First Time Lathe Play Advice

[mr haynes]

Assuming i can get the lathe to work, looking for some advice on what i need and what i need to do.....

I'm wanting to skim an oval brake drum, about 10thou difference between highest and lowest point.

Some pics below of current state of play and the bits i have.....

TIA

 

[Brad93]

You're in for a lot of fun

 

[Arc Tourist]

Wrap a rubber bicycle innertube around the outside of the brake drum. It will dampen the ear piercing squeal from machining.

 

[RobCox]

If that drum is cast iron, cover the ways with something to keep the abrasive chips/dust off them.

 

[brightspark]

good luck with that one, show us the results when finished its only in a 3 jaw as well there a few thou out before you start

 

[Barking Mat]

If it's your first time with a lathe, get some scrap, to learn with.

 

[ukracer]

I think that's good advice.
Practice first.

Having said that the boring bar can be used as a short stubby one to eliminate deflection. You will however need a new tip. That one looks shafted.
The hardest part will be lining it up in the chuck. I use a 4 jaw and it's hard.

Make a roller tool to press against the front to align the drum. That will get it as good as it gets.

 

[mr haynes]

If it's your first time with a lathe, get some scrap, to learn with.

Already done some practice, 40 odd yr ago , thought it's time to move onto productive stuff.
Only had the lathe over 3yr or so.....

 

[mr haynes]

I think that's good advice.
Practice first.

Having said that the boring bar can be used as a short stubby one to eliminate deflection. You will however need a new tip. That one looks shafted.
The hardest part will be lining it up in the chuck. I use a 4 jaw and it's hard.

Make a roller tool to press against the front to align the drum. That will get it as good as it gets.

Had issues with the 4 jaw, bought a die to tidy up the studs and new nuts....... found out today i arised up, got wrong size
No idea with regards to tips, what should i be looking for?

 

[mr haynes]

good luck with that one, show us the results when finished its only in a 3 jaw as well there a few thou out before you start

Still have to reattach the motor, only done checking with the DTI

 

[addjunkie]

That tool tip-in your pictures is well shot. Are the other two point the same?

 

[mr haynes]

That tool tip-in your pictures is well shot. Are the other two point the same?

No idea on the tool tips, boring bar been living in the tray since i got lathe. I take it they are 3 pointed?
Will have a closer look tomorrow hopefully.

 

[Kram]

4 jaw will grip it better and allow you to clock it in, except the jaws will be trying to deform it. Best to hold it in the same way its held on the hub. It may be worth turning a plate with the central register and then bolting it on like that, near exactly how its mounted to the car - the jaws wont be trying to stretch it.

Make sure to clock the face and insure its sitting square in the chuck.

While that bar with a fresh insert will work, hold the bar with short stick out as possible. A bigger diameter bar would help.

A smaller, finishing insert will usually have lower cutting forces, therefore less noise and chatter on big ringing items like this.

 

[Erie Fred]

A smaller, finishing insert will usually have lower cutting forces, therefore less noise and chatter on big ringing items like this.

Smaller nose radius on the insert is another way of saying this ^^^

Much less force trying to push tool away, and less vibration.

Larger radius gives smoother cut, but tends to make the part ring.

Your not looking for smooth, your looking for "round".

 

[addjunkie]

Smaller nose radius on the insert is another way of saying this ^^^

Much less force trying to push tool away, and less vibration.

Larger radius gives smoother cut, but tends to make the part ring.

Your not looking for smooth, your looking for "round".

Round and concentric to the bearings it runs on.

Assuming i can get the lathe to work, looking for some advice on what i need and what i need to do.....

I'm wanting to skim an oval brake drum, about 10thou difference between highest and lowest point.

Some pics below of current state of play and the bits i have.....

TIA

View attachment 482658View attachment 482661View attachment 482662

How did you measure to determine 10 thou?

 

[dieselsamurai]

if it was me I would use a face plate and turn up a piece to fit in the bore of the face plate and a very close fit into the center of the hub mounting on the drum should be dead square then. The closer you are to the spindle bearings doing this the better but TBH unless the lathe is super rigid any sort of hard spot in the cast of the drum it will bounce and not dig in

 

[indykid]

How easy is it to source a new drum?

By all means have a go if there's an option to easily buy another, but there's a fair chance you'll make it worse than better at your experience level. If it's a one off or rare, I'd find someone that has the facilities and experience to do it first time.

When you say it's oval, are the two low points in your measurement opposite each other or are you measuring run out in your setup on the lathe? It would be ideal in your setup if you could access both the centre bore and the friction face but the jaws are in the way currently (assuming it registers on the centre bore). This would be where a face plate or dummy hub would help.

To answer your question though, you need to get the inner hub face running true, then once the hub face is true, adjust the radial runout to get the drum running true to the spindle based on a feature that aligns it on the vehicle (centre bore probably), then check the face again and then check the bore, iterating until both are true at the same time. You want a short, stiff boring bar and a method to damp the vibration to prevent chatter. An innertube or long spring wrapped round the drum or a plastic hammer sat on the face you're turning all help, as will a face plate as it better constrains the part. Finally, if you're getting chatter, go slow - really slow. You won't get as good a finish, but you need it round. For everything else, there's emery tape.

 

[mr haynes]

Round and concentric to the bearings it runs on.


How did you measure to determine 10 thou?

Was the difference between highest and lowest points after initial setup in chuck. They were visually roughly opposite.
The values on the other 2 "sides were similar to each other and roughly half and halfway between highest and lowest point.
If that makes any sense
DTI and stand plonked on bed
It pretty much corresponded with the results obtained when i spun the drum on the van axle

 

[mr haynes]

if it was me I would use a face plate and turn up a piece to fit in the bore of the face plate and a very close fit into the center of the hub mounting on the drum should be dead square then. The closer you are to the spindle bearings doing this the better but TBH unless the lathe is super rigid any sort of hard spot in the cast of the drum it will bounce and not dig in

Lathe is a Lang Junior....

 

[addjunkie]

How easy is it to source a new drum?

By all means have a go if there's an option to easily buy another, but there's a fair chance you'll make it worse than better at your experience level. If it's a one off or rare, I'd find someone that has the facilities and experience to do it first time.

When you say it's oval, are the two low points in your measurement opposite each other or are you measuring run out in your setup on the lathe? It would be ideal in your setup if you could access both the centre bore and the friction face but the jaws are in the way currently (assuming it registers on the centre bore). This would be where a face plate or dummy hub would help.

To answer your question though, you need to get the inner hub face running true, then once the hub face is true, adjust the radial runout to get the drum running true to the spindle based on a feature that aligns it on the vehicle (centre bore probably), then check the face again and then check the bore, iterating until both are true at the same time. You want a short, stiff boring bar and a method to damp the vibration to prevent chatter. An innertube or long spring wrapped round the drum or a plastic hammer sat on the face you're turning all help, as will a face plate as it better constrains the part. Finally, if you're getting chatter, go slow - really slow. You won't get as good a finish, but you need it round. For everything else, there's emery tape.

This sums it up pretty well. Clock a flat surface before you start, bet its out a bit.

Good luck.