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Counter Sinking Questions

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Koloa

Plastic
Joined
Apr 2, 2021
Hi, looking for a little advise on this.
I'm just doing some work out of my garage and only have a drill press that only has a lowest speed of 500RPM.

Ive done a lot of shallower countersinking which has came out ok, but this time around Im given a job where I need to use a 45deg CS on a .175 DIA thru hole in some alloy steel plate .105 thick.

I'm supposed to go deep enough to get a 3/8 dia across, but my problem is, the last .050 of removal is creating a lot of chatter and running out. Ive tried clamping the work down and just pressing against a solid stop.

But im wondering if the problem is that the RPM is to high? or is it that the cut is too deep using a 45 deg tool? Or should I use a 45 degree endmill instead? The countersink I'm using is three flute HS steel.


Thank you if any advise!
 
The RPM is quite high for a csk operation IMO, for a machine with no real radial rigidity on the spindle. You may do better with a single-flute csk, and as you note clamping the work. I wouldn't recommend trying an endmill instead, especially in a drill press. Having a piece of back-up material (like aluminum, perhaps) to bury the csk tip into for each new hole may also help to reduce chatter.
 
You can c'sink close to finish or lightly against your stop, then shut off the spindle and as it winds down give it an oomph on the handle to scrape the last little bit on c'sink.
 
Thanks! both to you and to Matt.

Yeah, I really want to fix this going forward. Doing work for a friend and I will be getting a lot more of it in the future, So i was just thinking of picking up a used Heavy Duty drill press that is more rigid and goes slower.. i was thinking I should probably be down around 200.


With a machine like the one I currently have that only goes down to 500rpm... wouldn't that be too fast for a single flute CS?
 
Its just a belt and pulleys. And you're a machinist.

or maybe a 1700rpm motor instead of a 3200?

Somewhere around here I have a pic of a mickey mouse drill press
setup to get it turning real slow, it involved idler pulleys, angle
iron and about 12 Kant-Twists.

500 as the low is kind of high, what happens when you have to ream something.
You could just buy another drill press, but it might be easier to modify than
you think.

Maybe try a zero flute. Heavy countersinking always sucks without rigidity.
 
Its just a belt and pulleys. And you're a machinist.

Ha ha ha! ok!

Yes, it sucks right now. I know it must mostly be this light duty drill press. The countersink looks just fine up to about .300 DIA... then I think the tool pressure after that is just killing it. Probably also because they are requireing a 45 deg.

I guess maybe I could try some different pulleys. Thats not a bad idea, still thinking though to look for an old used machine.Not sure which would be more of a hassle, but then again if I get a heavy duty, i could probably do some tapping with it, that I cant even do right now with this one.

Saw some guy online whos selling an old Walker Turner for 500.. all fixed up and looking like new but it doesnt have the low speed attachment
 
Just tried using some cutting fluid.. doesnt really change much at all except add some flavor to the coffee, but was worth the try. Thanks!
 
500revs far too fast.ItS aIways temping to run then too fast.No harm in trying a lower speed say 200 and go from there think on the machine your using slower will be faster.When you get near the depth a squirt of WD40 then go to depth suspect its lack of power.Tool must be sharp even stoning the edges before you start will reap rewards
 
Yeah, I would try 200 but 500rpm is the lowest I have. I'm going to have to slog through this job and just feel bad about it cause they want them right now. I don't want to do this again though.

Oddly there is no difference when I clamp the work down or just press it against a solid stop. Thinking It really must be my speed, not enough rigidity, and then maybe I'll try one of those zero flutes next time.
 
Take the handles out of the drill press spindle down drive

Put a pipe wrench on it with a 4 foot extension pipe

Open the garage door to let out the smoke

Crowd that countersink until it glows

After the job is down throw everything away

Take up house painting
 
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