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Mini Lathe Operations #1: Facing



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hi it's Frank who's from mini live.com

first video of 2018 but I wanted to do

an introductory series on cutting

operations on the mini lathe some of you

may have gotten mini leis for Christmas

or recently and I hope to do this a

little bit earlier like prior to

Christmas but didn't get to it but I'll

do it now in a facing operation we cut

sideways across the face or the end of

the round piece of work this is

half-inch diameter aluminum and it's

been cut on the bandsaw so you can see

it has sort of a rough finish on it

right now and part of the purpose of

facing is to convert that rough finish

into a nice smooth finish I'm going to

use a three jaw Chuck for this operation

I like to use the three jaw for most of

my work just because it's quick and

convenient I also like the Forge off

about I save it for things that I can't

do with the three jaw I'll be using the

little machine shop dot-com it's a model

5100 lathe and this lathe if you aren't

familiar with it it's pretty much the

same as the other mini lathe except it

has a larger spindle it takes a 4-inch

chuck as standard rather than three-inch

which is standard on most of the other

mini lathes

a quick comment and passing in case you

see it and are wondering about it but

I've replaced the plastic safety shield

that goes over top of the chuck with a

small aluminum one the plastic one that

comes with the lathe tends to get in the

way out here when you're trying to do

certain operations if you're working up

close to the chuck or even more so if

you're working on a faceplate the real

purpose of the plastic guard is to

prevent you from accidentally turning on

the machine when you have the Chuck key

still in place in the Chuck and this

little guard will do the same thing and

when it's in the up position of course

the lathe cannot be started take our

piece of aluminum stock here and put it

down in the jaws usually I like to take

a little brush and clean up the jaws

make sure there's no chips or grit in

there

they could

keep it from seeding properly and for

this operation since all I'm gonna be

doing is working on the end here I want

to set it pretty far back in the jaws

and of course the farther back in there

you said it the more rigidity you get

but generally you want to avoid having

the work stick out more than two or

three times the diameter or it will

start to flex a little bit it may not be

much and you may not even be able to see

it flex but when you're talking about

dimensions of a thousandth of an inch or

a few thousandths of an inch even a

little bit of flex can affect your work

now this mini lathe I've equipped it

with a quick change tool post which I

really like and I strongly recommend

that you get one if you can or as soon

as you can because they'll really make a

make everything you do on the mini lathe

a lot easier and you'll actually get

better quality work because of the

ability to adjust the height as well see

but I have actually three different

tools here of different types and I'll

just show them to you briefly the one on

the right here is one that I ground on

the grindstone from high speed steel

blanks this one is a prefabricated

carbide tip that goes in a special

holder this one on the end here on the

left is actually a high speed steel

insert these are pretty nice I like to

use high speed steel on aluminum he

usually does a better job of cutting at

least on a relatively low speed lathe

like this and carbide works great on

steel and harder materials but usually

doesn't leave as good a finish on

aluminum but Bolla try it maybe one of

each and see what happens just for

comparison I'll start out with my shop

ground high speed steel tool and it's a

very simple grind I have a website mini

lathe comm and if you look at tool

grinding it will show you the basics for

grinding this particular type of tool

which I use a lot and someday I hope to

get around to making a video on that and

of course the big advantage of the quick

change tool post is the height of the

tool is already set I said it previously

and the tool stays with the holder so

that once you've got the height set in

the future when you got to use that tool

you just drop it in place and then lock

it with this cam locking lever and it

will be at the correct height but I'll

show you what happens with the facing

operations if it's not at the correct

height facing operation like most

operations it's important that you have

the tool right at the center height of

the lathe which is to say that's an

imaginary line that goes from the

tailstock to the headstock and it's the

would be the center line through your

workpiece so you want your tool right on

that center line I mean you get ready to

make a facing cut you have to have some

way to lock the carriage down and

there's basically two ways to do that

one is to use the half nut lever and

lock the carriage down to the lead screw

but of course you have to make sure the

lead screw is not turning and the other

way is to have some sort of carriage

lock and in this lathe I've built my own

which I'll show you in a minute but

let's talk for a minute about the

locking the half nut lever back here on

the back of the headstock there's a

lever a three-position lever that

controls the rotation of the lead screw

but in this case I want the lead screw

in the neutral position so if I turn the

lathe on if you look down here you see

that the lead screw is not turning

spindles turning the lead screw is

stopped

that's the situation we want so that we

can lock the carriage down to the lead

screw and it will hold the carriage in

place now ordinarily when the lead screw

is turning when you engage the half nut

lever you can just put a little pressure

on it and as the lead screw rotates it

around it'll lock in but when it's not

rotating you may have to wiggle the

carriage back and forth a little bit as

you're engaging the half knot lever so

that the threads on the half nut lever

engaged with the threads on the lead

screw the purpose of locking the

carriage to the lead screw is that the

cutting forces otherwise could push the

carriage back away from the work and

instead of getting a flat surface across

here you'd get some sort of a

cone-shaped surface as the carriage

drifts away from the work now I've

equipped my mini lathes with a shop-made

locking lever here that also locks the

carriage to the ways and that's actually

preferable to using the lead screw so if

you have an arrangement like this that's

what you want to use if you look on the

internet you can find lots of plans for

different ways of doing that and the

only difficulty is that a lot of maybe

most of them require the use of a mill

or if not a mill than some heavy duty

filing to accomplish it

okay now I'm about ready to begin the

cut but you want to position your

workpiece and you can now use the

compound hand wheel to move the tool

forward and backward if you need to

adjust the point at which it's going to

cut into the work but you want to take a

fairly like no more than say ten

thousandths or so if you take a little

bit more it'll probably still work but

if you get to the point where you're

taking a thirty or forty thousandths

that's probably going to be too deep a

cut and the lathe may stall or you get a

lot of chatter so I'm going to back this

off one way you can adjust that if

you're not confident with it is bring

the tip of the tool up until it just

touches then come out with the cross

feed and then use the compound hand

wheel and you can just dial in

about ten thousands or whatever you're

comfortable with

and it's not going to be exact because

the compound typically is at an angle so

the depth that you read off of the

compound hand wheel usually will not be

the exact depth that the tool is going

to move in unless your compound happens

to be parallel with the ways of the

lathe but with that Set let's go ahead

and turn the lathe on now I'm going to

use the cross feed or cross slide

just turn that slowly by hand

and make our facing cup

I don't have a tech on or so I don't

know what the actual RPMs is but I have

the dial set here on the control to

about if this is the six o'clock

position and this would be about the 10

o'clock position let's take a look at

our result here you can see that the

surface is basically flat but there's a

little nub there in the center and that

nub tells me that my tool the tip of my

cutting tool is either a little too high

or a little too low usually with

experience you can tell from the shape

of that nub whether it's high or low and

if it's low that note will usually be

cylindrical but if the tool tip is a

little bit above the center the nub will

end up being more of a conical or sort

of a mountain or cone shape in this case

it looks like it's my guess is and I

can't see too well but it looks like

it's a little bit low and I'll use that

as my starting assumption this is where

an adjustable tool post or a quick

change tool post is really handy I'm

going to just loosen this locking nut

here

now I'm gonna unlock the tool and then

turn this ring and that will raise the

tool up just by a few thousandths I

don't know exactly how much but one of

the interesting things about a facing

cut is you can actually use it as a way

or a gauge to determine if the tip of

your tool is on the centerline of the

lathe if it's not it will leave a little

nub but if you get it right on the

center line then you won't get that nub

there and that's what we want no nub

okay with the height adjusted now we'll

take another test cut

yeah and it looks like I got rid of the

nub let's take a closer look all right

now as you can see there's no nub in the

center and that's the way we want so if

you get a nub you have to play around

with adjusting the height of your tool

either higher or lower now if you don't

have an adjustable tool post you can get

yourself a set of automotive feeler

gauges and of course these are all if

you're probably familiar with them but

they are all marked with their thickness

usually in thousands but they may also

be marked in millimeter says these are

anyway you just pick up a few of these

usually starting with the thicker ones

and then place one or two or three or

how many you need to get the tool right

on the center height of the lathe just

take your stock tool holder and put your

tool bit in here and then just tighten

it down finger tight you can bring it up

to the work and see approximately where

it falls you know whether it's too high

or too low now this is a 5/16 inch tool

blank so it happens to be a little bit

low I could have started with a 3/8 inch

tool blank and it might have been a

little bit too high I like to use

smaller tool blanks in fact I often use

a quarter inch just because they're

quicker and easier to grind less metal

to remove an even quarter inch will work

fine on the mini lathe for just about

anything so next you can do a test cut

and see what kind of nub you get after

tightening my tool bit in the tool

holder and I'll lock down the carriage

now take a test cut to determine whether

the tool is too high or too level

you know as you can see we get a little

stock there and I could see clearly that

it was too low so put a couple of shims

under there and try again the trick you

can use that may help you speed up the

process to take your digital calipers

and measure the diameter that little

stock you need to make the stock long

enough that you can get the tips of your

calipers on there though alright and

it's reading about 68,000 I'm going to

try using a stack of shims that are half

of that or 34,000 so that should get me

pretty close but from my set of shims

I've chosen a 22 and a 13 so that should

give me 35 should put me pretty close to

center now we'll just loosen up the tool

and we'll put these shims underneath and

then tighten back up

all right so we'll tighten it up now and

now I'll do another test cut

okay well that worked out pretty well

looks like it got us very close to on

center and that may be all we need us do

one more pass with higher spindle speed

alright that looks pretty good now that

we've seen what it looks like with a

tool a little bit too low and the tool

right on center let's just out of for

the sake of demonstration here I'm going

to intentionally raise the tool up above

the center line and we'll take a cut and

see what we get

now you may even find if your tool is

too high the nub in the center will

actually prevent the tool from trying to

go past the center when you're turning

the hand wheel you'll start to feel a

lot of resistance there so if you feel

resistance as you're approaching the

center that's a good indication that

your tool probably is too high but if we

zoom in now and look at close-up you can

see that there's a very definite cone

shape there so whenever you see that

that's an indication that the tool is

too high but using this knowledge about

these little nubs that form here on a

facing operation you can take advantage

of that as a method to set your tool

height and in fact the method I use most

often for adjusting my tool Heights

they'll just take a piece of scrap

aluminum typically and make a couple of

facing cuts and tweak my fine adjustment

here on my tool height until I get a

nice smooth face across there and then I

lock that nut in there and that becomes

my tool height so I adjusted my tool

holder to bring that to light right on

center and that's what a nice clean

facing cut should look like one more

thing you may wonder about if you're new

to this is what angle should the tool be

at relative relative to the face of the

work and if you have the tool squared up

against the face you wouldn't get a nice

clean cut because the edge of the tool

would be just rubbing against that

surface for best results you'll want to

use a tool with a slight radius on it

and I like to use an angle between the

tool and the face of the work of

somewhere between about five and fifteen

degrees but you can experiment and see

what you find in your own shop for this

next test we're gonna just do a basic

facing cut but instead of the hand

ground high-speed steel tool I'm going

to use this factory made carbide insert

tool it's I got three points 120 degrees

apart

[Music]

well actually here again it's not too

bad

I think we got a better finish with the

high speed steel tool this has little

shows a little bit of surface roughness

that's been my experience with the

carbide tools as they work pretty well

but they don't give you quite as nice a

finish on aluminum this time all ticket

cut using the high speed steel insert

[Applause]

let's Savannah take a look well that did

a pretty nice job so I think you can see

any of the types of tools will work all

right

I think the carbide tool maybe gave a

little bit not as good a surface finish

but with some experimentation you might

be able to get good results with that

now one thing I didn't mention is

particularly with aluminum I often use

cutting fluid and I like to use tap

magic aluminum brand but it keeps the

chips from welding to the tip of the

cutting tool which can sometimes cause

problems and in fact I just noticed that

on this carbide tool here it looks like

there is some stuff welded to that tip I

think maybe the message here is that 6

or 6/1 aluminum is a pretty forgiving

forgiving material and even if your tool

geometry is not optimal you can still

get recently good results but for the

best results you'll want to use the tool

with a slight radius on it but those of

you who are steel workers I'm gonna take

this gnarly piece of steel it was given

to me by a friend it was cut from a long

piece of bar stock so I don't I don't

know anything about its history other

than it sat in a barn for many many

years but I think it's probably some

sort of some variety of cold-rolled

steel and has a saw kerf here where I

started to cut it and then changed my

mind for some reason it'll go ahead and

do a facing cut on that and see how it

looks

turn the speed down see if I could get

rid of some of that chatter but let's

try turning the speed back up and taking

a shallower cut

[Applause]

well that's not too bad it's actually

feels quite smooth so just to show that

you can do this with steel there we go

now one other factor that's really

pretty much a routine part of a facing

cut is when you're done facing you end

up with very sharp edges along here and

if you're not careful or not fully aware

you can cut yourself badly when handling

this material doesn't matter whether

it's steel or aluminum but steel is more

likely to cut you the harder the

material typically leaves sharper edges

so I always like to touch it up with a

file take that sharp edge off or use a

tool which I'll show you in a minute but

we'll first do it with the file when

working in the tight confines of the

mini ladies I'm sure most of you know

you need smaller tools than you would on

a big full-sized lathe but these are I

guess four inch files and I like I like

both of them but they're made by

Nicholson but this one I find

particularly handy because it has this

sort of tapered blade that comes to a

point or a nearly a point so it's able

to reach into spaces that you might not

be able to get access to with a wider

one like this many years ago I had a

picture on my website showing me filing

work like this and a viewer of my

website sent me an email which I'm

actually quite glad that he did and said

you know that's a bad way to use a file

because your hand is extending over the

rotating chuck so the trick here is to

hold the handle of the file in your left

hand then you can hold the tip for more

control in your right hand

but that way both of your hands are out

here out of the way of the Chuck now

you're still working pretty close to the

chuck obviously and you want to be real

careful by the way you should always

have a handle on your file so you can

get them cheaply and they last pretty

much forever but they can save you from

a really serious injury if the file were

to be pushed back

the tang of the file pushed back into

your palm you'd be looking at some

serious surgery so definitely invest in

some handles and you can get all kinds

just touching up this edge or breaking

this sharp edge we can use a pretty slow

spindle speed you don't need much speed

at all to do it you know maybe 100 rpm

so just take the file like so on that

sharp edge that's all we need to do and

now it's much safer to handle that but

an alternate way to do it is to grind

yourself a little tool similar to this

one and you can use that for the same

purpose justice with the facing cut we

want to lock the carriage down so it's

not going to move during this beveling

operation or chamfering so and again we

can use a pretty slow speed for this and

you really only takes a second just

barely touch that tool do the work and

the job is done if you want to you can

go a little deeper and actually put a

chamfer or a bevel on that work so

here's what we have now and of course

it's much safer to handle now with that

sharp edge go on and if you stuck this

away in a drawer somewhere and forgot

about it you reach in there you know a

month later or a year later grab that

piece of metal you can get cut without

expecting it so that's I often when I

have a piece left over I'm not going to

use it for a while I'll just touch it

gently with a file before I put it away

in the stock drawer well just for fun to

show that it can be done here's a odd

shaped chunk of brass that I acquired

from a junkyard probably about 15 years

ago and it was sort of a sharp metal

steak some sort of ground steak used by

utility as I guess for some purpose but

anyway it was a nice piece of brass and

I bought it and I've used it for various

projects in the years since then but I

had these sort of blades on the side

which I

sawed off with the bandsaw but this edge

or this face here has never been faced

and so I thought it would be interesting

just to put a facing cut on that and see

how it goes we're getting a little close

to the capacity of this three jaw Chuck

and got to be real careful yeah that you

aren't opening the jaws so wide that

they don't have any grip on the scroll

inside and they're gonna come flying out

so anytime you're gonna grip something

like this that is fairly large compared

to the chuck it's a good idea to test

your jaws and make sure that they're not

near the end of their range where they

might come loose like I'll set it back

in there a little bit farther just to

get the maximum gripping power of the

jaws and I want to tighten it off all

three scroll positions here make sure

that's tight this is a heavy piece of

material you definitely don't want that

working loose noise check sometimes your

work will get skewed in there

good way to check that is as you're

tightening the jaws rotate it gently and

if it's skewed at all you'll be able to

feel hopefully be able to feel that it's

not locking up evenly and smoothly so

another good thing to check

especially on a heavy workpiece like

this alright let's fire the lathe up

here and see what this does

what you hear there is the cutting tool

hitting these ridges on the edge but the

actual cut looks like it's a little

deeper than I want to take so I'm gonna

back the tool off a little bit

if you hear that it's still not making

contact all the way across

[Music]

looking good

take one more pass speed it up just a

bit

there's still a tiny little stock there

which tells me that the tool is a little

bit low just to give you an idea of the

size of this little nub here this is a

number eighty drill bit which has a

diameter of 13 and a half thousands so

you can see that little nub there is

really pretty tiny probably around ten

thousandths or so maybe a little larger

kind of makes me wonder how they make

these tiny drill bits in cut a helix

into them something to think about I

guess I wanted to comment on the cutting

speed or the spindle speed to use when

doing a facing operation now the

interesting thing about a facing

operation is as the cutting tool moves

in from the outside diameter to the

inside diameter the speed at which the

tip of the cutting tool traverses the

material is faster out here at this

larger diameter and it actually becomes

slower and slower and it approaches zero

as the tool only gets near the centre so

if you stop and think about it you know

the the speed at which a point on this

disc moves past the tool the farther out

on the disc that you get the faster it

moves so on a small workpiece like this

it's probably not too significant if you

imagine the industrial setting where

you're turning for example a large wheel

for a railroad steam engine or something

you know back in the industrial

revolution days on the outer edge of the

wheel the metal would be moving past the

cutting tool very very rapidly and of

course they turn those things at very

low rpms

I believe I've read that there are lathe

mechanical type lays that were used

historically that would increase the

rotational speed of the work as the tool

moved inward on a facing operation and

of course nowadays a lot of this type of

work would be done on a CNC or a

computer-controlled machine in which

that type of speed compensation is

pretty straightforward to arrange and

Bill

into your programming but for the type

of work we do on the mini lathe the

speed isn't very critical at all and I

usually start out you know with around

800 rpm or somewhere in that range and

either speed it up or slow it down

depending on the hardness of the

material and other factors but if you

look and listen you can tell quite a lot

about what's happening and whether the

the speed is working well or not and of

course with the variable speed control

you can make compensation on the fly and

if you really wanted to get tricky I've

tried this a few times if you have a

relatively large diameter workpiece say

four or five inches you could actually

change the rotational speed like the

automatic machines do except to do it

manually so if something you might want

to play around with but the good news is

that the mini lathe for the type of work

we do it's not a huge factor so find a

speed that works for the material and

the tool you're using and go with that

well that wraps up our tutorial on

facing operations if you like this video

I'll be doing some more on other basic

lathe operations on the mini lathe and

if you subscribe you'll get a

notification when those come out so

thanks for tuning in and we'll see you

next time