Noob Thread Redux

[Teenage_Machinist]

This is intended to be a recurring thread, feel free to ask your questions too.

What is the idea of a surface grinder? This sounds weird, I am sure.

Does anybody have a good noob's guide to hand scraping, internet or otherwise?

How does a surface grinder handle things larger than the wheel

Can a magnetic chuck possibly provide enough holding force

What is a "ledge" on a surface plate?

How usefull is a surface plate?

What is prussian Blue?

Is a tiny (like one inch) flycutter likely to jam?

If I make steel gears for my micromill, should I leave one plastic gear to be sacrificed for the others?

Should I use 12l14 to make gears? It sure would be stronger than that ^&*( white plastic.

Does hand scraping need a lot of time to get good at it enogh to not ruin something?

Does my mill leave a good enogh finish to make hand scraping unnecesary? for a screwless vise?
I would use a small end mill or a flycutter, and squirt cutting fluid but no "coolant" coolant.

Do I need an angle plate? I have 1-2-3 blox.---Mainly- for mill facing ends- Seems like the 123s might be a bit inconvineint, but I wonder just how usefull a dedicated angle plate is.

Why do you sharpen the end of an end mill whent he helix gets worn

What does an air bearing do in the context of end mill sharpening?

Can I put a grinding wheel in my mill spindle, block up my rotary table with paralells or a sine plate, and say, "SUCK IT" to the end mill sharpening fixture companies AS IN SHARPENING THE END like the semi-cheap fixtures do.


I can cover up the ways, and use a vacuum. There is not too much way to cover. ?

[A.K. Boomer]

This is intended to be a recurring thread, feel free to ask your questions too.





Are you trying to fit the entire general forum into one continuous question?

[dockrat]

I'm sitting here trying to think of what Wolfies reply would be :D

[Doc Nickel]

What is the idea of a surface grinder? This sounds weird, I am sure.

-It, er, grinds surfaces. It makes surfaces flat, smooth and parallel. Also, being a grinder, it can handle materials harder that can be easily cut with conventional mill tooling.


How does a surface grinder handle things larger than the wheel

-Same way a mill handles workpieces larger than the cutter diameter; by making multiple passes.


Can a magnetic chuck possibly provide enough holding force

-Considering they've been a staple for surface grinding for many decades, I'd say yes. For the most part, surface grinding is a finish operation- you're taking only a few thou, or even a few tenths of a thou off, so you don't need as much holding power as if you were hogging with an endmill.


What is a "ledge" on a surface plate?

-It's an inverted step on the ends of a plate, which provides a "lip" for clamping or fixturing.


How usefull is a surface plate?

-For the beginning machinist, not very. For the skilled amateur, fairly handy. For the experienced and expert, almost indispensible.


What is prussian Blue?

-A paste-type dye used to color metal. It's smeared on a workpiece, for example, to make scribe lines or punch marks stand out a little better. It's also used in scraping or lapping to see how close two surfaces match up (the dye from one side transfers to the other, and shows where the "high spots" are.)


Is a tiny (like one inch) flycutter likely to jam?

-Don't see why it would, assuming you have the tip geometry right.


If I make steel gears for my micromill, should I leave one plastic gear to be sacrificed for the others?

-Depends on the mill. I'm led to understand the belt-drive conversion is a better solution, and I believe off-the-shelf kits for doing so are available. Probably easier than hobbing some gears.


Does hand scraping need a lot of time to get good at it enogh to not ruin something?

-Do you know of any precision job that requires skill and practice, that is easy and fast to master?


Does my mill leave a good enogh finish to make hand scraping unnecesary? for a screwless vise?

-Open question that will depend heavily on the speeds and feeds, sharpness of the tool, quality of the metal, whether or not you use a cutting fluid or coolant, and about a dozen other factors.


Do I need an angle plate? I have 1-2-3 blox.

-First you're going to need to ask yourself what you'd need angle blocks for. If you just need them to sit on the shelf and look interesting, by all means. If you don't have anything you need to hold to the mill at an angle, they might be kind of a waste.


Why do you sharpen the end of an end mill whent he helix gets worn

-Actually, the point does the bulk of the cutting, and wears first. Grinding the end restores the point, and can be done much easier than grinding the flutes.


What does an air bearing do in the context of end mill sharpening?

-A collet is used to hold the endmill while sharpening. To grind the flutes, the collet must turn. An air-bearing provides a very free-moving and low-friction movement, so the flutes can be ground smoothly.


Can I put a grinding wheel in my mill spindle, block up my rotary table with paralells or a sine plate, and say, "SUCK IT" to the end mill sharpening fixture companies?

-Not really. To grind the flute of an endmill, the collet holding it must be able to both slide (in and out) as well as rotate. All the rotary table will do is rotate.

Besides the fact you'll be spraying grinding abrasive all over the ways of your mill, which will form lapping compound, causing rapid wear and loss of accuracy.

Doc.

[lane]

I am glad some one answered all that. TOOOO many questions at one time.

[potman]

Let me throw a few more questions at you, if I may.

Sawdust and oil or grease combine to make a great gum.
Metal chips scratch and embed themselves in wood.
Is a combination metal/wood shop practical?


Some lathes have only a threading leadscrew.
Others have that plus a power feed rod.
If they both make the carriage go back and forth why do you need both?

Do you get a better finish using a power feed as opposed to manually feeding the tool?

Is a power feed only useful if you are standing at the lathe all day long making the same cuts over and over again?


Besides the power tools in a shop I would imagine you would want a good workbench for assembly, filing, measuring, etc. Are there any particular attributes, other than sturdy, that make a good metalworking workbench?


On a drawing I might see something like 1 3/8" between center lines of two holes with a tolerance of 0.05". It's easy to plan something to exact dimensions but harder to implement. How do you decide how much tolerance to allow?

Thanks...
earl...

A little introduction is probably in order: Computer programming and data analysis are my vocation. I took a metalworking class in high school 40+ years ago, do some woodworking and have been making pottery for a decade or so. Pottery is fun because it can be freeflowing and spontaneous and I love things that glow yellow/white from heat but at times I just have to have precision and pottery is not a precision sport. Ergo, my interest in metalworking.

[Doc Nickel]

Sawdust and oil or grease combine to make a great gum.
Metal chips scratch and embed themselves in wood.
Is a combination metal/wood shop practical?

-"Practical" by what measure? For a professional, moneymaking shop, no. You'd want to separate the two to at least some extent. For us home-shoppers, that's itself not always practical, so allowances need to be made. A few dropcloths, good dust-control for the wood machines, and some movable curtains- as well as dilligent maintenence- should keep things under control.


Some lathes have only a threading leadscrew.
Others have that plus a power feed rod.
If they both make the carriage go back and forth why do you need both?

-Gearing. One might make the carriage advance by only a few thousandths per revolution, the other might make it advance by a whole tenth per. There's an issue with accuracy for the threads, too, but one of the others could probably describe that one better.


Do you get a better finish using a power feed as opposed to manually feeding the tool?

-Generally, you'll get a more consistent finish, which most will consider better.


Is a power feed only useful if you are standing at the lathe all day long making the same cuts over and over again?

-Nope. It's handy any time you need to make a cut of any fair length. It's not a requirement, oftentimes, but it's still handy.


Besides the power tools in a shop I would imagine you would want a good workbench for assembly, filing, measuring, etc. Are there any particular attributes, other than sturdy, that make a good metalworking workbench?

-Heavily built, level top, solid working surface, reasonably nonabsorbent so it doesn't soak up oils and cutting fluids, and of a comfortable working height.


On a drawing I might see something like 1 3/8" between center lines of two holes with a tolerance of 0.05". It's easy to plan something to exact dimensions but harder to implement. How do you decide how much tolerance to allow?

-Easy; you try and get as close to the given spec as is reasonably possible. For your example, if I were drilling it on the mill, with 0.050" tolerance, I'd probably do little more than locate the first center with a wiggler, drill, move the table 1.375" in the appropriate direction, and drill the next hole. My mill's fairly tight, and I can almost guarantee the holes will be less than 0.003" out.

If the spec called for 1.375 +/- 0.002", obviously I'd need to take a few additional steps to assure that accuracy.

But, just because the spec might give 0.050" of tolerance, doesn't mean I need to intentionally move one hole over 0.025" and the other 0.024". It's an allowable tolerance, not a mandatory tolerance. Fifty thou usually means a plain drilled hole is okay. Two thou usually means you're going to need to bore or ream the hole to maintain the tolerance.

Doc.

[Weston Bye]

Good job Doc!

[bollie7]

Some lathes have only a threading leadscrew.
Others have that plus a power feed rod.
If they both make the carriage go back and forth why do you need both?

When screwcutting the leadscrew has to turn at an exact ratio to the spindle for the thread pitch being cut. Therefore there has to be a direct & accurate mechanical connection between the spindle,leadscrew and the saddle. If you were using the leadscrew and clasp nut all the time as a power feed, the nut and spindle would rapidly start wearing.

With the feed shaft the accuracy is not as important and most machines have some sort of overload protection between the spindle and the shaft. It can be a shear pin, a small clutch or some other device that enables the feed shaft to stop turning if it is overloaded by taking too deep a cut etc. I had an old lathe that had the feed shaft driven by a Vee belt. Too much load and the belt would slip.



Do you get a better finish using a power feed as opposed to manually feeding the tool?
Definately, as Doc said, more consistant



Are there any particular attributes, other than sturdy, that make a good metalworking workbench?
What others have said, plus its been my observation over the years that it doesn't matter how much surface area a work bench has, you inevitably end up with a clear workspace of about 400mm deep X about 700mm long (thats about 16" X 28" to save anyone the effort of converting) the rest gets filled up with several layers of crap, totally unrelated to the job in hand, that seems to multiply quickly and quietly whenever your back is turned. It's even worse if its a general use bench in a multi person workshop. LOL



On a drawing I might see something like 1 3/8" between center lines of two holes with a tolerance of 0.05". It's easy to plan something to exact dimensions but harder to implement. How do you decide how much tolerance to allow?
From this I assumed you meant how does the person making the drawing decide what sort of tolerence to have?, rather that how to machine to a tolerance?
I'm not a designer or mech engineer so I don't do drawings so I'm sure there are others here who could explain this a lot better than I can.
There's all sorts of different standards for this sort of thing and the person making the drawing should be able to access these std's. The stds have been built up over years from experience, research etc.

regards
bollie7

[davidh]

Good job Doc!

excellent response for all the questions. all the stuff that gathers on ones work bench that cannot be easily removed have been referred to as
"BENCH GODS" and i have at least 30 feet of benches and can barely find room to do much more than write paid on an invoice. . .
davidh (the old "sanford")

[Just Bob Again]

Does anybody have a good noob's guide to hand scraping, internet or otherwise?

Does hand scraping need a lot of time to get good at it enogh to not ruin something?


Watching one Bob Ross oil painting course on PBS does not make you an artist. Doesn't even make you a better house painter. How long before you can scrape something to give it a nice cosmetic look? A while. How long before you can properly scrape in a lathe bed to tenths? Pretty much a lifetime. It's slow and picky work. A chunk of metal for a scraper, easy. All the precision straight edges and instruments will cost you. It isn't like taking a belt sander to an old piece of furniture. Most of what you see on fancy equipment is frosting, not scraping. It's there to hold oil and reduce friction. Essentially decorative. Done with power tools. Bucks up the price of cruddy worn-out used equipment. The number of people who can really do good hand scraping is tiny. When you find a guy, he's likely to be 97 years old and he'll sneer at whatever cheap equipment you think you want scraped.

[Fasttrack]

Wow Doc! I read this post when there was no answers and I chickened out. Looked like too much typing... :)

As far as the leadscrew and drive shaft goes, on old, "American made" lathes that only have the leadscrew, you will often find that there is a keyway cut into the lead screw. When you engage the feed lever on the carriage, it drives off of that keyway, thus preventing undo wear to the leadscrew. Then, when you want to thread, you use the half-nuts to engage the threads on the leadscrew. This is how the SB heavy 10's all the way to the big old cinicinattis are set up. I personally like the idea of having a seperate driveshaft better than driving off of the leadscrew, but for hobby work, its certainly not neccessary.

[Teenage_Machinist]

I understand not being able to read noob's guide and soon be an expert. My question is, does it take tons of practice to be able to scrape something better than I can mill it, or smooth out mill marks. I understand that I can practice on some scrap, mike it all over, try again, but I am wondering, "is this a skill that I can learn and make it useful enough to improve a homade screwless vise"

Somebody suggested that I could improve one in my screwless vise thread.