[Nelson_2008]

No matter how I try to adjust things, I cannot get the Y axis to move across its range of travel without being sloppy at the ends and tight in the middle. If I tighten it down so there's no perceptible play at the ends, it takes at least twice as much (or maybe three times more) torque to turn the hand wheel to get the saddle through the middle 3 inches or so of its travel.

Since I'm new to milling machines, I don't know if I should accept this situation or not. The thing is, I didn't have this problem with the old base (the one that came with the Micromark) and the x axis doesn't have an issue like this, even though it has a longer travel.

The only conclusion I can come to is that the ways are too far "out-of-parallel". So I'm wondering, is there any way to fix this, or am I being too "picky", or should I send it back for exchange with another one or a refund?

Any advice/opinions would be appreciated. Thank you.

[hoss2006]

Have a read here on lapping and scraping.
http://www.g0704.com/Shop_Info.html#dovetail
Getting another replacement is no guarantee but do it before scraping this one.
Hoss

[Nelson_2008]

Thanks very much for your reply Hoss.

Do you think I should ask for a replacement before I do ANYTHING, or should I try lapping it first? To put it differently, would it be (1) Ask for a replacement (2) Lapping (3) Scraping; (1) Lapping (2) Ask for a replacement (3) Scraping?

[hoss2006]

yeah, replacement first, they wouldn't want a lapped/scraped one returned, if the replacement needs help, lap first with emery for a minor deviation as shown here with emery paper and a flat surface or with an angled flat bar wrapped to fit the dovetail.
Hoss

[wizard]

There are two possibilities here. The casting wasn't machined correctly is one possibility. The other is that the casting distorted after machining. Either way I'd call LMS first to see what they have to say. It really sounds like an exchange is in order as it appears to be an out of box defect.

There is always a third possibility of a dinge or other damage done to the ways during the swap. You would want to be sure that isn't the case.

If LMS balks at a return then scrapping is in order. Do no lap ways!!! Scrapping is an easy to learn and worthwhile skill. The big issue with scrapping though is the reference surfaces, that is the straight edges and the like. They are hard to come buy though DIY solutions are possible. If scrapping is not your cup of tea look for a local tool rebuilder with a way grinder.

If I had to guess I'd say the casting distorted after machining in some way. Mainly because you have indicated that it is tight in the middle.

No matter how I try to adjust things, I cannot get the Y axis to move across its range of travel without being sloppy at the ends and tight in the middle. If I tighten it down so there's no perceptible play at the ends, it takes at least twice as much (or maybe three times more) torque to turn the hand wheel to get the saddle through the middle 3 inches or so of its travel.

Since I'm new to milling machines, I don't know if I should accept this situation or not.

If you believe you have properly assembled the machine then do not accept it. Fix it one way or another with the first course of action to be sending it back.

The thing is, I didn't have this problem with the old base (the one that came with the Micromark) and the x axis doesn't have an issue like this, even though it has a longer travel.

The only conclusion I can come to is that the ways are too far "out-of-parallel". So I'm wondering, is there any way to fix this, or am I being too "picky", or should I send it back for exchange with another one or a refund?

Any advice/opinions would be appreciated. Thank you.

From what you have described I wouldn't call it being picky at all. If the saddle can be moved back to the old base and it functions fine there then you have a legitimate problem. The only thing to question is the setup of the gibs but I have a hard time seeing this as an issue as you say the saddle loosens up at each end of the travel. There might also be an issue with the definitions of sloppy and tight, but at this point I'm not thinking you are unreasonable.

[amyers]

Do no lap ways!!!

what nonsense, read some of the links on hoss page, lapping is an effective means to fix the problem, scraping is for more severe problems. lots of the old timers are set in their ways.

[mduckett]

For my SX2 conversion I had a similar problem with the replacement saddle and base I bought for the conversion. For mine, the saddle was very tight when pulled to the front, and loose when pushed to the back. Adjusting the gib for no play at the back made it nearly impossible to pull the saddle completely flush with the front. I used a sharpie to mark up the surfaces and found that the dovetail on the left side of the base was not cut properly, starting from about 1/3 of the way back. The saddle dovetail was wiping only a strip of the sharpie instead of contacting the whole surface. It had a kind of rounded look instead of being flat. The reason I didn't want to lap it is because lapping would have resulted in removing material from both the saddle and the base when only the base needed correction. Can't remember who suggested it here on the form, but what I did instead was to cut strips of emery about the width of the dovetail and used these strips between the saddle and dovetail to work down the areas that needed correction, using plenty of oil (I used synthetic motor oil and wore those blue nitrile gloves from harbor freight). I think I used 400 and 600 grit. The base needs to be clamped down to something solid. The strips need to be long enough to allow folding/holding them against the saddle while working it back and forth. This took some time, probably about 3 hours working in the evenings, but in the end the saddle moved smoothly from end to end. It still had a hint of tightness at the front, but I stopped once it moved smoothly and could be adjust for no play from end to end.

-md

[wizard]

what nonsense,

It is very good advice in this situation, especially in the common situation described here where one attempts to lap in a surface with what should be another machined surface by rubbing the two together. The very nature of such a lapping attempt means that both surfaces get ground down in an uncontrolled manner.

It is one thing to use lapping to smooth rough but otherwise good surfaces. Here though we do not have good surfaces to work with. More so you don't know where the distortion is other than the obvious binding in the middle of the travel. Trying to lap that distortion out will do a couple of things that are highly negative with respect to the life of your machine. For one it will wear both the saddle and the ways it runs on in ways you can't predict. In this case you would effectively ruin the saddle or at least have a saddle that no longer mates well with the ways. The second thing to realize is that aggressive lapping, in an uncontrolled manner, leads to curved surfaces. Just take a minute to consider how telescope makers hand grind their lenses or mirrors.

read some of the links on hoss page, lapping is an effective means to fix the problem,

Lapping might clean up rough surfaces but it is no way to correct distorted surfaces. Everything about this post indicates that the surfaces are indeed distorted. This is due to the indication that the saddle tightens up in the middle of the ways.

scraping is for more severe problems.

Utter rubbish! Scrapping is used to establish flat surfaces, flat surfaces that are parallel to one and another or better stated coplanar when they need to be. Further scrapping establishes a bearing surface on cast iron that lowers stiction and friction.

lots of the old timers are set in their ways.

It isn't a question of being an old timer but rather the reality that there re right ways and wrong ways to do something. Scrapping is a long established and refined process for establishing a proper bearing surface on cast iron ways. If scraping was outmoded, companies like Dixi wouldn't be using the technique to build their horizontal Jig bores nor would any other company building machinery on plain bearing ways.

Ideally when working on equipment, you fit the technique used to the problem at hand, in this case lapping isn't it. You can argue all you want but the fact remains that lapping to correct massive errors just leads to wear on both pieces being rubbed together. The very nature of that wear means that surfaces won't be flat afterwards especially on the saddle.

[wizard]

A very interesting read and an interesting approach to a problem.

For my SX2 conversion I had a similar problem with the replacement saddle and base I bought for the conversion. For mine, the saddle was very tight when pulled to the front, and loose when pushed to the back. Adjusting the gib for no play at the back made it nearly impossible to pull the saddle completely flush with the front. I used a sharpie to mark up the surfaces and found that the dovetail on the left side of the base was not cut properly, starting from about 1/3 of the way back. The saddle dovetail was wiping only a strip of the sharpie instead of contacting the whole surface.

I hope people reading this grasp what you did, you diagnosed the problem before taking action!!

It had a kind of rounded look instead of being flat. The reason I didn't want to lap it is because lapping would have resulted in removing material from both the saddle and the base when only the base needed correction.

Exactly! This is why I object to lapping to correct significant geometry errors.

Can't remember who suggested it here on the form, but what I did instead was to cut strips of emery about the width of the dovetail and used these strips between the saddle and dovetail to work down the areas that needed correction, using plenty of oil (I used synthetic motor oil and wore those blue nitrile gloves from harbor freight). I think I used 400 and 600 grit. The base needs to be clamped down to something solid. The strips need to be long enough to allow folding/holding them against the saddle while working it back and forth.

This is an interesting solution that puts action where the problem is.

This took some time, probably about 3 hours working in the evenings, but in the end the saddle moved smoothly from end to end. It still had a hint of tightness at the front, but I stopped once it moved smoothly and could be adjust for no play from end to end.

-md

I hope everybody reading this grasps how this differs from random lapping. Further this is a gross error in geometry where the common lapping techniques describe here would be counter productive. I'm not sure I'd do it that way but you have certainly addressed the major issue with lapping and focused your efforts on the area that was obviously wrong.

[amyers]

relax pops, i didn't realize you were psychic and could KNOW that it is a major flaw having no empirical data to go by. we'll just have to disagree just like the many posters in the big lapping vs scraping thread.

[handlewanker]

Hi, it must be realised that only one of the dovetails in the saddle is a fixed point....the other is determined by the jib strip that follows the dovetail in the base, and this can be variable as it slides across the base male dovetail.

First you need to ascertain the condition of the base dovetail, it must be DEAD PARALLEL and this is best done with two rollers placed into the dovetails and then measured across all the way from end to end......a micrometer is best for this, but a gauge can be made spanning the dovetails using an indicator to test for any out of parallelism.....it's parallelism you are checking not size.

This will reveal if the dovetail in the base is parallel.

Next, if no inconsistency is found, a small wedge shaped gauge is made to test the angle of the dovetail in the base, (assuming the base of the dovetail is also dead true in the horizontal plane), and this is slid all along the length of both dovetails in the base, using a .04mm feeler gauge to see if there is any hollow spots......using blue is not advised unless the gauge piece is accurately made as it will just give confusing indications.

If the base dovetail is pretty consistent .....in it's angle all along both lengths and no deviation of angle is found you can then mark the base dovetail, side and bottom, with blue, the one opposite to the gib strip face, and then carefully slide the saddle onto the base, making sure NOT to make contact with the base dovetail until the saddle is fully entered.

Next, press the saddle against the base dovetail and move it back and forth FOR A DISTANCE OF NOT MORE THAN 10MM, back and forth.....then carefully remove it and look for the contact area indicated by the blue marks on the saddle and the bare spots on the base dovetail.

If you make a dummy dovetail out of hardwood, about 50mm long, to fit into the base dovetail you can charge this with grinding paste.......shock horror.......or put some wet and dry paper between the faces and spot lap the high points off.

You will have a lot more control over the areas that get rubbed down than if you just put a strip of sand paper between the faces and hope for the best.

Personally, I abhor anything that pertains to sand paper or grinding grit when working on slide faces, and the scraper is a tool that will give best results if you take the time to learn how to make and use one.

Once you have the dovetails (opposite the gib) in the saddle and base with true contact all along the length, and the BASE of the dovetail on the gib strip side too, you can mark the gib strip side in the base with blue, and insert the gib strip and do another back and forth move ALL ALONG THE DOVETAIL to mark the dovetail angle face, just nipping up the jib with the screws.

It will be difficult to get the bottom slide faces of the dovetails in the base true to one another without a reference table to run an indicator on, and one slide face or the other could be out of flatness to the other.......a large milling machine table would do in that case.

You should get an indication of any high spots on the base dovetail angle face and can lap these down as before......the jib strip will be too flexible to warrant any flattening operation.

Oil the dovetails both sides.

You should be able to slide the saddle across the base without any point being tight and no slop.
Ian.

[Nelson_2008]

I took the saddle off the base, removed the feed screw, wiped off the lubricant, reinstalled the saddle (but not the feed screw), tightened the gibs somewhat, and moved the saddle back and forth over its range of travel, by hand, maybe a dozen times or so. And then I looked at it, and I noticed some "shiny spots" in the area where it gets tight.

There was a series of "periodic" shiny spots on the right hand side lower horizontal surface of the dovetail...that I would attribute to "rough" machining. In other words, when looking at the base from the front, the dovetail on the right hand side would have a "Z" shaped cross section (and the one on the left a backwards Z) and the bottom horizontal surface of that "Z" has the shiny spots...which to me implies that it is pushing "up" on the saddle in this area.

So I stood there for about a half an hour, moving the saddle back and forth, and the shiny spots got a little bigger. Then I cleaned and lubricated it and put it back together, and now it seems somewhat better. (It sort of reminds me of "breaking in" a 22 caliber semi-automatic rifle, where you don't get maximum reliability until you've fired a few hundred rounds out of it).

Anyway, I'm wondering, should I get some #600 sandpaper and maybe use a 1-2-3 block as a sanding block and try to take a few ten-thousandths off of that apparent problem area?

[handlewanker]

Hi, short answer....yes you could do that, if you are not "engineering" enough to use a scraper, all roads lead to Rome etc.

I would concentrate on the "shiny" spots as they indicate high points that will eventually, after a fair bit of time, wear down, break in as they say, but because they are high spots will wear the opposite part in small areas unequally.

When two slides are scraped to a good contact surface, the slides will ride on an even film of lubricant, but with high spots present this prevented from happening as the lubricant just squeezes out and pools in the hollows.

You have to be hyper carefull with cast iron (even more so with mild steel) in rubbing a dry slide on another dry slide as this is a recipe for instant metal galling......one of the reasons you employ marking blue (one one surface only) is to not only indicate the high spots, but also, by nature of the oiliness of the compound, prevents the surfaces from rubbing each up to death...LOL.

Make sure you wash the slides with kero before assembly to remove any grinding grit.

Best of luck.
Ian.

[Nelson_2008]

This thing is still driving me crazy.

I had to take a little time away from it because I injured my shoulder, but now my shoulder's feeling a little better, and I'm back at it again, but now I'm having trouble tramming it.

After many hours of disassembling, sanding, cleaning, reassembling, adjusting...disassembling, sanding, cleaning, reassembling, adjusting...I was finally able to adjust the Y axis gibs so that there's no perceptible slop in the table as it travels throughout its range, although there is still some noticeable drag; i.e., it takes more torque to turn the hand wheel while the table moves over a certain part of the travel.

Anyway, with an arbor and chuck in the spindle, I set up a dial indicator on a radial arm about 3.5 inches long (clamped to a rod held in the chuck), and using that I was able to shim the column to make the X axis perpendicular. I now have it so that as I rotate the spindle 180 degrees and the dial indicator goes from from X = 3.5" to X = -3.5", delta Z is only about 0.0005" or something like that, and that seems reasonable to me.

The problem is the Y axis: The "slope" is not constant across the range of travel.

When the table is near the front end of the base, the slope (delta Z/delta Y) is about 0.0005" per inch...but after it moves about 2.5" towards the back, the slope increases...to over 0.001" per inch, and then almost 0.0015" per inch over the last two inches or so.

I'm wondering, is this kind of problem fixable?

When I had the first problem, Chris at LMS did send me another base, but UPS (I believe) dropped it and damaged it, so I sent it back - but when I quickly looked it over before sending it back, the machining on it seemed rough also, not much better than the one I have, so I asked LMS not to send me any more while I try to get this one working to my satisfaction...but now I think I'm at the end of my ability to deal with this and my patience is also at an end.

I wonder if I should try to find a place that repairs/reconditions machinery and pay somebody to look at it or whether I should just send the whole thing back for a refund and forget about it?

[handlewanker]

Hi, the problem is indeed fixable, you just need to come onstream with some very quick machine tool fitting expertise.

First of all you need to work on the base Y slide dovetails to ensure they are both in line, and that means a level flat surface so that you can run an indicator along and across each one to see if they slope away from the straight and level.

A level flat surface is in the first instance a surface plate of known characteristics but can be a mill table or a bigish lathe bead with flat ways.....anything that has a surface you can consider reasonably flat....IE previously machined and rendered flat and true.

Without a flat surface to go by, you have nothing to refer to.....you are actually making the new surface flat by referencing it from the standard surface.

If you can get a granite surface plate, or beg borrow or steal one, you are home and dry, as this will make slideway fitting and machine allignment perfect.....even a big old lathe face plate could be used if you are desperate enough and manage to find one at a scrap yard etc.

Without a true flat surface to go by, your only option is to find someone who has anything that resembles a flat machined surface......big mill table etc, and see if you can't beg some hands on time on it......or send it out to have it remachined LIGHTLY, as you don't want to make the slides so far out of wack they can't be refitted.

If you can access a flat surface of sorts, the rest is just ascertaining the run out and correcting it with surreptitious scraping....NOT SANDING WITH EMERY PAPER....EVER.

let us know your situation as anything further depends on the flat surface you can access.
Ian.