP blew the fuse. Cr@p. Ran to radioshack bought some more. Took the motor back apart. All looked good. Put it back together again and POP again. It will spin for a millisecond and then pop the fuse.

Started searching the web as to the reason why... I found this troubleshooting check list from LMS.

Figured out I have a busted switch in the POT, but that isn't is causing it to blow the fuse. It has been like that for a while now and I didn't have issues before. It is perm on.

I tested the MOSFETs per the PDF. Everything is fine until I get to step 8. It says I should see 120k to 140k. It comes up infinity (1). 

Would that let the motor spin for a second and then blow the fuse?   

Eric

[John Rudd]

Eric,

You can test the speed controller with a lamp as a load...Take a household lamp/bulb whatever you guys call them, wire that in place of the motor and see what happens.........

Testing the motor....If you have access to a variac, connect the output to a bridge rectifier ( plese take care to connect it properly...) connect the dc out from the rectifier to the motor and see if it spins...Connect a 2 amp fuse in series with one of the leads for protection...

Let us know how you get on......

If you were a bit nearer I'd help more, I've repaired motors and speed controllers for mini lathes before you know...

[Brass_Machine]

Eric,

You can test the speed controller with a lamp as a load...Take a household lamp/bulb whatever you guys call them, wire that in place of the motor and see what happens.........

I will probably do that tonight.

Testing the motor....If you have access to a variac, connect the output to a bridge rectifier ( plese take care to connect it properly...) connect the dc out from the rectifier to the motor and see if it spins...Connect a 2 amp fuse in series with one of the leads for protection...

Nope. I don't have access to a variac or even really know what one is 

Let us know how you get on......

I will!

Eric

[andyf]

The motor (in the US they are 90V DC) should turn, though slowly, if connected up to a car battery. It will probably draw a fair old current, so best use jump leads.

Andy

[Stilldrillin]

Eric.
I had the same problem. Among many others, over time.

Dave Bluechip brought a variac. Nowt wrong........ 

I put it back together. POP!! 

I bought a new motor, and control box..... Perfect! 

The motor was sent to Portugal, where it's working perfectly! 

The control box is still on Dave's bench. 

Funny stuff, electrikery........   

David D

[Brass_Machine]

I have thought about hooking it up to the Mini Mills controller to see if it works on that.

This GUY is saying the MOSFETs need to be out of the board to test. See 'testing components'. I haven't watched his vid yet.


Getting frustrated.

 

[John Rudd]

The motor (in the US they are 90V DC) should turn, though slowly, if connected up to a car battery. It will probably draw a fair old current, so best use jump leads.

Andy

No need for jump leads... the current draw isnt that great..A small spark mebbe when connected..but you will need more than just one battery..2 at least         

3 would be better

Taking the mosfets out of the board requires some degree of skill...there's a  possibility that you may damage the copper lands in an attempt to remove the mosfets...I normally cut them away from the board then remove the small remains...

[Brass_Machine]

Ok. This has been driving me crazy. The only thing I have done is take it apart and put it back together. And dropped the motor, but I have fixed all of that. It doesn't explain WHY the board may have issues.

So I went through the board and connections AGAIN.

That was when I found it. There is a jumper wire that goes from on port on the wire clamp to another port. I somehow had knocked that lose with the dis-assembly. However, the wire was curved and was putting just enough pressure to look like it was connected. I popped it back in and screwed down the clamp.

Ran downstairs hooked it all up and risked my last fuse.

IT SPINS!!!!!!!!

 

Now to get it all back together!

Eric

[andyf]

 

Well, there you are! The moral of this story is that things should be given a good coat of looking at and wire-wiggling, to save all the

Ive been there myself. For me, the fuse blew as soon as the lathe was plugged in and switched on. Took me ages to find that I'd trapped a wire from the (now discarded) chuck guard switch under a panel, and nicked though the insulation.

Isn't it a great relief when faults which bring expense to mind can be fixed without resort to the wallet?

Andy