Thread: A Boys Dreams does come true

Wow, that overhang made me wince. You should use the tailstock on that.

No wonder you got harmonics.

Rob

Originally Posted by nearnexus

Wow, that overhang made me wince. You should use the tailstock on that.

No wonder you got harmonics.

Rob

Thanks Rob exactly what I figured. Yet some material I have read suggests doing an 8" turn like this to test for lathe level.

In turning wood that far out I have suffered same thing. I will in future always use the tailstock.

If you measure that shaft I would expect it will be smaller diameter as you approach the chuck.

Unsupported work will always flex away from the cutter as you move away from the chuck, effectively cutting a widening taper.

Always support your work where possible.

Rob

Originally Posted by nearnexus

If you measure that shaft I would expect it will be smaller diameter as you approach the chuck.

Unsupported work will always flex away from the cutter as you move away from the chuck, effectively cutting a widening taper.

Always support your work where possible.

Rob

I cut towards the chuck which is what was explained to do in the text and video I saw.

I think I'll get a mate who has engineers levels to call round and set it up.

Yes, that's correct.

But if you cut unsupported work like that, it will flex away from the cutter and be a larger diameter the further you are away from the chuck.

As you cut in towards the chuck, flex will be less and the diameter will also be less as the cutter can bite in and take more off.

If you support your work with the tailstock, the only flex will be towards the middle of of the job where it can still flex away from the cutter.

You have to consider how the cutting forces will push against the job.

If you support your work with a tailstock, and the lathe is set up correctly, the diameter of the machined shaft will be same at the chuck and the tailstock.

You don't need to be an engineer to set up a lathe. You just have to adjust the tailstock so that the above situation is true.

Rob

Originally Posted by nearnexus

Yes, that's correct.

But if you cut unsupported work like that, it will flex away from the cutter and be a larger diameter the further you are away from the chuck.

As you cut in towards the chuck, flex will be less and the diameter will also be less as the cutter can bite in and take more off.

If you support your work with the tailstock, the only flex will be towards the middle of of the job where it can still flex away from the cutter.

You have to consider how the cutting forces will push against the job.

If you support your work with a tailstock, and the lathe is set up correctly, the diameter of the machined shaft will be same at the chuck and the tailstock.

You don't need to be an engineer to set up a lathe. You just have to adjust the tailstock so that the above situation is true.

Rob

Thanks Rob

I will mic both tomorrow and see how they are. Would be still nice to know via levels how far my floor is out. I can't bolt down as renting and floor is cracked enough already, I may even have to move the lathe which will be ARPIA.

Not being familiar with the Myford tool post it would appear that the post is large or the piece of tool steel you are using is small,there only appears to be one hold down working on the tool.Unless you have the hold down very tight on the tool bit,you may find that this could contribute to your poor finish/vibration.

Looking also at the way the tool is held in the post,it appears that you have a packing piece not running the full length of the tool bit.

Have you set the tool bit on centre of the work piece,if you have,have you sharpened the tool to compensate for any negative rake that may be present due to the way the tool bit is supported by the packing piece.

When you turned the piece of M/S what rpm were you running also what feed rate and depth of cut.

Having a piece 8" out of the headstock unsupported should not of been a problem for what you were doing as long as all other machining parameters were set for the job.

Hi,

I'm not sure if you have this book:

http://lathesonline.com.au/estore/index.php?main_page=product_info&products_id=29

It's a good and easy read. While not written just for Myfords it may have well been. There's other seller's on the net you just gotta look (my copy came out of the Clarence Rivers Libary from the 50's).

Ben

Well spotted Peter. A QCTP would be high on my list of things to get, they make life much easier...

I don't know what you know and don't so please don't think i'm talking down to you!

When we say "level" we really mean that the bed has no twist in it. At your stage, and since you cannot bolt the lathe down i would just level it with a good carpenters level. Let it settle a few weeks and re-check.
Whilst this is not the place for general leveling discussions (which seem to always cause a stir), turning with the TS and just setting the TS so that you are turning straight does not fix the problem of a twisted bed. If your bed is twisted, setting the TS alignment only works for that one spot you have set it at, move it up or down the bed and it will be out again.
Generally when you cut a test bar, around 4" is enough to see the error, you don't need to turn 8" (not on lathes of this size anyway)
The rule of thumb i use for unsupported work is 2.5 times the diameter is the max you can have hanging out of the chuck.

Originally Posted by pipeclay

Not being familiar with the Myford tool post it would appear that the post is large or the piece of tool steel you are using is small,there only appears to be one hold down working on the tool.Unless you have the hold down very tight on the tool bit,you may find that this could contribute to your poor finish/vibration.

Looking also at the way the tool is held in the post,it appears that you have a packing piece not running the full length of the tool bit.

Have you set the tool bit on centre of the work piece,if you have,have you sharpened the tool to compensate for any negative rake that may be present due to the way the tool bit is supported by the packing piece.
Tool was to small and yes packing to put on centre tool was sharp to start with. I will make a new one and try again in a few days have some other woodwork to do first.


When you turned the piece of M/S what rpm were you running also what feed rate and depth of cut. This I believe was 200rpm, the belt setting was on lowest. Depth of cut not sure, but light if I recall 2 div on the cross feed but there seems to be some slack prior moving. This I have to look into..

Having a piece 8" out of the headstock unsupported should not of been a problem for what you were doing as long as all other machining parameters were set for the job.

Thanks for this it will all help me for sure.

I require better tooling what I was using was what came with the lathe I have HSS to make some.

Originally Posted by bwal74

Hi,

I'm not sure if you have this book:

http://lathesonline.com.au/estore/index.php?main_page=product_info&products_id=29

It's a good and easy read. While not written just for Myfords it may have well been. There's other seller's on the net you just gotta look (my copy came out of the Clarence Rivers Libary from the 50's).

Ben

See post thanking Anorak Bob with photos of the Myford book and your suggestion.

Originally Posted by Ueee

Well spotted Peter. A QCTP would be high on my list of things to get, they make life much easier...

I don't know what you know and don't so please don't think i'm talking down to you!

When we say "level" we really mean that the bed has no twist in it. At your stage, and since you cannot bolt the lathe down i would just level it with a good carpenters level. Let it settle a few weeks and re-check. Level as in bed level as well as floor level. The day it was brought in we/sons leveled with carpenters level as best could ATT that needs checking now the machine has been run. Two leveling wedges were used to bring it up in one corner, darn floor It will get time to settle more as I have other work to get on with.

Whilst this is not the place for general leveling discussions (which seem to always cause a stir), turning with the TS and just setting the TS so that you are turning straight does not fix the problem of a twisted bed. If your bed is twisted, setting the TS alignment only works for that one spot you have set it at, move it up or down the bed and it will be out again. This is what I thought also same as on almost anything.

Generally when you cut a test bar, around 4" is enough to see the error, you don't need to turn 8" (not on lathes of this size anyway) I will do another test with shorter piece an see how that goes.

The rule of thumb i use for unsupported work is 2.5 times the diameter is the max you can have hanging out of the chuck.

Thanks its all great stuff and I do appreciate all the in put.

Ray

Mic'd the Alli .004 difference less at chuck end, didn't bother with the mild steel knew it would be way out.

Today put in another mild steel bar same size about 19mm and took lighter cuts only 4" out and reduced rpm down to 35 with much better result.

Thanks Ray

Originally Posted by wheelinround

Mic'd the Alli .004 difference less at chuck end, didn't bother with the mild steel knew it would be way out.

Today put in another mild steel bar same size about 19mm and took lighter cuts only 4" out and reduced rpm down to 35 with much better result.

Thanks Ray

Ray I think you need to read up on metal turning.

For a 19 mm bar you should be turning quite fast (400 - 600 rpm depending on cutter type).

The rule of thumb is that as the diameter reduces, the speed increases, and vica versa.

32 rpm is way too slow.

I suggest you download and read this book - Text Book of Turning. It's old but good. See page 21 for cutting speeds.

http://www.bbssystem.com/manuals/Lathe-Tutorial.pdf

Cheers

Rob