Drilling Misshap

[AbbandonZK]

I started drilling my baffles this week with the help of a friend. This friend has a degree in metallurgy and offered to help drill out the baffles with a bench-drill. I left to go buy a hacksaw and came back to him drilling the cones and spraying WD-40 into them to cool off the drill. He had already gone thru 3 drill bits before I stopped him. It appears I need to do the drilling myself. I've ordered new bits and I need to know a few things.
What RPM to use when drilling these out?
The best size pilot hole for a 23/64 final hole?
Are these cones beyond use even if I bore them out to .410 which is the size of the cones plateau?

The damage in the pictures was done at 720RPM and the slowest drill press I can find goes down to 300 RPM.
The baffles look like this now

[John A.]

This might help.

http://www.morsecuttingtools.com/Techni ... d_Feed.pdf

[yondering]

Assuming those are stainless steel? Do you know what alloy? Most likely those colored areas are work hardened and you're going to have trouble drilling them out without a lathe and carbide tooling.

Obviously they were drilled way too fast, and without enough feed pressure. Most of the common cheap drill presses only go down to 500 rpm and are really for wood, if you find one that goes slower, that's a good thing. You should consider pilot drilling and then drilling to size in a couple steps. Also, if you're not already, get some good 135* jobber drills for steel, not the cheap wood drills they sell at home depot and most hardware stores.

[jnjproto]

Also, get some real cutting oil not wd40. What is the material? As stated if it is 300 series stainless it is now work hardened. Get some135 degree split point cobalt drill bits. As Yondering suggested go up in steps. If you search surface feet per minute for your material, you can plug that number into an online speed and feed calculator and find the recommended rpm and feed rate for drilling.

[AbbandonZK]

Assuming those are stainless steel? Do you know what alloy? Most likely those colored areas are work hardened and you're going to have trouble drilling them out without a lathe and carbide tooling.

Obviously they were drilled way too fast, and without enough feed pressure. Most of the common cheap drill presses only go down to 500 rpm and are really for wood, if you find one that goes slower, that's a good thing. You should consider pilot drilling and then drilling to size in a couple steps. Also, if you're not already, get some good 135* jobber drills for steel, not the cheap wood drills they sell at home depot and most hardware stores.

Its 17-4PH. Carbide Depot is recommending that I have a SFM of 30-60 while the Morse cutting tools website is recommending 20. I found a 220 RPM drill press I'll pick it up and use it to get a SFM of 19.7.

Thanks for the help everyone.

[fishman]

Sharpen your bits.
Sharp Sharp Sharp Sharp. Need I continue?

If you don't have a drill doctor, buy one.

I lost count how many times I sharpened drill bits drilling titanium and 17-4 on my first f1.

[T-Rex]

@fishman

While I agree that properly sharpening bits, and keeping them sharp, is important, I feel you're making the task seem daunting.

I just finished 8 baffles, an endcap, a blast chamber, and a mount. All from 17-4 bar stock. I pilot drilled all holes with a single 17/64 Cobalt bit (about 16" of material) and didn't need to sharpen it once. A few drops of cutting oil were used to push passed the center drill hole. After that, holes were drilled dry and, TBH, it drilled better dry.

I think 2 important notes are:
1. Quality (sharp) cutting tools are invaluable.
2. The operators ability to manage the appropriate tooling and machinery, for a specific task, is paramount.

@AbbandonZK
Your friend owes you some beer

[fishman]

The key word there was 'cobalt'. I was using high speed steel and I assume OP is as well.

Even then, just because cobalt wont dull nearly as fast doesn't mean that it doesn't need to be sharp.

[Fulmen]

Its 17-4PH. Carbide Depot is recommending that I have a SFM of 30-60 while the Morse cutting tools website is recommending 20. I found a 220 RPM drill press I'll pick it up and use it to get a SFM of 19.7.

He/you were pushing 60sfm which is quite high for hard steels. 30 would probably be safe (assuming sharp quality drills), but 20 is much safer. Did I mention sharp, quality bits? Also, take your time. I assume you don't have to make dozens of these, so the net time saved isn't worth accidents like this one.

[John A.]

4 flute Endmill bit in the appropriate size would be the most ideal rather than a drill bit.

[3strucking]

Invest in a lathe and milling machine. I still use my drill press every once in a while but it isnt nothing compared to my Index 645.

[Historian]

Sharpen your bits.
Sharp Sharp Sharp Sharp. Need I continue?

If you don't have a drill doctor, buy one.

I lost count how many times I sharpened drill bits drilling titanium and 17-4 on my first f1.

+2!

Last year I purchased Drill Doctor (DD) and it cost was dwarfed by the time, cost, and
accuracy attained.

For example I purchased hi-speed cobalt drills from US top vendor.
Tested with drill press on SS. Then sharpened with Drill-Doc and retried.
The improvement was very noticeable.

Found a 50 year old dull and rusty ½" drill. Soaked it overnight in 10cc glacial acetic
acid ( dark room supply ) in 20 cc H2O ( very strong 'vinegar').
Rust peeled off. Steel wooled it. Then sharpened
it with DD. Placed it on Atlas 618 tail stock with chuck.

Center drilled a test cylinder of SS. Like butter at 800 rpm.

DD is one of the few products that actually performs as advertised.

Before I use a new drill from index I automatically DD it first.

For cutting oil I use CASTROL VARIOCUT C MOLY-DEE TAPPING FLUID.
Worth the messy 'sludge'.
Best.

[jnjproto]

The Machinery's Handbook shows 50 sfm down to 20 sfm depending on hardness. I have used carbide end mills in lathes to get past hard spots in parts. It only works if your setup is extremely rigid. Drill presses and end mills are not compatible in my opinion. Moly D is great stuff for SS, however it does come with increases in safety and handling.

[cdhknives]

Threading oil in the plumbing aisle is cheap and works well as a cutting oil.

[AbbandonZK]

Invest in a lathe and milling machine. I still use my drill press every once in a while but it isnt nothing compared to my Index 645.

If I considered getting a lathe it would be this one.

https://www.harborfreight.com/7-inch-x- ... 93799.html

However in 7 years I have never once needed a lathe for any of my projects, right now my current projects would benefit from me being able to drill into metal boxes with a slow drill press. What sort of use once then sell value could I get out of this thing?

[John A.]

That's just about exactly the same as my lathe, only mine is marketed as a Cummins 5278. And is Blue.

Truth is, most of the small lathes come out of the same asian facility with just a different nameplate on the side of them.

Wanna hear something funny, the cummins and grizzly g8688 and harb fright 7x12 are just painted a different color.

And the Grizzly is on sale for $515 right now instead of $599.

Here is a link that may help you "compare" models.

http://littlemachineshop.com/info/minilathe_compare.php

While I never thought I'd "use" a lathe except for building cans, I have found that cutting and threading my own barrels alone has paid for the cost of what I have invested in my lathe ($225-used)

And I often make extended bolt handles for my guns, a couple of F1 cans under my belt. Made some guide rods for some of my handguns that came with plastic guide rods.



http://mossbergowners.com/forum/index.p ... les.16624/

http://mossbergowners.com/forum/index.p ... one.17140/

You'd be surprised how creative you may become if you had the ability to make more stuff.

Oh, and I rigged mine up to be able to mill too. Can you say the 80% lower isn't 80% anymore?

http://www.mossbergowners.com/forum/ind ... ods.16880/

[Bah21963]

The condition of the cones will be difficult to drill on center with a drill press.. The best way to salvage these cones is contact Rusty over at form 1 suppressors and have him fix your cones. He has done machining others said could not be done. In addition he has built more silencers of all types thst have tested better than most commercial cans. Rusty is a ffl 07/02 so he can legally help you out.

[AbbandonZK]

The condition of the cones will be difficult to drill on center with a drill press.. The best way to salvage these cones is contact Rusty over at form 1 suppressors and have him fix your cones. He has done machining others said could not be done. In addition he has built more silencers of all types thst have tested better than most commercial cans. Rusty is a ffl 07/02 so he can legally help you out.

Thanks but I already went to a FFL 07/02 and he said he couldn't help me legally. My friend bought a lathe and we are planning to either face off the cones or just burn thru bits. The lathe goes down to 174 RPM so we are optimistic.

[T-Rex]

Just to set the record straight,
An 02/07 can absolutely drill your baffles. This has been covered many times and is proven in Section 6.4 of the NFA Handbook. Link

The 02/07 you went to was being an asshat and didn't have the balls to simply tell you he wasn't interested in your business. If anything, he might even have been able to list it as a repair. If he doesn't know this is legal, he should cancel his FFL status

Your buddy letting you use his machine can be a grey area, but as long as the lathe is owned by him, as opposed to his business, than you should be ok. Just don't thank him with beer or a pat on the back. Could be construed as payment rendered.

[Robgunbuilder]

You have damaged the surface and possibly workhardened it. That needs to be cleaned up first on a mill or surface grinder, otherwise any attempt at drilling will be off- center. I'd find a mill, use a carbide end mill and clean up the surface. Then I'd indicate the true center of your baffle and using a carbide center drill start the hole. Use a slow speed and good cutting oil. I'd probably then use a carbide drill of the right size and drill the hole. You could try a quality coated HSS drill bit but if you don't immediately see chips and it doesn't cut stop and go to carbide. Should go through like a knife through butter! Find a machinist to show you how to indicate the center of the baffle if you don't know how. This should take at most 15 min. You could do the same on any decent lathe using the tooling I described. I would not think of doing this on a drill press.

[fishman]

You have damaged the surface and possibly workhardened it. That needs to be cleaned up first on a mill or surface grinder, otherwise any attempt at drilling will be off- center. I'd find a mill, use a carbide end mill and clean up the surface. Then I'd indicate the true center of your baffle and using a carbide center drill start the hole. Use a slow speed and good cutting oil. I'd probably then use a carbide drill of the right size and drill the hole. You could try a quality coated HSS drill bit but if you don't immediately see chips and it doesn't cut stop and go to carbide. Should go through like a knife through butter! Find a machinist to show you how to indicate the center of the baffle if you don't know how. This should take at most 15 min. You could do the same on any decent lathe using the tooling I described. I would not think of doing this on a drill press.

With access to a mill and lathe, it'd probably be easier to just face the cones, center drill, then bore.
Theres many ways to "correctly" accomplish the task at hand, but I agree, just taking a drill to then isn't a good option anymore.

[cdakers]

If you don't have a drill doctor, buy one.

What model did you purchase? I've been wanting/needing one, but have heard mixed reviews on the some of the lower end models.

[fishman]

If you don't have a drill doctor, buy one.

What model did you purchase? I've been wanting/needing one, but have heard mixed reviews on the some of the lower end models.

I've been using my dad's, it's like 20 years old. Idk what model.

[T-Rex]

This is my Drill Dr

[Historian]

If you don't have a drill doctor, buy one.

What model did you purchase? I've been wanting/needing one, but have heard mixed reviews on the some of the lower end models.

"Drill Doctor® Model 750X Bit Sharpener, 3/32" to ¾""

This model covers full range of drills. I also purchased a spare diamond wheel as
back up ... always have a back up.

Just used it again yesterday prior to drill in SS + Castroil Moly.
'Like cutting butter'

Best