How to make a slot inside a cylinder ?

[compact8]

I am trying to make several slots of width 2.5 mm and length 14 mm on the inner face of a brass cylinder as shown in the photo. This is not a keyway as the slot does not go all the way to the other end. I have tried to use an extended 2.5 mm carbide end mill to do the cutting in four steps with each one cutting 1/4 of the total length but I end up in having steps on one side of the slot. Function wise this is OK but I am just wondering if there are better ways to do it.

 

[jwmelvin]

There appears to be a relief on the bottom of the part (far end of the slot) such that broaching would be possible, like a key way.

The steps show something is out of tram or moving between passes. I’d check machine alignment. What machine?

A smaller cutter would let you rough like you are (several depth steps of full radial slot) and then side mill or plunge to clean up the full depth slot. If the cutting length isn’t sufficient on your tool, seems like plunging would be the only option, and that will leave some further cleanup to do.

 

[compact8]

There appears to be a relief on the bottom of the part (far end of the slot) such that broaching would be possible, like a key way.

The steps show something is out of tram or moving between passes. I’d check machine alignment. What machine?

A smaller cutter would let you rough like you are (several depth steps of full radial slot) and then side mill or plunge to clean up the full depth slot. If the cutting length isn’t sufficient on your tool, seems like plunging would be the only option, and that will leave some further cleanup to do.

The machine is a EMCO FB2, so just hobby grade. The alignment of the machine and the squareness of the head is good though. I think the steps are caused by the flexing of the tool. Will try plunging on the next piece ( need to make 4 in total ).

 

[mmcmdl]

Predrill it and then plunge to full depth with that endmill .

 

[Bi11Hudson]

If the project were longer, I probably would attempt something with the shaper. For that short of a job, I would make a slug to a snug fit out of a similar metal, then drill and/or mill the slots as needed. A similar metal to prevent the drill from drifting. That's just my take on the job and not a recommendation. Finishing could be with most anything from a scraper to a broach to a reamer.

I have built a sacrifical slug many times when working with offset centers on pipe and existing cylinders. Never needed to slot something like that but the answer is about the same.

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[mmcmdl]

Also , hard to tell by the pic , but it doesn't appear the end mill is undercut or relieved below the cutting flutes . If not , that will leave you those visable steps .

 

[tq60]

Put it in the lathe and make a plunge cutter and place it in tool holder.

Use like shaper

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[Weldingrod1]

If the rounds are not functional, you could do it with a keyway broach and a carrier with an indexing pin/key added.

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[rabler]

The endmill is turning clockwise, so when cutting from the center of your part outward it is deflecting to the left, bending your endmill to the left. The amount of deflection depends on the load and the flexing of the tool and mill. So more depth of cut, rate of cut, and smaller tool (especially long length to diameter) will increase that effect. Since an endmill turning clockwise, it always deflects 90 degrees counterclockwise of the cutting face when side milling. Stiffer endmill (carbide vs HSS) will reduce it.

Several approaches to work around this.
Drilling, or plunging with an endmill into full material (not on an edge) balances the sideways load on the endmill so it is purely twisting. Actually any plunge that is symmetric around the center of the endmill will be pure torque. Taking smaller cut steps would reduce the sideways force. Another way to do this is to use a 2 mm endmill and cut the right (clockwise) edge in steps, then shift over counterclockwise by .5 mm and cut again, being careful to cut no deeper than the first pass.

 

[compact8]

If the rounds are not functional, you could do it with a keyway broach and a carrier with an indexing pin/key added.

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That's interesting. In fact I don't want those rounds. I have got hobby-grade machines only : an EMCO FB2 milling machine and a EMCO Compact 8 lathe. Will it be doable ?