Milling Rite

[RaisedByWolves]

Pictured: Friday afternoon, 4:47 PM.

View attachment 489418


Like, I know this the location of this bore doesn't exactly matter so long as it's providing support to the elevator screw nut, but damn.

I've putzed around with a lot of machinery over the years, but I've not often torn something down to the base/frame...and that makes me wonder how often things like this are done. I suspect it's far more often than I suspect...and that was a very Austin Powers-esque sentence, but I'm leaving it as-is because it's funny and accurate, unlike the aforementioned bore.

Also, I thought I had a 1.25" bit...but I don't, so evidently it's time to add another bit to the "Stuff I'll Never Use Again" drawer. And I don't even have that drawer, yet, but I'm starting to need it.

Meh, that’s pretty common with castings.

 

[Dave Bonzo]

Warning: This post contains graphic images. Viewer discretion is advised.

The tl;dr version of today is "the wooden clamp-block idea worked; thank you"...and unless you want to see some Colonel-Kurtz-Tier horror, stop reading now.

Pictured: This is the good part. It goes downhill from here.




I'm not much of a hand with metals yet, but I can turn scrap wood into useful things...and this worked perfectly; sincere thanks for the idea. I got the top nut off with very little effort... although in doing so I learned that the elevator nut that sits within the base doesn't come off, so now I'm going to have to do some thinking on how to fix that. In the meantime, I did manage to get both of the elevation gears loose, and I got the screw and shaft free; I even left one of the stop collars in place on the shaft so that I'll have a rough idea of its indexing in the future...and that is where the good news stops.

Pictured: Now, the fun begins.




That's the least-terrible thing that we're about to see...and that's mostly - but not entirely - due to my suspicions being confirmed regarding something being stuck in the teeth of one or the other gears. And what was it, exactly, that was stuck in the teeth?

Pictured: Other teeth.






Those popped out into my hand with barely any pressure from a small pick...and then they crumbled. Like, seriously, two pieces became three, and then three became about sixteen; whatever happened in here effectively turned the broken parts of those teeth into greasy glitter. And I'm honestly not surprised about that, because the condition of the back side of the gear can only be explained by it having been worked on by an escaped fiend.

Pictured: Or a chimp. Or a concrete guy.




Okay, no jokes here: I don't get this. I genuinely have no idea why someone would have to hammer on the back side of this gear in this way; that's not how it comes off the shaft. It wasn't really that difficult to remove, either; I just left the wooden clamp on the screw and used a small hammer and a length of wooden dowel to tap it off...and it didn't complain much. The shaft itself looks okay...

Pictured: At least, I hope it's okay...




...but the gear itself is smurfed. Royally smurfed.

Pictured: I got 99 problems, but an intact tooth ain't one.




Lots of damage, there. Some of it can be lived-with, methinks, but somewhere around two dozen of those teeth have some kind of cracking/crumbling damage to them...and some of the others are impact-damaged: look up around the 10:00 portion in that photo. Those look peined in the same way that the back of the gear does; I have no way to prove it, but I'm betting that the same concrete guy that went full chimpo on the back is responsible for this damage on the front. I do think that the outright breakage and the jamming occurred recently - specifically, when I was futzing with things - because I honestly don't recall detecting a problem with the table elevation mechanism beforehand...but I think the damage that allowed the breakage was caused in the past. And if the gears aren't evidence enough, I will now humbly submit an image or two of the taper pin that flagged me and then started this entire process.

Pictured: A tiny metal banana.




I didn't cause that bend when I tapped it out, because it basically fell out...because that's how tapers work. They work so well that even with the pin end completely deformed there wasn't enough resistance to cause the pin to seize in the hole...but that deformation was definitely enough to keep it from going all the way through and seating properly.

Pictured: Who uses something like this?!?!




And with that, Dear Reader, I am stepping away from things for a few hours. I'll clean up the gears and start measuring them here in a bit, and then I'll hope that there's a set in a catalog somewhere that can be made to work. Failing that...well, we'll see. That's a problem for tomorrow, and tomorrow is another day.

In the meantime: to whomsoever did this...f*** you, man. You knew better, and I know that because I know that you couldn't get this far inside without knowing better. You knew it...and you did this anyway. Bravo, Johnny Chimpo...bravo.

 

[Ischgl99]

I don't get this. I genuinely have no idea why someone would have to hammer on the back side of this gear in this way; that's not how it comes off the shaft.

When I worked as a field engineer, we called guys like that ”hammer mechanics”, and unfortunately, we saw that far too often.

It’s heart breaking to see this, and I would feel the same way to the person who did this. When you get the gear measurements, post them here, we can help look and see if we can find something that fits, or possibly come up with an alternative solution.

 

[Dave Bonzo]

When I worked as a field engineer, we called guys like that ”hammer mechanics”, and unfortunately, we saw that far too often.

I think that's what gets me: the fact that someone was proficient enough to get that far inside the machine, and then chose ineptitude.

It’s heart breaking to see this, and I would feel the same way to the person who did this. When you get the gear measurements, post them here, we can help look and see if we can find something that fits, or possibly come up with an alternative solution.

I'm kind of muddling my way through that part, right now; I just don't know much about gears and their measurements, yet. Thus far, I know that it's a 2:1 ratio, 32 and 16 teeth on each, bores of .750" and .625" respectively, and it looks like a mounting distance of somewhere around 2.125"...but that last number is pure conjecture, because I'm just estimating. And the diameter of the larger gear is 2.7-ish, I think; I just threw a caliper on it to see where it was, because it's kind of a weird shape. I'm going to sit down later today and write it all out, because I didn't get very far in the Boston catalogue before realizing that nothing looked like an obvious match.

 

[Dave Bonzo]

Okay...stuff that I know after a few measurements:

• Ratio is 2:1, with 32 teeth on the larger gear and 16 on the smaller.
• I'm assuming the pressure angle is 20° but I'm honestly not sure how to measure it.
• The larger gear has an overall diameter of 2.712" and a bore of .751". Its overall depth is 1.190-ish" to the top of the teeth, and 1.160" between the flats. It doesn't really have a pitch diameter that's different from the overall diameter, as best I can tell...so that's about 2.712" as well. Tooth face is somewhere around .550" give or take a lot, and the mounting diameter is about 2.165"... I think. It's really hard to tell because I'm basically shoving the gears together and approximating.
• The smaller gear has a hub diameter of 1.187-ish", a bore of .626" and an approximate pitch diameter of 1.375". Overall diameter across the teeth is 1.533-ish, but I don't think that matters. Depth is 1.248". Tooth face is about .541" and the mounting depth is possibly 1.700".

Turns out that I'm really not very good at measuring gears, I suppose. I don't see anything even close in the Boston catalogue...so I hope that means I'm even worse at measuring than I suspect; otherwise, it means they just don't have anything. I just started by scanning 2:1 gears and I didn't find anything, and then I started looking at mounting depths and diameters and I still didn't see anything.

 

[Ischgl99]

I came across this site that does the gear calculations, it looks like it is a 12DP gear set.

Bevel Gear Calculator

Boston Gear didn’t seem to have anything that would work, but Martin Sprocket might, I haven’t dug too deep there yet. You can try looking at BDI to find some other brands to check into. Their search parameters are a bit basic, so lots of choices to go through.

www.bdiexpress.com

 

[pontiac428]

Keep in mind that you don't need an exact replacement fit. A gear pair with a 90 degree axis and say a 2" big gear against a 1" pinion with a 2:1 tooth count could be bored and spaced to fit and function.

 

[Dave Bonzo]

I came across this site that does the gear calculations, it looks like it is a 12DP gear set.

Bevel Gear Calculator

Cool! Thank you! I'll play around with that; I think it'll give me a better grasp of what's happening, spatially.

Boston Gear didn’t seem to have anything that would work...

Oh good, I was right about that part! Go me!

...but Martin Sprocket might, I haven’t dug too deep there yet. You can try looking at BDI to find some other brands to check into. Their search parameters are a bit basic, so lots of choices to go through.

www.bdiexpress.com

I'll look that one up as well. Thank you again!

Keep in mind that you don't need an exact replacement fit. A gear pair with a 90 degree axis and say a 2" big gear against a 1" pinion with a 2:1 tooth count could be bored and spaced to fit and function.

I understand the concept - I think I do, at least - but I guess I'm having trouble envisioning the overall envelope; there has to be a series of physical constraints that allows certain gears to be used while prohibiting others...so, maybe it's just a question of literacy on my part. Without having seen a set that looks like it might work - i.e. big enough to turn down, re-bore, etc - I'm having trouble deciphering what will work.

 

[Dave Bonzo]

I checked BDI; nothing seemed very close, but that's still probably my lack of understanding showing up. I think I do better with diagrams that show me physical sizes; once I know the overall dimensions, I can start extrapolating where I have to modify things in order to make them work. Without knowing all of that data it's hard for me to envision it all in my head.

 

[RaisedByWolves]

When I worked as a field engineer, we called guys like that ”hammer mechanics”, and unfortunately, we saw that far too often.

It’s heart breaking to see this, and I would feel the same way to the person who did this. When you get the gear measurements, post them here, we can help look and see if we can find something that fits, or possibly come up with an alternative solution.

We call that “Fixin the **** out of it”.

Hey boss, we have a spare part for the new guys project?

He’s fixing the **** out of it…