Drilling Large Holes in Wood Question...

[Joe AutoDrill]

More of a tooling question as I can figure out how to drill, etc...

If a customer of mine decided to run his tooling at 3,000 RPM for a 1" hole in wood and the thing smokes like a bandit... Is he possibly ruining the "drill bit" by overheating it? I've got a chart with very conservative drill speed / feed numbers but I've also got this one customer who doesn't care if he burns a bit on his production drilling process and I don't know whether to warn him about ruining his tooling or not. Probably a spade-type bit. 27/64" diameter in green wood... And yes, it is smoke, not steam. :)

Here is the speed / feed chart if anyone finds it useful:

Agro, Jr. [phone]

01.908.542.0244 Automatic / Pneumatic Drills: Spindle Drills:

[Leon]

Yes, it is possible to have ruined a bit by overheating. The bit can loose its temper and not stay sharp very long after or after retargeting.

[Joe AutoDrill]

Thanks. I know this is not just possible, but guaranteed at higher speeds in metals... I didn't know how likely it was in wood... Much appreciated.

[Leon]

The smoke is probably coming from the burning wood also. Spade bits are not so bad although I seldom use them but twist bits, brad point bits, and especially Forstner bits will over heat and also burn the wood if running too many RPM's.

[Joe AutoDrill]

No doubt the smoke is coming from burning wood... The question is basically whether the burining wood / heat build-up could de-tempter the metal drill tooling.

Personally, I like the smell of burnt wood but I want to sell a machine that works. This guy is drilling 250 holes at a time with my machines... And he is doing it everty 3 minutes, 24/7 on a production line... That's a lot of mistakes if I get it wrong. :)

Regards, Joe Agro, Jr. [phone]

01.908.542.0244 Automatic / Pneumatic Drills: Spindle Drills:

[dpb]

Oh, most definitely it can...the moisture in the wet wood will provide a small amount of cooling until it's "steamed-off", but after that wood is even less effective than steel for carrying away heat from the hole although the amount generated is far less owing to the material being so much softer. Of course, the high rpm makes up for a lot of that... :)

...

What are you using at present for the bits and who's the supplier? Might try talking w/ Amana or whoever you deal with regularly for tooling and get suggestions for such a specific purpose. Of course, if thruput is high enough and the wearout rate isn't too excessive, perhaps it could be cost-effective to just use HSS and replace/sharpen on a shift or determined basis.

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[Joe AutoDrill]

LOL... It's a tit-for-tat-type calculation then. :)

The tooling is up to the customer, thank God! Too many choices / variables.

For the size hole he is drilling 5.5" to 6" deep, I suggested 1000 RPM. He ran a test on a drill press 3" deep at 3000 RPM and got minimal to no smoke... Deeper bound up a bit and we included a peck cycle to overcome that but he still smokes through a little... So I'm guessing that 2000-2500 RPM is going to work well for him. The whole reason I asked the question is so I could say with some authority that going too fast may not hurt his piece (burning isn't an issue for him) but will kill tool life.

Regards, Joe Agro, Jr. [phone]

01.908.542.0244 Automatic / Pneumatic Drills: Spindle Drills:

[John Martin]

If it's a carbon steel bit, he's likely ruined it. If it's high speed steel, however, it should be fine. You have to get HSS pretty hot to draw the temper.

What color are the bits? If you can still see oxidation colors on them, they haven't gotten too hot.

John Martin

[Joe AutoDrill]

Customer is doing the testing. I always tell people to use HSS or better tooling. In his case, he may want to use a carbide insert spade drill made for the job since it is such high volume, etc.

[dpb]

Yep... :) I've not seen any engineering calculations for the problem but that doesn't mean they don't exist, at least approximately.

For that depth, it may be that something with chip ejection would be even more beneficial than just the material -- of course, other than the secondary feedback it sounds like the choice is the customer's not yours. If throughput and/or tool cost becomes excessive w/ time, though, that would be an area to suggest investigation into.

As another responder noted, HSS will take quite a bit of heat, but at that throughput tooling isn't going to have much time to cool off between uses so the start temperature is going to gradually be higher as the shift progresses which will raise final tip temperatures as well. It may reach a tolerable steady state, though; only time/experience will tell. I'd say the lower rpm will help significantly on the temperature at some expense in throughput, perhaps, depending on the material.

Good luck; not a trivial problem by any means...

OBTW, if it doesn't go away w/ a satisfactory solution, you might look into what you can find on the issue at the US Forest Products Laboratories -- if there's published information for such production issues readily available there or one of the University laboratories in the wood-manufacturing areas (NC, MI, etc., ...) would be my starting point.

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[Lee Michaels]

"Joe AutoDrill" wrote

I vaguely remember an old girlfriend saying something similar to me.

[Twayne]

Whjy worry? He's going to know from experience soon enough.

[Joe AutoDrill]

We are designing in a prehistoric pneumatic cooling system... Whenever the drill that I'm selling "vents" out air from the front or rear port, it does so onto the tooling... That should help a little bit. But he didn't want to do anything fancy so I think he is limiting his RPMs to the limitations of the tool without any coolant for the most part.

[Joe AutoDrill]

Customers call me whether the problem is mine or not. I don't want the trouble call if I can avoid it.

[spaco]

As another poster said, it is critical to find out what kind of material his bits are made from. HSS isn't going to be affected by just "smoke". The smoke actally will cool the bit to some degree. His wood will ignite at about 700° or so, so if he doesn't have a fire, HSS shouldn't be a problem. In my limited experience with spade bits, they seeem to take more down pressure to get them to cut. This could be causing more heat, especially as they start to dull. Can you even buy them in HSS?

As the other poster said, try to get a look at the temper colors on the bits as they emerge from the hole some time.

See:

for a chart. HSS wouldn't be temper-affected at any of these colors, but plain carbon steel could start to loose hardness from "orange" upwards.

Pete Stanaitis

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Joe AutoDrill wrote:

[Swingman]

"Lee Michaels" wrote

LOL ... that's what you get for hanging out with fast women!

... thank goodness! :)

[Phisherman]

800 to 1,000 rpm is closer to the proper speed. At 3000 rpm you can easily burn a 1" bit.

[mac davis]

Joe.. I think you would/wood generate enough heat to weaken or "untemper" the bit..

My question is WHY drill wood at 3,000 rpm and is the wood still intact?

You'd think that the wood has to at least discolor.. I drill on the lathe and it I use too much speed the wood will darken and sometimes the heat will crack it..

mac

Please remove splinters before emailing

[Joe AutoDrill]

Cycle time in a production drilling environment is critical... Faster is ... er... faster if it can be done at all.

The wood held up just fine. Imagine this is rough sawn lumber pallets... The finish is not critical at all as long as I don't burst through the product and cause problems that way.

These are clearance holes for fasteners so finish is not important.

[me]

the carbide tipped

--Shiva--