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My Round Column Mill Drill

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I'm going to continue with some of the project work I've been doing on my Enco mill drill here, since it doesn't quite fit the Electronics section where I was talking about my DIY bluetooth DRO project.

One of the mill's problems, is that there is a lot of radial play in the quill. Investigating, it turns out that there is a guide slot and a threaded guide pin and stop nut on the left side of the mill, as you face it. The fit seemed poor. and that allows a lot of play.

Well today, I decided to check both the threaded pin and the slot to see whether I could fabricate a better fitting replacement. Turns out the pin end is 7mm in diameter, and the slot is 8mm. It looked like neither was worn, so that was the actual factory fit!

I checked the threads quickly with my calipers -- a little under 10mm diameter , so probably a 10mm screw (with a turned 7mm tip). So off to town -- 30 mins of driving, there and back -- to buy a single 10 mm bolt. I don't have a 10mm threading die, or a 127 tooth gear for the Craftsman lathe. So a bolt it is. We're still heavily into inches here at most hardware stores;  metric fasteners are specials, and cost more. I don't keep much on-hand, and I didn't have a 10.

Just before I headed out the door, on a whim, I picked up the narrow stop nut and tried it against a 3/8" piece of all-thread leaning nearby. Well, it screwed on easily!  :scratch:

What the? Why would they put inch fasteners in a Taiwanese mill drill? Didn't make sense. But coincidentally I had just seen a "Winky's Workshop" video where Winky himself stated that the cover plate holding his similar mill's crank handle was also an inch size -- quarter inch bolts! So well, I believed this must be more of the same thing.

What the heck, that's easy, I had plenty of 3/8" - 16 bolts, but I needed to mail some letters for my wife in town, having volunteered earlier -- thinking to make getting a single bolt run seem more reasonable. So I decided to go as promised, maybe I'd find an unusual longish 3/8" setscrew in town, which would be easier to hold in the lathe when turning the tip down to 8mm. No head to deal with.  :dremel:

I got to town, and after finding an allen head machine screw of the right size and length, I brought it to the counter. And then found that I'd forgotten my wallet!  :bang:

Well, not to be done in by a damn bolt, I asked the lady clerk to hold onto it for me, ran back out to the parking lot, and scraped enough quarters out of the car glove compartment ...and back seat... to buy it. Which was admittedly, pretty pricey at a buck forty-nine, but, by golly, that bolt was the whole purpose of this mission, and I wasn't going home empty-handed! Well, besides mailing those letters at the post office.  :thumbup:

Driving back home I was still thinking about why that mill had inch fasteners. Or how many it had. Were they mixed? Why would they do that? Not complaining, it's actually convenient, but you know, surprising! I looked forward to getting that damn play out of the quill so I could move forward with my Z axis DRO scale mount. Something very satisfying about improving a tool by removing play that has bothered you for, well years.

Well you've probably already guessed where this story is going... downhill..... The bolt wasn't right. I mean it seemed to be right for about 5 or 6 threads deep. It screwed right in, maybe a little too loose at first, but getting tighter as it went. But uhhhhh, then it stopped.....

Hmmm. Why is that? Is it hitting the column slot? Nope doesn't seem to be...... :scratch: :scratch:

Uhhhhhh, maybe it really is 10 mm........ Is that possible? Are they that similar?  :scratch: :scratch: :scratch:

Well, you learn something new every day. Or maybe something old. Or maybe you never learn.....  :wack:

And that's what I accomplished today on my mill drill.

I do have a vague recollection that when Taiwan was being heavily supported by the US back in the mid 1960ís to develop an industrial base they set up a Design Bureaux to produce machine tool designs that were freely available to any local firm wanting to produce such things. This resulted in many machines being to all intents identical even though made by different companies. However some companies inevitably made changes particularly if they were already tooled up in (say) metric fasteners despite the design calling for Imperial. So you find metric threads on bolts with Imperial hex heads and vice versa.

What didnít develop at quite the same rate was the concept of standards and testing. Much the same happened in Japan after the war where quality was atrocious until they developed extensive quality standards and enforced them. BS5750 which translated later into the ISO9000 series of standards was based closely on this early work in Japan.

 . . .  But where this leaves your screw thread Iím not sure Steve !


--- Quote from: vtsteam on April 28, 2022, 08:48:39 PM ---Uhhhhhh, maybe it really is 10 mm........ Is that possible? Are they that similar?  :scratch: :scratch: :scratch:

--- End quote ---
Hi Steve

I have come across this before on a car I own. The engine and gearbox are different ages, the bolts into the gearbox are 10mm and the bolts into the the engine are 3/8.  It is possible to put the 3/8 bolts in the wrong (10mm) holes but not generally the other way around. :loco:

Worse - I also found 3/8 threaded brake pipes threaded into 10mm threaded brake calipers. :bang:

However this doesn't help because if it's a 10mm hole or a 3/8 hole I'd expect the 3/8 bolt to fit. :scratch:


Thanks guys, I see another trip to town in my near future! I think buying a 10mm die and tap would probably be smarter than just a 10mm bolt. After all, steel of all sorts is plentiful here, and a bolt would require modification anyway for this particular function.

Even more radical (read sensible) would be completing my lathe electronic leadscrew project, since that is functionally tested, mounted in a nicely painted aesthetically matching housing, the stepper and tach mounted to the lathe already, and basically just requires putting the power supplies and wiring in place in a separate box. It should do any of the pre-programmed pitches at the flip of a few switches.

Hey, it also does this amazing thing, too, called power feed. I'll have to experience that some time. Of course the downside is that the knobs on my handwheels will start to lose their present amazing shine.

Andrew, I worked in a quality systems software house once upon a time in Boston doing ISO 900x software troubleshooting support and datatbase documentation. The system ran under Lotus notes with 32 separate databases, all integrated together. Customers were 3M, Kodak, Chrysler, Cummins, Motorola, etc.

Okay, back to this unknown size screw hole in my mill......

10mm it is.

Picked up bolt, tap and die for 10mm, and 8mm, too, for good measure. I already have a 6 and under set.

On with the show....


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