Adventures in 7x16 tuning.

[Ed McDonnell]

When I first got my microlux 7x16 lathe the tailstock was out of alignment with the headstock enough that when turning a 3" long cylinder the diameter varied by 0.01" over the length of the piece. Great if I wanted to turn tapers, but I didn't, so not so great.

After playing around with the horizontal adjustment on the tailstock I got it to within 0.004" over the 3" length. Not too bad, but I could do better on my wood lathe by hand!. The vertical alignment was off and I haven't had the time to try to adjust it until this weekend.

I needed to lower the tailstock, so I disassembled the tailstock and removed a little bit of metal from the bottom of the top piece of the tailstock. Not wanting to end up having to use shims to raise the tailstock or buy a new tailstock ($80), I only took off a tiny bit at a time. Disassemble, remove metal, reassemble, test, repeat. After doing this countless times I can now disassembe or assemble the tailstock in under a minute. Not sure what I can do with this newly learned skill, but I've got it if I need it.

If I had a mill this would have been a very simple quick task. Rubbing the tailstock on sandpaper on a flat surface and guessing about how much I was taking off took a lot longer.

It took me almost 6 hours to get it completely aligned. I can now turn a 3" long cylinder with less than 0.001" change in diameter. I wanted 0, but we can't always get what we want.

I used a razor blade between centers to indicate the direction of adjustment needed. I'm surprised how close to zero I was able to get with such a low tech approach.

The other thing I learned is that the scale on the compound is not real accurate. I am going to make some angle gauge blocks for setting the angle on the compound when I need it.

The only thing left that I want to work on is the backlash in the cross slide. It's not too bad, but I would like to eliminate as much as possible.

What kind of adjustments have you made to your lathe to get the performance you wanted?

Ed

 

[Rich L]

I think it's pretty neat you tackled the problem the way you did with the equipment you have and congratulations on getting it dialed in. It's disappointing to hear that the lathe came to you so out of alignment. A few comments below. Good show, Ed.

Wasn't there another Ed that said that? :biggrin:

Cheers,
Rich

When I first got my microlux 7x16 lathe the tailstock was out of alignment with the headstock enough that when turning a 3" long cylinder the diameter varied by 0.01" over the length of the piece. Great if I wanted to turn tapers, but I didn't, so not so great. There are four axes for misalignment of that kind of tailstock: (using lathe axis terminology X = in and out to you, away from you, Y up/down, Z lathe bed axis direction through the main spindle. There are others but you don't have them. You really don't have Y except for alignment purposes)

vertical rotational axis (Y) through the tailstock which can give you a misalignment in the XZ plane with respect to the spindle axis;

horizontal rotational axis (X) through the tailstock which can give you a misalignment in the YZ plane with respect to the spindle axis;

translational axis along Y in the ZY plane;

and translational axis along X in the XZ plane.

You worked on the Y in ZY and X in XY, truly, bravo! When you do take material off the "XZ"plane (the bottom of the tailstock) you have to make sure you do it evenly so as not to adversely affect alignment in the other axes. Learn hand scraping techniques against a reference flat (just joking)

After playing around with the horizontal adjustment on the tailstock I got it to within 0.004" over the 3" length. Not too bad, but I could do better on my wood lathe by hand!. The vertical alignment was off and I haven't had the time to try to adjust it until this weekend.

I needed to lower the tailstock, so I disassembled the tailstock and removed a little bit of metal from the bottom of the top piece of the tailstock. Not wanting to end up having to use shims to raise the tailstock or buy a new tailstock ($80), I only took off a tiny bit at a time. Disassemble, remove metal, reassemble, test, repeat. After doing this countless times I can now disassembe or assemble the tailstock in under a minute. Not sure what I can do with this newly learned skill, but I've got it if I need it.

If I had a mill this would have been a very simple quick task. Rubbing the tailstock on sandpaper on a flat surface and guessing about how much I was taking off took a lot longer. That's the point, isn't it?

It took me almost 6 hours to get it completely aligned. I can now turn a 3" long cylinder with less than 0.001" change in diameter. I wanted 0, but we can't always get what we want.

I used a razor blade between centers to indicate the direction of adjustment needed. I'm surprised how close to zero I was able to get with such a low tech approach.

These alignment issues can be complex and tedious to accomplish and the lathe makers tackle them, or not, within the price point at which they wish to be. My old Jet lathe surprised me one day a long time ago when I took off the tail stock and saw that the bottom casted surface had only be rough milled. That's what is today still sliding against a ground V and flat way. It's enough for pretty good concentric turning along a good foot of steel stock. I was just surprised at just how badly the tailstock surface had been prepared.

I don't know what you used for a flat surface to sand your tailstock but I invested in a small 1 foot square granite block for such things. It has been invaluable for all kinds of sanding chores and I'm guaranteed just about as flat a surface as I could wish for.

The other thing I learned is that the scale on the compound is not real accurate. I am going to make some angle gauge blocks for setting the angle on the compound when I need it.

What would be your reference surfaces against which you would place your angle blocks? Are these surfaces really what you think they are? Are they flat, are they perpendicular, etc? (don't need to answer)

The only thing left that I want to work on is the backlash in the cross slide. It's not too bad, but I would like to eliminate as much as possible.

How bad is it? More than .040? If not, I wouldn't worry about it and it may be hard to adjust rack and pinion offsets (if that's how it's driven).

What kind of adjustments have you made to your lathe to get the performance you wanted?

Ed

 

[Ed McDonnell]

Hi Rich - Thanks for the response.

You asked "What would be your reference surfaces against which you would place your angle blocks? Are these surfaces really what you think they are? Are they flat, are they perpendicular, etc?"

My plan was to set the angle using the side of the cross slide and the side of the compound slide. I used a square to set the compound at 90 degrees to the cross slide. I then cut a 1" cylinder using the compound to advance the toolbit. Using my calipers, I checked the diameter along the 1" length and there was no deviation. So, if I can reliably set to 90 degrees, it seemed to me I should be able to set to 30 degrees (or whatever) by having an an angle block of the correct angle. I would cut the angle blocks on my CNC so they should be pretty accurate. I put a rule up to the sides of the cross slide and compound and they seemed flat.

With respect to the backlash on my Cross Slide you asked "How bad is it? More than .040? If not, I wouldn't worry about it and it may be hard to adjust rack and pinion offsets (if that's how it's driven)."

I guess I'm going overboard with the tuning of the lathe. I measured the backlash and on the compound it's ~0.002" and on the cross slide it's ~0.004". The compound is about where I expected, but the cross slide feels like it's a lot worse. The cross slide feels much looser than the compound. The compound has no slop in the handle. On the cross slide you can jiggle the handle a couple of degrees back and forth. It just feels sloppy. Maybe it's not a backlash issue that is bugging me. I'll have to look at it some more.

The cross slide is a leadscrew, not a rack and pinion. The lead nut gets angled to adjust for backlash. Pretty crude, but I guess a lot less expensive than using a good quality anti-backlash nut.

The flat surface I used was the ways on my Powermatic 3520b. They are dead flat and were more than wide enough to cover the area I was sanding down on the tailstock. I've also got a polished granite floor tile that I bought for a couple of bucks that makes a good surface for this kind of work. Not as good as a nice thick granite slab like you have, but it works (as long as you don't put so much pressure on that it would crack). Unfortunately, I couldn't find it in the shop. The powermatic worked in a pinch.

Thanks again.

Ed

 

[Rich L]

If all you've got is .002 and .004 for backlash you're in great shape!

Looking for a "thumbs up" thing but couldn't find it, ... so this thing mean Rock On!

:RockOn:

Cheers,
Rich

 

[BKelley]

I had a Grizzly 7x12 and it was pretty much on the money. I upgraded to a LMS 8.5x16 and I have not put a indicator on it, but in turning pens using bushings if I adjust the crossfeed to just bearly missing the bushing on the tail stock end, automatic feed to other buhing it is dead on. I bought the 8.5x16 mainly for turning pens and it does a wonderfuf job. Maybe later I will venture into some small steam engines or other equally challanging projects.

Ben

 

[randyrls]

If I had a mill this would have been a very simple quick task. Rubbing the tailstock on sandpaper on a flat surface and guessing about how much I was taking off took a lot longer.

Ed; Actually it is a good thing to sneak up on a measurement.

I used a razor blade between centers to indicate the direction of adjustment needed. I'm surprised how close to zero I was able to get with such a low tech approach.

I have always used a thin leaf from a thickness feeler gauge. It doesn't have sharp edges.

The other thing I learned is that the scale on the compound is not real accurate. I am going to make some angle gauge blocks for setting the angle on the compound when I need it.

Check out this protractor available at Lowes. Little Machine Shop also has them. AND lots of other goodies!
http://www.lowes.com/pd_15003-56005-17_0__?productId=1018383&Ntt=protractor&pl=1¤tURL=&facetInfo=

I suspect you already know this, but I'll mention it anyway. You can get angle gauges to accurately set angles, but these come in sets that are like building blocks. If you want 34 degrees, you need to use a a 30, a 3, and a 1. It's difficult to line these up to set the compound. I usually line up the blocks, then use the protractor to set the angle, and transfer it to the compound. It is rare that I need such precision.

The only thing left that I want to work on is the backlash in the cross slide. It's not too bad, but I would like to eliminate as much as possible.

The easiest way to eliminate back lash is to always move in the same direction. If you have to crank out, go at least one full turn out and then reverse in.

 

[Ed McDonnell]

Hi Ben - Looks like you pick up some nice features when you step up to the 8.5 x 16. Do you turn all straight sided pens or do you do curves on the metal lathe?

For a challenging project you could add stepper motors to the lead screw and cross slide, buy a controller and have a real nice cnc lathe.

Ed

 

[IPD_Mr]

Ed do you want to be notified when Micro-lux has their mill on sale? :biggrin::tongue::biggrin:

I love reading stuff like this. Almost anything is manageable with a little clever thought and persistence.

 

[Ed McDonnell]

Hi Randy -

"Actually it is a good thing to sneak up on a measurement."

For sure. It's hard to put that metal back on! I was really paranoid about that and seemed to be going way slower than a sneak.

"I have always used a thin leaf from a thickness feeler gauge. It doesn't have sharp edges.]"

The razor blade I used has been laying around the shop for 30+ years. A sharp edge is just a distant memory to that guy.

"Check out this protractor available at Lowes. "

Thanks for the link!! I can cut angle blocks on my cnc out of scraps for free and they are dead on. But looking at your link, I find myself thinking "why have a bunch of blocks laying around and never being able to find the one you want". I noticed a different protractor at the bottom of the page that you linked. It is digital, locks and is easy to read from a distance (my eyes are not so hot these days). Looks like it might do the job if it will fit. There's not a lot of room on these little 7x16 lathes. I'll check the protractors out next time I'm at Lowes.

I don't have angle blocks. I don't have anything left over from my metalworking days (it's been 40 years). I probably will never need anywhere near the precision I'm trying to get out of this little lathe, but I enjoy tinkering with it almost as much as I enjoy making stuff with it.

For backlash, I remembered the "move in the same direction" stuff from my days (40 years ago) of working in a machine shop. I've now concluded that the sloppy feel on the cross slide that was bugging me is not related to backlash. I'm going to work on getting that sorted out today.

Thanks for the tips and links!

Ed

 

[Ed McDonnell]

Ed do you want to be notified when Micro-lux has their mill on sale? :biggrin::tongue::biggrin:

I love reading stuff like this. Almost anything is manageable with a little clever thought and persistence.

Hi Mike - The work bench I built is 12 feet long....the lathe is only using a small part of it.....hmmmmmm.......

My next project was going to be a small bench top 4 axis CNC router. The last one I built has a 14" swing which is a bit of overkill for working on pens! But now I'm thinking "If I had a mill I could make almost all the parts for the cnc myself instead of having to buy them. " . Of course I would need to think about a metal cutting bandsaw of some sort as well, and then there's the challenge of finding space to start storing all the metal stock I would want to have on hand. That might mean having to give up some of the 5 lifetimes worth of tropical hardwoods I've got squirreled away in the shop. I can barely walk around in my shop as it is....there's just never enough room.

Ed