# Flycutting on the lathe



## SeanG (Jan 26, 2010)

I'm about to try fly cutting on my lathe, (so far I've only done a bit of centre drilling, facing and turning) and so would like to run a stoopid test first 

The thing I'm making is the surface gauge from Harold Halls Lathework course book and I've reached the stage where it looks like the ASCII art below (no picture upload access in work)


     .--.
     (  )
     |~--~|
     |  |
     |  |
     |  |
     |  |
     |  |
     |  |
     |  |
     |  |
     |  |
     |  |
     |  |
  _..--|  |--..
 .-~   |  |  ~-.
 |.         .|
 |"-..____________..-"|
 |          .`
 "-..____________..-" 
 

No sniggering at the back!!!


My next step is to mill a flat onto the small diameter, from my reading, the fly cutter should cut on the downward stroke (to force the cross slide down onto the apron and bed rather than lifting against the various gib strips).

To do this I'm proposing to mount the work horizontally in a machine vice on the vertical slide. I will have the work at roughly centre height, with the cross slide toward me. I will then move the cross slide away from me, into the path of the fly cutter, until the length of the flat has been cut.

I would then stop the cutter, move the vertical slide down below the cutter, turn back on and move the vertical slide up to form a flat end on the cut section.

Does this procedure seem right?

All advice gladly taken

Sean the Nervous


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## Bernd (Jan 26, 2010)

Sean,

I've got some pics showing how to do that on a Sherline lathe. Same concept weather it's a big lathe or small one.


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## ieezitin (Jan 26, 2010)

Sean.
You got it. 

Hard to explain but see if this makes sense.

If you think of force as a straight line. It has a start and a finish. Now think of the starting point of the tool hitting the surface and where is that force going to be distributed in a straight line.

Your lathe or mill is designed to absorb the force ( stresses ) in certain ways. When you are going to do a job set up on either machine think in your minds eye the applied force is such and such and it is going to be absorbed there there and there. Being its a straight line its easy to think of it this way. Always plan your procedure, when your designing or looking at a piece think about the machining side, sometimes this creates or dictates what the piece is going to be.

Dont be scared to attempt anything with fear of failure, if you screw up make another one. It builds character and your learning will be accelerated, plus were here to help with all questions which I know you will get great advice from many quality people here.

Rule about machining in the unknown is SAFETY. Pay close attention to your task and ask yourself what are the hazards where will they come from what can I do to protect myself. This advice is worth more than gold. When machining in the known. DONT get comfortable be alert always.

By the way you over come your need to express that drawing, I know youre a thinker 
Now go and machine and have fun.
Post piccies when your finished.  All the best.  Anthony.


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## SeanG (Jan 27, 2010)

Thanks Bernd and iezitim

Setup has gone slowly due to too few hours in the garage 

This is roughly my intention - the packing bolt is temporay and will be replaced by something better and I'm a Tee nut short in the box of useful "bits" that came with the lathe. Prep-ing the studs for the vertical slide is a story in itself :-[ only one parting off blade broken though.... lesson learnt - two nuts is not enough to lock a thread for holding in the chuck : 

oh yes - and I've turned the cutter in the fly holder by 90 degrees too







Sean


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## Foozer (Jan 27, 2010)

Looks scary

Hard to tell what's holding the stock in the vise and I'd shorten up the bit in the fly cutter.
Hanging way out there its gonna really be a spinning. Thought of the piece being worked rattled out of the vise, shivers.

Just be careful, fly cutting, interrupted cutting can sure set up a vibration fest that ell knock them eye teeth loose.


Robert


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## SeanG (Jan 28, 2010)

Scary is the word Foozer!

The work is clamped across the diameter and recessed into the clamp so that as little as possible is protruding, none of the pictures I took show it that well, but is is tightly gripped, the vice was tightened with a Tommy bar as well.

I was trying to extend the cutter so that it didn't cut a few thou off the end on the upstroke (having read that lathes face concave by design).

Speed-wise, I'm on the lowest backgear setting which will give me 48 rpm and the cutter is definitely rotating rather than spinning - if you know what I mean...

I won't be able to try it tonight, work is making go out to drink beer so fingers crossed for Friday.

I've got, and happily use a spindle moulder with some big blades for cutting my own skirting board profiles and could never understand the trepidation other woodworkers showed to using the "finger eater" - I knew the cutters were well secured, my work is well guarded, held down and supported at either end of its travel - so no problems and well within my comfort zone, but I'm kinda seeing where they were coming from now, this fly cutting looks like a pretty dangerous operation to me!!

Hopefully the next pic isn't of bandages :-\


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## Foozer (Jan 28, 2010)

SeanG  said:
			
		

> Scary is the word Foozer!
> 
> Hopefully the next pic isn't of bandages :-\



Ditto on that 

Done some fly cutting on the lathe, I shorten up the bit as much as possible to reduce the stress on the machine. The bit about cutting on the up stroke is valid yet, well for me I try to start the operation feeding the stock into the down cut. By time the up-cut side hits the stock it just barely kisses the material (provided I squared it all up). 

I tend to take too big a cut on my little lathe to which a while ago I sheared the spindle and set the chuck a whizzing cross the barn. Its a hobby, but not one worth fingers being relocated to the "Wall of OOPS"

Keep the body parts clear and have fun, can always get another piece of stock 

Robert


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## IanN (Jan 29, 2010)

Hi,

Wouldn't it be much quicker and easier to use a file and make the flat by hand?

Ian.


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## SeanG (Jan 29, 2010)

"Wall of OOPS" - brilliant 



Valid point Ian, but for me this project as more about the machine skills than the final item, the flat on this project will be a couple of mm deep - so it would probably take as long to file as I've spent flappping about with the setup on the lathe anyway ;D


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## IanN (Jan 29, 2010)

Sorry - didn't mean to take the fun out of it!

Given the choice of "get the job done quickly" or "let's play in the workshop for a few hours" I would go for "play time" every time! That is the point of a hobby, isn't it?

 Ian.


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## SeanG (Jan 29, 2010)

Very true 


Besides, if I actually finished something, my wife would go into shock :big:


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## Foozer (Jan 29, 2010)

SeanG  said:
			
		

> Very true
> 
> 
> Besides, if I actually finished something, my wife would go into shock :big:



I find that if I approach the bride with a big smile on my face, pointy finger under da chin, chanting "Look what I can Do!!" while standing on one leg, I'm quickly directed to go back to the barn.

Robert


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## ieezitin (Jan 29, 2010)

Sean.

I see the set up and your concept, As long as you are square and like Foozer said shorten the length of the cutting tool as much as you can your going to be fine. 

Make sure you put a parallel behind your job. Use HHS bits and shim stock, even feeler gages will work. If you dont have parallels get some! dont buy regular straight parallels not even Chinese ones , there a waste of money too many things out there you can substitute for them.

On the other hand a Full Set of Adjustable parallels are a must, imagine the ease you would have in just sliding open your adjustable parallel and fitting on the back of you job in the vice you have now!. Starret, Brown & sharpe, get quality treated right will last you a life time. Ebay is a great place you should get a great deal.

Let me know what lathe you are working on so I can get an idea of the size machine you have, some of the smaller lathes may need a different way to tackle a project.

Hope the beer was good.   All the best.   Anthony.


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## SeanG (Jan 30, 2010)

The beer was nice  - turns out I quite like it, I might even try it again.....


I got some packing material today but had to spend the time I was hoping to be in the garage out in the garden - best time of year to hack at fruit trees apparently ???


Have to wait until tomorrow now.


My lathe is a Myford ML10 (you can see it in it's cramped confines on page 22 of the "Show us your lathe" thread. small(ish) but I don't forsee any size issues on this task.


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## SeanG (Feb 15, 2010)

Got there at last...

I gave the procedure a trial run on some bar stock before risking my workpiece, unsurprisingly, using the fly cutter without shaping the cutting edge gives a very poor result and tries to knock the horizontal slide off the lathe 

A hunt around the internet lead to some posts from McGyver on fly cutter tool grinding and sharpening, so armed with a few prints of what the tool should look like I headed out to the grinding shed to do my first ever tool grinding. I did a bit of practice on some wood first to get the hang of how to present the tool to the wheel and then bosh bash bish - all over in 30 seconds. Freehand tool grinding is something I've avoided until now, I've relied on carbide cutters so far, but it was pretty easy - I'm not saying I produced a perfect profile and the sharpest tool in Shed-dom but it wasn't bad and after a skim with a diamond stone it cut like a dream.





http://picasaweb.google.com/lh/photo/0B3KjSTDz2yaS8uJWKUQwg?feat=directlink





http://picasaweb.google.com/lh/photo/ewbvBh_VNhEUZLBPn-1glg?feat=directlink





http://picasaweb.google.com/lh/photo/VKqgqJcdrJHLn7qLkFpceg?feat=directlink





http://picasaweb.google.com/lh/photo/YqLEvUUMd4ClzlaWKEcHdA?feat=directlink



Back in the garage, I set the work square in the vice using a dial indicator, and found the start point where the cutter would be just touching the workpiece, noted the values on the crossslide and the leadscrew dials and worked out what the finish values on the dials needed to be. The intension being to skim 2mm deep for a length of 450mm. I prefer to work off dial values rather than marking the workpiece up, avoiding having to peer intently at the work as the cutter and chips fly past.

I performed the pre turn on checks, everything tightened up, slide moved through the cutting range to check nothing would hit the cutter, all moved back to the start and away.

I increased the depth by 10 thou on each pass (The saddle lock was used when cutting) and set my dial indicator on the bench as a tell tale for the crossslide movement, for the 450mm travel on my ML10 this was 17 (and a bit) full rotations of the slide screw and I'd rather have the D.I. telling me when I was close to the end rather than lose count.

The work was set above the centreline of the cutter to ensure that the forces were pushing against the crossslide screw rather than pulling into the backlash. So once the full depth had been cut I moved the vertical slide up and then moved it slowly down through the cutting zone to give a straight end to the cut.





http://picasaweb.google.com/lh/photo/qbUUR8VHJN4fmUralQNrPw?feat=directlink





http://picasaweb.google.com/lh/photo/Br_VFRrWJMKk72MpklAjdw?feat=directlink

Not the best finish - oh well :-\

Any comments are welcome, my skin is thick enough for forum banter but I don't want to risk it on the lathe


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