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YG1 Spade drill insert question


Nov 18, 2018
Southern Illinois
So, I am currently running a YG1 through coolant spade drill body and HSS inserts. Been using this setup for probably the last 6 months or so. Inserts range in size from 1" to 1 3/8". 99% of what I am drilling is D2. Drill half way through the part, bore, flip, and repeat.

Cutting parameters are 65 SFM and .006 per rev on an 1 1/4" insert. The drill is on center and runs smooth and quite.

The issue: What I've noticed is that the inserts seem to be chipping pretty consistently on the inner most chip breaker gash on one side or the other after 10ish parts. The insert never seems to chip on the opposite side, so I just keep using it and it seems to still run ok.

Has anybody else had a similar issue with YG1 spade drill inserts? Too much feed on the breakthrough? The reason I am asking is that I have been running parts exactly like this for years using an Allied Engineering drill body and HSS inserts. Exact same cutting parameters and setup, but very rarely would I have an insert chip. We decided to try the YG1 stuff after the Allied holder had an accident a while back.
65 SFM seems slow to me, but that is D2. But I imagine it’s in the annealed condition. I run 5/8-3/4 deep drills in 4140 Prehardened at 150SFM but .004 per rev. The 4140 is around 28-30 HrC

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Havent rin the yg1. Sorry.

I never like to run a spade drill through from both sides because of the breakthrough in the middle. But you said the allied tool worked ok so whatever works. How different do they look from the yg1? Different point geometry or maybe margins are different allowing more nastiness when you break through?
I always get that same issue with YG spade drills, and most regrinds.
The split point geometry from them is garbage.
It doesn't take much to plug them up.

The only spade drill inserts that run reliably for me are AMEC.
65 SFM may be a little slow, but the drills lasted well in the past so I haven't pushed it. Also we do pretty small batches of parts (10-20 usually) so saving a few seconds on the drill Op doesn't make any really difference time wise, compared to setup, inspection, etc. And yes, this is annealed D2. After both sides are machined, they get hardened to about RC 58-60 and then hard turned.

I've got one Allied insert left, and the geometry looks very similar to the naked eye. I agree that it might be better to drill through in one shot, but a lot of the parts are 6"- 8" long and I'd rather use a shorter more rigid drill body (the one I have) drilling only half way. Is my thinking backwards on this?

Ah, so it's not just me then. Sounds like I need to try and convince the boss to switch back to Allied. Glad to have my suspicion confirmed.

I appreciate everybody's input, I think I'll be able to get this straightened out now.
AMEC are good, but my very favorite spade drill I've ever tried is Madison Duo-Dex. The geometry on those is really good, they are the freest cutting spades I've ever used. Plus they're double-ended, which is nice.
Sorry for the late reply, but yes the Allied inserts will fit in the drill body I have. When we first got this holder I ran a few Allied inserts in it that I had left over.