Author Topic: Micro lathe refurb  (Read 22777 times)

Online Jo

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Re: Micro lathe refurb
« Reply #30 on: September 02, 2014, 07:57:11 AM »

Jo, didn't you make headstock oilers for one of yours? Was that the high speed mod you refer to?

Yes I made drip oilers for C1, which allows me to work for longer without having to add a drip of oil every 20mins or so which is much better. But I do have to watch I do not knock the oilers off when I use the chuck key. The later machine has flippy cap oilers, they do not hold as much oil but more than adequate for most normal operations.

But they redesigned the entire headstock on the later machines, the headstock cast was a bit thin either side of the bearings so they squared them up adding much more material.

Jo
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Offline ths

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Re: Micro lathe refurb
« Reply #31 on: September 02, 2014, 01:02:54 PM »


Jo, didn't you make headstock oilers for one of yours? Was that the high speed mod you refer to?

Yes I made drip oilers for C1, which allows me to work for longer without having to add a drip of oil every 20mins or so which is much better. But I do have to watch I do not knock the oilers off when I use the chuck key. The later machine has flippy cap oilers, they do not hold as much oil but more than adequate for most normal operations.

But they redesigned the entire headstock on the later machines, the headstock cast was a bit thin either side of the bearings so they squared them up adding much more material.

Jo

Do you think it is the rate of oil feed that allows the higher speed?

From memory, you made your oilers wick fed with cotton thread draped into the delivery hole, didn't you? How have they performed?

Sorry to sound demanding! I'm not.

Hugh.

Online Jo

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Re: Micro lathe refurb
« Reply #32 on: September 02, 2014, 01:25:11 PM »
I think the rate of oil feed effect the streak down my walls  :LittleDevil: Without sufficient oil the headstock will get hot.

As long as I do not leave the tops off the oil pots when I am not using the lathe (which allows the oil to seep out all over the place  :() they have performed well.

But to be honest I made them last year and I did not do that much on C1 last winter as it was a warm year and I could happily go out to the main workshop in the evening. If it is cold this winter both C1 and Sexy will be getting more of my attention in the evenings in the week  ;).

Jo
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Offline Allen Smithee

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Re: Micro lathe refurb
« Reply #33 on: September 03, 2014, 10:00:30 AM »
At the risk of making a complete prat of myself and exposing my abject lack of understanding on this, can I ask a silly question? If you want to run at speeds higher than the plain bearings might allow, and given that it looks like you're going to make a new mainshaft anyway, is there any reason why you can't machine the headstock castings to take tapered roller bearings (or angular-contact ballraces) and then just adding a suitable flange at the front of the mainshaft and threaded collar at the back so you can preload them to eliminate the play? The lathe would then be good for much higher speeds (10,000rpm if desired!)

Just a thought,

AS
Quidquid latine dictum sit altum sonatur

Offline tangler

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Re: Micro lathe refurb
« Reply #34 on: September 03, 2014, 03:20:22 PM »
If you're a prat then you and me both!  I had seriously thought about that.  Unfortunately, I don't think there is enough meat in the headstock to fit rolling ball type bearings  :( .  My thoughts were that this would be a relatively quick refurb  :lolb:  so I didn't really want to make a new headstock.  I've got engines to make!  Since I'm making the new spindle (update later), I've decided to add a threaded collar at the back to take up the end float.  Even if I thread this 1/2" x 40 I shall need to lose some diameter off the fine feed worm to get the collar nut over it,  so it looks like the fine feed will have to go but I think the end float issue is more important.

Cheers,

Rod

Offline Allen Smithee

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Re: Micro lathe refurb
« Reply #35 on: September 03, 2014, 03:49:40 PM »
I see what you mean - would it be TOO tragic to use a smaller diameter mainshaft (so that tapered roller bearings could be accomodated), given that yo're not exactly going to want to use this machine a new flywheel for the QE2?

AS
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Offline Allen Smithee

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Re: Micro lathe refurb
« Reply #36 on: September 03, 2014, 05:13:53 PM »
...or failing that machine a rebate inside the ront and rear bearings and put poured white-metal bearings in them...

 :mischief:

AS
Quidquid latine dictum sit altum sonatur

Offline tangler

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Re: Micro lathe refurb
« Reply #37 on: September 04, 2014, 03:53:23 PM »
AS,

STOP right there.  This is taking up far too much time as it is   ;) .

The new spindle will be made out of this lump of Leaded free cutting steel.  In my naive way, I'm sort of hoping that the lead content may help with the lubricity.



I'm going to need an external lap so here's a lump of ally, drilled a half inch which should be oversize enough to slip over the spindle which will be turned to 1/2" + .002".



The lap needs a partial cut on one radius to allow it to compress



and a slanting cut through



This was an idea from an article by Duplex that Ron put up on his website http://www.modelenginenews.org/duplex/duplex_laps.html



before turning the spindle I thought it prudent to check the lathe for turning parallel by mounting the length of silver steel in the collet chuck



I turned a centre in the test bar



and checked the tailstock as well



All seems OK.  I turned the spindle to 0.502".  Micing it up showed a taper of 0.0005" with the small end at the tailstock (I wonder if this means that the tailstock is slightly high - could be a bit of swarf trapped underneath).  The lap would just fit on.



Here's the SiC powder and a little jar with some powder mixed with cutting oil.  I went straight to the 400 grit.  I think it took about 2 hours to get the spindle to 0.0002" over size all along. 



Very satisfying.  I finished off with another half hour of 600 grit.



The turning had left some cyclic variation in the right hand third which wasn't really evident until the lapping started.  It hasn't quite come out but we're going to lose that bit anyway.



Offline Allen Smithee

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Re: Micro lathe refurb
« Reply #38 on: September 04, 2014, 04:08:30 PM »
AS,

STOP right there.  This is taking up far too much time as it is   ;) .


<sigh> So typical of the youth of today - no time to do the job properly. Now a REAL engineer would be taking moulds from the headstock and digging a mine in the garden to mine the ore from which the iron will be extracted to cast into those moulds. That's the way we'd have done it when *I* were a lad, but these days everyone just wants the instant solution...

 >:D >:D

AS

Quidquid latine dictum sit altum sonatur

Offline tangler

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Re: Micro lathe refurb
« Reply #39 on: September 04, 2014, 04:35:27 PM »
I mentioned before that I want to add a locking ring to control the end float.  This is threaded 1/2" x 40tpi.  the M3 locking screws have both got brass pads on the end.



I held the lapped spindle in the collet to turn the register and nose thread, which I finished off with a 1/2" BSF (16 tpi) die.  I then turned the spindle around, held the register ind the collet and with tailstock support, cut the 40 tpi thread on the other end before finishing this with a die as well.

The lapped spindle is a snug but free turning fit in the journals.  I've also cut the recess for the pulley locking screw.



At this point I was still undecided about the fine feed worm, which is why I'd left that long thread.  Looking at the fit of the worm with it's wheel, the wheel is pretty worn.  I turned a shade over 16 thou off the worm radius ( that's the depth of the 40tpi thread) and there still seemed to be adequate engagement.  I decide to cut the worm off the old spindle and Loctite into a suitable recess in the new spindle.

The new spindle was mounted in the fixed steady, I'd used a Sharpie to mark where the position of the bearings so that the steady didn't score my freshly lapped surfaces.



I parted off the surplus end, drilled as much of the 9/16" through hole that I could manage from this end and bored the recess for the worm.



It remains to be seen whether the Loctite can cope with the torque of turning the lead screw.



I then remounted the the spindle in the collet and completed the through hole from this end.  I set up the topslide to cut the short 0 MT.  This shows a commercial full 0MT centre held between male and female centres.  Having used the DTI to set the topslide



I bored the taper and finished off with a reamer.



Trial assembly seems OK,



I've now glued in the worm so I'll wait a couple of days for the Loctite to go off before fiddling with it any more.

Thanks for watching,

Rod





Offline tangler

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Re: Micro lathe refurb
« Reply #40 on: September 04, 2014, 04:41:19 PM »
AS,

STOP right there.  This is taking up far too much time as it is   ;) .


<sigh> So typical of the youth of today - no time to do the job properly. Now a REAL engineer would be taking moulds from the headstock and digging a mine in the garden to mine the ore from which the iron will be extracted to cast into those moulds. That's the way we'd have done it when *I* were a lad, but these days everyone just wants the instant solution...

 >:D >:D

AS

That's probably why I became a physicist.....

Rod

Offline ths

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Re: Micro lathe refurb
« Reply #41 on: September 04, 2014, 09:16:20 PM »
Great update Rod, 2 hours on the lap earns a good outcome. I lapped the spindle for the UPT sensitive drill attachment, but I only had valve grinding paste! coarse and fine, fine leaving scratches so noticeable I used a bit of silver steel instead. I still have that piece of .375" steel in the drawer, too much the product of hard work to discard.

Hugh.

Offline tangler

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Re: Micro lathe refurb
« Reply #42 on: September 06, 2014, 04:01:39 PM »
I rather enjoy doing things like lapping these days, I guess (some) patience comes with age.   :old:

It doesn't look like the outrunner idea is going to work just at the moment - food for thought though, thanks AS.  I'm certainly interested in the concept.  One of my might come in useful one day is a motor salvaged from an AEG washing machine.  Most white goods seem to have very skeletal motors but this one is at least cased.  I've no idea of the power, somewhere around 1/6 HP I guess from the size. There is a particularly small pulley shrunk (?) onto the spindle.  I've now got some 8mm Roundthane belt so I was able to lash up the motor and countershaft.  Motor is 1480 and the countershaft speed is now 650 giving a max speed at the spindle of 1200.  There is still some slip on the lathe spindle pulley.  I haven't got particularly good tension here but I think there may be better options than the Roundthane.



As can be seen from this photo, there is a large capacitor to house somewhere and I think the motor will need some protection from swarf not to mention keeping the electrical connections away from the operator.  I'm currently toying with the idea of putting the motor in a box under the lathe.  The motor feet are temporary, there were just a pair of M5 holes tapped into the end casings.



The Loctite seems to be good enough to hold the worm in the lathe spindle   :) , I'm beginning to have trust in glue - the un-pinned Wyvern crankshaft shows no sign of failing either.

<a href="http://www.youtube.com/watch?v=6hof00q1E2A" target="_blank">http://www.youtube.com/watch?v=6hof00q1E2A</a>

I think that will do for now, I'm not really up for doing some woodwork just at the moment.  Thanks for your input guys,

Rod


Offline Allen Smithee

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Re: Micro lathe refurb
« Reply #43 on: September 06, 2014, 04:16:43 PM »
It doesn't look like the outrunner idea is going to work just at the moment - food for thought though, thanks AS.

No worries. We may shortly be trying an experiment using a small 150w outrunner to drive the drill in a UPT - we'll be posting the details if it works!

AS
Quidquid latine dictum sit altum sonatur

Offline John Hill

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Re: Micro lathe refurb
« Reply #44 on: September 08, 2014, 12:33:14 AM »
I found the local sewing machine repair man had some belts that are ideal for my Flexispeed.