Help drilling SAE Set Screws
I am a maintenance technician not a production machinist. I need to drill a 1/8" hole through the length of 30 3/8" - 16 x 1 -3/4" long cup point set screws. I have been trying to do this on our engine lathe without much success. The coolant system on it is long gone. I do not have auto feed on the tail stock, so I was using firm pressure but not forcing the drill.
My first attempt was with coated HSS drills and a lot of oil at 270, 430 and 560 RPM. The drills just don't cut in very deep.
For my second try I got some Carbide Tipped drills from McMaster they were CJT Durapoint Style 125, 135° split point, jobber length drill bit #12501250. I started to have success until I backed the drill out to make sure I am getting oil on the point. The carbide tip seems to stay in the hole and that is it. I tried a few speeds as well.
Could anyone suggest a better speed, drill bit, and way of lubricating? Thank you.
You're presented with a workpiece of designed in different hardness zones. The cup point is the hardest portion, the body of the setscrew can be drilled with HSS. Penetrate the cup point of the setscrew with a carbide die drill to about .1" deep and have at it with a HSS drill, the interior isn't nearly as hard as the tip. Break through into the hex socket gently or the HSS drill is toast.
This is no job for jobber lenght drills. Think about it, how deep is the hole you want to make?
you don't really need carbide
a good 135° split point tin coated high speed will do it
your on the right track already
you just have to be the drill bit grasshopper
peck it often
keep it cool with a spray bottle
be every so gentle on the breakouts
get a 10 pack of drill bits
are you pecking? as in running in a bit then backing out to clear chips with a brush or whatever, re apply coolant, repeat.
if not there is most likely your problem
We have used some carbide tipped drills to do a job on the manual mill and had the same problem with the carbide coming out if it gets TOO HOT. You can even try cobalt drill bits.
here are 3 good bits to choose from
Jobber Length Drill Bits - Metalworking & Multipurpose Drill Bits | MSCDirect.com
and if your a mcmaster guy try this # 27995A515
You need more speed. I'd do it in a drill press at 1000 rpm or so with HSS drills. The DP will also make it easier to retract to clear the chips and give you a better feel for what's happening at the tip. If the hole must be perfectly centered, spot drill it in the lathe with a center drill or something carbide then move it to the DP for the through hole. I've done smaller setscrews this way to make metering jets. Use some tap magic or coolant and keep it wet. Change drills as needed.
Be sure to spot drill or center drill before you run the drill bit.
The pessimist says "it can't be done".
The optimist says "it's all in the technique".
The engineer says "what the hell are you doing?".
I suspect these are metering orifices, and somebody dug through the junk boxes and found the setscrews?
So....are these expected to function as setscrews, or orifices, or both?
If only as orifice, kill the heat treat with annealing and then listen to the optimist.
Spot it, keep it cool, high speed.
I was pecking to keep the bit lubed. but I might not doing it in short enough cycles.
Originally Posted by vanguard cycle
These are being used as screws for handles. It is a poor design and the often break. The hole is to put the screw extractor in so I can change them quickly when the break. I would call it the realist.
Originally Posted by S_W_Bausch
Thank you for the advice in method. The jobber length is on the carbide tipped drill only and they are just barely long enough to cut 1 -3/4" deep. The HSS drills were standard length.
Originally Posted by DaveE907
Set screws, or cap screws?
Originally Posted by DKarasin
What sort of "handle" destroys 3/8" fasteners?
I suggest the base of the handle is rounded, not square, etc. and acting as fulcrum, thereby multiplying the force and destroying the fastener.
Take a good hard look at the base of those "handles".
Id try on a B.port, tap a hole in a pc. of scrap,install set screw, locknut,peck away at desired speed.
can you get a picture of this "handle" and it's mating part maybe someone on here can help you come up with a solution for the constant problem you are having.
That is the opportunist,.... talking now
The handle is a Kipp style. You can lift and turn the handle and not make it any tighter. It allows you to still tighten in confined spaces or leave the handle pointing in a certain direction when done. I have on occasion used just a 3/8 HHCS if we are out of good handles, but I get complaints because the operator needs to have a wrench handy to make adjustments.
Originally Posted by racen857
The problem is not thew handle it is what is attached to it. Below it is about a 12 piece of stock 1/2 or so with a 4" x 4" x 1/8" thick sheet steel welded to it. It vibrates back and forth to get paper to line up in a pile after being printed on. I am constrained on the top by a slot that allows the jogger paddle to adjust to different width paper. I think leaving the handle loose might be worse than tightening it too much. When they over tighten they strip out the inside of the cast Kipp handle.
My place has these stackers in two ends of production printing and binding. I have noticed that the bindery almost never breaks these but the printing end of the shop will destroy up to 3 in a week. I don't see a real difference in usage.
I think they would be thrilled if you just went with SHCS and supplied a cordless 1/4" impact wrench. That 1/4 " hex is, at first look, useless, but 1/4" hex to 3/8 or 1/2 square drive socket adapters are easy to source.
I get complaints because the operator needs to have a wrench handy to make adjustments.
Set up the charger near the point of use, engrave all components of the new system with the department name, and supply spare hex bits.
Is that specific department a bit chaotic, "fast paced"? That might be a factor. If you can trace the excessive breakage to a specific person, is it possible to gently inquire what the situation is, perhaps contrasting the two different departments. Morale may be an issue.
It sounds like a potential repetitive use injury scenario. A pinched nerve, loss of range of motion, etc. may encourage the person to use a cheater bar, kick it tight with a foot, hit it with hammer, some other coping tactic, etc.
You may have other options, perhaps.
A clicker-type torque wrench, to allow increased (but controlled) torque.
CCTV camera, watching "what the hell is going on".
Asking what can be done to make the process easier.
Last edited by S_W_Bausch; 07-17-2012 at 01:00 PM.
Drilling out the screws is not making them any stronger.
Sounds like you need a bigger size clamp screw.
Use a standard gr8 hex cap screw. Get a small offset box wrench to fit. Put a compression coil spring, ID a little bigger than the screw shank, over the shank of the screw, braze a washer under the wrench box opening. Spring will lift wrench into engagement with the hex head so you can adjust it. Push down o nthe wrench to disengage to reposition. Washer keeps spring from pushing wrench clear off. Same idea will work if the screw functions as a clamp screw instead of a set-screw, only use a shoulder screw instead of a capscrew. If you can't find a shoulder screw with hex head, slip a short piece of pipe over a capscrew to make a shoulder, spring fits over pipe, hole in washer must clear pipe OD.
Not losing all that much strength by drilling
The part in the middle that I am removing does not add all that much strength in bending or torsion. The material that does all off the work is at the outer diameter. The threads are a problem in that they act as a stress concentration. You do lose some strength in tension but that does not look like a tensile failure/
Originally Posted by magneticanomaly
Think of an I beam, the part doing the work is the flanges and not the web. The taller the web the stronger the beam if you held the flanges the same. The same goes for drive shafts (often hollow).
Sounds as if you have a poorly designed jogger where the adjuster clamp screw is doing double duty ;clamping position and absorbing impact.Without seeing it is hard to know.I do know that badly designed mechanisms cannot be repaired until they are redesigned.We have air operated joggers on the delivery of our 55" presses supported by the motor driven trapezoidal screws and if they were set to tight they would just "stall" as the air pressure isn't high enough to break anything.We have an old sheeter as a standby machine that has mechanical joggers that are moved by eccentrics on gears that will not stall if to tight.They will move the load or shake the mounts loose or fatigue the paddles and break them eventually.Operator setup error.Seldom use the machine so I don't worry about improving it.Don't know what our Marquip sheeter uses because it has never failed.You can't afford to keep making redundant fixes;retrain the operator or redesign the jogger.I feel for you either way BTDT.