I have just purchased a Boxford Lathe

[Seadog]

The toolpost needs to be welll positioned on the compound for rigidity, that's not to say you can't move it about. If you're expecting any degree of accuracy you need to ensure the compound is set correctly, which means that you can't rely on the graduations. A quick and easy way to set it is by using a 30°/60°/90° setting gauge - http://www.kristeel.com/product-det...ement-main&subproduct=angle-measurement&id=72 or a vernier bevel gauge if you've one to hand. The feed screw and nut also need to be in good condition.

 

[123hotchef]

The toolpost needs to be welll positioned on the compound for rigidity, that's not to say you can't move it about. If you're expecting any degree of accuracy you need to ensure the compound is set correctly, which means that you can't rely on the graduations. A quick and easy way to set it is by using a 30°/60°/90° setting gauge - http://www.kristeel.com/product-det...ement-main&subproduct=angle-measurement&id=72 or a vernier bevel gauge if you've one to hand. The feed screw and nut also need to be in good condition.

so is the compound angle set in relation to the head stock with the set square? I have some old set squares and a few bevel gauges somewhere

 

[Brad93]

so is the compound angle set in relation to the head stock with the set square? I have some old set squares and a few bevel gauges somewhere

Set your compound slide off a straight edge of the cross slide or off of the face of the chuck.

 

[Tinbasherdan]

Radius. Never diameter. Whatever cut you put on, it is cutting that off the radius.

The cross slide will take 2.54mm for one full turn.

The compound would take 1.27mm if set at 30°

Our m300 is graduated in diameter rather than radius. Caused me great stress the first time I used it

 

[Brad93]

Our m300 is graduated in diameter rather than radius. Caused me great stress the first time I used it

I’ve just been taking cuts with the compound then out a cut on with the cross slide. Just took off 0.2mm too much

 

[addjunkie]

My advice while your learning, keep it simple. I rarley use the top slide for general turning, just put it in a good stable position and leave it. Just work off the cross slide. Its rare you need to work to super rooper high tolerences.

You need to concerntrate on things like finish at a reasonable tolerence. One excercise is to make a sleeve to fit over a pin youve machined. If you want to be mighty technical you can make it to a certain fit using your zeus book. H7 G6 or something (that was a fit off the top of my head, its been a while since I looked) .That should focus the mind. Something about 3/4 of an inch diameter.

 

[Pete.]

I'd be wary of relying too much on the compound off-set for fine adjustments. One day you'll need that compound for making adjustments on a different axis then what will you do?

You should be able to hit your size within a thou on a lathe PROVIDED that you take consistent amounts off. If you try to creep up on a size it's very easy to over-shoot. It takes some time (and guts) to do it the right way but once you get used to the machine it'll be a breeze, but you gotta do 2 things.
1. take the same amount off several times in a row.
2. trust your dials.

So you measure the part and touch off on the tool then take a 20 thou cut and it removes 18 thou (because when you touched off there was no load on the tool but the cut pushed the tool back a couple of thou when the load came on). You do it again and it removes 20 thou (becuase you've advanced 20 thou from the point where the tool was loaded. You do it again and the same happens - 20 thou comes off. You have 35 thou left so you decide to take off 20 thou and creep up on the finish size. Now you have 15 thou to take off, so you think "I'll take off 10 and leave 5", so you take off 10 thou and measure, damn, it's took off 12 thou. Why? because there's now less load pushing back against the tool so it cuts deeper. Now you got 3 thou left, what to do? Take off 2 and hope you hit 3 or take off 3 and hope it don't over-shoot? you go for 3 and all of a sudden you're 2 thou small, plus your finish has gone all to hell because you're taking tiny cuts.

Basically when you're removing 20 thou at the time the load on the tool is the same, you're getting the same amount of flex in the cross- and compound slide assembly so every time you're doing it you're getting the same results. When you try to creep up on the finished size there's less load on the tool so less flex in the stack and because the cutting loads are less the tool cuts deeper. What you do is take time to learn how your lathe behaves. If you machine of comfortable taking 20 thou cuts in EN8 or whatever work out how many cuts approximately that deep you need and stick to it.

Here's an example. You put a piece of stock in the chuck and you want to turn it down about 200 thou or so. You know that your lathe can take 20 thou cuts so that's 5 cuts at 20 thou. Touch off and take off 20 thou (making the part 40 thou smaller). Measure. Take off 20 thou, measure. You got 3 cuts left but need 65 thou of cutting. Take off 22, then another 22, measure. you need a 23 thou cut to finish. Not a problem because the cutting load for a 22 and a 23 thou cut is the same. So dial in 23 thou of cut and bingo you hit your finished size within a thou plus you got a lovely finish and you haven't messed about creeping up on a size and wondering if you'll over-shoot.

Try it - it works and works well. Once you work up the courage and learn what your machine will do you'll hit your finished size with confidence every time.

 

[123hotchef]

I'd be wary of relying too much on the compound off-set for fine adjustments. One day you'll need that compound for making adjustments on a different axis then what will you do?

You should be able to hit your size within a thou on a lathe PROVIDED that you take consistent amounts off. If you try to creep up on a size it's very easy to over-shoot. It takes some time (and guts) to do it the right way but once you get used to the machine it'll be a breeze, but you gotta do 2 things.
1. take the same amount off several times in a row.
2. trust your dials.

So you measure the part and touch off on the tool then take a 20 thou cut and it removes 18 thou (because when you touched off there was no load on the tool but the cut pushed the tool back a couple of thou when the load came on). You do it again and it removes 20 thou (becuase you've advanced 20 thou from the point where the tool was loaded. You do it again and the same happens - 20 thou comes off. You have 35 thou left so you decide to take off 20 thou and creep up on the finish size. Now you have 15 thou to take off, so you think "I'll take off 10 and leave 5", so you take off 10 thou and measure, damn, it's took off 12 thou. Why? because there's now less load pushing back against the tool so it cuts deeper. Now you got 3 thou left, what to do? Take off 2 and hope you hit 3 or take off 3 and hope it don't over-shoot? you go for 3 and all of a sudden you're 2 thou small, plus your finish has gone all to hell because you're taking tiny cuts.

Basically when you're removing 20 thou at the time the load on the tool is the same, you're getting the same amount of flex in the cross- and compound slide assembly so every time you're doing it you're getting the same results. When you try to creep up on the finished size there's less load on the tool so less flex in the stack and because the cutting loads are less the tool cuts deeper. What you do is take time to learn how your lathe behaves. If you machine of comfortable taking 20 thou cuts in EN8 or whatever work out how many cuts approximately that deep you need and stick to it.

Here's an example. You put a piece of stock in the chuck and you want to turn it down about 200 thou or so. You know that your lathe can take 20 thou cuts so that's 5 cuts at 20 thou. Touch off and take off 20 thou (making the part 40 thou smaller). Measure. Take off 20 thou, measure. You got 3 cuts left but need 65 thou of cutting. Take off 22, then another 22, measure. you need a 23 thou cut to finish. Not a problem because the cutting load for a 22 and a 23 thou cut is the same. So dial in 23 thou of cut and bingo you hit your finished size within a thou plus you got a lovely finish and you haven't messed about creeping up on a size and wondering if you'll over-shoot.

Try it - it works and works well. Once you work up the courage and learn what your machine will do you'll hit your finished size with confidence every time.

great write up Pete thanks, I will give that a go I was taking 20 thou cuts today er well I think I was

 

[123hotchef]

yes I was the cuts are quite nice at 20 thou with a carbide bit too

 

[northwest]

Now you got 3 thou left, what to do? Take off 2 and hope you hit 3 or take off 3 and hope it don't over-shoot? you go for 3 and all of a sudden you're 2 thou small, plus your finish has gone all to hell because you're taking tiny cuts.

Absolutely spot on and very well explained. "chasing thou's" is a fools errand.

 

[brightspark]

its not too bad if you have some spare meat on the end of your job .take the last cut about 1/8 th in. measure it if its spot on just carry on if it isn't you can correct it and then carry on nothing worse than finishing a job and cocking it up on the last cut

 

[indy4x]

I guess it is all too easy to forget the chuck key!

It's not always a case of forgetting the chuck key

I have posted this before but worth repeating, when I was in comprehensive school we had some big old Harrisons, model number evades me but they had a big clutch lever on the headstock.

One day I disengaged the clutch, put a chuck key in the chuck and just as I'm about to undo the workpiece the clutch lever moved and engaged drive

Chuck key was ripped out of my hand, hit the bed and shot off narrowly missing my head

 

[slim_boy_fat]

It's not always a case of forgetting the chuck key

I have posted this before but worth repeating, when I was in comprehensive school we had some big old Harrisons, model number evades me but they had a big clutch lever on the headstock.

One day I disengaged the clutch, put a chuck key in the chuck and just as I'm about to undo the workpiece the clutch lever moved and engaged drive

Chuck key was ripped out of my hand, hit the bed and shot off narrowly missing my head

Funny how these incidents stick in your mind until the end of time. It's called learning, I suppose

 

[mtt.tr]

I'd be wary of relying too much on the compound off-set for fine adjustments. One day you'll need that compound for making adjustments on a different axis then what will you do?

You should be able to hit your size within a thou on a lathe PROVIDED that you take consistent amounts off. If you try to creep up on a size it's very easy to over-shoot. It takes some time (and guts) to do it the right way but once you get used to the machine it'll be a breeze, but you gotta do 2 things.
1. take the same amount off several times in a row.
2. trust your dials.

So you measure the part and touch off on the tool then take a 20 thou cut and it removes 18 thou (because when you touched off there was no load on the tool but the cut pushed the tool back a couple of thou when the load came on). You do it again and it removes 20 thou (becuase you've advanced 20 thou from the point where the tool was loaded. You do it again and the same happens - 20 thou comes off. You have 35 thou left so you decide to take off 20 thou and creep up on the finish size. Now you have 15 thou to take off, so you think "I'll take off 10 and leave 5", so you take off 10 thou and measure, damn, it's took off 12 thou. Why? because there's now less load pushing back against the tool so it cuts deeper. Now you got 3 thou left, what to do? Take off 2 and hope you hit 3 or take off 3 and hope it don't over-shoot? you go for 3 and all of a sudden you're 2 thou small, plus your finish has gone all to hell because you're taking tiny cuts.

Basically when you're removing 20 thou at the time the load on the tool is the same, you're getting the same amount of flex in the cross- and compound slide assembly so every time you're doing it you're getting the same results. When you try to creep up on the finished size there's less load on the tool so less flex in the stack and because the cutting loads are less the tool cuts deeper. What you do is take time to learn how your lathe behaves. If you machine of comfortable taking 20 thou cuts in EN8 or whatever work out how many cuts approximately that deep you need and stick to it.

Here's an example. You put a piece of stock in the chuck and you want to turn it down about 200 thou or so. You know that your lathe can take 20 thou cuts so that's 5 cuts at 20 thou. Touch off and take off 20 thou (making the part 40 thou smaller). Measure. Take off 20 thou, measure. You got 3 cuts left but need 65 thou of cutting. Take off 22, then another 22, measure. you need a 23 thou cut to finish. Not a problem because the cutting load for a 22 and a 23 thou cut is the same. So dial in 23 thou of cut and bingo you hit your finished size within a thou plus you got a lovely finish and you haven't messed about creeping up on a size and wondering if you'll over-shoot.

Try it - it works and works well. Once you work up the courage and learn what your machine will do you'll hit your finished size with confidence every time.

That's really the art is learning to correct for backlash but it does become instinct

 

[123hotchef]

Ok so i have 20 thou of backlash in the cross slide can I take this slack up or do I have to account for it when taking material down

 

[brightspark]

Ok so i have 20 thou of backlash in the cross slide can I take this slack up or do I have to account for it when taking material down

makes no odds what backlash there is all threads have it. just take the reading off the dial of your last cut .back the tool off and wind it back in to the desired cut

 

[dobbslc]

Just keep winding it in and don't back off at all. Once you've touched off keep going. As soon as you back up you'll loose your reference and have to start again.

 

[123hotchef]

Ok thanks guys. I thought it may have been abnormal

 

[123hotchef]

A little mod to the new live center to help eject it

 

[Hopefuldave]

makes no odds what backlash there is all threads have it. just take the reading off the dial back the tool off and wind it back in to the desired cut

Yep, zero the dial after each cut, wind out a full turn then advance to zero plus the cut, always approach the measurement in the same direction so you always take up the backlash also in the same direction, no probs

Dave H. (the other one)