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Milling Questions

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Downwindtracker2

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#1
I slotted a piece of 1/4" CRS 5/16" x5". I did it in .050 passes between two 5/16" holes, lowering it at each end. I tightened the y axis and the column. I ended up with a stepped side. I used a new 4 flute HSS end mill. It's not critical .But there will come time when I want to make something to size. Where is this coming from ?

The machine is Rong Fu 45 dovetail column mill/drill. I bought it and lathe from a cabinetmaker when he was closing his studio, some metal wood design?. It had been CNCed some time in it's previous life .

THX Ray
 

JimDawson

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#2
Slotting is normally done with a 2 or 3 flute end mill. A 4 flute will tend to walk sideways. It's also best to use an endmill smaller than the slot and step over to get the correct width. If the head is badly out of tram, it would be possible to get steps as you increment down. This is less likely.

You just need a little more practice. You'll get there.:encourage:
 

Karl_T

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#3
Just some more thoughts for you...

The machine is telling you it was pushed too hard. Remember all machines are made of cheese; push too hard and they move where you don't want.

Do you have table clamps to lock the axis not in use? they sure help.

I used a clapped out bridgeport for over ten years. I found chain drilling with a just undersize drill the slot first, then going 1/3 diameter from each hole and plunging the endmill, only then go back and forth with the end mill, was the way to produce a slot exactly the size of the end mill. This work cuts the side forces to almost nothing.

Jim's suggestion of using an undersize endmill is spot on for larger diameter slots. 1/4" an under, not so well. Just undersize endmills are spendy, going a full 1/16 less is too much smaller vs. the chain drill idea.
 

Downwindtracker2

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#4
Thank you. I'm a retired millwright, with a woodworking hobby. When I retired, I realized I was going to have to make some parts for these older machines., so the mill and lathe. The mill has been invaluable in making a Taiwanese clone of the Powermatic# 65 wood shaper 's fence work smoothly and accurately. Aftermarket fences are expensive. And for most woodworkers the only solution to the fence problem. That alone pays for half the purchase price, but not the parts or tooling. Right now I'm working on a shop built 6" metal shaper.
 

homebrewed

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#5
What type of end mill holder did you use? Some materials can pull the end mill into the work and cause problems. Holders that engage the slot on the end mill shank (if it has one) are better in this regard.

I ran into this problem on the little Sherline we had at work. Although its end mill holders do use a set screw, I had installed the end mill so the set screw was at the bottom of the slot -- so the end mill could move down. And it did, ruining my work. I was machining some sticky hardware-store aluminum at the time. After that I made sure the set screw was always at the top of the slot.
 

Downwindtracker2

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#6
When the mill closed down ,I bought some tooling from their RF-45, Lyndex TG 100 collets and holder. The collets were almost never used. That RF-45 was rough, being used, mostly abused as a drill, said to have a bent spindle, and it went high. I also got a Delta Toolmaker surface grinder at the auction.
 
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