Toolpost (or other) grinding in the lathe

[ajoeiam]

Totally agree, Just out of shot in my picture is a whopping great Magnetron magnet directly under the cut and in the coolant flow. It sticks nicely to the bedway and collects pretty much all of the grinding dust.

Sorry - - - - that will collect most (all if you're lucky) the metal bits - - - - it doesn't collect the spent grit from the wheel - - - - there is some you know.
I was taught to cover up the ways most carefully and then clean up very very carefully after this kind of operation.
It was quite fascinating to see the setup (and some of the operation) where the 'old timer' in the shop - - - only some 46 years of machining experience at that time - - - he trued up the hard jaws on the lathe chuck.

 

[ajoeiam]

I know this is a bit crude but it did the job but the method could be used for occasional grinding.

Dunno if its crude - - - - it got the job done and you did it yourself.
The big advantage that you have doing it yourself is that you can even do three spark out passes (where you're cutting the same each time at your desired setting). That should make for a great surface finish!

 

[Lofty76]

Sorry - - - - that will collect most (all if you're lucky) the metal bits - - - - it doesn't collect the spent grit from the wheel - - - - there is some you know.
I was taught to cover up the ways most carefully and then clean up very very carefully after this kind of operation.
It was quite fascinating to see the setup (and some of the operation) where the 'old timer' in the shop - - - only some 46 years of machining experience at that time - - - he trued up the hard jaws on the lathe chuck.

that machine is nearly twenty years old and used nearly every day, I reckon I keep it clean

 

[petertha]

Decent overview of dedicated cylindrical grinder for interest sake.

 

[reproturn]

I rebuilt the spindles on my Waldown C0 toolpost grinder a few months back and was surprised to find that it used two-part magneto bearings (M13 or equivalent). Preload was achieved via an o-ring under the bearing retainer. Bearing adjustemnt was to run the grinder at max speed (around 30,000rpm) a slowly tigthen the retainer till the grinder slowed then back off a fraction. Bingo.
Very little lubrication is required - Waldown recommends ISO32.
Thought this may be of use if you plan to build your own.

 

[ALEX1952]

No one has mentioned balancing grinding wheels, which could explain the strange vibration mentioned in an earlier post. This is most important for safety and accuracy, also be very careful not to exceed the rpm limits of the wheel if making your own drive train. balancing units are available but expensive so probably a bit out of our league, however
the aircraft moddeling fraternity do balance propellors with a very similar piece of equipment, which could probably be utilised for grinding wheels or as a pattern. Forgive me if I'm reiterating what you already know.

 

[goldstar31]

So far the grinding wheels on the Quorn, the Stent and the Kennet are in balance but
1, They are small
2, They are only running at about 7000 from 1/6th HP 2880rpm motors.

Regards

Norman

 

[ALEX1952]

It was really a general observation mainly because larger wheels from off hand grinders were being used, another potential problem is lighting, under the right circumstances lights that flicker i.e flourescent can act like a strobe and give the impression of a stationary wheel. We had a very large grinding shop and it did not have florescent lights for this reason, I believe they were sodium.

 

[SPOTTER]

this is my grinder machine, i hope you like it as a project, even if it is to be completed with a protection on the abrasive stone.

 

[SmithDoor]

Most do not know that if angle the compound to about 11° and use compound for feed it will feed to 0.000,1

Dave

 

[goldstar31]

Dave
Can you justify your statement with Pythagoras, please?
I once challenged a similar assertion and I was met to a LOUD silence.
I got a book in which (about) 20 degrees is quoted-- and again , Have my doubts.
In the Good old Days, Model Engineer did a Christmas howler of :-

a ladder of 12 feet and a box of 4 feet square and the question was how far up the wall would the ladder extend if its feet were on the ground and the box was against the wall and the ladder touching the corner of the box. Of course that has in Pythagorean terms a know hypotenuse but the cross slide on a lathe can range anywhere between what the feed screw can extend and retract.
As a clue( or something) the Morse Taper was designed for a sine bar in multiples of 5 for the hypotenus. For practical purposes , let us say the sine is/was 10 inches and the infeed was a quarter of an inch. That was the design-- and those at Morse couldn't machine it accurate enough and NNE of the tapers - now standard- can fit the original design criteria.
Incidentally the box/ladder thing introduces the Binomial theorem - with TWO( and only Two) answers.
It's better than counting sheep

Happy New Year!

Norman

 

[petertha]

I get something like this: 11 degrees compound angle yields 0.00019" cross bed infeed per 0.001" of compound infeed. So closer to 2-tenths than 1.

for rounder cross bed numbers, just rearrange equation
2-tenth cross bed in-feed per 0.001" of compound infeed, set Angle = ArcTan(0.0002/0.001) = 11.31 deg.
1-tenth cross bed infeed per 0.001" of compound infeed, set Angle = ArcTan(0.0001/0.001) = 5.71 deg.

Whether we can actually achieve this is another matter LOL

 

[SmithDoor]

Petertha has a good drawing.
This was printed in old machinist hand books and tool post grinding manuals

If ever would why on old lathes put the compound at 60° is the would direct reading.

Dave

View attachment 121665

Dave
Can you justify your statement with Pythagoras, please?
I once challenged a similar assertion and I was met to a LOUD silence.
I got a book in which (about) 20 degrees is quoted-- and again , Have my doubts.
In the Good old Days, Model Engineer did a Christmas howler of :-

a ladder of 12 feet and a box of 4 feet square and the question was how far up the wall would the ladder extend if its feet were on the ground and the box was against the wall and the ladder touching the corner of the box. Of course that has in Pythagorean terms a know hypotenuse but the cross slide on a lathe can range anywhere between what the feed screw can extend and retract.
As a clue( or something) the Morse Taper was designed for a sine bar in multiples of 5 for the hypotenus. For practical purposes , let us say the sine is/was 10 inches and the infeed was a quarter of an inch. That was the design-- and those at Morse couldn't machine it accurate enough and NNE of the tapers - now standard- can fit the original design criteria.
Incidentally the box/ladder thing introduces the Binomial theorem - with TWO( and only Two) answers.
It's better than counting sheep

Happy New Year!

Norman

 

[SPOTTER]

In this video we talk about 5.74 °.

 

[Asm109]

If ever would why on old lathes put the compound at 60° is the would direct reading.

Dave

What does this even mean?

 

[goldstar31]

What does this even mean?

It's a trifle obtuse but the remaining angle is a useful 30 degrees.

 

[SmithDoor]

On the old lathes the dials where mark for feed.
The turn the compound to 60° the dial will give direct read.

Dave

What does this even mean?

 

[MRA]

This is an interesting thread. I was given a 'concrete vibrator' a while ago - an 11000rpm 110v ac/dc brush motor which will run slow on a variac, and which drives the vibrating head by more-or-less a massive speedo cable - 4' long, rubber outer is about 1.5" diameter, spring drive has 1/4" AF square ends. I have been wondering about making a spindle to mount on the end of it - I have an ER collet chuck on a 25mm cylindrical shaft, maybe I could base it on this. I have a little tacho too - it's important not to overspeed wheels! Really like those waterjet ones - wonder where the sheet of abrasive came from. cheers, M

 

[Larry G.]

This is an interesting thread. I was given a 'concrete vibrator' a while ago - an 11000rpm 110v ac/dc brush motor which will run slow on a variac, and which drives the vibrating head by more-or-less a massive speedo cable - 4' long, rubber outer is about 1.5" diameter, spring drive has 1/4" AF square ends. I have been wondering about making a spindle to mount on the end of it - I have an ER collet chuck on a 25mm cylindrical shaft, maybe I could base it on this. I have a little tacho too - it's important not to overspeed wheels! Really like those waterjet ones - wonder where the sheet of abrasive came from. cheers, M

Sheet of abrasive?
Bring a wheel of the desired grit, bond, etc. to any local water jet cutter. They'll cut it like cheese, any size, any shape, preferably round.
Also check Dan Gelbart's videos on prototypes and precision on Youtube. His "home-made" lathe and grinder hold one micron and he shows abrasive wheels cut to size and the parent material looking like Swiss cheese.

 

[user 43684]

I built the tool post grinder that was in Home shop machinist or projects in metal. The motor is a trim router and the belt is on the wheel end of the spindle. this makes for a nice compact unit that mostly eliminates the tailstock issue. I have also acquired a Dumore TPG that has a much higher motor mount than the Themac. I mostly use the TPGs for grinding valves and sharpening hardened cutters of just about any shape.