How to mill a slot without a mill?

[Jimsehr]

I've got a piece of round aluminum which has a 1/4" wide by 1/4" deep slot axially milled into it. I need to make the same size slot 180° on the other side, problem is I don't have a mill .

I could try it on the my drill press using a chucked end mill or mortising bit, the spindle does have a DIY drawbar so it won't fall out, but it's hard on the machine, even with lots of light passes.

I have a mini lathe with a milling attachment, not sure if the vise is big enough to hold the workpiece, and there's barely enough cross slide travel, I may have to stop and and move the piece in the vise.

My best bet is having someone with a mill do this, I'll keep trying to locate someone.

Suggestions solicited, thank you!

View attachment 504793

Is there a hole or bore clear thru the part?

 

[Eddyde]

Yes, I have an X-Y table on the drill press, I may try that approach first.

Use a 2 flute end mill, run the machine fast a possible, take light .01-.02 cuts and use WD 40 for lube.

 

[ChazzC]

Yes, I have an X-Y table on the drill press, I may try that approach first.

In addition to using the X-Y table I’d urge you to get an ER16 or ER20 collet holder to suit the taper on your drill press spindle rather than gripping an end mill in the chuck. You still have the issue of lateral loads on the taper without the benefit of a drawbar, but there won’t be the added problem of the hardened end mill shank slipping in the chuck jaws.

EDIT: There’s a current thread on “creating” a through hole on a drill press spindle:

https://www.hobby-machinist.com/thr...ugh-drill-press-spindle-for-a-drawbar.114426/

 

[GeneT45]

Easiest is definitely finding someone to cut the slot for you, but there are probably a lot of other approaches. Here are a couple ideas:

Do you have a router? I can see holding the workpiece in a vise, establishing a fence for the router and cutting that (shallow passes so you don't lose control). Or drill a ~3/8" hole where the slot ends, mount the piece in your lathe, and use your apron and toolholder like a shaper / slotter to cut the slot. I'm assuming that you don't mind the slot going all the way to the end of the work. If you need a stop a SHCS can be inserted when the slot is done.

GsT

 

[dml66]

Is there a hole or bore clear thru the part?

Yes, the center is bored through to accept a 7/8" diameter acme post.

 

[dml66]

In addition to using the X-Y table I’d urge you to get an ER16 or ER20 collet holder to suit the taper on your drill press spindle rather than gripping an end mill in the chuck. You still have the issue of lateral loads on the taper without the benefit of a drawbar, but there won’t be the added problem of the hardened end mill shank slipping in the chuck jaws.

EDIT: There’s a current thread on “creating” a through hole on a drill press spindle:

https://www.hobby-machinist.com/thr...ugh-drill-press-spindle-for-a-drawbar.114426/

The drill press does have a DIY drawbar installed, as well as an ER25 holder.

 

[dml66]

Easiest is definitely finding someone to cut the slot for you, but there are probably a lot of other approaches. Here are a couple ideas:

Do you have a router? I can see holding the workpiece in a vise, establishing a fence for the router and cutting that (shallow passes so you don't lose control). Or drill a ~3/8" hole where the slot ends, mount the piece in your lathe, and use your apron and toolholder like a shaper / slotter to cut the slot. I'm assuming that you don't mind the slot going all the way to the end of the work. If you need a stop a SHCS can be inserted when the slot is done.

GsT

I do have a router, a 3hp Hitachi and a smaller Bosch; either can be table mounted. My concern with the router, as you pointed out, is keeping control of the workpiece.

I'll play around with the lathe later today to see if I can make it work.

 

[Eddyde]

I have milled aluminum with both, a router on the drill press. I'd recommend the drill press, especially with the set-up you have. When I milled on my drill press I never had a drawbar and held the mill in the chuck. I certainly wasn't the best arrangement but it worked and I never had a mishap. With a router, you need to make a secure jig and plunge cutting that slot would make it a dicy operation, IMHO...

 

[rwdenney]

Yes, I have an X-Y table on the drill press, I may try that approach first.

Tighten the gib screws on the X-Y table as much as you can and still be able to move the relevant axis. If you can concoct a support for the edge of the table that can slide with the motion, that will help, especially if you lean on it as it slides. Start with a row of holes plunged with a center-cutting end mill tightly chucked. Arrange the table so the drill-press quill is retracted as much as possible, and lock the quill for the lateral cuts. If your drill-press head lowers on the column, lower it so that you can work off the base plate instead of the adjustable table. My Delta will do that, and it helps.

For a shaft like this, use V blocks and clamp everything at a minimum of two points. Even if you have to cut the slot a half at a time to work around clamps, the clamping will make a big difference.

Use as little side pressure as will make progress. The chuck is mounted on a taper and will pop off with side pressure. Use a sharp four-flute mill to minimize tool pressure.

All that has worked for me at least acceptably.

Rick “has been ‘milling’ with a drill press for years” Denney

 

[RaisedByWolves]

I do have a router, a 3hp Hitachi and a smaller Bosch; either can be table mounted. My concern with the router, as you pointed out, is keeping control of the workpiece.

I'll play around with the lathe later today to see if I can make it work.

I would make a broach and broach it in the lathe.