Proper way to cut a Slot

[WarrenP]

The aluminum bar is 2”x5.5”x0.5” thick, the slot is 4.24” long (should go down to 0.5” deep)

Are you saying your piece of work is .5 inches thick and your going to make a slot .5 inches deep? Wouldnt that mean you are cutting it in half? If so then they will come apart as someone else said, correct? Maybe you are just saying it can go up to a .5 inch depth but your not going that deep?

 

[oskar]

Are you saying your piece of work is .5 inches thick and your going to make a slot .5 inches deep? Wouldnt that mean you are cutting it in half? If so then they will come apart as someone else said, correct? Maybe you are just saying it can go up to a .5 inch depth but your not going that deep?

Perhaps I’m missing something which is normal for a beginner but the bar is 5.5” long and the slot will be 4.25” long so there is enough material on the ends to keep the bar together. It’s true that the slot will go right thru to the bottom

You may overlook the fact that my vice is a Taig mini vice and there is no way I can put enough force on it to squeeze the 1/2” thick aluminum because if I tight it too much the 1/4” threads on the vice screw will strip. It would have been a different story if I had one of these expensive precision vices with the big handle and screw

 

[Video_man]

Recently made such a slot, I clamped the work in a t-slot groove on the mill table. I milled a clamping flat on one end to locate the work in case it needed to be removed and replaced, and to prevent it from turning while working. I used a 3/16 mill to hog out most of the material then switched to the 1/4 inch mill to finish the slot, which I've found to help keep the bit from wandering a little wide. Worked fine.

 

[oskar]

I would use a 3/16" roughing end mill but assuming you don't have one and the slot width is not critical then you can use the 1/4" finishing end mill. I would use a 1/8" depth of cut, speed as fast as the mill will run and feed so you feel a slight resistance to the feed as you turn the hand wheel. Repeat as needed.

For slotting, you can feed in either direction; there is no conventional vs climb milling when slotting. I normally start on one end and feed in a consistent direction but that is just preference.

If you can, use air to clear chips and lots of WD40 for lube.

Regarding what you said Mike about “…speed as fast as the mill will run…” my question pertains to the belt between the motor and headstock.

In my setup I have the Taig ER16 Headstock along with a Sherline 90VDC VS motor and both have the Sherline 10000RPM pulleys which allow 2 belt positions and I wonder how long the small belt will last at high speeds.

 

[mikey]

Didn't know you had a high speed spindle. For a slotting operation with an axial depth of cut of 1/2 the cutter diameter, cutting speed is about 375 SFM; this gives you an RPM of about 5730. With a high speed spindle, I assume you have a tach so just dial it in and adjust speed and feed to your liking.

 

[oskar]

I understand and thanks for your time Mike

Nicolas

 

[MrWhoopee]

Are the jaws on the vise wider than 4.25? If not, then once the roughing cut is done, the stock will move in the vise and you will not be able to hold it without collapsing the slot.

 

[oskar]

The vice jaws are only 2” wide and I finished the slot without collapsing the aluminum bar. Honestly I just can’t see why some believe the 1/2” thick bar could have collapse by cutting a 3/16” slot in the center. Anyway the job is done and perhaps I was lucky?