Author Topic: Fly cutters  (Read 19319 times)

Offline BaronJ

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Fly cutters
« on: March 01, 2014, 02:23:34 PM »
Hi Guys,
I posted this as part of another thread but since I seem to be making fly cutters lately I thought I'd post it/them here.
The first one is a simple 1/2" inch thick disc, in this instance stainless steel, with a 2.5" inch length of 16mm silver steel rod for a shaft, turned down on one end to be a press fit into a 1/2" inch hole drilled in the centre and an 8mm hole drilled near the edge to hold a 6mm square toolbit secured with a 2Ba grub screw.  There are a couple of pictures of the toolbit cutting edge.
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                     Baron

Offline BaronJ

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Re: Fly cutters
« Reply #1 on: March 01, 2014, 02:35:16 PM »
Hi Guys,
This is the second fly cutter.  Similar to the first one but intended for a different job.  Here I used a cast iron disc 3" inches in diameter with a milled a slot to hold a 6mm toolbit horizontally the tool bit is held in place by two M4 grub screws.  Also I used a M10 threaded spindle cut from a short length of 1/2" silver steel rod so that I could use the spindle for another job. 


I think that I cut the threaded part a bit small since the threads have a flat top on them.



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                     Baron

Offline rick barnes

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Re: Fly cutters
« Reply #2 on: March 01, 2014, 03:00:01 PM »
Still need to make one of these.  Mine does not perform as well as it could.
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Offline BaronJ

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Re: Fly cutters
« Reply #3 on: March 01, 2014, 03:08:30 PM »
Hi Rick,
They are pretty easy to make.  Both these were made with scrap bits culled from various places.  The second one using a cast iron disc is more complex but still not difficult.


As you can see from the pictures I made a small error in the diameter when turning down for the M10 thread but it fastens securely and buts up to the flange dead square.


I'll take some more photos of the second one showing the toolbit and fastening screws.


 
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Offline rick barnes

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Re: Fly cutters
« Reply #4 on: March 01, 2014, 06:57:08 PM »
I was thinking of making a head I can attach to my Taig slitting arbor.  Then I just have to make the disc.  I should start a list of what to make, so I quit forgetting what I need when I get in the shop. 
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Offline Brass_Machine

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Re: Fly cutters
« Reply #5 on: March 01, 2014, 09:05:03 PM »
Hi Baron,

Those look pretty stout. How do they cut?

Eric
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Offline BaronJ

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Re: Fly cutters
« Reply #6 on: March 02, 2014, 10:35:13 AM »
Hi Baron,

Those look pretty stout. How do they cut?

Eric

Hi Eric,
Do you mean my fingers or metal. ;-)

It really depends on the toolbit shape and angles.  I did some tests with a semicircular tip on BMS and got good results, on cast iron just have a look at the second fly cutter pictures.  I found that a sharper edged toolbit seemed to be better on aluminium and a much higher speed around 1000 rpm.  I did try an uninterupted cut of 0.5mm on a piece of black plate, fairly low speed but found that the mill struggled quite a bit.  A learning experience really, discovering what the mill was capable of without pushing it too hard.

 
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Offline BaronJ

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Re: Fly cutters
« Reply #7 on: March 02, 2014, 10:46:58 AM »
Hi Guys,
Here are the rest of the photographs as promised of the second fly cutter.  You can see a couple of mistakes that I made along the way, though neither affect how the cutter functions.  They seem quite rigid since the shaft goes completely into the collet or drill chuck.


   
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                     Baron

Offline BaronJ

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Re: Fly cutters
« Reply #8 on: March 02, 2014, 11:08:17 AM »
I was thinking of making a head I can attach to my Taig slitting arbor.  Then I just have to make the disc.  I should start a list of what to make, so I quit forgetting what I need when I get in the shop.


Hi Rick,
I would be a little cautious about using an existing arbour.


The first one shown has the 16 mm silver steel shaft turned down to form a shoulder, the spigot of which is a good press fit into a 1/2" inch hole drilled in the disc.  Also the disc of this one is a bar end offcut of 314 stainless steel.  Which is why I avoided trying to thread a large hole in it and used a press fit.  This stuff work hardens if you look at it the wrong way.  Drilling the smaller holes wasn't too bad, but you have to keep the drill cutting.  The hole for the grub screw tapped easily.


If I were going to make another I would definitely go for BMS or cast iron for the disc.  I also would drill a second hole for a toolbit 10 or 15 mm further in.  Then I would drill and tap the grubscrew hole right through both.


This fly cutter was designed to cut a 65 mm diameter surface and it would have been useful to have a second tool position for a smaller diameter.





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                     Baron

Offline rick barnes

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Re: Fly cutters
« Reply #9 on: March 02, 2014, 02:47:29 PM »
The diameter is about 30mm, so it's pretty small.  Is there a danger in the existing arbor, or a accuracy problem? 
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Offline BaronJ

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Re: Fly cutters
« Reply #10 on: March 03, 2014, 03:42:31 PM »
Hi Rick,
No problem using an existing arbour !

Just me typing some distracted thoughts.  I really ought to go and delete those words.  Sorry !

When you say "the diameter is pretty small"  do you mean the arbour or the cutting diameter.  I only used 16 mm silver steel for the spindle on the first one because it was to hand.  The second one was 1/2" turned down so I could put a M10 thread on the end.

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                     Baron

Offline rick barnes

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Re: Fly cutters
« Reply #11 on: March 03, 2014, 10:05:26 PM »
No, the cutter holder will only have a diameter about an inch and 5/16th the cutter will be 1/8 square.  Mostly because I enjoy making square holes... I was afraid it would jump off and bite me.  I have the head socketed into a shoulder on the arbor, and a countersunk screw holding in place. I'm hoping it will run true.
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Offline BaronJ

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Re: Fly cutters
« Reply #12 on: March 04, 2014, 04:01:48 PM »
Hi Rick,

It won't matter if it wobbles a bit.  That is from side to side.  If it wobbles up and down you may not get a surface that is square to the table.

Re the arbour, I really would consider making one.  That way you can ensure that it is true and square.  I trued up both cutters in the lathe after attaching the spindle.

Which reminds me of why I mentioned caution a couple of posts back.  With an interrupted cut the spindle will get hammered once or twice per revolution.  This will have the effect of tightening the countersunk screw to the point where you may not be able to undo it.  On my slitting saw mandrel I have ground a pair of spanner flats so that I can release the saw when it tightens up to the point of twisting the hex out of the screw.



Talking about slitting saw mandrels, I have to make a new one !  I got a new 150 x 1.0 x 72T x 32.2H today and don't have a suitable arbour to fit it.  I intend to use a short length of 16 mm silver steel and use a threaded collar to retain the saw blade.


 :proj:



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                     Baron

Offline rick barnes

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Re: Fly cutters
« Reply #13 on: March 04, 2014, 09:21:50 PM »
Does silver steel need to be annealed prior to threading with a tap?  When making the head, I finished it on the arbor.  It is accidentally indexed with a drill bit.  But I see your point about not having a dedicated way to mount it.  I have some 0.685 drill rod I may make the mandrel with. 
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Offline BaronJ

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Re: Fly cutters
« Reply #14 on: March 05, 2014, 04:31:41 PM »
Hi Rick,


I'm not sure that there is any difference between silver steel and drill rod,  either way the only time that I heat up silver steel is when I am making a tool that I want hardened so that it will cut BMS or black bar.   The threads on mine were cut without any preparation other than turning to size and using cutting compound.


The attributes of "Silver Steel, Drill Rod and Gauge Plate" are that as you buy them they are soft, ie machinable, ground accurately to size and able to be hardened by heating to a specific temperature, often described as "Cherry Red or Bright Red" and then quenched in oil or water.  You can buy grades of these steels that are intended to be water quenched and those that are intended to be oil quenched.  It usually specifies on the package wrapper exactly what temperature you should heat up to, to obtain a specific hardness and how long and at what temperature to anneal at.


I have only used these steels because I happened to have them to hand.  You could equally well use anything convenient to you, particularly if you have a scrapyard or engineering works accessible.


I hope that you are going to take some photos of your work.  It would be nice to see them.


 
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                     Baron

Offline rick barnes

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Re: Fly cutters
« Reply #15 on: March 05, 2014, 11:33:58 PM »
Silver steel and drill rod share every property but name and geography.  Same stuff.  I have a nice scrapyard.  They keep the aluminum inside and charge $1.50 per pound. The steel is outside.  In Michigan, so I'll get back with you on that in a month or so. :-).   I have yet to take photos because my iPad takes poor resolution photos, and that coupled with how much my hands shake don't really provide a picture worth a thousand words.  Maybe 10.
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Offline BaronJ

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Re: Fly cutters
« Reply #16 on: March 06, 2014, 03:49:57 PM »
Hi Rick,
There are a couple of guys on this forum that use an Ipad to take pictures. 
I've got the bar to make the new slitting saw arbour and just need some time to turn the blade holder up.



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Offline Arbalist

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Re: Fly cutters
« Reply #17 on: March 07, 2014, 05:36:29 AM »
I have a third gen iPad and picture quality is very good provided there is enough light.

Silver Steel is specifically BS1407 here in the UK and is supplied annealed.

http://www.silver-steel.co.uk/aboutsilversteel.php

Drill Rod in the US can be one of at least three or four different steels each with different hardening requirements, ie Air, Oil or Water hardening.

Offline rick barnes

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Re: Fly cutters
« Reply #18 on: March 07, 2014, 06:05:00 AM »
It's either the poor light or my hands.  I usually snap three or so pictures and pick the best one.  Just always seem pixelated. My drill rod is O1, and annealed.  I checked.  Put a 1/2-40 thread on it last night.  Learned a smooth surface is a good idea for threading.  I'll try finding better lighting and try to send some pictures. 
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Offline rick barnes

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Re: Fly cutters
« Reply #19 on: March 07, 2014, 06:06:15 AM »
Oh, fly cutter is done.  The 1/2-40 thread was for another tool I'm messing with. 
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Offline BaronJ

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Re: Fly cutters
« Reply #20 on: March 08, 2014, 11:37:17 AM »
Oh, fly cutter is done.  The 1/2-40 thread was for another tool I'm messing with.


Oh good ! Are we going to get to see it ?  :palm:
Isn't 1/2" - 40 a micrometer thread ? It seems very fine, what are you doing with that I wonder...


I got some more cast iron discs yesterday.  These are only 2" x 1/2"  but its lovely close grained metal.  I wish I could get a billet of the stuff...  Well beggars can't be choosers.  :thumbup:

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                     Baron

Offline Arbalist

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Re: Fly cutters
« Reply #21 on: March 08, 2014, 11:44:42 AM »
I push my Fly Cutter quite hard at times so use inserts now so I don't have to sharpen so often! Still use HSS sometimes though.


Offline rick barnes

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Re: Fly cutters
« Reply #22 on: March 09, 2014, 04:16:55 AM »
I got pictures

My fly cutter

Not quite happy with the finish yet.  Working on cutter geometry



The use of the 1/2-40 thread.  To make a jig/fixture to cut 40 tpi in any diameter on my taig lathe that has no threading capabilities as sold

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Offline Arbalist

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Re: Fly cutters
« Reply #23 on: March 09, 2014, 06:19:06 AM »
To ensure pictures taken with an iPad appear the correct way round the lens needs to be at the top left corner as you hold it in landscape mode. DAMHIKT.

Offline BaronJ

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Re: Fly cutters
« Reply #24 on: March 09, 2014, 01:51:09 PM »
I push my Fly Cutter quite hard at times so use inserts now so I don't have to sharpen so often! Still use HSS sometimes though.




Nice !  I like the round insert.
I can see me trying that on the end of a bit of 3/8" round in my disc fly cutter.
What is the insert ?



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                     Baron