8xD carbide tip drill drifting of center

Drilling some parts using a sumitomo smd carbide tipped 8xD drill. Holes start on location, but then exit any where from .005 to .025 off center. material is 1020 plate, hole is thru, 4 inches deep. Part is held rigid in vise. Here are the details.

hole is .656 diam.
50 taper Horizontal HMC
side lock holder
.001-.0015 run out at drill tip
1000 psi thru coolant
Ive ran every where from 280 sfm to 450sfm
.006 to .012 IPR
Ive tried pecking
Ive added a spot using a larger smd drill with the same tip geometery
I called sumitomo, they were very helpful, we tried some different parameters, and then they even sent me a different body and tip profile to try ( same style body, just out of a different lot)
Holes are getting better, but still inconsistent, are .005 to .015 off.
chips are beautiful, 6 and 9s
Im told I do not need a pilot hole for this length drill (but???)
Short from buying another 3xD drill and tip to drill a short pilot hole, do any of you guys have any other suggestions??? Or is it just the nature of the beast in this cheaper material?
I could live with .005 off, but I need it to be consistent, not .005, then .01, then .012 etc. etc.
Ive had great luck with these drills in 5xD in 4340 and 4140.

I would either mill a start hole about 1" deep, or use a stubby drill to make sure the hole is straight to begin with. If possible use a gun drilling type cycle to start your long drill after having the pilot hole done.

Do you have a collet to hold the drill instead?
Can you drill halfway thru,flip over and drill from other side halfway to minimize location deviation?

Using the 3x drill to full depth, then changing to the 8x sounds like the best plan. But talk to Sumitomo about best strategy for following one drill with the other. You need to make sure you won't damage the tip of the following drill, so you may have to hard code a slow feed in for the first +.1" to -.05" (or so) to give any remaining chips a chance to wash out, then stabilize the long drill.

Once it's stable you can ramp up the feed to normal.

I use the 21mm 8xD size quite a bit. Like you I had some issues drifting, surface finish at the beginning of the hole, and hole over size at start from the drill wandering a bit before it settles.

Close fitting pilot hole did the trick. Just deep enough to fit the whole insert. Maybe .3" deep if I remember. Fixed finish issue and drift under .003" drilling thru 6" thick. Worked great on our flimsy Haas. We use a sidelock holder too, but runout is less. Just under .001" TIR at the insert.


The 3 & 5xD lengths seem to work fine for me with no spot or pilot, but the 8xD gets much better results with pilot hole.

Thanks for all the great advice guys, I think I got a little tunnel visioned on making it work with no pilot. Just not gonna happen! Hind sight, probably should of done like Mtndew suggested with a 5XD and just go both ways. Got more holes to do on the vertical, but 6 inch deep, so Im gonna just get a shorter drill to pilot with when I do those. Thanks again for all the options!

I'm guessing that the main issue is that you are trying to start on HR plate?
Was the surface faced true first or not?

Have had to use the pilot hole routine before with 20D (?) drills before, but that was in a lathe.


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Think Snow Eh!
Ox

Ox said:

I'm guessing that the main issue is that you are trying to start on HR plate?
Was the surface faced true first or not?

Have had to use the pilot hole routine before with 20D (?) drills before, but that was in a lathe.


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Think Snow Eh!
Ox

Click to expand...

yep, faced true on both entry and exit. I just tried drilling from both sides (via rotate B180.), drilled half way, and got a pretty good discrepancy at the intersection point on one hole, but not to bad on the other (part has two holes in it). So Im thinking like others have suggested, need a pilot hole. Gonna mill a couple .3 deep pilot bores and try that.

cpifer3 said:

Drilling some parts using a sumitomo smd carbide tipped 8xD drill. Holes start on location, but then exit any where from .005 to .025 off center. material is 1020 plate, hole is thru, 4 inches deep. Part is held rigid in vise. Here are the details.

hole is .656 diam.
50 taper Horizontal HMC
side lock holder
.001-.0015 run out at drill tip
1000 psi thru coolant
Ive ran every where from 280 sfm to 450sfm
.006 to .012 IPR
Ive tried pecking
Ive added a spot using a larger smd drill with the same tip geometery
I called sumitomo, they were very helpful, we tried some different parameters, and then they even sent me a different body and tip profile to try ( same style body, just out of a different lot)
Holes are getting better, but still inconsistent, are .005 to .015 off.
chips are beautiful, 6 and 9s
Im told I do not need a pilot hole for this length drill (but???)
Short from buying another 3xD drill and tip to drill a short pilot hole, do any of you guys have any other suggestions??? Or is it just the nature of the beast in this cheaper material?
I could live with .005 off, but I need it to be consistent, not .005, then .01, then .012 etc. etc.
Ive had great luck with these drills in 5xD in 4340 and 4140.

Click to expand...

.
usually slower feeds helps but drifting is also from uneven hardness in metal (drill will drift to softer side) and drill tip uneven dulling has a effect. obviously check tram of spindle and make sure you are not leaning at a angle. harder you push longer drills the more they bend while drilling and they drill curved holes. i have seen many problems stop or are less by reducing feed to 50 to 20%. at 6 ipm feed if less than 6" thick part obvious that 60 seconds or less drilling a hole. often somebody will waste literally 10x that time or more (drilling 30 ipm feeds or faster) and deal with breaking drills (expensive) when so called times savings of a few seconds is actually taking vast amounts of time
.
got to watch full pecking. deep holes often still have chips still in hole. you fast rapid back in hole down to 0.10" where you left off it packs the chips at end of hole at high density (can be hard on drill tip) also if chip sticking up where you left off (hole bottom) its also hard on drill tip. usually a parameter can be adjusted to raise where peck left off. so 0.5 peck rapid stops you see distance to go of 0.6 or more
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short peck or G73 often is enough to break chip and let drill straighten out a bit from short peck backup. again usually a parameter short peck can backup .010" at peck or more. sometimes increasing distance (usually parameter adjust) helps
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if you use shorter length drill then use the longer drill to finish watch diameters of drill. many carbide drills have a back taper often alot (often .020") and if long drill tip dia is .001" bigger than the pilot hole, the longer the drill the more it makes a bad reamer and will cause vibration in the tight hole. 8x might not be a problem. you get 30 to 60x in length it can be a big problem. the back taper normally helps with drilling but obviously hole drifting can increase with a very large back taper

Horizontal is not your friend. Really can't help that. Vertical would be better.
Holder, holder , holder. The better the holder , the better chance to get it done.
The issues you are seeing from coming from two directions, shows that the machines drifting slightly. Not a surprise, as you are indexing the pallet, changing tools and such. Lot's of movement to overcome for needed repeatability.

I would just get the straightest holder-tool assembly and then see how that works. Also, at 1000 psi, you should not peck. It is built to engage and go.


Good luck.

cpifer3 said:

. Gonna mill a couple .3 deep pilot bores and try that.

Click to expand...

Why only .3"? I would go at least 1 diameter deep, but probably 2 or 3.

R

thesidetalker said:

I use the 21mm 8xD size quite a bit. Like you I had some issues drifting, surface finish at the beginning of the hole, and hole over size at start from the drill wandering a bit before it settles.

Close fitting pilot hole did the trick. Just deep enough to fit the whole insert. Maybe .3" deep if I remember. Fixed finish issue and drift under .003" drilling thru 6" thick. Worked great on our flimsy Haas. We use a sidelock holder too, but runout is less. Just under .001" TIR at the insert.

The 3 & 5xD lengths seem to work fine for me with no spot or pilot, but the 8xD gets much better results with pilot hole.

Click to expand...

Anybody else pucker up a bit watching that 8XD drill change into the spindle?

CNC_Chip_Thin said:

Anybody else pucker up a bit watching that 8XD drill change into the spindle?

Click to expand...

Nope.
Not after watching my Siemens stuff a Chamdrill into some angle iron 100mph this noon.

First G1 of the program.
Copy/paste/ and then edited, and took the first and last holes out, and apparently missed the F rate, so apparently Siemens decided that a G1 w/o an F = full tilt boogie?

A Fanuc would have just tossed an error and said "NO Feedrate you Gomer!" and sat there....



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Think Snow Eh!
Ox

Ox said:

Nope.
Not after watching my Siemens stuff a Chamdrill into some angle iron 100mph this noon.

Click to expand...

Only 10500 IPM? You're getting slow old man.

litlerob1 said:

Only 10500 IPM? You're getting slow old man.

Click to expand...

I've been in similar situations, that's why I bought a carbon fiber cane - so I could move quicker.

Well job is done, and I got my ass kicked! Never got the holes to straighten out. Last time I did these I used some cobalt tipped Allied spade drills I had, gen2 I believe. Could not break a chip unless you pushed the snot out of it, then it looked like you chewed your way through the hole. But the damm things were on center! Did use a pilot drill with those. This time the chips were great, the finish was great, all good but location. I tried milling a .700 deep pilot bore in four holes,(gun drill style entry into pilot) may have been a bit better, but still off close to .01. Strange thing is that they go left, right, up etc. no consistency . I got some 6 inch deep holes to do in the vertical, Im going to order a 3XD drill to pilot with, guess I should of done that from the start. I hate pulling birds nest of drills mid cycle, and with these drills I had none of that. Thanks again for the help

It might be worth trying a different holder. With the setscrew holder you might be getting a tiny bit of "tipping" perpendicular to the setscrew, especially if the shank isn't right on size. This could lead to a small deviation, then to drill wander.

Can you measure the bore of the holder and the diameter of the shank and see what the real clearance is?

Milland said:

It might be worth trying a different holder. With the setscrew holder you might be getting a tiny bit of "tipping" perpendicular to the setscrew, especially if the shank isn't right on size. This could lead to a small deviation, then to drill wander.

Can you measure the bore of the holder and the diameter of the shank and see what the real clearance is?

Click to expand...

I was thinking, I would try a different Drill, instead of buying a 3x to try and fix something that isn't working. But that's me.

R

cpifer3 said:

...... Last time I did these I used some cobalt tipped Allied spade drills I had, gen2 I believe. Could not break a chip unless you pushed the snot out of it, then it looked like you chewed your way through the hole. But the damm things were on center!

Click to expand...

Was it on the same machine?

litlerob1 said:

I was thinking, I would try a different Drill, instead of buying a 3x to try and fix something that isn't working. But that's me.

R

Click to expand...

Wow that's new litlerob1 was thinking instead of just slinging crap.

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