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Arbo
08-24-2005, 07:24 AM
I have a very nice South Bend 9A with very little wear on the ways. Problem is, I am cutting a slight taper. When I say slight, i am measuring about .005 larger on the headstock end of a workpiece 6" long. This is with the work being held in a four jaw chuck, and using the tailstock for support. If the tailstock were to be slightly misaligned would it cause the taper when holding in a four jaw chuck? Or, am I looking at a possibly twisted bed?

I had a fellow call me last night that is experimenting with Stirling engines, and we will need to be within .0005". I know I can do the work, but my machine needs a bit of tweaking to keep up with that!

JCHannum
08-24-2005, 07:32 AM
Even with a perfectly aligned lathe, when using tailstock support, tuning may be necessary.

If the part is small on the tailstock end, adjust away from the cutting tool. Using a dial indicator on the T/S will assist adjustment.

Having accomplished this, do not move the T/S until the part is completed, as it may not return to the same location.

egpace
08-24-2005, 07:33 AM
Yes, a twisted bed will cause a taper. See the link below. It's for Atlas lathes, but the principle is universal.
Have fun,
Ed

http://www.atlas-press.com/tb_bedlevel.htm

GregC
08-24-2005, 08:24 AM
Hmmm....this is from the Atlas link. I'm all for proper setup, but I have to wonder if they aren't issuing a 'catch-all' statement to cover themselves.... "Satisfactory performance is impossible if the lathe bed is out of level as little as one thousandth of an inch." That's pretty hard to ever meet, repeatably, across a distance of several feet. I'm surprised they don't mention that a temperature and humidity deviation of more than 1% is disallowed.

* A properly leveled lathe is the first essential for accurate work and long service life.
* The built-in accuracy of the lathe can be permanently destroyed by improper leveling.
* Satisfactory performance is impossible if the lathe bed is out of level as little as one thousandth of an inch.

AN IMPROPERLY LEVELED LATHE WILL

* CHATTER
* TURN TAPER
* BORE TAPER
* FACE CONVEX OR CONCAVE
* SCORE BED AND CARRIAGE WAYS
* SCORE SPINDLE
* RUIN SPINDLE BEARINGS
* MAKE CARRIAGE BIND
* TWIST HEADSTOCK AND SPINDLE, BED, CARRIAGE AND TAILSTOCK OUT OF ALIGNMENT RESULTING IN EXCESSIVE UNEVEN WEAR.

SGW
08-24-2005, 08:32 AM
Try turning something parallel that's held only in the chuck and not supported by the tailstock. Make sure it's hefty enough so it won't deflect significantly from the pressure of the tool. If you can turn something parallel that way, your tailstock is off and needs adjusting. (A misaligned tailstock can indeed pull something out of line that's held in a chuck.)

If the part comes out tapered when held only in the chuck, your lathe bed is twisted (or warped). Raise/lower the right front leg of the lathe with shims, making test cuts, until the lathe turns parallel. A precision level may get you close, but the ultimate test is turning a piece of work held just in the chuck and verifying that the lathe turns parallel.

As far as making a Stirling engine: no matter how good your lathe is, you may need to lap the bore and piston with an internal and an external lap to get the accuracy you need for good performance.

phil burman
08-24-2005, 09:51 AM
For bed alignment try Rollie's Dad's method. You don't need to include the tail stock (or worry about its misalignment)

http://www.John-Wasser.com/NEMES/RDMLatheAlignment.html

However to set a lathe up properly you need to follow the correct sequence or else you will be chasing your own tail for a week.

A comprehensive test certificate is one good source of the correct sequence.

Regards
Phil

Forrest Addy
08-24-2005, 10:04 AM
I think you guys promoting "twisted bed" problems as the root of all evil in turning operations need to take a step back.

It's tempting to invoke a mystery to account for a problem. The first thing I'd look at if my tailstock supported work was tapered would be the tailstock offset. Unclamp it (you can't force the tailstock over if the clamp is holding the two castings together) and dial over half the taper and you're there.

If the machine is in otherwise fair shape, the bed will have to have quite a twist to show 0.005" taper in 6". In South Bend lathes there's a couple of set screws on the tailstock end pedistal to make removing the twist easy.

They bear against a rocker assembly. To adjust them, run the carrage close to the head stock, back off both adjustments to relx the bed, make sure the screws turn freely, finger tighten them until they just bear and alternately snug them until they're in firm contact (NOT cheater tight). Re-level as needed.

Just becuase something authoratative sounding appears on a website doesn't make true. There are parts of the list Greg posted that I'd be skeptical of attributing to bed twist.

"Satisfactory performance is impossible if the lathe bed is out of level as little as one thousandth of an inch." Funny, I've run lathes teetering on wood blocks and got good performance after a little fiddling.

AN IMPROPERLY LEVELED LATHE WILL

"CHATTER" BS. Chatter is a tool/work interaction producing a self-excited mechanical oscillation and bed twist has nothing to do with it.

"TURN TAPER, BORE TAPER, FACE CONVEX OR CONCAVE" Yes, in rough proportio to twist but lathe beds are very stiff. A lathe would almost have to be teetering on opposite corners to cause the ptoblems I've seen here.

"SCORE BED AND CARRIAGE WAYS" Possibly over time in cases where lube was neglected.

"SCORE SPINDLE" BS. How would that happen?

"RUIN SPINDLE BEARINGS" total BS.

"MAKE CARRIAGE BIND" Certainly in extreme cases particularly if the lathe was in near new condition and tight in consequence.

"TWIST HEADSTOCK AND SPINDLE, BED, CARRIAGE AND TAILSTOCK OUT OF ALIGNMENT RESULTING IN EXCESSIVE UNEVEN WEAR? Certainly in proportion to twist and the machine's sensitivity.

"Bed twist" "spindle slop" and other dire sounding machine tool ailments produce more needless concern than actual problems.

Some new guys can be subject to a kind of "machine hypchondria." The least little pronouncement makes them jittery. Many a time I've looked over a new guy's proud new war production S/B (or whatever) and casually stooped to look at the underdrive, cycle the belt lever, or something. Doing so compresses my belly sometimes forcing a grunt. Over my shoulder would come a voice quivering with angst "What's wrong? What did you find?" "Nothing, looks good here."

You guys gotta relax and work through the problem through the optons before you decide "bed twist" has come to call.

Don't get me wrong, machine tools have to be in accurate alignment and leveling is the simplest way to go about it. Just don't obsess about the wrong things. Plant the machine, then level it. If you have to move it, level it again. Once a year or after an earthquake go around and check the leveling.

Here's a general rule: If your lathe is turning tapers look at tailstock offset, part deflection, and tool wear first.

(fixed stupid typos)

[This message has been edited by Forrest Addy (edited 08-24-2005).]

Pete Burne
08-24-2005, 03:47 PM
Forrest:

Good reply. That list of "problems" sounds like it was written by a philosophy major.

My experience has agreed with all of your comments; however, I am not a machinist and didn't feel qualified to reply.

It was good to hear it from you.

Pete

knutz
08-24-2005, 03:52 PM
<font face="Verdana, Arial" size="2">Originally posted by Forrest Addy:
I think you guys promoting "twisted bed" problems as the root of all evil in truing operations need to take a step back.
Etc etc etc... (edited down for simpicity's sake.</font>

I agree 100%, Good call.

jeff

egpace
08-24-2005, 07:25 PM
Simply stated, I prefer a leveled lathe, without a twisted bed…

A 15 x 36 Clausing Colchester, was re-located to a new spot in the shop. Evidently, the machine was never leveled after being moved. The concrete floor was uneven, after the machine was jockeyed into place, a johnson bar was used to swing the tailstock end, about the headstock, to angle the lathe. This act imparted a twist in the bed. The first time it was used, it cut a .004 taper in roughly 5” Multiple attempts at the cut yielded the same results. After discovering the problem and leveling (“Untwisting” the bed) the lathe, with the same job in the chuck, same tool, and taking the same cut the taper was reduced to .0007”

This is not “I think” or “one would guess” this is an actual event.

Ed http://bbs.homeshopmachinist.net//wink.gif

knutz
08-24-2005, 07:42 PM
<font face="Verdana, Arial" size="2">Originally posted by egpace:
Simply stated, I prefer a leveled lathe, without a twisted bed…

A 15 x 36 Clausing Colchester, was re-located to a new spot in the shop. Evidently, the machine was never leveled after being moved. The concrete floor was uneven, after the machine was jockeyed into place, a johnson bar was used to swing the tailstock end, about the headstock, to angle the lathe. This act imparted a twist in the bed. The first time it was used, it cut a .004 taper in roughly 5” Multiple attempts at the cut yielded the same results. After discovering the problem and leveling (“Untwisting” the bed) the lathe, with the same job in the chuck, same tool, and taking the same cut the taper was reduced to .0007”

This is not “I think” or “one would guess” this is an actual event.

Ed http://bbs.homeshopmachinist.net//wink.gif</font>

I'm not disagreeing with you that leveling your lathe is a good Idea and highly reccomended. But... a lot of people will chase this to no end. When in fact it isn't the problem at all. Eliminate the easy stuff first. Also did you ever think the reason the bed was twisted was because you swung it around by the tail stock? I no when moving machinery you can't always do it by the book, but swing the tail around with a bar while leaving the headstock on the ground will put a good amount of force on the bed.

This post is not a "I think" post either. I've moved probably 25 - 30 lathes small to very large.

jeff

egpace
08-24-2005, 08:03 PM
Jeff,

"did you ever think the reason the bed was twisted was because you swung it around by the tail stock?"

Re-read my post, that was my point, moving the lathe by the tailstock end caused the problem. I didn't move the lathe, I was told they humped the tailstock end around to angle it.

As far as eliminating the easy stuff first, there is nothing easier than to place a level on the bed in a number of places for a relative relationship of the bubble. My lathes were leveled 10 to 20 years ago. I've haven't had to re-level them since. If I noticed, one day, for no apparent reason one started cutting a taper. I would take the 2 minutes to check the bed for level.
Ed

egpace
08-24-2005, 08:04 PM
Sorry about the hiccup.

[This message has been edited by egpace (edited 08-24-2005).]

knutz
08-24-2005, 09:59 PM
<font face="Verdana, Arial" size="2">Originally posted by egpace:
Jeff,

"did you ever think the reason the bed was twisted was because you swung it around by the tail stock?"

Re-read my post, that was my point, moving the lathe by the tailstock end caused the problem. I didn't move the lathe, I was told they humped the tailstock end around to angle it.

As far as eliminating the easy stuff first, there is nothing easier than to place a level on the bed in a number of places for a relative relationship of the bubble. My lathes were leveled 10 to 20 years ago. I've haven't had to re-level them since. If I noticed, one day, for no apparent reason one started cutting a taper. I would take the 2 minutes to check the bed for level.
Ed</font>

It's cool, I just misunderstood or can't read well. http://bbs.homeshopmachinist.net//biggrin.gif

All I was trying to say was that some people will chase the leveling till they go mad. My Howa isn't level. I set it up with a slight bit of drop towards the tailstock.

It is level from front to back (or side to side) just not from headstock to tailstock and I've never had a problem with taper.

When i set a machine I always use my "precision" level, but I've seen people who just keep chasing it and chasing it even though to me it looks fine.

jeff

egpace
08-24-2005, 10:24 PM
Jeff,
I agree, I don't run through the streets yelling make sure your lathe beds are level. To me the issue is like the first question in an appliance trouble shooting instructions...

"Make sure your toaster is plug in to 110 volt wall outlet"

You really never should have to ask that question, but the original post by arbo said...

"Or, am I looking at a possibly twisted bed?"

To me, that meant I haven't check to see if my bed was twisted. The level would give him a good indication.

Regards,
Ed http://bbs.homeshopmachinist.net//smile.gif

J Tiers
08-24-2005, 11:26 PM
<font face="Verdana, Arial" size="2">Originally posted by Forrest Addy:
I think you guys promoting "twisted bed" problems as the root of all evil in turning operations need to take a step back.

It's tempting to invoke a mystery to account for a problem. The first thing I'd look at if my tailstock supported work was tapered would be the tailstock offset.
</font>

I'll agree, it must be second only to "my spindle must be bent"... locate the most expensive piece and blame it.


<font face="Verdana, Arial" size="2">

"Satisfactory performance is impossible if the lathe bed is out of level as little as one thousandth of an inch." Funny, I've run lathes teetering on wood blocks and got good performance after a little fiddling.

AN IMPROPERLY LEVELED LATHE WILL

"CHATTER" BS. Chatter is a tool/work interaction producing a self-excited mechanical oscillation and bed twist has nothing to do with it.

"SCORE BED AND CARRIAGE WAYS" Possibly over time in cases where lube was neglected.

</font>

I'll question your blanket statement on these.....

Lets say "level" means not twisted.... so much for teetering..... we'll leave that out

Chatter? Sure... if the carriage is not contacting evenly due to twist, and has the effect of a chair with one tall leg....

Yeah, it would have to be quite the pretzel, but.... in teh process of buying a lathe, I looked at a couple of real doozies....

Score the bed? Sure, if the twist was as above and let grit get onder the high side....

Is it LIKELY? Probably not, as it would have to be pretty darn bad, or have a very wide carriage.... But it is certainly *possible*.

The rest I'll take as you read 'em off.

Arbo
08-25-2005, 07:49 AM
Let's get some things straightened out. First, I was just looking for some answers and advice to what I thought was a fairly simple question. Second, If I owned one of those fancy Starrett levels that cost hundreds of dollar even used, I surely would have checked it myself. According to my 9" torpedo level, things look pretty good overall. I know that isn't the proper tool for the job, but I use what I got, and you can't very well rent a super precision level. I have been under a tremendous amount of stress lately, and am in no mood for an argument. I'll figure it out on my own, or find some FRIENDS who want to help instead of bickering like old women.

knutz
08-25-2005, 08:09 AM
WTF?

Calm down man, I didn't really see this as an arguement, more of a discussion.

As long as your level is of good quality it "aughta" get you close enough so as you wouldn't have .005 taper.

jeff

Forrest Addy
08-25-2005, 08:46 AM
Arbo. No-one's zinging you. Your post (as the so often do) took on a life of its own and us anal types started picking nits. There was no reflection intended on your shop, equipment, or abilities.

I'm as mush to blame for the turn the thread mand when I suggested "You guys ... need to take a step back." If I upset in my zeal to split a hair even finer you I am truely sorry.

A torpedo level if carfeully used will get you to a couple of thousandths per foot. It takes keen eyes to center the bubble that slosely and you have to be careful you don't reeverse the level and introduce an error.

jr45acp
08-25-2005, 08:56 AM
Arbo, my first step, as indicated by Mr. Addy would be to check the tailstock. BTW, if you need to vent, just shoot me an email. Am always willing to listen. I know how the "joint" can be and then with family issues on top of that, it can get overwhelming. At any rate, am here if you need to talk.

John B

nheng
08-25-2005, 07:31 PM
Forgot to read the original post so, indeed, check the tailstock adjustment FIRST.

Here's my $0.02 on RDM:
I'll 2nd the use of Rollie's Dad's method for testing parallel carriage travel. If the lathe has only light wear and the headstock is scraped into the ways (Southbend is, AFAIR), it's pretty safe to use a somewhat straight bar and RDM to adjust twist out of the bed.

Once you understand RDM, you should be able to use the underlying technique and a dial test indicator to get down to low tenths over 10 - 12". RDM basically finds the true center of the bar and when repeated at both ends, can give a very accurate picture of parallel ways, without cutting (initially).

I've done this and got my lathe down to around 0.0001" over 7". As a sanity check, I used a precision level afterward and it was dead nuts on (not absolute level but matching vial readings). RDM was a lot quicker http://bbs.homeshopmachinist.net//smile.gif Den

[This message has been edited by nheng (edited 08-25-2005).]

J Tiers
08-25-2005, 09:57 PM
If you have a constant taper, I would think the TS would be able to fix it, as Forrest and others said.

A twisted bed, corrected with the t/S, would I think, turn a barrel or hourglass shape, right on both ends but maybe not in the middle.

If you want to find out, you can always go and do the RDM or whatever.........

But what I would do is to ditch the 4 jaw, put in centers both ends, make up a piece a "typical" length, center it, and turn it to have 3 collars on it. One at each end, and one in the middle. Leave room (or a spigot) for a dog. You'll need the spigot first, so the 4 jaw might be handy for that before you pull it. Don't make it so skinny that it sags a lot....

Then I'd turn it with a light skim, just so none of the collars "wink", so you know you turned them all over. Measure them, and all 3 should be the same.

If the t/s end is large, move it towards you half teh difference, if small, away the same.

When the ends are the same, and so is the middle, you don't need to worry any more.

If the middle isn't the same, and its more off than you can deal with, either there is bed wear (tilting the carriage) or else there is warp. Then you can get fancy with RDM, measuring or whatever.

After you get it perfectly the same, you can put it aside, and use it later, with an indicator, to get back to in-line, or check twist, etc.

Carl
08-26-2005, 06:49 PM
Dial in a piece of stock in the four jaw and turn a 60 degree point on it (check it with a center gage). Place your work to be turned between this center and the tailstock center and adjust the tailstock to eliminate any taper. You should be able to adjust it to any degree of accuracy you need.

[This message has been edited by Carl (edited 08-27-2005).]

JCHannum
08-27-2005, 12:16 PM
<font face="Verdana, Arial" size="2">Originally posted by GregC:

Hmmm....this is from the Atlas link. I'm all for proper setup, but I have to wonder if they aren't issuing a 'catch-all' statement to cover themselves.... "Satisfactory performance is impossible if the lathe bed is out of level as little as one thousandth of an inch." That's pretty hard to ever meet, repeatably, across a distance of several feet. I'm surprised they don't mention that a temperature and humidity deviation of more than 1% is disallowed.

* A properly leveled lathe is the first essential for accurate work and long service life.
* The built-in accuracy of the lathe can be permanently destroyed by improper leveling.
* Satisfactory performance is impossible if the lathe bed is out of level as little as one thousandth of an inch.

AN IMPROPERLY LEVELED LATHE WILL

* CHATTER
* TURN TAPER
* BORE TAPER
* FACE CONVEX OR CONCAVE
* SCORE BED AND CARRIAGE WAYS
* SCORE SPINDLE
* RUIN SPINDLE BEARINGS
* MAKE CARRIAGE BIND
* TWIST HEADSTOCK AND SPINDLE, BED, CARRIAGE AND TAILSTOCK OUT OF ALIGNMENT RESULTING IN EXCESSIVE UNEVEN WEAR.</font>

Interestingly, I have been perusing a copy of the Connelly book a friend loaned me.

In Sec. 26.81, Connelly verifies the Atlas statement that improper leveling will cause chattering, may result in bearing damage and will cause a host of other problems.

nheng
08-28-2005, 09:03 AM
I would definitely expect chattering if on a twisted bed, the carriage does not uniformly contact the ways. Sounds extreme but it is pretty easy on a smaller machine, where just about everything seems to contribute to chatter.

I'm dealing right now with a larger lathe (13x30) whose base is so rigid that it rocks before it achieves level.

Any suggestions for this, short of pulling it down to the floor ? Den

Forrest Addy
08-28-2005, 03:05 PM
Before we get into an unproductive debate on chatter we should first identify what chatter is, its modes, and its origin. Anyone care to take a shot at it?

Mr nheng. You write "I'm dealing right now with a larger lathe (13x30) whose base is so rigid that it rocks before it achieves level.

Any suggestions for this, short of pulling it down to the floor?" Rejoice that you leath is strong and stiff. I Assume you jest with your question.

For those who may be puzzled Let me state that all machine tools having length and relative flexability to their guiding ways require alignment of thise way soe their sliding elements move in a single plane. It doesn't matter if they are level only that they (the bed ways) are "flat" and in alignment.

The simplest way to do this is to "level" the ways to a close enough tolerance that the machine will acheive the accuracy built into it and warranted by the factory. Most lathe have reference leveling points built into the ways. In the case of South bend lathes it's the flat crests of the two carriage V ways. With other lathes it's the carriage V and the tailstock V or the carriage flat. Sometimes a precision spacer is necessary for the level to rest on to bring it to the proper height above the flat way.

The process for leveling a lathe is well covered and illustrated by "How to Run a Lathe" published by South Bend and available on eBay as re-prints.

The neophyte is often dismayed that a $450 10 arc second Starrett #119 master precision level is required to level their machine tools. There's plenty of "close enough" options. 8" and 12" 10 arc second levels are available on eBay and through catalog houses for $60 to $100. A Starrett #98 precision level has 0.005" per ft graduation and the graduations are spaced wide enough so the eye can estimate the amount of out of level to a fifth that.

For the record even an excrutiatingly careful leveling job with a cheap torpedo level from a homemaker's tool kit is better than no alignment at all. These levels usually have 15 minute vials that with good technique can be read far closer than that. Be sure the level is reversed twice for each reading and the bubble meniscus is read relatave to the same line. A long hair tied around the vial is a convenient and adjustable reference.

So Mr nheng. Please don't pull your lathe bed down to an uneven floor. If one leg is unsupported the bed will have a slight (to you: but very significant (to the machine's operation) twist in it regardless of its apparent rigidity. Shim the under the legs until the bed is level to 0.001" or so per foot through our its length and the spindle axis is parallel to the carriage motion within 0.0005" per foot.

[This message has been edited by Forrest Addy (edited 08-28-2005).]

nheng
08-28-2005, 06:58 PM
Forrest, I have to apologize for miximg lttle apples and big oranges here. I have seen chatter in smaller lathes where a rigid carriage did not make good contact with a twisted bed (pulled to a twisted bench).

I was not very clear with the big(ger) lathe problem. When I bolt the lathe firmly to the steel base (Harrison M300), I end up with a slight twist that cannot be removed with the levelers at the 4 corners. I think the problem may be caused by some sort of bedding compound or sealer between the lathe and the chip pan / base. I'm using a few machinist jacks to lift one end off the base and see what's between the casting and the chip pan.

Harrison's original instructions say bolt it to the floor (including levelers, of course). If that is not possible, they say to simply level it, then repeat again to fine tune.

What they seem to imply is that there should be no stress introduced into the bed from the base and this is not the case with my machine. It seems like I may need to shim between the lathe and the base after adjusting the levelers for more or less equal distribution of the weight. Does this sound reasonable?

Den

[This message has been edited by nheng (edited 08-28-2005).]

Harold_V
08-30-2005, 03:04 AM
nheng said:

"What they seem to imply is that there should be no stress introduced into the bed from the base and this is not the case with my machine. It seems like I may need to shim between the lathe and the base after adjusting the levelers for more or less equal distribution of the weight. Does this sound reasonable?"

It is not only reasonable, but likely. I own a Sag 12 Graziano, purchased new in '67. From day one, it has had that problem. The base is extremely heavy and easily overcomes the rigidity of the bed. The machine has a slight twist in the bed, obvious when leveled, but tightening the appropriate tailstock base adjustment does nothing to change the condition. The machine will gladly operate on three point suspension, but I keep the 4th adjustment snug enough to prevent the lathe from rocking. If it was a problem, I'd do as you suggest, shim between the bed and base, but it has not been a significant problem for me in these many years.

Harold

beckley23
08-30-2005, 08:59 PM
The 4 corners on the base of my Harrison L-6 have 7/8-9 tapped holes. I used a plate with a piece of 1/2", all thread, 6-8" long, welded to it(actually threaded and welded). The plate was lagged to the floor in the appropriate spots. I used some 7/8-9 all thread, 3-4" long, with a 1/2" through hole and a nut welded on one end, the top. The 2 pieces together make nice push-pull levelers, and they sure beat shimming.
Harry

nheng
08-30-2005, 10:12 PM
Harold, I performed several experiments tonight. With the bolts loose at the tailstock end, the bed indicates quite straight on a precision ground test bar. I proceeded to support the base at that end by a single point near what looked like a good balanced spot. I then tightened the bolts again and the bed twisted, introducing about 0.005 over about 10".

That Harrison welded steel base is pretty darned stiff. I can get the bed straight by leaving the bolts on one side just touching, similar to what you've done. I will probably shim the bed to base when time permits only in the interest of overall rigidity.

Den

Harold_V
08-31-2005, 12:34 AM
<font face="Verdana, Arial" size="2">Originally posted by nheng:
Harold, I performed several experiments tonight. With the bolts loose at the tailstock end, the bed indicates quite straight on a precision ground test bar. I proceeded to support the base at that end by a single point near what looked like a good balanced spot. I then tightened the bolts again and the bed twisted, introducing about 0.005 over about 10".

That Harrison welded steel base is pretty darned stiff. I can get the bed straight by leaving the bolts on one side just touching, similar to what you've done. I will probably shim the bed to base when time permits only in the interest of overall rigidity.

Den</font>

You've proven beyond a reasonable doubt that your base (or how the bed relates to it) is the culprit, and I heartily endorse the shimming idea, in particular to avoid chatter, and to insure rigidity. I'd not wait to add the shims. Should be fairly easy to accomplish, especially the way you describe the inspection procedure. Relax the bolts as you already did, then insert a feeler gauge until you get a snug fit. A thou extra would likely be a good amount to compensate for irregularities. I'd enjoy hearing the end result.

Frankly, I'm astonished at the amount you found. I gather the welded base has moved, or it was messed up when originally machined. Regardless of reason, it's easy enough to rectify. I fully expect that my Graziano has only a small fraction of the error you found in yours.

Harold

MikeHenry
08-31-2005, 10:39 AM
I had a Craftsman 12x36 lathe (made by Atlas and similar to the 10" mdel) for several years and using shims to level it drove me nuts. The bottoms of the legs on the bed were rough and each time a new shim was inserted or removed the stack of shhims would shift a little and change the elevation. I must have spent hours chasing a level condition using a Starrett 199 level (0.0005" per foot) and never could get it right.

Eventually I made up a screw leveling arrangement at both ends of the bed with 1/2-13 threaded rod and aluminum plate. It took about 1/2 hour with that arrangement to level the lathe.

About then I discovered that merely leaning on the carriage had a significant effect on level. That's when I decided to upgrade to a better lathe and ended up with a Clausing 5914 which is far more rigid and has leveling screws built into the pedestals to boot.

It's no where near the quality of Harold's Sag but is much better than an Atlas/Craftsman.

Mike

nheng
08-31-2005, 09:31 PM
Harold, Took it the next step tonight. Put an indicator on the right rear foot of the lathe bed relative to the chip pan. When the bolts were loosened to where there was close to zero (few tenths in 10") indicated taper, it looked like 0.010" shimming was required.

Using machinist's jacks to lift the end of the bed, it appears that rock hard sealing / bedding compound worked its way under the feet. It is so tough that I believe it is now preventing proper seating.

Anyway, slipped in 0.010" shim, can now tighten all of the bolts down against the bed and now ... the levelers take care of any remaining, very small error http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif

Someday I'll chip away all of the compound around and under the bed, re-seal it and touch up the paint. For now, the machine has about 0.0001" in 2" of 1" dia. 6061. Will tweek it further in the days to come.

Den

Harold_V
08-31-2005, 10:10 PM
<font face="Verdana, Arial" size="2">Originally posted by nheng:

Someday I'll chip away all of the compound around and under the bed, re-seal it and touch up the paint. For now, the machine has about 0.0001" in 2" of 1" dia. 6061. Will tweek it further in the days to come.

Den</font>

Way cool!

Congrats on a job well done. You've given me an incentive to pursue the minor error I've tolerated for so long with my Sag 12.

Harold

Harold_V
08-31-2005, 10:18 PM
<font face="Verdana, Arial" size="2">Originally posted by MikeHenry:

It's no where near the quality of Harold's Sag but is much better than an Atlas/Craftsman.

Mike</font>

It's nothing short of amazing how machine tools improve in performance and quality as you approach commercially rated machines.

I can well imagine your level of satisfaction with your Clausing after running a light duty machine the likes of which you mentioned. I owned a small Craftsman early on and was more than pleased to see it go when I sold it.

Harold

[This message has been edited by Harold_V (edited 08-31-2005).]

MikeHenry
09-02-2005, 12:07 AM
<font face="Verdana, Arial" size="2">It's nothing short of amazing how machine tools improve in performance and quality as you approach commercially rated machines.</font>

I really was impressed with how much the quality of my work improved with the "upgraded" lathe, not to mention the new opportunities it opened for accessories that make the job at hand easier and therefore more fun to do.

Some very talented model engineers have turned out superb work with Atlas/Craftsman lathes. I'm not at that level, but the better lathe moves me a bit closer.

Mike

[This message has been edited by MikeHenry (edited 09-02-2005).]

nheng
09-02-2005, 12:22 AM
Mike, The Clausings are nice machines. I came close to getting one myself. Not heavyweight but a good performing machine. You'll find that tighter tolerances and better finishes become more routine, with less fussing. Den

MikeHenry
09-02-2005, 12:39 AM
Nheng,

I've learned that heavyweight is a relative term having started with a Sherline lathe & mill. The Craftsman 12x36 was a definite improvement (accuracy excepted) over the Sherline and the Clausing lathe yet again over the Craftsman. Unfortunately, 1,000 lbs is about the limit of what can be reasonably moved to the basement shop withot extreme measures or cost so the Clausing is about as far as I am likely to go in lathes.

Likewise, the Clausing 8520 and 8540 mills now in the shop were very substantial improvements over the Sherline mill but work envelope is still a somewhat frequent problem there. Possibly a Deckel would satisfy the need to upgrade there, but I really do like the Clausing mills.

Still got the Sherlines and use them occasionally.

Mike