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7x16 Spindle to Tailstock Alignment Test Outcome

 

I¡¯ve installed a new 16in bed on my 7x12 LMS 4200 mini-lathe and added a new tailstock with DRO. I sent for a 350mm MT3 Test Bar from India rated 0.0001¡± runout (not defined) and mounted it between the spindle and a live center in my fully retracted tailstock quill. After a low speed spin as I tightened the tailstock up. I mounted an indicator on top of the compound slide and ran it ~8in from the tailstock end as close as I could get my carriage to the spindle.

With the indicator vertical on the top surface of the bar, maximum change was 0.004¡±, horizontal on the front surface the maximum was 0.0025¡±.

Given the tolerance stacking across all the stationary/moving parts, that comes to a maximum deviation of 0.0005¡±/inch Z-axis. For such a mini-lathe, is that in the expected/acceptable range for hobbyist work?

BRET
 

It depends on your expectations, Bret. I would have expected better but have lived with worse!? ?Bill in Boulder


On Sun, Dec 10, 2023 at 9:34?AM CBJessee-N4SRN <cbjesseeNH@...> wrote:
I¡¯ve installed a new 16in bed on my 7x12 LMS 4200 mini-lathe and added a new tailstock with DRO. I sent for a 350mm MT3 Test Bar from India rated 0.0001¡± runout (not defined) and mounted it between the spindle and a live center in my fully retracted tailstock quill. After a low speed spin as I tightened the tailstock up. I mounted an indicator on top of the compound slide and ran it ~8in from the tailstock end as close as I could get my carriage to the spindle.

With the indicator vertical on the top surface of the bar, maximum change was 0.004¡±, horizontal on the front surface the maximum was 0.0025¡±.

Given the tolerance stacking across all the stationary/moving parts, that comes to a maximum deviation of 0.0005¡±/inch Z-axis. For such a mini-lathe, is that in the expected/acceptable range for hobbyist work?

BRET

 

If you got those numbers with no shims under your headstock and no adjustments to your tailstock I'd say that is pretty darned good.? Since you now have a nice test bar you can tweak it as much as your patience and ambition allow.

Mark
 

Like Mark says, it's basically up to you. If you're happy with that you're good to go!??I wanted better so I tinkered and adjusted a lot. I replaced the two bolts in the back of the headstock with hex heads so I could work with them easier than the allens that came factory in mine. A shim here, a tap there with a rubber mallet, tighten, cut test adjust... Over a 8" test bar I got mine under .001" vertical and horizontal with a dial indicator on the saddle and with a live center in the tailstock I can turn 11" of a 12" length of 12L14 within .001" from tail to chuck. If you're happy with .005" over 10" you're good to make chips but if you're going to be doing some longer parts ( I was and needed more precision ) the lathe is capable of doing it if you're willing to put the time into adjusting it.?

Ryan?
On Dec 10, 2023 at 1:21?PM -0500, Mark Kimball <markkimball51@...>, wrote:

If you got those numbers with no shims under your headstock and no adjustments to your tailstock I'd say that is pretty darned good.? Since you now have a nice test bar you can tweak it as much as your patience and ambition allow.

Mark

 

Thanks for all the thoughts and suggestions!

It comes to mind, I should check with the test bar in the spindle alone, without the tailstock. There should be no deflection issue running an indicator down the bar, so I might find whether the headstock or tailstock has greater influence on my machine.
 

Just remember what doing .
A dial indicator reading to 0.000,1 is great but most work 0.001 works great .

My self I keep most of my work to under 0.000,5".?

Dave?
 

If I put the test bar MT3 in the spindle loosely, put the liver center tip in on the tailstock loosely, then seat them by sharply pushing in the tailstock while turning slowly, the system aligns to 0.0015¡± max deviation over 8¡± - better!

The headstock alone appears a culprit, with up to 0.008¡± deviation when mounted in the spindle alone (several times). That would be worth some bolt adjustment and shimming, as recommended. I gave the ways and headstock surfaces a good wipe down before reassembly.

I scraped some paint off both the ways and headstock contact surfaces - I dunno if the factory adjusts for true after assembly or if my machine was even farther off before I cleaned it up.
 

I've never thought the factory adjusted anything! I've always thought the lathes were shipped assembled because it was cheaper than packaging all the components separately ;-)

The first thing to check is the spindle bearing pre-load. There should be little to no free play; there are some upgrades for the spindle bearings, which are the lowest quality (cheapest) bearings on the market.

Roy
 

The OP's lathe alignment is far better than mine (LMS 5100).

Now that the tapered roller bearings are in the headstock, I may start the tedium of getting a proper headstock to bed alignment.
--
Lone Tree, Colorado? ?USA
 

I was think most mini lathes use 6206 ball bearing not tapper.?

FYI If buying the 6206 as a manufacturer it cost $1.10 each. Try buying that bearing at the retailer leave.?
I think the other number for ball bearing is 80206 it same bearing?

Dave?
 

ALL mini-lathes have ball bearings on the spindle.? ?The tapered roller bearings are an upgrade.
--
Lone Tree, Colorado? ?USA
 

That is good to know.?
Thank you

A good deep Grove ball bearing with seals will last a long time. I do not know what mind has probably shield a sorter life than seal.

Tapered roller bearings are pain to upgrade.? They do make on tapered roller bearing that has built in seal a little easier.??

My last lathe was fully tool south bend.?
This is first mini lathe so all new to me.?

Dave?
 

I started wondering if I could trust my 350mm MT3 test bar, so set up my indicator to zero on the top surface and ran it 10¡± to the end of the unsupported test bar (it¡¯s ~1¡± diameter) to confirm 0.008¡± deviation from spindle to 10¡± out. Then I popped the test bar out, rotated it 180 degree and mounted its MT3 taper again, with the same results. So, the test bar is pretty straight. Is it fair to conclude that the 0.008¡± rise is headstock/ways misalignment? I¡¯m mounting my indicator on top of the locked compound/locked cross slide.

I think I need only remove the control box and motor cover from the LMS 7x16 to get to all three headstock bolts. When I reassembled, I ran a bronze brush with WD-40 over the headstock surfaces to remove any paint overspray and gummed lubricant residue, wiped them well and lightly oiled before progressively snugging the bolts down.

Would the strategy be to loosen the left-end ?bolt and tighten the two right-end bolts to try and drop the tilt down?
 

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In Ted Hansens mini lathe book he uses aluminum foil shims under the front/rear of the headstock.



I really recommend this book. He goes through aligning (and improving) the Mini-lathe to create a much more accurate system, and the advertised ¡®every project only requires the Mini-lathe and a drill press¡¯ is correct.?

He¡¯s also published a few more articles in Home Shop Machinist since the book came out for further refinements



On Dec 14, 2023, at 11:03 AM, CBJessee-N4SRN <cbjesseeNH@...> wrote:

I started wondering if I could trust my 350mm MT3 test bar, so set up my indicator to zero on the top surface and ran it 10¡± to the end of the unsupported test bar (it¡¯s ~1¡± diameter) to confirm 0.008¡± deviation from spindle to 10¡± out. Then I popped the test bar out, rotated it 180 degree and mounted its MT3 taper again, with the same results. So, the test bar is pretty straight. Is it fair to conclude that the 0.008¡± rise is headstock/ways misalignment? I¡¯m mounting my indicator on top of the locked compound/locked cross slide.

I think I need only remove the control box and motor cover from the LMS 7x16 to get to all three headstock bolts. When I reassembled, I ran a bronze brush with WD-40 over the headstock surfaces to remove any paint overspray and gummed lubricant residue, wiped them well and lightly oiled before progressively snugging the bolts down.

Would the strategy be to loosen the left-end ?bolt and tighten the two right-end bolts to try and drop the tilt down?

<IMG_2635.jpeg>

--?
Bruce Johnson

The less a man knows about how sausages and laws are made, the easier it is to steal his vote and give him botulism.

 

Don't forget to check the height of the TS; it should match the HS height. Getting an assortment of brass shim stock is worthwhile - once you have it on hand, you'll be amazed at how handy it is.

Roy

 
Edited

I have rebuilt a lot of old tools .
I get tail stock and head stock real close.
The chuck a Morse tapper reamer. The re-ream the tail stock quill.? Now it is very accurate and is simple.?

Did like parts of you book you posted on what say about it would have great 50 years ago.?


I would here storeys of casting of machine tools not age. You could see the casting with curve.? Hot castings to machine shop. I think have learned by now or maybe on mini lathes.?

Dave

 

I¡¯ve got ¡°The Complete Mini-lathe workshop¡± on order, thanks.

As noted in??bolt torque appears to be good for only 0.0005-0.001¡± vertical at best and I¡¯m 0.008¡± high at 10¡± from the spindle, so it¡¯s looks like shims are the next option. Fortunately, I have some 0.001¡± brass shim stock to try - easy to cut with titanium scissors.

The headstock base has a nasty surface, with just a few contact points roughly ground for contact. Wiping with any cloth leaves fuzz, so I¡¯m flushing with WD-40 and blowing with canned air to clean the contact surfaces. Should those be flushed with solvent or is the lubricant film thickness below concern?

 

Got a friend with a surface grinder? Setting the headstock up with the spindle bore parallel to the table and cleaning up the base of the headstock would do wonders! The cheap way might be to use small?shims until level and then apply a thin coat of filled epoxy before torquing the screws down. After hardening you should have a flat , true, and level headstock.


On Sat, Dec 16, 2023 at 7:42?AM CBJessee-N4SRN <cbjesseeNH@...> wrote:
I¡¯ve got ¡°The Complete Mini-lathe workshop¡± on order, thanks.

As noted in??bolt torque appears to be good for only 0.0005-0.001¡± vertical at best and I¡¯m 0.008¡± high at 10¡± from the spindle, so it¡¯s looks like shims are the next option. Fortunately, I have some 0.001¡± brass shim stock to try - easy to cut with titanium scissors.

The headstock base has a nasty surface, with just a few contact points roughly ground for contact. Wiping with any cloth leaves fuzz, so I¡¯m flushing with WD-40 and blowing with canned air to clean the contact surfaces. Should those be flushed with solvent or is the lubricant film thickness below concern?

 
Edited

Following that GadgetBuilder protocol, I cleaned surfaces, applied DyKem and mated the headstock and ways, sliding them 1/8" forwards and backwards.

Contact areas are left and right rear flats and only the left outer prism. No contact unbolted on right prism. That must be a pivot contact, assuming it contacts at all when bolted.

As my headstock appears to tilt up and back, maybe that¡¯s the first bolt I should snug?

 

Bill,

Your filled-epoxy suggestion got me thinking. I wonder if what I thought was paint under the headstock was the vendor adding epoxy to correct an overgrind? It was in the right place to have shimmed properly. I brushed that out with a bronze brush and solvent. ?

After another thorough clean and tightening the left front nut first, I'm down to 0.005" high, so shimming is definitely needed.

Bret

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