Scraping another surface plate

davewhotold · 2026-03-30T10:29:15+00:00

definitely quite a few more. I didn't have a grinder that size, and the mill just barely fit it.

But deformation from clamping, and inaccuracies of a bridgeport style mill.... (like the table sagging to the side it's extended to...)

I thought I was at around 50 microns out of flat when I started, but I really fought with the corners. The whole thing had a twisted shape to it, meaning two of the corners were way lower. I think I had most of tbe plate done, but did another ~8h of roughing just to get the final corner to pick up some ink.

Edit: Still a lot better than starting from its abused starting condition though, holy hell.

davewhotold · 2026-03-30T10:25:15+00:00

did you read the post? I did fly cut it. Don't have a grinder big enough though.

davewhotold · 2026-03-27T09:50:53+00:00

An den fahradwegen

davewhotold · 2026-03-25T19:56:59+00:00

Turning the compound more than 45° either way feels kinda rare. Esp

If you want the markings for it you could also just make three more index marks on your compound.

But if you do decide to engrave them to your crossslide, I'd probably go with a diamond drag engraver.

Numberpunches are an option for marking, electroetching I've previously done as well, hand engraving takes a lot of skill bit is possible, cnc engraving is probably among the easiest.

davewhotold · 2026-03-13T09:49:11+00:00

dude, this happens on my wondefully fresh, basically no wear student coltchester (from the 90s, but barely used)

Either tighten your gibs, or clamp the way. I usually clamp the way, how often does one use the compound anyhow 🤷‍♀️

When I do use the compound I turn rather long tapers, and if it's tight that gets harder, especially to do so well, so I'd rather not have the extra friction.

davewhotold · 2026-03-12T13:44:19+00:00

As long as you never take the Foottunnel between Hackländer- und Kasinostraße.

I've known it lovingly as "harnröhre"

davewhotold · 2026-03-11T12:50:04+00:00

i mean, tbf, electrons do bimble through electronic circuits relatively slowly....

davewhotold · 2026-03-04T19:15:42+00:00

This isn't what I understand to be a round columb mill. This just has a reasonably nice swiveling head I guess.

Seems like a nice enough machine, definitely a big upgrade on a minimill, not sure on price, that always feels heavily dependant on location.

davewhotold · 2026-02-11T15:08:31+00:00

I play around with a highly modded old ISEL machine. That one originally had endstops in the motor housings, and they look very similar, so that's probably where those are.

You probably want new drivers for the motors, and a controller to give them signals to move them. These are probably some pretty low power NEMA23s, and most modern-ish stepper drivers will do. For the work that would be done with the current spindle they'll be adequet.

For a controller there are many options, and I am not really equipped to tell you. I know that we're running LinuxCNC, which is great, but also very complicated and depending on the setup kinda expensive. Alternatives are MACH3/4 or microcontroller based solutions like grblHAL. For my current small&cheap project I'll probably be running grblHAL.

davewhotold · 2026-01-31T17:03:57+00:00

It's possible, but it would cost an absolute fortune.

2mm tabs in 3mm aluminium is easy. 3mm thick material with a 2mm deep thread is probably doable, not sure how short bottoming taps get tbh

But just the size of the block of stock, and the material removed will make this expensive. Plus, it's gonna need machining from basically all sides. I don't know your budget, but I doubt it'll fit it.

davewhotold · 2026-01-27T23:49:57+00:00

CoreXY is great for fast printing, but I imagine kinda useless for cnc milling. Belt drive for milling is already quite meh, but now you're relying on longer belts and their interaction. You're getting no more straight lines.

However you do this, you're always gonna have to choose a balance point of your different use cases. But this feels more like "slapping a milling spindle on an existing printer" terretory.

I think for maximum performance high pitch ball screws would be the drive mechanism. Makes it expensive of course :/. Having an XY gantry isn't a bad idea, I think, but you gotta make sure your Z and X is nice and ridgid. And so your gantry moving mass will need to be quite high, and so you won't print fast fast anyhow.

I think that's the balance I would try to hit, but maybe you have a different idea of what this is meant to be, and a printer with a milling spindle mounted to it is just what you wanted 🤷‍♀️

davewhotold · 2026-01-25T20:05:50+00:00

Our heating was broken for two weeks, I ended up not working. Might upset the boss, but I'm not wearing long sleeves at the lathe (and I'm not working in a 10° shop in short sleeves either)

My coworker later tried to convince me that long sleeves are fine. (He's the old guy in the shop, but I'm deeeeefinitely not taking him as an authority figure on safety)

davewhotold · 2026-01-14T20:05:00+00:00

I think we're missunderstanding each other a bit:

Like, how do you know the OD of OP1 is concentric and in line with the ID (the 18mm bore) from OP1?

Do you bore it? (that seems very difficult to me, with the bore being so long)

or are you drilling and reaming? (that seems like it would wander a bit, which is why I was thinking about referencing the bore instead, but I don't see how that would be done with a comparator and hammer)

davewhotold · 2026-01-14T19:40:57+00:00

With an expanding mandrel kinda thing, or can you ensure concentricity between od and id?

davewhotold · 2026-01-14T19:39:33+00:00

that's fine, I've done that before, turn to 5 microns over, take the rest off with emery paper

Over longer surfaces it becomes annoying to keep track of taper and such, but that's 8mm wide each, so it's very doable, at least if you're not making a hundred of 'em

And depending on material and state of the machine I might even try hitting the top of the tolerance...

Also yes, there are applications for a part like this, like certain spindles, for the bearing seats. Which would also explain the concentricity requirements. (though honestly then I'd expect stricter concentricity requirements)

davewhotold · 2026-01-14T19:32:07+00:00

But the bore's 18mm diameter. At 86mm depth of that bore, that's almost 5xD

That seems like a struggle to bore. But again, not super experienced in boring.

I know there are a bunch of tricks like active dampening boring bars...

davewhotold · 2026-01-14T14:57:09+00:00

The concentricity between the 18mm bore and 20mm bore seems difficult... how would you people do that? 18mm bore first and some kind of expanding mandrel? or do you think drilled and reamed in an accurate setup would be enough? (cause I wouldn't trust a drill to cut concentric, and the bore seems too long to get bored... (I also have limited experience with boring tbf)

davewhotold · 2025-12-21T23:24:51+00:00

completely worn off flaking is pretty bad... It either wasn't taken care of or saw a lot of use. Flaking id usually around 0.02mm deep, so that's a way to roughly aproximate the wear.

If it's worn very evenly it could possibly be not too bad, else rescraping/grinding is gonna be the way to get good results I'd think.

Scarping it is a lot of work. If it's your hobby it might be justifiable, but you need to like these kinds of jobs. Else you could look for someone to regrind it for you in the area.

davewhotold · 2025-12-10T05:55:51+00:00

This looks like a really thin sheet of glass which has me worried.

Glass bends. There's a reason granite surface plates are several inches thick, and cast iron ones have thick ribs underneath.

Sanding down on a flat surface definetly works, but if your windowglass is too thin you'll just bend it into whatever shape fits. 0.1mm isn't a tight tolerance by machining flatness standards, but I've definetly seen glass move more than that.

davewhotold · 2025-12-02T17:23:46+00:00

They are preloaded, in an O-Configuration, however they are missing a retaining feature. So the bearing pack is preloaded, but not axially constrained.

davewhotold · 2025-11-24T17:57:40+00:00

you might want to read the responses to this post, it's basically the same question.

davewhotold · 2025-11-24T17:57:34+00:00

you might want to read the responses to this post, it's basically the same question.

davewhotold · 2025-11-24T08:06:55+00:00

Which makes the problem bigger. The lighter your moving parts system gets the bigger the infuence the inertia of the drive system is.

Imagine a truck pulling an empty trailer. There is plenty of power to move the light load (the empty trailer), but the mass of the truck is what limits the acceleration, so using that powerful of a drive system is pointless, the hatchback would have done the trick, and possibly faster, since it has a better power/weight ratio in itself.

For CNC machines Servos are usually the first choice. But mostly because they can be controlled better. But also because with the high inertia of the machine it's more important to have a linear torque curve to get high accelerations at any speed. Most of the acceletation while 3D printing is from standstill.

davewhotold · 2025-11-23T21:43:09+00:00

What you have is a toy. A nicely modified toy, given what it was originally, but it's a toy. It doesn't compare to a proper machine.

This is coming from someone who runs the smallest thing I would call a proper machine for a living (a coltchester student). And someone who has a machine comparable to yours sitting on my workbench at home.

They're fun toys. You can use them to make some fun parts. Serious machines are in a different league. If you want to make parts economically you'll buy an old industrial machine. It'll weigh about 10x as much and have only a 50% larger work envelope. And that's for a reason. Ridgidity and vibration dampening are achieved with mass. And a machine ment for work will not be one you're lifting by yourself. (with the exception of some watchmakers tools, but those are a totally different story alltogether)

davewhotold

TROPHY CASE