Cutting T-Slots in Ally. Advice please

[ImanCarrot]

Is there something I'm missing about cutting T-Slots cos my machine was screaming like a banshee and the aluminium melted onto the cutter. Here's what I was trying to do:

Cutter- T-Slot cutter, 16.5mm X 5mm, No teeth= 6, Dormer HSS.
Material- Aluminium 6" long bar flattened off so that it was half a bar (milled
it along the long axis)
Spindle speed- 1500RPM
Feed- Manual, dead slow.
Method- I used an end mill to to cut a square "trough" wide enough to take the T-Slot cutter shank and deep enough to reach the bottom of the T-Slot cutter. Manualy fed the T-Slot cutter travelling in the X direction. The material was held in a V-Clamp and was solidly held. Oh, and I used flood coolant.

Any advice, as always, very gratefuly received. Thanks in advance!

[d.dixson]

Hello,
1500 seems a bit fast for that diameter... I'd slow it down to half that and work my way up... 2 tricks I use for tee slots: 1. Don't cut full depth on the clearance slot. Leave about .25mm so the bottom edge of the bit is engaged in the material. This helps to reduce chatter - stablizes the cut. 2. Use a blow gun to evacuate the chips. Might be a mess with your flood coolant (portable shields with magnetic bases can help with this). The fewer chips that get recut the longer the edges will stay sharp and the better the finish. I saw one of your other posts regarding the correct flood coolant for material so you seem to be savy on that point. However, I like to use A-9 on aluminum. Smells like parifin and contaminates the bit to the point that the ally normally won't stick to it. May not be available in the UK but I'm sure like products are. Won't go through a flood coolant pump tho. So you'd have your hands full manually cranking the table, holding the blow gun and trying to swab the oil on... maybe mount the blow gun near the spindle, huh?
I hope you find this helpful,
Doug

[ImanCarrot]

[Edit]Leave about .25mm so the bottom edge of the bit is engaged in the material. This helps to reduce chatter - stablizes the cut[/Edit]

Thanks Doug! that's one of them tips that made me go *doh* (Homer Simpson voice) and slap my forehead with the back of my hand. Wish I'd thought of that! it makes perfect sense as it will reduce tool deflection and chatter.

The other tip of using compressed air to remove the chips makes perfect sense too. I can rig up a 120PSI compressed air line. What I'll do is point the coolant at the far end of the milling "trough" and force the coolant through the "trough" with compressed air behind it towards the T-Slot cutter.

Many thanks again mate! much obliged!

[d.dixson]

I am glad to hear that helped! Sometimes a new perspective is all thats needed. I know I tend to miss the obvious sometimes.
As to the blow gun: I try to get the thing pointed right into the cut. I guess I'm a mag base nut, I like to have them for everything from blow guns to mirrors. But if I can get one secured properly to the head and pointed right into the cut, that seems to work best. And as to the chips getting into my socks: thats not so bad... its when the misses finds them in her underware when things start to get tense
d.

[Geof]

Originally Posted by ImanCarrot ..The material was held in a V-Clamp and was solidly held....

Both ends held in a V-clamp or just one clamp in the middle?

What diameter (width) bar?

If you have it held at only one point you have a tuning fork, aluminum is not rigid.

Feeding by hand on a manual machine or using handle jog on a CNC? Either way it is difficult to get a smooth feed and a surge causes a big chip that gets caught and things go downhill from there.

I have cut many feet of tee slot in 6061 with that type of cutter using 1200 rpm, flood coolant and a feed of about 5ipm, maybe a bit less. I always make the initial clearance groove .01 to .015 deeper than the bottom of the slot and always make sure the part is clamped in several places or held in a vise.

[JWB_Machining]

Also 120 psi is Kind of high, i'd regulate that down unless you feel like breathing coolant and chips, also I wouldn't have any food or drink around. If you're close enough 40 - 50 psi should be fine if not overkill even at that, but man you'll have crud all over everything if you hit it with 120 psi.

[ImanCarrot]

Thanks for all the input guys.

The bar is 2.5@ dia and is only clamped in the middle, I'll stick it in my vise and try with a feed of 100mm/min and make sure the bottom of the tool is cutting.

The 120 PSI was way too high as suggested- it was like it was snowing in the shop lol. Chips in your underpants is scarry! lol. I'll choke this down.

I'll start again with a new tool using all the tips suggested.

Many thanks again chaps!