First Time Lathe Play Advice

[Kram]

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".

Not just nose radius but a postive geometery small insert designed for light finishing. You dont want to be taking a 0.25mm cut with most inserts that have a 0.5mm minimum as it will rub more than cut. And a brake drum I imagine you want to remove just the minimum to get it round.

The inserts I use will take a 0.01mm cut upto 2mm cut with no issue.

A sharp large HSS bit would also do it quite adequately.

 

[addjunkie]

Not just nose radius but a postive geometery small insert designed for light finishing. You dont want to be taking a 0.25mm cut with most inserts that have a 0.5mm minimum as it will rub more than cut. And a brake drum I imagine you want to remove just the minimum to get it round.

The inserts I use will take a 0.01mm cut upto 2mm cut with no issue.

A sharp large HSS bit would also do it quite adequately.

I did two trailer drums a few years ago, just used a home made hss round nosed tool, really slow. Back plates had corroded / ripped off and drums seized, cleaned up ok. Worst bit was cutting off the rough corroded edge, even after Id dressed it up with a flap disc.

The more daunting task was putting the complete axle in the lathe, to machine off the old back plates!

 

[indykid]

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

If 12 o'clock is high, 6 is low and 3 and 9 are between the two, it's not (likely) out of round, you're more likely measuring runout. Make sure the hub mounting face and centre bore are true and then measure it again.

If you turn it with runout in the setup as it appears you have now, you'll just as likely increase the error as fix it

 

[mr haynes]

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.

New drums are unavailable, think this is about a 37yr old drum.
I measured the face of the drum in the chuck to set up. I want to say i also measured against the small bit of lip where the jaws are but can't exactly remember now lol.
Same type of figures were obtained with the drum reversed on the axle and spun.
Interestingly, the drum has the wheel studs installed and the hub sits over the studs i.e. inboard drums.

Thanks for your answer, will start again by measuring the lathe first and take from there

 

[Brad93]

@pressbrake1

lang

 

[ukracer]

Not just nose radius but a postive geometery small insert designed for light finishing. You dont want to be taking a 0.25mm cut with most inserts that have a 0.5mm minimum as it will rub more than cut. And a brake drum I imagine you want to remove just the minimum to get it round.

The inserts I use will take a 0.01mm cut upto 2mm cut with no issue.

A sharp large HSS bit would also do it quite adequately.

What code and numbers do you use out of interest.

 

[Melvyn Best]

NEVER, EVER leave the chuck key in the chuck! That was the first thing I was ever taught when I first used a lathe , still as relevant now as then.

 

[pressbrake1]

@pressbrake1

lang

I do like a lang especially if it’s in double digit tonnage!

 

[mr haynes]

I do like a lang especially if it’s in double digit tonnage!

This one is more than heavy enough for me
Also now less than double digit mileage from it's birthplace

 

[mr haynes]

Today i took some measurements as suggested by members.

As per pic below, my old imperial Mercer gauge barely flickered on rotating by hand



The next two showed similar results approx 0.0005" of movement.



Not sure how i measure with chuck in place, the jaws being an issue.

Thoughts please.

 

[Brad93]

Today i took some measurements as suggested by members.

As per pic below, my old imperial Mercer gauge barely flickered on rotating by hand

View attachment 482943

The next two showed similar results approx 0.0005" of movement.

View attachment 482944 View attachment 482945

Not sure how i measure with chuck in place, the jaws being an issue.

Thoughts please.

It's a Lang! That spindle can probably support half a tonne! Unlikely to have any major runout.

Regarding the jaws.
All three jaw chucks, especially old used ones will have runout.

Even the best new Super Precision three jaw chucks will have between .001"-0.002" / 0.05mm runout when chucked up on ground bar.

Two or three methods to do that part.

1.)
You take a big lump of steel, chuck it up and turn it to be an interference fit into the bore of your flywheel, you drill and tap for a M16+ bolt and a big spacer to hold the job to the billet.

This should give very little radial runout but there could be some runout on the face of the part. Tapping the job around could correct this at the expense of radial concentricity.

2.)
You stick it on a faceplate. Probably the best option, you can centralise and shim the part to your hearts content.
This is likely to be the most rigid method and give the least squeal and chatter.

3.)
Use a four jaw with chuck gripping the outside edge. You can move the job around and tap it into alignment.
Completely dependant on the size of your four jaw and whether the jaws are deep enough to hold the part safely.

 

[roofman]

Today i took some measurements as suggested by members.

As per pic below, my old imperial Mercer gauge barely flickered on rotating by hand

View attachment 482943

The next two showed similar results approx 0.0005" of movement.

View attachment 482944 View attachment 482945

Not sure how i measure with chuck in place, the jaws being an issue.

Thoughts please.

Be very careful...it all started with trying to make an old brake drum more round than round...your now half convinced you need new head stock bearings at about £800. should of just "scratched" it out yourself and just shown us the results, another 10 posts and the ways will be scrap

 

[Pete.]

Lathe is a Lang Junior....

View attachment 482749

Well whatever goes wrong it won't be the lathe's fault.

By the way once you get it fitted in the chicken get some long studding and nuts/washers and make a drawbar to go through the spindle and hold it against the chuck jaws. That way it won't walk it's way out if the chuck and give you an awful fright.

 

[mr haynes]

Well whatever goes wrong it won't be the lathe's fault.

By the way once you get it fitted in the chicken get some long studding and nuts/washers and make a drawbar to go through the spindle and hold it against the chuck jaws. That way it won't walk it's way out if the chuck and give you an awful fright.

Bugger! Knew i should've gone the cheapo chineseium way

 

[mr haynes]

Be very careful...it all started with trying to make an old brake drum more round than round...your now half convinced you need new head stock bearings at about £800. should of just "scratched" it out yourself and just shown us the results, another 10 posts and the ways will be scrap

Actually started as a better give the brakes a clean as van been sat few weeks. Wheel cylinders, shoes, wheel bearings later.....everything worked fine before i decided to tinker

 

[mr haynes]

It's a Lang! That spindle can probably support half a tonne! Unlikely to have any major runout.

Regarding the jaws.
All three jaw chucks, especially old used ones will have runout.

Even the best new Super Precision three jaw chucks will have between .001"-0.002" / 0.05mm runout when chucked up on ground bar.

Two or three methods to do that part.

1.)
You take a big lump of steel, chuck it up and turn it to be an interference fit into the bore of your flywheel, you drill and tap for a M16+ bolt and a big spacer to hold the job to the billet.

This should give very little radial runout but there could be some runout on the face of the part. Tapping the job around could correct this at the expense of radial concentricity.

2.)
You stick it on a faceplate. Probably the best option, you can centralise and shim the part to your hearts content.
This is likely to be the most rigid method and give the least squeal and chatter.

3.)
Use a four jaw with chuck gripping the outside edge. You can move the job around and tap it into alignment.
Completely dependant on the size of your four jaw and whether the jaws are deep enough to hold the part safely.

3jaw isn't original, has a label on it that says TOS
An adataptor has been machined to allow it to be mounted.

Don't have a faceplate but do have, what appears to be the original 4jaw.
Awaiting a die and nut to tidy up one of the mounting studs.
Tinterweb suggests it is 16" diameter and i can say it is a flippin heavy lift into position!
From memory the drum inner is 10" diameter

 

[Kram]

3jaw isn't original, has a label on it that says TOS

TOS are decent, Polish? Same quality as Bison if I remember correctly.

The best 3 jaw chucks allow you to slightly offset the chuck mecahnism to correct any runout. The poor mans version is to machine a loose register in the chuck back plate so that you can tap it true. The big problem with that, is any crash or overload condition, could throw the chuck out of alignment, and you may not realise until its too late. That has happened to me and ruined a couple of parts where I kept turnjng after replacing my inserts.

I dont have one of these fancy adjustable 3 jaws but I do have a reasonably good condition 10" Bison 4 jaw

By the way once you get it fitted in the chicken get some long studding and nuts/washers and make a drawbar to go through the spindle and hold it against the chuck jaws. That way it won't walk it's way out if the chuck and give you an awful fright.

That is a useful idea that has not previously occured to me on any chucked work I have done, thanks.

 

[indykid]

Today i took some measurements as suggested by members.


Thoughts please.

If this was on the back of any of my comments, I wasn't intending you to measure the spindle, only the part when mounted on the spindle.

A dependent 3 jaw chuck, as a trade off of its design, introduces variation in runout. Not only are all 3 jaws joined by the same scroll, (but even if we assume the jaws and scroll are perfectly accurate) the scroll itself has to rotate in the chuck body and thus has to have some clearance. Going from one side of the clearance to the other moves all 3 jaws, which is why runout is worst if you only use one pinion to tighten the jaws and use a random pinion each time. The scroll of a very high quality chuck when produced will be practically a transition fit on the chuck body but any amount of wear creates clearance that allows the scroll to move relative to the chuck body.

If you have a 16" 4 jaw, that's definitely a better chuck to be using. As Brad said, grip it on the outside to give far better support, just be careful not to crush it out of round. Don't try to get the length of the jaws fully engaged either as it may stop you truing the back face up. Given it's a cast surface and may have some pattern draft, I'd definitely follow Pete's suggestion of the security pull stud once you have it all clocked up.

 

[mr haynes]

If this was on the back of any of my comments, I wasn't intending you to measure the spindle, only the part when mounted on the spindle.

A dependent 3 jaw chuck, as a trade off of its design, introduces variation in runout. Not only are all 3 jaws joined by the same scroll, (but even if we assume the jaws and scroll are perfectly accurate) the scroll itself has to rotate in the chuck body and thus has to have some clearance. Going from one side of the clearance to the other moves all 3 jaws, which is why runout is worst if you only use one pinion to tighten the jaws and use a random pinion each time. The scroll of a very high quality chuck when produced will be practically a transition fit on the chuck body but any amount of wear creates clearance that allows the scroll to move relative to the chuck body.

If you have a 16" 4 jaw, that's definitely a better chuck to be using. As Brad said, grip it on the outside to give far better support, just be careful not to crush it out of round. Don't try to get the length of the jaws fully engaged either as it may stop you truing the back face up. Given it's a cast surface and may have some pattern draft, I'd definitely follow Pete's suggestion of the security pull stud once you have it all clocked up.

Lathe was bought on a whim and i've done nothing with it until now. It is all learning and nowhere near attempting to power it yet.
Using the 3 jaw allowed me to confirm the similar results i obtained whilst spinning drum on vehicle axle. Don't think there was any great movement at the inner bore surface whilst doing this, hence suspecting ovality. Mounting in lathe was initially a means to confirm previous findings.
Now want to play with the big toy

 

[mr haynes]

Actually started as a better give the brakes a clean as van been sat few weeks. Wheel cylinders, shoes, wheel bearings later.....everything worked fine before i decided to tinker

Also means now i will have to do the diff oil......gawd knows what will happen then
I need a restraining order