# Decent quality center drills



## hman (May 29, 2014)

I nearly always use a center drill (aka combination drill & countersink) when making holes with my lathe or mini-mill.  All too frequently on the mill, I've been notice an irritating "chatter" when using them, especially the larger sizes.  Not really so much of a chatter, but they tend to make the head shake when they're drilling into a part.

First off, I checked the runout of the drill chuck ... 0.003" TIR or a bit less.  Shouldn't have caused as much shaking as I'd been seeing in some cases.

So a couple nights ago I gathered together all 12 of my size 2 thru 5 center drills and tested both ends of each.  I was drilling into a piece of steel and holding the center drills held in the appropriate collets (measured 0.001" TIR or less).  Lo and behold, *all* of them caused head shaking to some extent on at least one of their ends!  I measured for relative motion between the table and head a couple times, and in at least one case, they were moving what looked like 0.009" with respect to each other.

I know this would be much less of a problem with a more rigid mill, which might well overcome the out-of-centerness, but the mini is all I have for now.  And even so, I don't think it's right for a *center* drill to be off center to the extent most of mine are.  

Is it that the drills were no good to start with ... or is there some failure mode or bad practice that causes these drills to go off-center?????

Does anybody have a suggestion for where to get decent, reasonably priced center drills?  What I've seen so far is cheap sets of 5 for around $10-15 and singles for under $3, then what looks like a pretty big gap, and then singles in the $10-20 range.  I'm a firm believer in "you get what you pay for," and I've previously been going low-ball (though from some relatively good suppliers).  But the high-end ones seem overpriced to me.

Thanks!


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## JimDawson (May 29, 2014)

Cheap.  I bought a set from HF, junk, major chatter and run out

Mid Priced.  I have some from an unknown US manufacturer, pretty good, sometimes I get chatter, little run out.

High end.  I have a set from DoAll, the ones with a radius not sure what they are called.  Very accurate, no chatter.

The above applies to use in both my lathe and mill.


So I guess you get what you pay for.


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## Dan_S (May 29, 2014)

Try keo brand from enco.


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## NightWing (May 29, 2014)

The ones with the radius are called bell type center drills.


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## DMS (May 29, 2014)

I have a 5 piece set from Keo, and have been pleased. I don't recall them being all that much. If you are just spotting holes for drills (not a lathe center), you may also try a spotting drill.


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## mikey (May 29, 2014)

I use Keo, Titex and Chicago-Latrobe. Never had chatter from any of them, not even once.


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## Bill Gruby (May 29, 2014)

I agree with KEO being top of the heap. They are the only ones I use.

 "Billy G"


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## Bill C. (May 29, 2014)

JimDawson said:


> Cheap.  I bought a set from HF, junk, major chatter and run out
> 
> Mid Priced.  I have some from an unknown US manufacturer, pretty good, sometimes I get chatter, little run out.
> 
> ...



Never tried HF center drills.  I didn't like their sizes. I am referring to their package of various sizes of center-drills. 

I bought a extended length center-drill for my drill press so I wouldn't have to move the table up and down to accommodate the different length of drill bit and center-drill.  I am fortunate to have a couple of supply houses in my area.


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## samthedog (May 29, 2014)

Living so close to Sweden I have a bunch of SKF center drills. Excellent quality. I don't tend to use cheap cutting tools or tool steel. Too many cases where I have been frustrated and disappointed so I stick to decent quality now.

Paul.


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## chips&more (May 29, 2014)

The center drills with the radius/curve are called... wait for it, wait for it…”radius center drills”. They are handy when you have for example a project in the lathe between centers and the tail stock is set off center. A normal center hole with a 60° solid angle would ride funny on high spots in that situation. But when you have the curved 60° angled hole the centers ride better. A “bell center drill” has a shoulder and straight 60° angle. It does not have a curved 60° angle…Good Luck.


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## hman (May 29, 2014)

Thanks to all of you.

I just went to Enco, and found that the keo center drills had "web special" prices.  Plus I was able to use MAYFS to get free shipping.

Yee-Haaaaa!:ups:


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