Drill speed

[Eric Estlund]

PS- We're a bunch of geeks. Shop talk discussions on drill speed math and bit type- way to wind us up! I you guys.

[drewgh2o]

At that point I don't think even a carbide bit would work.

You'd be surprised what carbide can handle.

Yeah, what they said. Center drill it. I think the Keo products are the best bang for your buck.

[steve garro]

The shortness also helps with not snapping bits and the aforementioned drilling through the back side of the tube. I've had longer spiral bits get caught and "screwed" down into the other side of the tube. That will drive you bat sh!t in a hurry. Not an issue with these.

Yep - I'm a fan of Stubbies & Jobbers for those very reason.
This setup is going to have a long bit fully extended as I am going to use it in my chair.......
Either that or I need to build a shorter stand for it.
Taking it slow & doing it right as I have been doing it all these years without so I want to nail the process, equipment, set up and location.
Thanks all - definitive "put a hole in it" thread.......
- Garro.

[Mike Mcdermid]

Speeds and feeds go out the window U drill everything

[SPOKE]

Steve,
If your drill press and work holding setup are reasonably rigid then I suggest using a screw machine length (short) Precision Twist mfg list #040832 (MSC #040832, about $12 each). Run it between 40-50 sfm (306-382 rpm). The hard part is managing the feed rate. For this drill in the 4340 HT tubing feed rate between .005-.008/rev. If you are hand feeding then you'll have to apply enuf pressure to create a good chip thickness so you don't work harden the surface. Use some type of cutting fluid to manage heat and aid cutting. Be sure to setup a spindle stop so you don't bump into the other side of the tube when the drill breaks through. If I'm not mistaken this drill is a parabolic design that centers up good and will create a good quality hole. Just make sure your drill holder clamped the drill nice and tight so it doesn't spin when the full diameter starts to engage the tube.
If necessary you can chuck up a 3/8 dia 4 flute endmill to create your pilot hole then run the 1/2 drill thru it.

As someone else mentioned above....for building frames one by one no need to get fancy with carbide tooling.

Cheers.....SPOKE

[drewgh2o]

If I'm not mistaken this drill is a parabolic design that centers up good and will create a good quality hole.

Screw machine length drills are not parabolic. Parabolics are for deep holemaking 5-10x diameter. If you are just wanting to use one 1/2" jobber length drill to pop the holes, a standard split point jobber will work. They have a thick web, making them more rigid than a parabolic and they have a wide land, (the OD that rubs on the hole and stabilizes the drill.) I buy cheapo large diameter taper shank drills for my lathe (1-1.5") and have the structural steel outfit next door resharpen them on their $10,000 drill sharpener. They put a "brad" point on them and very little drill point angle. The little tit acts to center the drill on contact and the flat tip angle makes it so the drill breaks through quickly. They kinda look like an endmill with a center drill nose. another option would be to take an aircraft drill which has maybe 2" of flute and cut it down so you have a solid shank for your hold out and rigidity requirements.

[steve garro]

Awesome thread.
- Garro.

[SPOKE]

Screw machine length drills are not parabolic. Parabolics are for deep holemaking 5-10x diameter. If you are just wanting to use one 1/2" jobber length drill to pop the holes, a standard split point jobber will work. They have a thick web, making them more rigid than a parabolic and they have a wide land, (the OD that rubs on the hole and stabilizes the drill.) I buy cheapo large diameter taper shank drills for my lathe (1-1.5") and have the structural steel outfit next door resharpen them on their $10,000 drill sharpener. They put a "brad" point on them and very little drill point angle. The little tit acts to center the drill on contact and the flat tip angle makes it so the drill breaks through quickly. They kinda look like an endmill with a center drill nose. another option would be to take an aircraft drill which has maybe 2" of flute and cut it down so you have a solid shank for your hold out and rigidity requirements.

Drew is correct regarding the parabolic flute designed drills but his info is a bit dated now. http://www.guhring.com/documents/catalog/drills/GT.pdf
Guhring is just one of several manufacturers that offer parabolic flute designs of all lengths these days. They also offer a variety of tool materials ranging from HSS, HSSCo, powdered metal, & carbide and a variety of coatings for various applications.
Cheers....SPOKE

[RyanHeller]

Blair Rotabroach cutters work really well on tubing and should last a long time on 4130 if you use cutting fluid. They have an 1/8" pilot and will drill much cleaner than a stepped bit. The drill stop will also prevent any cut-through on the opposite side.

Fractional Rotabroach Cutters


IMG_0089 by RyanHeller, on Flickr

[Bobqzz]

Blair Rotabroach cutters work really well on tubing and should last a long time on 4130 if you use cutting fluid. They have an 1/8" pilot and will drill much cleaner than a stepped bit. The drill stop will also prevent any cut-through on the opposite side.

Rotabroachs are awesome

[drewgh2o]

Looks like the rotabroach is really the way to fly, Garro. Regarding hold out, tho, you mentioned needing to modify the base of your drill press to bring it lower. I just did a project for the ski resort where I had to drill 1" holes in a huge gear, so I made a new foot and mast for my old Delta drill press, essentially making a poor mans mag base. I used some 3 1/2" tubing welded to a foot that I could then clamp to the gear. I'm not sure it qualifies as portable,( sumbitch still weighs #150+) but I was able to get the job out the door. Might be worth it in the long run to lower your drill press and reduce hold out is what I'm tryin to say.

[steve garro]

Looks like the rotabroach is really the way to fly, Garro. Regarding hold out, tho, you mentioned needing to modify the base of your drill press to bring it lower. I just did a project for the ski resort where I had to drill 1" holes in a huge gear, so I made a new foot and mast for my old Delta drill press, essentially making a poor mans mag base. I used some 3 1/2" tubing welded to a foot that I could then clamp to the gear. I'm not sure it qualifies as portable,( sumbitch still weighs #150+) but I was able to get the job out the door. Might be worth it in the long run to lower your drill press and reduce hold out is what I'm tryin to say.

I think so too - I love the look and finish those are giving.
Is it some form of arbor they thread on to?
Basically, my deal is that I'm effictively 4'6" tall in a wheelchair, so I have to "Hobbit Shop" everything out - Garro.

[RyanHeller]

I think so too - I love the look and finish those are giving.
Is it some form of arbor they thread on to?
Basically, my deal is that I'm effictively 4'6" tall in a wheelchair, so I have to "Hobbit Shop" everything out - Garro.

They do use a threaded arbor. The kit I have has one thread arbor and cutters from 3/8" to 3/4". They make cutters ranging from 1/4" to 1 1/2". The easiest way to remove a cutter is leave it chucked up in your drill and a set of slip joint pliers.

Fractional Rotabroach Cutters

[Zimmermanbicycle]

Ha! you said "wind us up"!

PS- We're a bunch of geeks. Shop talk discussions on drill speed math and bit type- way to wind us up! I you guys.

[Eric Estlund]

[Eric Estlund]

Big ones are 1/2" end mill, smaller ones are a 1/4" step bit.