Drilling selector hole in 80% lower

[Intimid8tor]

For those that have done a lot, do you peck drill or go straight through.

Not talking about drilling undersize, etc as I am already going that route and reaming to final size.

But, when I did my holes tonight, I had a lot of problems getting the chips to clear when I was pecking. I have the tip of the drill set just above the guide so that when I raise the quill, it can throw clear the chips on the drill.

I figure I am doing something wrong in my technique so I thought I would ask the question.

I am using a spotting drill first, then drilling slightly under then reaming to final size.

When I went to do the smaller holes I had a similar problem, but used a couple short pecks and then retracted the quill and that seemed to help a bit. On the smaller holes I was also using fast twist rate drill to see if it would help me clear the chips better.

[milotrain]

The selector hole is big enough that I'd spot first, peck a 1/8" hole then drill undersized, then ream. Also throw a little WD-40 on it and it'll keep the chips from clogging the drill.

[kcstott]

the problem with 7075 is the chips are not stringy like 6061 is. Using a drill guide only compounds this problem.

In these cases what we use to do was peck a shorter depth, fully retract the quill, use a good cutting oil, kerosine, WD-40, something then use some compressed air to clear out the guide It does sound like it's a long arduous process but in reality with everything set up it goes quick. Just have an air nozzle handy to blow out the guide

Heres the other thing too. If you are using a guide you should also be using a 135 degree split point drill. the guide keeps the drill from walking and the split point allows the drill to cut on center.

[Intimid8tor]

Originally Posted by kcstott

the problem with 7075 is the chips are not stringy like 6061 is. Using a drill guide only compounds this problem.

In these cases what we use to do was peck a shorter depth, fully retract the quill, use a good cutting oil, kerosine, WD-40, something then use some compressed air to clear out the guide It does sound like it's a long arduous process but in reality with everything set up it goes quick. Just have an air nozzle handy to blow out the guide

Heres the other thing too. If you are using a guide you should also be using a 135 degree split point drill. the guide keeps the drill from walking and the split point allows the drill to cut on center.

OK. I don't have compressed air handy at that location, but I'll pull a line over from the compressor. I am going to drill all my remaining paper weights today so that part of the operation is done. I absolutely noticed the chip difference between the 7075 and the 6061.

I'm still learning the difference between different drills. 118 vs 135 tips, etc. I was using a 135 split point. In fact I have switched from jobber length the machine screw length for drill to reduce any flex, etc.

[Lostsheep]

If the chips are not coming out of the drill bit, then you need to peck, always.

I would say that for anything except the shallowest of holes, peck drill.

[Intimid8tor]

I think one of the problems I was having was I was not pecking deep enough. I found that if I drilled until I just started getting some shavings out it cleared the hole better. I stopped every couple pecks and vacuumed the hole out which helped. It's a pain, but it is better than the alternative.

[kcstott]

Originally Posted by Lostsheep

If the chips are not coming out of the drill bit, then you need to peck, always.

I would say that for anything except the shallowest of holes, peck drill.

You can't get 7075 to flow up the flute of a drill it's the material that's the issue not the technique per say. 7075 has short brittle chips you'd be lucky to get a chip longer then a half inch

[Lostsheep]

Originally Posted by kcstott

You can't get 7075 to flow up the flute of a drill it's the material that's the issue not the technique per say. 7075 has short brittle chips you'd be lucky to get a chip longer then a half inch

Hmm, I normally cut 6061 so I can't really address the alloy issue except with anecdotal evidence. All of the TM lowers I have done, which are 7075, drilled no problem with respect to chip evacuation, I just pecked through like I always do.

I'll have to watch the chips closer next time.

[kcstott]

And what I mean by chip flowing up the flute is that you don't get a long stringy chip. You get a a lot of little chunks. They will pile up in the flute and eventually come to the top but pecking and clearing the drill and hole is best.