# Internal Threading Tool And Flycutter



## mattthemuppet2 (Dec 14, 2015)

couple of little projects, one intentional and one not 

I need an internal threading tool to thread the chuck backplate I'm making, so I got a piece of scrap (ex-treadmill roller rod) which had a handily sized hole in the end and make this:


the rod was 7/16 or thereabouts and turned down to fit the 3/8 bore of my tool holder. If I need a longer one I'll just make a new tool holder so I can adjust stickout. Hole was filed (poorly) square and a set screw put in the end. Cuts PVC very nicely! I need to get another project done before trying it out on steel..



The unintentional project was the flycutter. I set out to make a copy of my lathe spindle nose to use to check for fit on the backplate I'm making, but cut the blank 1.5thou to small. After sleeping it off, I decided to make it into a flycutter instead, which I've been meaning to make for ages. Lots of different designs, but I liked the look of the dual cutter type, where you have a rougher and a finisher cutter. The rougher having less nose radius is a little higher and (theoretically, I need to check) a little further inboard, so it takes a chunk and then the finisher shaves the final few thou. That's the theory anyway.

finisher shown



rougher shown. Cutting edges are about 1 1/8in apart, give or take
	

		
			
		

		
	



cutting bits are 2 pieces of cut down 1/4in drills that some previous owner ground really weirdly. Drilled undersize with a D drill and then finished with a 1/4 reamer (1st time ever!) after drilling and threading the 8-32 set screws. Bits were a tight sliding fit, so they're not going anywhere.

Finished off by heating and dunking in oil for rust prevention. No effect on hardness as it's mild mystery steel scrap



the results! Took a bit of fiddling with cutting angles to reduce chatter (far left) but I ended up with what is a very good finish (close to) for my drill press pretending to be a mill.
	

		
			
		

		
	




close up. Still a wee bit of chatter (don't forget, drill press+collet chuck+heavily modded HF XY vise!) but it feels smooth and looks waaaay better than any surface finish I've managed before. Once I get the treadmill motor on my drill press I'll play with speeds a bit more - this was ~800rpm and seemed to work fine in alu, but would be way too fast for steel, if I even dare to use this cutter on steel.
	

		
			
		

		
	




now I just need to make that spindle nose copy


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## brino (Dec 14, 2015)

Hi Matt,
Neat dual fly cutter.....I've never seen one like that!
-brino


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## mattthemuppet2 (Dec 14, 2015)

thanks Brino! It's not a common design, but one of its purported benefits is less hammering as there should always be 1 tool in the cut at any time. As I'm working waaay out of my machine's envelope I figured it would be worth a shot. Less milling to make it too


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## Ulma Doctor (Dec 14, 2015)

nice job matt,
looks like the flycutter is doing the job!


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## alloy (Dec 14, 2015)

I like the design of the fly cutter.  I'm going to need a spot face tool for an aluminum housing and I can use your design to make one.


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## mattthemuppet2 (Dec 14, 2015)

thanks guys! It's going to be way quicker to get stock square and flat with this than a 3/8 end mill 

I never thought of that alloy, what an awesome idea. You could theoretically make a spot face tool for pretty much any size and a pilot wouldn't be hard to add either.


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## alloy (Dec 14, 2015)

Hadn't thought of a pilot.

The hole will be plunged with a 1.75 end mill, then bored to 1.765 with my boring head.  Then I need a shallow spot face 0f 2.060.  Thought of getting a 2-1/8" end mill and have it ground to the correct size,  but I think a spot face tool would be easy to build and much less expensive.

But my first problem is fixturing the housing up to machine it.  The hole isn't at a right angle, in fact it's at a compound angle.   Still thinking about how to do it.  I may post a pic of it and ask for ideas.


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## mattthemuppet2 (Dec 15, 2015)

also think about chatter too - at full plunge you're going to have a really wide cutting surface, just like on a countersink. Not sure how to deal with that, but something to consider


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## JimDawson (Dec 15, 2015)

mattthemuppet said:


> also think about chatter too - at full plunge you're going to have a really wide cutting surface, just like on a countersink. Not sure how to deal with that, but something to consider



Ridged setup, and turn it slow!


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## alloy (Dec 15, 2015)

The spot face will only take about .050 in depth, and be .100 wide at the outside of a hole.   I'll take a pic later and post it.


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## alloy (Dec 15, 2015)

Ok, not trying to steal your thread, but here is a pic of the spot face I'm going to need to do.


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## mattthemuppet2 (Dec 15, 2015)

interesting! I can see how that would be tricky to set up. One way you could make a spot facer for that would be to turn a cylinder to fit the OD of the spot face, then turn the end down to fit the ID. Turn the other end to fit whatever collet you want it to go in (3/4?). Then mill 2 opposed 1/4in slots down the sides, ideally offset so that the cutting faces will be on the centerline. Add setscrews. Then you can grind 2 1/4in lathe bits and be able to position them for both depth (move them length ways along the tool) and cutting width (shim them out from the tool centerline) to tweak the cutting diameter.


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## alloy (Dec 16, 2015)

That's a good idea.   I'm gathering tools now for the project.  I got a 1.75 end mill with a 3/4" shank off Ebay for $10 plus shipping.  I'll use that to plunge in, then use my boring head for final diameter.  

But again my biggest problem is fixturing it.  I'm guessing the hole is probably 20 degrees positive in one direction, and the same in another direction.  
My plan to get the hole perfectly vertical is to take a 2" piece of stock and turn a 3/4" spud on it to go into my collet on my mill, then turn the other end to fit tightly into the hole.  I'll put  a shoulder on it and it will bottom on the spot face, and I'll drill an tap that end and make a strap clamp I can put inside the housing to clamp it to the end of the rod.   This will get the hole vertical, then I need to square it up in Y axis.  

Next comes trying to design a fixture that will hold it tilted it to the right.  That gets the face of the housing secure.   Then the second fixture will both up to the transmission mounting holes with a forward tilt to it.  The position needs to repeat accurately.  What I'm doing is duplicating the hole you see in a housing in a similar housing that is cast for it, but isn't machined.  

I hope my description isn't to hard to follow.   If I can get the rod turned and mounted in the mill with the housing on it and take a pic, it will be much easier to understand.


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## mattthemuppet2 (Dec 16, 2015)

that's tricky - I wonder how they would have done it at the factory? Are there any reference surfaces in the original that you could use, if only to make a fixture? Or once you have the new housing secured to the spindle with your spud, use jack screws to support the housing at the right angle then bolt it to the table?


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## JimDawson (Dec 16, 2015)

mattthemuppet said:


> I wonder how they would have done it at the factory?



Use a 6 or more axis machine with articulating heads.  

I would build a spud that fits the hole and the other end in a collet in the spindle.  That would hold the housing in position.  Then build up a fixture that bolts to whatever convenient holes you have available.  Build the fixture from the bolt holes down.  Bolt the fixture together until you can get it off of the machine and over to the welder.


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## alloy (Dec 16, 2015)

Jim, I just need you to build that 5th axis we talked about and I can farm the work on this out to you 

I'll make the spud as soon as I find a lathe to use.  I don't have a 3 jaw for mine yet, just the 5C collet closer.

I have another housing I do and I attach it to a fixture plate that's bolted to a 6" angle plate.  I ream 2 holes in the housing for accuracy, and they go onto 2 dowel pins on the fixture.   I want to do the same thing on this one.  

The spud will give me a perfectly vertical hole, then I'm thinking of bolting a plate onto the mounting holes on the housing where it bolts to the back f the trans.  The I need to square it up and figure a way  to attach it to the table parallel to X axis.   I am considering making a large plate that will register on the T slots and have both the fixture plates parallel to X and Y on it.  Then I just put the fixture on and it will be square, bolt it down, and dial in my origin point.  It will cost more for materials, but will be much easier to set up that 2 separate fixtures.

I'm still thinking of how to do this.  I have about 10 days off at Christmas and this is one thing I'm hoping to work on.


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## JimDawson (Dec 16, 2015)

I think I know somebody with a lathe and a chuck


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## alloy (Dec 17, 2015)

I'll take you up on that.  

Would be nice to brainstorm how to make the fixture.


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## alloy (Dec 19, 2015)

Went out to Jim's yesterday and got the spud made.  We were looking at the housing and Jim came up with the idea of using the angle mount that came on the Acer mill head I got at the auction as a fixture.   I had thought about an angle plate but a 12" one was expensive.  So this will work perfectly.

The idea is to use jack screws with a swivel base to set the angle on the angle plate.  So I'll just need to square the plate up, dial in a corner and go the the position where the hole needs to be machined.

I trammed the head in on the Kent today and used it to set everything up.  I'm not using it right now, am waiting for the DRO to come in. So it's not a problem leaving the fixture on it while I order parts in to finish up everything.

The hole looks like it's about 16 degrees to the right, and with tilting the angle plate I can just rotate the housing on the plate to get my second angle.    Started drilling the holes to mount the housing to the plate and realized I didn't have a 7/16" tap.  So  I'll find one and work on it tomorrow hopefully and order in the jack screws.


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## mattthemuppet2 (Dec 19, 2015)

that's a neat solution - it'll be fun to see the finished product!


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