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Happy Camper
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Discussion Starter · #1 ·
Anyone done this? This is a groove inside a bore that runs parallel to the axis (linear) vs. alond the radius like threads.

The store's keyway broach sets are pricey:

http://www.grizzly.com/catalog/2004/483.cfm?

I'm thinking about using a dremel 90-degree cutter head, and mount this along a piece of PVC pipe that is fitted to the ID of the bore, and use a simple routing bit to cut into the material. The PVC would be the "jig" to ensure the router bit stays in the correct location, then just run it up/down the bore of the tube.

If this doesn't work, I'm thinking about cutting a slit down the bore, then putting a shim of some sort down it that will mimic a keyway.

Any other ideas? I don't want to spend a great deal of time building a tool...
 

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Internal keyways are usually broached. If the torque load is not high you can use a round key(rod) and drill the keyway. What is the bore dia. and what is your application? The other way is to put a round bar in the bore, drill a round hole and then square it up with a file.

Enco sells individual broaches.
 

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Happy Camper
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Discussion Starter · #3 ·
Thanks, Plinker! For the helical Bizon mag I'm working on. It just needs to reliably guide that follower, and be small enough so that 9mm and 7.62x25 bullets don't lodge in the keyway. ;)

I'm working with a 2-inch bore and need a relatively small keyway to guide a follower up/down the bore.

I'm going to work with the low-tech approach for now, because the prototype is plastic and is relatively easy to work. It certainly doesn't need to be hi-tech and could even be off-bore. I think I've figured out a nice low-low-tech way to get a normal saw blade (!!!) to do the job. Later on, whether I use a plastic of some kind or aluminum, the saw blade should still be able to make the groove and therefore should work for the production batch.

- Jerry
 

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was thinking maybe stacking some fine tooth hacksaw blades might work , some thicker wall 1/2" or 3/4" pvc tubing slit long wise to act as a clamp along the spine for the blades - then you could change widths of your cut as you please . could ever drill thru the pvc every couple of inches to slide small bolts/screws thru to act as retainer clamps and to hold the depth and tension on the blades equal in the pvc. maybe ever be able to mount the wholw thing on hacksaw frame for trueness???......poor mans keyway broach....
 

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Another way is to make a single point tool to mount in your mill. With mill not rotating, use spindle feed to move it up/down and feed part with table feed. Would work like a single tooth broach.
 

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combine carguy and samuel and you have a prety dam good way to rough cut quick and end up with an accurate result.
 
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