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Cutting small groove on the lathe ??...

56type

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#1
I have a gunsmithing project I'm working on and one of the thing I need to do is cut a small groove (0.095 wide X 0.086 depth) into the work piece. The tool bits I have are the pre-ground 1/4" in. set from littlemachineshop.com that includes the LH & RH cutting bits, parting bit, round nose cutting bit, 45 degree chamfer cutting bit, and boring bit. Also using the lantern tool post and toolholders for same.

My question is can I use any of these tool bits to cut the grove to the measurements I listed or will I need to special grind a tool bit for it ?? Complete newb and this is the first project I'm attempting on my new-to-me Atlas 10100 Mk.2 so I know "Zilch" when it comes to tricks & tips to make the cut I need. Here is a pic of what the finished product should look like...Notice the groove about middle of the piece. That's the one I need to cut. Thanks.

 

ghostdncr

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#3
I've often wondered why they chose to put that groove in there. I've only ever seen this thread protector used on commercial "post-ban" AK variants sold in the US, so it's not like a suppressor interface or anything like that. Perhaps it simply serves as clearance for machining the wrench flats on the end during the manufacturing process?

Anyway... Travers Tool usually has great prices on square tool blanks for these projects that need a custom grind. Here's a link to their page showing regular M2 and cobalt HSS blanks. At these prices, I think it's worth keeping a half dozen or so lying in the toolbox: http://www.travers.com/square-ground-tool-bits/p/37616/?
 

David S

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#4
My parting tool is 0.040" wide. I use if for similar applications cutting O-ring grooves and cir-clip groves. Choke the cutter up so very little sticks out from the tool holder, cut to almost finished depth in a couple of passes, and the final finishing pass can be made by running the parting tool with the X feed.

David
 

56type

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#5
I've often wondered why they chose to put that groove in there. I've only ever seen this thread protector used on commercial "post-ban" AK variants sold in the US, so it's not like a suppressor interface or anything like that. Perhaps it simply serves as clearance for machining the wrench flats on the end during the manufacturing process?

Anyway... Travers Tool usually has great prices on square tool blanks for these projects that need a custom grind. Here's a link to their page showing regular M2 and cobalt HSS blanks. At these prices, I think it's worth keeping a half dozen or so lying in the toolbox: http://www.travers.com/square-ground-tool-bits/p/37616/?
The reason the groove is there is to serve as a "locking mechanism" for the cleaning kit cap that serves as a bore guide for use with the included buttstock cleaning kit. It works like this...Take the cap off the cleaning kit included with the rifle, you'll notice it has a small dimple in it that engages a notch in the cleaning kkit body that retain the cap on the cleaning kit. Those "wrench flats" are actually clearance cuts to allow the dimple in the side of the cap to pass over the forward end of the muzzle nut, then the cap is turned 90 degrees relative to the flats which locks the cap to the muzzle nut. The steel cleaning rod is then guided down the bore of the rifle by passing it thru the small hole located in the end of the cap. The cap should be placed on the cleaning rod before attaching the bore brush/cleaning jag, then carefully started into the bore, slide the cleaning kit cap down the cleaning rod and lock it into the muzzle nut.

Curiously the same groove is present on the traditional "slant brake" for the same purpose. Thanks for the link, I really NEED to get a bench grinder and learn to start grinding my own tool bits.
 

56type

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#6
On using the parting tool for this cut...My parting tool bit is not the blade type but looks more like a mini LH cutting bit. So it has that slight angle on the front tip that would make it cut deeper on one side than the other when cutting a groove. If I narrow it to the width of the groove to make the cut (it's listed as 0.1 in. wide and I need 0.095) in a simple, single, plunge type cut, can I also remove the front angle so it will cut "square" ?? Or would removing that angle destroy it's ability to cut ?? Here's a link to the tool bit in question...Thanks for all the help.

http://littlemachineshop.com/products/product_view.php?ProductID=1969
 

David S

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#7
Ok I guess what I am using are what LMS calls cut off blades. I use them in the parting tool holder for the QCTP. On one end I grind it square and on the other end I have a slight angle on the tip so that it doesn't leave a tit on the cut off piece.

I don't see any reason that you can't grind the tool end square, and make it narrower and then plunge cut the groove.

David
 

ghostdncr

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#8
Well, thanks for the schooling on that thread protector! I'm in Louisville and just noticed you're in the Salem area. We're practically neighbors! I've owned a few AK's but apparently have never tried cleaning one full-on military style. Unless you're running a serious production shop and using all inserted tooling, I strongly recommend picking up a bench grinder and learning to dress your own cutting tools. A HSS blank's possibilities are mostly limited by your imagination and ability to work up a proper edge. I've got a drawer full of profiles I've ground over the years for a specific cut and oddly enough, I'll sometimes pick one up and remember the job I ground it for twenty years ago. Can't remember what I had for breakfast yesterday, though...
 

mikey

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#9
On using the parting tool for this cut...My parting tool bit is not the blade type but looks more like a mini LH cutting bit. So it has that slight angle on the front tip that would make it cut deeper on one side than the other when cutting a groove. If I narrow it to the width of the groove to make the cut (it's listed as 0.1 in. wide and I need 0.095) in a simple, single, plunge type cut, can I also remove the front angle so it will cut "square" ?? Or would removing that angle destroy it's ability to cut ?? Here's a link to the tool bit in question...Thanks for all the help.

http://littlemachineshop.com/products/product_view.php?ProductID=1969
I think our terminology needs to be clarified. The link you posted shows a HSS ground parting tool upside down. The angle in front of the tool is called a relief angle. Most of these tools will have a relief angle of about 7-8 degrees to allow the tool to cut just at the upper edge. Most are also ground square across the front edge and will have a few degrees of clearance ground along both sides.

If you grind this tool, you simply need to thin it a little. A grinder would make it faster but you can also do it by hand with a coarse diamond stone. Maintain the side relief angle and just grind the outside flat until you are under your required groove thickness.

Hope this is clear.
 

56type

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#10
I think our terminology needs to be clarified. The link you posted shows a HSS ground parting tool upside down. The angle in front of the tool is called a relief angle. Most of these tools will have a relief angle of about 7-8 degrees to allow the tool to cut just at the upper edge. Most are also ground square across the front edge and will have a few degrees of clearance ground along both sides.

If you grind this tool, you simply need to thin it a little. A grinder would make it faster but you can also do it by hand with a coarse diamond stone. Maintain the side relief angle and just grind the outside flat until you are under your required groove thickness.

Hope this is clear.
The angle I'm referring to is the one facing the "111" in the pic below. In the pic the tool bit is positioned as it would be in the tool holder. That angle that increases from left to right is the one I am wanting to remove to square up the tool bit so it doesn't cut the groove deeper at one end than the other, if it can be done without destroying the tool bit's cutting ability...Is that what's referred to as the Relief angle ?? or does relief angle refer to the angle that in all the pics of tool grinding is below the centerline of the workpiece and angles back away from the uppermost cutting edge ??

Hope I'm not confusing the terminology further with my description on the angle in question...

 

mikey

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#11
You're right; the relief angle is the angle underneath the cutting edge. That angle that increases from left to right can be ground off so the front is flat with no angle. Then you just need to thin it a little and again, I would just thin it from the right side with a diamond stone.
 

jbolt

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#12
I use the Nikcole Mini-System tools for small grooves, parting thin wall tubing and fine pitch threading . They have grooving inserts from .019" to .073".

7868099AD-24.jpg
 

bfd

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#13
ive seen hacksaw blades mounted to a piece of steel (keystock) used to cut grooves. the thin hacksaw blades cant be used to move back and forth to clean up the bottom but you might have a larger power hacksaw blade. anything that is made of hss and can be mounted to your lathe will work. make sure you use the teeth side of the blade. ( newer blades are weld edge and the back side is just carbon steel and wont work. you could even use an old file ground on the front to what you need and mount it somehow on your lathe and cut your groove. go slow though files are high carbon steel and wont take the heat. any thing that will cut steel will work. bill
 

56type

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Actually been making some progress on this,though rather slowly as I'm taking my time and trying not to rush/break anything. Seems to be coming along good just discovering more tools/accessories I could use to make the job easier (like a carriage stop). Still need to drill it to the final bore dimension & thread it 14x1mm LH (have a tap for that). Then cut the flange the muzzle device locking pin will engage once the flange is notched like the in the pic...

 

56type

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#15
ive seen hacksaw blades mounted to a piece of steel (keystock) used to cut grooves. the thin hacksaw blades cant be used to move back and forth to clean up the bottom but you might have a larger power hacksaw blade. anything that is made of hss and can be mounted to your lathe will work. make sure you use the teeth side of the blade. ( newer blades are weld edge and the back side is just carbon steel and wont work. you could even use an old file ground on the front to what you need and mount it somehow on your lathe and cut your groove. go slow though files are high carbon steel and wont take the heat. any thing that will cut steel will work. bill
Thanks...I've been thinking of using something similar for parting. Just need to make a bracket that will hold a spring to keep tension on the blade to keep it cutting.
 

bfd

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#16
you keep tension on the blade to keep it cutting by feeding the cross slide forward as the tool cuts keep cutting fluid on it and keep it feeding toward the stock. you don't need a spring. maybe I just don't understand what you are saying bill
 

56type

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Here's a video I believe was posted by another member show the set-up I was referring to...
 

bfd

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#18
I saw that and thought it was for cutting off parts could work to cut grooves what I'm talking about is cutting a short piece of hacksaw blade off the end and machine a piece ok keystock to allow the hacksaw blade to sit in the groove set the hole in the blade to screw it to the keystock then sharpen the end like a square nose parting tool and use it to cut the groove it will be better if you could find a used industrial power hacksaw blade its thicker and would therefore be stiffer. bill
 

kd4gij

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#19
There is a wright up on here some where they cut cutoff blades from carbide tipped circular saw blades.