Member postings for Ignatz

Lionel, see PM

The next step was to join the spacer to the larger of the two main gears. I temporarily slid the spacer and larger gear onto the main spindle to line them up, and tacked them together. I then removed them from the spindle to finish the rest of the weld-up on the bench. You will see in the photo that I elected for a series of deep, spotting welds around the circumference of the spacer. I chose for this approach instead of a continuous weld seam in order to avoid potential distortion. I’m certain it is strong enough for purpose. The welds did pull the gear ever so slightly out of line, but a very light skimming cut with the boring bar on the lathe allowed the welded-up pair to slide back over the spindle.

The three-piece stack having been converted to a two-piece stack with the topmost gear driving the shaft through the welded-on spacer, the short spindle key was no longer an issue. So I proceeded to reassemble the transmission.

But what to do about lubricating the new metal gears? Easy enough to apply grease while putting it together, but what about later on when that original grease gets flung off the gears to leave them run dry? I didn’t want to jam all of that original grease back into the transmission again. So at this point I made one alteration to the mill transmission housing. I drilled and tapped a hole (6mm threading) into the side of the transmission housing just in line with the intermediate drive shaft. A short bolt with a rubber washer does duty as a plug to seal the opening.

This hole serves as a handy lubrication port through which I can squirt discrete amounts of grease directly onto the intermediate shaft and gears as required. I really wonder why the factory never thought to include lubrication access in the original design.

Now it was finally time to reassemble the mill head and bring everything back to running condition. But again another fly in the ointment…

The transmission and main spindle case needs to be bolted to the mill head section that rides in the dovetails on the column. Naturally, the spindle must be aligned axially with the column, but sadly the two units are not keyed to one another and lining them up proved most annoying.

In his article, “Improvements to an X2 Mill”, Neil Wyatt refers to this procedure with the following:

“Before completing the setup, you need to refit the two parts of the mill head to each other. Careful inspection seems to indicate the upper surfaces of the two parts are the reference faces for their alignment.”

Well, that is how it is done for the old Sieg X2.

On the other hand, owners like me of the even older CH-10M will be most disappointed when they realize that there are absolutely no flat, clean reference faces on the two parts of the mill head to facilitate this operation. Obviously there must have been a jig for assembling these parts in the correct relationship to one another in the factory. But for the end user, out in the field, the re-assembly of these parts is a matter of some frustration.

My solution for lining up the two mill head sections was to mount my ER25 collet holder in the spindle. Into the collet holder went a length of hardened 8mm shafting from an old computer printer. The two parts of the milling head were then lightly bolted together, this assembly then being slid onto the column and locked in place

There is absolutely no provision for delicate adjustment of the relationship of the two parts one to the other, so it was then a matter of tap-tap-tapping the head this first this way and than that while holding a machinist’s square from the X-Y table against the length of hardened shafting.

Complicating this procedure is the fact that the bolts which secure the two parts of the mill head to one another are not accessible for tightening while the mill head is mounted on the column. So of course it took repeated iterations of tapping to what seemed to be correct alignment, pulling the mill head up and off to tighten the bolts a bit more and then sliding it back onto the column once more to again repeat the checking and tapping. I achieved what appears to be a reasonable alignment, but, please, don’t anyone ask me to hold a dial test indicator to the end result.

The mill is now completely reassembled and running (and rather nicely, at that). It will serve me for a while longer while I make a decision as to which newer, larger model will replace it

I’ve succeeded in repairing the transmission of my old CH-10M mill/drill and thought it might be instructive to others if I shared some of my experiences gained during the process.

As already reported in a previous post - **LINK** - I had the misfortune to overtax this unit and tear out the teeth of the low end of the two-speed drive. In the picture just below you will see the two original plastic gears in somewhat sorry condition. Behind them will be seen a tub of grease which some previous owner had stuffed into the transmission and which I had to dig out of there to even see what I was doing. What a mess that job was. This is perhaps 80% of the grease, the rest being smeared over an assortment of rags and paper towels in the trash bin. The transmission casing had never been designed (nor sealed) for that amount of lubricant and the mill had been constantly weeping and flinging gobbets of grease during operation ever since I purchased it. More on that later...

The plastic gears in these little mills is something of an Achilles heel, being prone to breakage and also very inconvenient to replace. Fortunately, there are metal gear replacements.

My original thought was to just use a metal replacement gear on the main spindle, that to be running against one of the plastic ones on the intermediate gear in the hopes of quieter operation. Too, should it break, the plastic gear on the intermediate shaft is much simpler to replace as compared to the drive gear on the main which entails a lengthy operation to pull the main spindle and bearing(s). But ultimately I decided that the effort of disassembling the mill’s head unit was something I would just as soon totally avoid in the future if at all possible and so opted for metal gears on both the intermediate shaft as well as main spindle. These metal replacement gears are the same ones as fit the old Sieg X2 Mini Mill and were secured from Arc Eurotrade.

The gears, upon arrival and inspection, looked quite reasonable. The intermediate gear had a bit of hobbing flash, but a few minutes of work with some needle files brought that round right. The main gear, however, proved to be a problem.

The original, plastic gear for the main spindle on the CH-10M is a one-piece injection molded unit. The metal replacement offered by AET is actually a three-piece stack-up arrangement of two gears with a spacer between. Two difficulties immediately presented themselves.

The first problem was that the total height of the three-piece, gear-spacer-gear stack-up was not equal to that of the original one-piece, plastic main spindle gear - measuring 2.25mm too short.

The second problem was rather more vexing. It turns out that main spindle shaft key on this unit is not quite as long as required for the metal replacements. The keyway length is not an issue at all if using a one-piece plastic main spindle gear as originally designed. Unfortunately, the three-piece stack-up arrangement of the metal replacements means that when assembled on the main spindle the topmost gear in the stack is doing little more than just kissing the rounded end of the drive key and would never be able to transmit driving power to the spindle.

Now, of course, the simple approach would be to mill the main spindle keyway a bit longer, slip in some longer key stock and ‘job done’… or at least, that’s what I would have chosen to do. Obviously, with my only milling machine in pieces this approach was out of the question. Instead, I opted to solve the two problems using my TIG welder and metal lathe.

My first task was to make up the the missing height in the gear stack-up. To this end I added filler metal to build up one end of the metal spacer.

The spacer was made from some unknown steel mix that seemed perilously close to pig iron and did not play nice under the heat of the torch - spitting and smoking most unpleasantly. Nevertheless, after six or seven passes around the rim I had built up sufficient metal after which I chucked the spacer in the lathe and turned it back down to the correct size - it now having the necessary 2.25mm extra length.

Edited By Ignatz on 09/07/2018 07:59:54

Seems pretty good.

Oh... and not to be too cynical about it... are those figures actually written in with a ballpoint pen, or perhaps written once and then printed with the form? I've seen evidence of that sort of chicanery on the internet with some other machine brands.

Of course, your actual measurements are what really count.

One would hope that the figures are indicative of a general level of quality across the machine offerings.

The 836VS looks pretty good, but is about three times larger than the space available in my tiny shop

XD 351 - You may have a point about keeping the mill for delicate and/or light drilling work, but since this is the older unit made of aluminum castings I just can't see the value of investing my time in a belt drive conversion. I would already be content with the transmission gear repair.

Edited By Ignatz on 30/06/2018 12:34:47

Finally got around to pulling the main spindle out of the mini-mill and thought to post this photo of the arrangement I used.

Of course, I was referencing Neil Wyatt's article, but having no large, metal tubing at hand I elected to go the fussier route and stack up spacing blocks. Considering the small size of this mill I found I could happily use elements from my clamping kit as the spacing blocks. True enough, as Neil states in his article, the blocks did tend to (* ahem *) fall out at the most inconvenient moments, but they did ultimately get the job done.

Lionel was kind enough to send me a replacement for the the intermediate shifting plastic gear (thinks again, sir!), but I still need to order a replacement for the gear that fits round the spindle.

I see that I can order either plastic or metal for that main spindle gear and I was thinking that a plastic gear on the intermediate shaft running against a metal gear on the main spindle might make for (A) slightly quieter operation as well as (B) more or less guaranteeing that if the mill is overloaded in the future then it would be the plastic intermediate gear that would fail first - this being the one that is really quite easy to replace as there is no major spindle pulling required.

Anyone have any thoughts or comments on this approach?

Lione,

Thanks for the offer.

See my PM

Well, I finally got around to disassembling the old mill to see the damage to the gear teeth. Big Ouch! The gears are the plastic acetal kind and didn't take it so kindly when that end mill fetched up on my work-piece. The low-end gears are properly borked: having shed some teeth on the shiftable, intermediate gear as well as the on the main spindle gear.

So far, I've only removed the intermediate gear (12/20 tooth), but it appears to be identical in count and measurement to that for the old Sieg X2 mini mill. Too, it appears that replacement gears are still offered by such places as AET.

...however...

I'm not exactly sure that it is really worth my time and effort to replace the gears on this old mill. Although the CH-10M is more or less the same as the Sieg X2 it has the disadvantage of having aluminum castings, aluminum column and an aluminum table. So if I put in new gears (even the stronger metal versions), even if I put in better main spindle bearings, the mill will still have its basic lack of rigidity as compared to the newer (old) version.

By the way, I happened upon that article by Neil Wyatt, "Improvements to an X2 Mill". (Hats off to you, Neil. You're a prince!) The article explains the mysteries of disassembly very, very well. Nevertheless, I see it is anything but a simple wave-of-the-hand, drop-in exchange.

...so even IF I had the parts in hand - for free - the work hours themselves - along with the preparation - are not inconsiderable. Might just button it up and use it high-end only until I've decided on which larger mill to purchase.

Oh, and a last amusing note:

I don't know this for sure, but I really suspect that this is not the first time this thing has some shed gear teeth and been repaired. I'm making this assumption from the fact that the label across the motor plate was cut through and the top spacer on the spindle - the one with the spindle locking hole - had been inserted upside down so that locking the spindle was kind of... impossible.

Anyway, when I opened up the unit I found it absolutely - and I do mean absolutely - filled up with lithium grease. I dug out something like a soft drink can's worth of the stuff before I could even see anything inside.

I figure that one of the first owners also lost some gear teeth, went through the trouble of replacing them and was so panicked about it happening again that he kind of overdid the lubrication in supposed self-defense.

So now I know why the bearings were always dripping grease when it was running.

Or it could be normal (???). What do I know.

Anyway, feel free to comment or suggest.

Cheers!

Thanks, Thor. I'll give it a look later on tonight.

I'm one step closer to (having to) make a decision on a new mill...

... the low range in this little thing just tore out some gear teeth (ouch! ouch!)

This leaves me with a device that is even more handicapped than before.

By the way, does anyone know if the gears for this old thing can still be obtained? I'd hate to try to sell it on in only semi-working condition.

Besides the initial cost, I'm curious about the supposed tolerances of any mill I purchase.

To date, the only company I have found that makes any claims about their tolerances is Optimum in Germany.

They claim that the runout of the spindle on their smaller mills is only 0.015mm (= 0.0005905494 inch)... although I'm sure that bad collet holders and/or tooling could negate that in a heartbeat.

Are there any other companies that make claims regarding the accuracy of their milling machine offerings?

Edited By Ignatz on 16/06/2018 10:53:30

Niels, love that second picture. What kind of tolerances does that puppy hold?

Thank you. Those are all helpful comments. But, there are two things I forgot to ask.

First of all: Assuming that I set up one of those mills correctly, using quality cutters, what kind of tolerances might I reasonably expect to hold?

Secondly: If to equip the mill with digital readouts is it better to purchase the unit with the DRO factory-installed or are there any advantages to attaching the required unit (or some other DRO) by myself?

I have finally come around to the conclusion that it is time for me to upgrade my current milling machine - a somewhat tired, old CH-10M vertical mill/drill - because it just lacks the range, rigidity and precision for the bits of hobby work that I want to do.

Any comments that would help me to make a more informed decision would be richly appreciated. [ By the way, I'm located here on the continent which might be a factor in terms of availability and/or shipping. ]

The space in my shop doesn't allow for one of those beefy, old industrial units and so it sort of looks like I'm in the market for one of the Warco's, Optimum's or what have you. I'm thinking that the ultimate size of the unit should not be more than two fellows working together could comfortably move.

Note: I'm sort of suspecting that a lot of those machines come out of the same factory, but may differ in terms of attention to detail and/or fit and finish.

The reason I actually went and put a readout on the spindle was because I just purchased one of those 'cheap-n-cheerful' Chinese-made er25 thread-on collet holders for the Myford.

Now from everything I've seen on the web, I know that those collet holders are notorious for some rather loose tolerances. And indeed when I put the DTI on the internal ground area where the collet would be seated I was getting runout of something like 0.05mm...

...and that started me wondering what the accuracy of the lathe spindle, itself, was. And from all of your responses, it would seem that the lathe isn't so bad in that area.

Of course, the lathe bed, cross slide and so forth, now those areas have had a harder life... But that is for me to possibly work out at another time.

I've recently had reason to check the main spindle of my old ML10 modelbuilders lathe. This is one of the early models with the spindle running direct in the cast iron of the headstock casting with full loss oil drip lubrication.

I find that the measured runout on the outside of the threaded mount is about 0.01 millimeter ( = 0.0003936996 inch ). I'm getting more or less the same runout reading inside of the Morse Taper socket inside the main spindle.

Also worth noting:  If push sideways or up and down on the spindle I don't see any movement on my dial test indicator.

My question being: Given the advanced age of this beast, is this level of runout acceptable? Should I be happy with this? And if it not, is there anything I can do to improve this?

Edited By Ignatz on 01/06/2018 17:32:38

Just thought to post a few pictures of this steady rest I fabricated for my ML10. Lots of fun to make and rather instructive for me at that.

The clamping base is made of 6mm hot rolled strip stock, the vertical portion and moveable arms from 5mm hot rolled and the guides from sections of leftover square rod.

The construction is stitched together with TIG welding and then milled where required... and vice versa. Those are cast-off bearings purchased from the flea market... the only thing not visible being some tiny brass tubes I turned to reduce the 7mm bores of the bearings down to 6mm to match the bolts.

It seems to serve well enough so far. I'm planning to extend the width of the support arms on the ends opposite the bearings and then add on a 'pad' of silicon bronze for use on parts that might be a tad soft and thus too sensitive for the hardened outer race of the bearings.

Thanks, everyone, for the feedback. I think that i can safely alter the design of the replacement countershaft to use those captive straight 'feather' keys. There is a tiny bit more fuss-n-bother making multiple passes with a small slotting end mill, but the end result should be far easier on the pocketbook.

PS  Illustration prepared using Blender 3D software with a few adjustments in the Photoshop.

Edited By Ignatz on 10/08/2017 14:56:26

I've got to make a replacement countershaft for my ML10 lathe. This shaft has Woodruff keys at either end for the drive pulleys.

I see that the cost for the correct Woodruff key milling cutter is pretty steep... most especially when considering that this is essentially for one-time use.

Would an alternate straight, 'feather key' work just as well in this situation?  This is something that I could mill out much more easily with the tooling at hand.  (see illustration)

Edited By Ignatz on 10/08/2017 08:15:44

My path is clear. EP 90-weight oil to keep the countershaft happy and running in the short term.

After that I order some 3/4" ground stock and machine a replacement shaft. This should bring me up to (only) slightly sloppy but workable runout on the countershaft.

When time permits I can the think about possibly reaming the journals and machining a slightly oversize shaft to match.

Jim, the suggestion to bore out the casting and insert Oilite bearings sounds great... except that the ML10 is currently my largest machine tool and otherwise I do not have access to anyone here who could do that sort of work. I'll have to leave that as a future possibility.