# 8530 Y Axis Problem



## Richard Melloh (Jun 9, 2015)

I have a beloved 8530 that has done production for me daily for many years. It has always been a reliable and precise machine for my purposes. I chase .0001 on it to get consistent .001's. Anyone has to love the generous dials that allow the splitting of .001" on a consistent basis on what used to be a high school shop class machine in CT.

A problem has arisen, for which I need some advice.

Problem: Y axis is consistently dropping .003/.100 on the in-feed. I am currently accommodating this and it is driving me crazy when I have to repeat tolerance on the Y axis.

Causes?

Solutions?

This is my first post. I have my fingers crossed.


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## Terrywerm (Jun 9, 2015)

You are seeing that loss because of wear on the lead screw and the lead screw nut.  There are two solutions: either make and replace the lead screw and the nut, or purchase and install a DRO. If it were me, I would go for the DRO.

Oh yeah, welcome to H-M!


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## Richard Melloh (Jun 9, 2015)

terrywerm said:


> You are seeing that loss because of wear on the lead screw and the lead screw nut.  There are two solutions: either make and replace the lead screw and the nut, or purchase and install a DRO. If it were me, I would go for the DRO.
> 
> Oh yeah, welcome to H-M!


Thanks, Terry. I'll take that into consideration. Sadly, the 8530 does not facilitate an easy mount on the Y axis, though I agree, once accomplished and calibrated, it would work. I would have done bad things just to have had a stop system on the Y axis. So many times I have wished for it. That's a lot of bad things and there is still no stop system on the Y.

Any chance I can purchase a new lead screw on the open market? I'm surprised the wear showed up on the Y instead of the X. X is still near perfect over long travel, though much more heavily used. It might be all that hard coat anodized, .25" aluminum plate I have been machining for years. The Y screw and nut might be more exposed to debris. The hard coat anodizing dust is like diamonds.


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## wa5cab (Jun 10, 2015)

Richard,

Are you saying that when, after taking out the slack due to backlash, you crank the table in 0.100" it actually only moves 0.097"?  And another 0.100" on the dial (without backing up) again only moves the table 0.097"?


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## Richard Melloh (Jun 10, 2015)

Yes, Robert. That's exactly what I am saying. If I travel the Y axis out .300 and then back in .300, I need to travel in .309 to get back where I started. Mentally, it really keeps me on my toes, but is very frustrating and is costing me time and money. I am ready to get aggressive on addressing this problem. I am going to look for a new lead screw and lead screw nut on the web today and study what's involved in replacing them. I am not sure new parts such as these exist. What I really need is to be concentrating on production, not this problem. If I knew of any other mill of this particular size and weight, build quality, features (the large, legible dials) and especially the higher speed range for machining plastics, I would just buy a new one. The machine would pay for itself in a matter of a few months. I don't have the shop room or the floor for a one ton machine.

Terry's preceding advice on adapting the machine to DRO is another way to go, but it is a little tricky on the Y axis, as there are no distinct surfaces available for mounting the strip. I will do more research on that when I can.


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## RJSakowski (Jun 10, 2015)

Richard Melloh said:


> Terry's preceding advice on adapting the machine to DRO is another way to go, but it is a little tricky on the Y axis, as there are no distinct surfaces available for mounting the strip. I will do more research on that when I can.


While I am not familiar with the 8530, it looks like a DRO Y axis scale could be mounted on the right hand side without too much difficulty.  On installs that I have done on other machines, I made a mounting plate for the scales from 3/4" aluminum.  It provides a solid base for the scale. I made tapered shims to account for the draft in the castings.   For the X axis, I mounted a bar of CR steel on standoffs to clear the table lock, stops,  and limit switches.


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## Richard Melloh (Jun 10, 2015)

Thanks for the advice, Terry. Shims are definitely the solution. I have plenty of tools and materials to do the job. I'll probably end up dressing it up for DRO on the X and Y axis. I didn't really need it when everything was hunky dory. The big dials are right in my face. They're easy to read and reliably split and even fraction .001's. A new day has dawned. I guess things do really wear out in 25 year's time. I'll have to move into the late 20th century. Sigh. I'm still gonna do a search for a fresh screw and nut when I get a chance, though DRO might actually be quicker, easier and cheaper than the parts and a rebuild. I would probably work faster with DRO, when I start thinking about it. I have never used it. I am so old school.

I'll post a picture of the solution some day.


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## wa5cab (Jun 10, 2015)

Richard,

OK.  If you back out 0.600" and then move back in 0.600" by the dial just as you did previously with the 0.300", how much further in must you move the dial to get actually back to 0.600"?  0.609" or 0.618"?


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## Richard Melloh (Jun 10, 2015)

Robert,

.003 x 6 = .018 every time.  I do most of my repeated close tolerance work on the Y axis within a fairly narrow range for a specific product. I make what are called "combs" out of .030 Delrin, repeating .023" wide slots, .161" long at specified mm spacings, plus a mounting slot to each end of the comb on an offset to the comb teeth which brings a few more .003's into play. The total width of the Delrin object is .591 in relation to the Y axis. If I do 8 slots in a row, the discrepancies will start to show up dramatically with even just a .0005 variance, if said variance keeps creeping in one direction.  

I managed to keep it together on a four slot comb this morning, but it is a pain keeping track of those .003's over and over. Yesterday I made three different variations of the comb product, some in multiples. I am loath to change the plot standards permanently to address what I hope is a temporary condition. I have dozens of different coordinate plots for different comb configurations. Gah!

I can't say for certain that the .003 discrepancy is constant for the entire travel of the screw through nut on the Y axis, only for the narrow zone I am working in. It is there that I must stay. The discrepancy showed itself when suddenly, combs started coming out looking more like stair steps as I dropped .003 on each slot. It was easy to measure and see what was consistently happening. Could it be that the Y screw nut is wobbling regularly in its seat/mounting point? I don't even know why that would make a difference in one direction and not the other. My schematic makes it appear that the Y axis screw nut is simply pressed into its position. I don't see any fastener in the exploded view for the Y screw nut.

My brief search for a new screw and nut was unsuccessful today. I have part numbers but no matches online. I haven't given up yet. I am studying different DRO kits. My table is only 7 x 26. I could use a 6" Y and 18" X horizontal strip and be in business regardless of the discrepancy. 

Good night and thanks for pondering my problem.

Richard


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## Terrywerm (Jun 10, 2015)

Richard, fitting a DRO to your 8530 is not too difficult at all, not nearly as bad as it looks, anyway. I did my 8520 in a day with no problems. First the X, then the Y, and finally the Z. I wrote a thread on it, here it is:   http://www.hobby-machinist.com/threads/igaging-absolute-dro-installation-on-clausing-8520.26412/

One thing to keep in mind with DROs is that the kind with the glass scales typically have larger read heads than the newer magnetic models. And yes, room will be a factor when installing on the 85xx machines.


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## wa5cab (Jun 11, 2015)

Richard,

First, I'm a little more familiar with the 8530 than I thought earlier.  I had it temporarily confused with the horizontal mill.  I don't have a manual on the 8530 but do have the 8520/8525  manual.  And my understanding is that the area that we are concerned with is the same on the 8520 and the 8530   Just today, in fact, I noticed that on the last page showing the cross feed (Y-axis) screw and nut, and the knee, there is nothing shown as holding the nut to the cross slide above.  The screw that holds it, 696-018, is shown on the previous page.

None of this really makes any sense.  If the error were due to variable pitch due to differential wear in the screw, it would repeat.  If the error were due to failure to take up slack or backlash in the cross feed screw and nut after the first slot, all of the rest of the slots would show the same error, not progressively greater.  The only three things I can think of that would cause a progressively shorter slot would be that the table was getting progressively farther away from the column as it moved from right to left, the part is not held down parallel to the X-feed motion (which would also mean that the slots wouldn't be perpendicular to the edge that the cut started from) or that the part is gradually moving on the table during or between each slot.


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## Richard Melloh (Jun 11, 2015)

Terry,

Access to that thread would be great. Please recommend a kit if you can. I appreciate your description of the differentiation between the glass and magnetic DROs. See, I'm learning something here ahead of the curve.

Looking forward.......


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## Richard Melloh (Jun 11, 2015)

wa5cab said:


> Richard,
> 
> First, I'm a little more familiar with the 8530 than I thought earlier.  I had it temporarily confused with the horizontal mill.  I don't have a manual on the 8530 but do have the 8520/8525  manual.  And my understanding is that the area that we are concerned with is the same on the 8520 and the 8530   Just today, in fact, I noticed that on the last page showing the cross feed (Y-axis) screw and nut, and the knee, there is nothing shown as holding the nut to the cross slide above.  The screw that holds it, 696-018, is shown on the previous page.
> 
> None of this really makes any sense.  If the error were due to variable pitch due to differential wear in the screw, it would repeat.  If the error were due to failure to take up slack or backlash in the cross feed screw and nut after the first slot, all of the rest of the slots would show the same error, not progressively greater.  The only three things I can think of that would cause a progressively shorter slot would be that the table was getting progressively farther away from the column as it moved from right to left, the part is not held down parallel to the X-feed motion (which would also mean that the slots wouldn't be perpendicular to the edge that the cut started from) or that the part is gradually moving on the table during or between each slot.


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## Richard Melloh (Jun 11, 2015)

Robert,

Parallelism is not the issue. I am so careful on this, loath to change a perfect set-up of my 6" Kurt 688 vice, though occasionally I must change for some 45 degree slots. Getting perfection takes a little time on some occasions. Sometimes we get lucky the first try. I use a lighted sensor to check my work. I always work towards zero tolerance. My customers expects all like parts will be interchangeable on all like machines, and they should.

The X axis functions perfectly. This is the axis I think would be showing wear first. I am surprised by the Y axis acting up before the X, though they both do endless repetitions within a fairly small range of travel. Come to think of it, maybe the Y axis is doing the lion's share.

The travel distance between the slots I am machining is typically in a range of 2.0 mm to 4.5 mm. To lose .003 on the X axis between one slot and the next, the table would be visibly and obviously more than 10 degrees out of alignment.

Nothing gets loose in my Kurt 688. The way I machine the .030 Delrin is by laminating it to .25 " expanded PVC with 3M industrial contact adhesive. I precisely machine .591" x 6.0" strips (billets), making sure they are .591 at both ends. I stock them to make the wide variety of combs required by my customer. I clamp the strip in the vice, resting on parallels to get the required clearance above the vice jaws, the majority of the .25" PVC engaged in the jaws. I install a stop in the jaw to give further protection against the strip shifting on the X and as a backup reference in case there is a reason I might need to pull the part or change mills during the process. After machining the comb profile, I carefully pop the finished Delrin product off the PVC with my fingernail (and a little firm effort) and clean it in solvent, debur as necessary while inspecting under a magnifier. The lamination is not shifting in any way. The .o23" dia. cutter is spinning at 3250 rpm and makes negligible lateral force as it passes through the Delrin, insufficient to cause shifting of the lamination by creep of the adhesive bond.

I am going to look into the difficulties of checking whether that fastening screw for the Y screw nut has come loose. Not sure what that will entail. Back to the manuals. Meanwhile, I did still get a lot of production done yesterday. Time to head out to the shop. Coffee's done.


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## wa5cab (Jun 11, 2015)

OK.  I didn't know what the distance between slots was.

I think, from looking at the 8520 parts drawings, that to get at the screw holding the cross feed nut, you will have to remove the table.


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## Richard Melloh (Jun 11, 2015)

Robert,

Big news: The access to the set screw for the Y axis screw nut is from the front of the table. There is a centrally located hole accessed through the compression plate that holds the Y axis, rubber, way scraper to the front of the X axis bed. It provides access to a 3/8" Allen set screw about three inches in.

Here is the interesting part: My set screw was backed off a full half turn. I think I have found my discrepancy. As soon as I have time, I will verify this.

Meanwhile, back to work.

Rick


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## wa5cab (Jun 11, 2015)

Well, I hope so.  At least you found something to "fix".    It is still weird, though, that it seemed be so consistent.


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## Richard Melloh (Jun 11, 2015)

Robert,

While fingers are still crossed, and I walk in from the shop at 6:58 pm, after a long day of buffing tiny PEEK dispenser parts, I am hopeful this answers my problem. 

I can only thank you and Terry for encouragement and particularly that lead about the set screw for the Y axis nut.

Whew! Time to make something yummy for dinner. My sweetie just pulled in the driveway.

Rick


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## spongerich (Jun 11, 2015)

If tightening the nut hasn't fixed your problem, you might give Clausing a call.  They still stock some parts for the 8520/8530.  A leadscrew and/or nut (if they have them) will likely be ridiculously expensive, but it sounds like they'd pay for themselves in your case.


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## Terrywerm (Jun 14, 2015)

I never gave a thought to the setscrew!  Hope it helps to resolve your problem.



Richard Melloh said:


> Terry,
> 
> Access to that thread would be great. Please recommend a kit if you can. I appreciate your description of the differentiation between the glass and magnetic DROs. See, I'm learning something here ahead of the curve.
> 
> Looking forward.......



The link to that thread was in the post where I brought it up. All you need to do is click on it and it will open in a new window.

Sorry I was't more on the ball on this thread this week - I was out of town for work so ended up falling behind, so to speak.

Looking forward to seeing how this all plays out.


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## Richard Melloh (Jun 14, 2015)

Thanks, Terry. I am too. Took the weekend off. Staying away from the shop for a change. I'll have a chance to verify this coming week, but only if I take time from real work. If I ever made the same comb twice in a row, I'd invest in a couple for stock. That's probably what I'll do, regardless. There's a chance the test will bear fruit in the end. 

I'll be checking you threads soon.

Rick out.


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## wa5cab (Jun 14, 2015)

Richard,

I'm still on the 300 baud connection through whenever I call it quits tonight (I'll be back in Houston and a decent connection late Monday) but I don't see a SITREP since Thursday evening.


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## wa5cab (Jun 14, 2015)

Well, 15 seconds after I sent the previous, your post this morning showed up.


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