Do you ever peck with your spot drill?

[[email protected]]

Hi all, I have a few questions regarding spot drilling with HSS/Cobalt Spot Drills. Maybe it will make a good poll too. Do you ever peck with your spot drill? I usually never did but I noticed my setup guy changing my G81 to G83 especially on Stainless parts with 1/2 inch or 3/4 dia. spots. He said he felt that the tool was building up too much heat while spotting which definetely seems like a valid point. But I recall going to a training event where the instructor said entering and exiting the cut will always be the most stress on the tool. This question is mostly concerning HSS/Cobalt spot drills because from what I understand you rarely peck with carbide...

[JParis]

Depends...

Many times though, I don't spot at all

[[email protected]]

I'm guessing that's in scenarios where you are using stubbier carbide drills?

[JParis]

Just now, [email protected] said:

I'm guessing that's in scenarios where you are using stubbier carbide drills?

Not necessarily stubby only...a longer drill with the proper spoint for it as well....and I use a lot of carbide drills

[[email protected]]

I don't use carbide drills as often as I maybe should. I'm usually just doing prototype quantities no more than 5-10 pieces, so I don't typically like to add the cost of those drills but I am starting to think I should stock some common sizes in Carbide for SS. I had used HSS and Cobalt my whole career as a setup guy so I had very little experience with Carbide. Then the first times I was programming at a larger shop that could afford Carbide drills the Setup guys would break them too often for the cost so I went back to usually using Cobalt for Steel...Now though I have successfully used thru spindle coolant carbide drills on some steel production jobs and I am amazed!!! What type of point allows for no Spotting with a longer drill?

[JParis]

1 minute ago, [email protected] said:

I don't use carbide drills as often as I maybe should.

Well, using them in aluminum, thru coolant, 18,000 RPMs on many, I can push small drills from 55IPM or so to larger drills well over 100IPM...no pecking, straight thru..

Admittedly, we're a bigger shop and protypes are a way of life here but we have a good selection always on hand, so having them isn't a problem. As we do protoype on our HMC's, many times I'll use a drill that's already available in the carousel.

[nickbe10]

4 hours ago, [email protected] said:

He said he felt that the tool was building up too much heat while spotting which definitely seems like a valid point.

If you notice on spot and center drills there is no back relief, hence the heat buildup.

You can get good quality cobalt drills with a split 135 degree point which don't require spotting. We do short run stuff here too; however, I will often use them just to capture the tip of a long drill (small spot) where I can't pilot drill for one reason or another

[Tim Johnson]

5 hours ago, JParis said:

Well, using them in aluminum, thru coolant, 18,000 RPMs on many, I can push small drills from 55IPM or so to larger drills well over 100IPM...no pecking, straight thru..

Admittedly, we're a bigger shop and protypes are a way of life here but we have a good selection always on hand, so having them isn't a problem. As we do protoype on our HMC's, many times I'll use a drill that's already available in the carousel.

I rarely use spot drills for pre-drilling but quite often I will use mill-drills for chamfering tap holes and edge chamfering.

[cruzila]

Not much discussion on the actual poll here. I found that tool life in spotting with a HSS SD is related to chip load more than anything. I like to have the hole chamfer there prior to drilling so use a spot more often just for that rather than location.