Machining the dogs for the drive gear on the Kearney and Trecker. I came close to RUINING the gear!
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- เผยแพร่เมื่อ 29 ส.ค. 2024
- The LAST bit of machining to get this drive gear usable for the K&T. after MORE THAN TWO YEARS! I can't believe I have had this thing for that long. And I nearly RUINED it!
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Breaking a tap is never fun. Ever. The drive dogs/keys I mounted to the back of the gear are not held in place only by the screws. They are also notched into the tapered tool holder. Is it the strongest connection? No. Could they shear off? Maybe, but I really do doubt it. It's something I will keep an eye on, but I don't anticipate that it will be an issue. Time will tell.
Greg, you need to back track a couple steps. Start again ! Make new drive keys, DO NOT mill them thinner, countersink 1/3 to 1/2 of the drive keys into the face of the new gear. The design in this video will not drive the universal head! It will shear the #10 screws off in the gear.
In low range the K&T 2HL spindle will put out a over 200 ft-lbs of torque. (quite a bit more with cutting tool or gear backlash ringing shock load) I have done jobs that come close to 200 ft-lbs with my 2HL mill !! You need full dimension drive dogs to transfer that torque to the universal head!
Breaking taps and making parts over is all part of paying your dues learning and gaining skills in the machine shop. Some machinists keep a box of these parts to remind them of their learning process....
Chuck
We shall see. I can always modify it later. Don't forget that the keys are set into notches in the taper. The taper in the spindle is where MOST of the drive forces come from anyway. Not the drive keys.
Exactly what I was about to suggest
I have do some napkin math and the screws, assumed they are grade 8, could handle 610 Nm (450ft/lb) of torque. Any more and they would shear off... That is about 5 hp at 60 RPM or 10 hp at 120 RPM... assuming you do some sort of calculation before taking a heavier cut and stay within the torque limit of the screws it will be fine.
Forgot power that motor has in that mill but assuming it's 5 hp you shouldn't be able to break them above like 80 RPM (some safety factor included) even if you stall the motor SLOWLY... shocks would most definitely break the screws
@@MyLilMule that is true but you still have to transfer the torque from the arbor into the gear
there is a screw screwed from the front but that screw alone would strip immediately after you would take a cut
@@Cjarka_ It's a 3HP motor. I'll assume all of your math it correct (I am no engineer). But I still think there are other factors not being considered. Only time and trying it will tell for sure!
The most horrible sound in the world is sound of a snapping tap. Ugggh!!! So glad you were able to get it out!
Me too! I ruined a part once tapping some aluminum. Ugh. That was painful.
Good video, Greg. Kinda lost count of the number of gears I’ve ruined…some reversibly, some not…nice job saving this one! Of course I have a somewhat endless supply!
I've made a splined shaft on this machine, have yet to make my first gear. Maybe I'll get lucky and find a stash of gear cutters at an auction some day.
Hi Greg, I liked the vice clamp and the super glue trick. The other commenter may be right that the dogs need to sit in a pocket on the back of the gear. Cheers
Only time will tell. If I shear the scres, it can be fixed. I know a guy. 😉
Well I second what I read in other comments here. On the other hand if something goes wrong while using the mill, it will sheer the two screws instead of exploding the whole machine.
With proper drive keys if something goes wrong to cause an overload the spindle clutch in the K&T 2HL mill will slip, also V belts would slip or even stall the motor. Then the spindle and table feed drive train will stop before doing any damage to the milling machine. Cutters, work piece or machinist's temper may not fare as well .....
I don't think those screws are in any danger. The drive keys are also notched into the arbor. MOST of the force comes from the taper anyway. There's very little on the keys.
That click makes your heart fall through the bottom of your shoes. You want to say bad words, maybe throw things. But none of that will help the situation. So you go to plan b. You fix it. And go on. 😊😊 yeah 😂
Oh, bad words were said. I muted them when editing. 😂
Those little flat head screws holding the keys are going to shear in a New York second when you give it any torque. Why aren't you milling keyseats into he gear ? ? ? Be prepared to dig out those broken screws. --Doozer
We shall see. I don't think you're prediction will come true.
Don't You think it is a little weak with just two relative small screws transmitting all the force to the head? Don't You think the drivedogs should be sonken in the gear also?
/m
The majority of the force transfer happens in the taper.
@@MyLilMule Yes that will sure be fine from the mill to the taper but If I remeber correct my reaktion was from the taper to the gear?
@@magnuscarlander2464 The drive keys are sunk into notches in in the tapered part of the tool holder. I don't think it will be an issue. But if it is, I can always go back and make changes. If those screws get sheared off, it would be a disappointment and a delay, but not the end of the world. As a hobbyist, there's nothing in my shop that makes me any money, so I can afford to be down down for a bit to fix a mistake.
Your drive dogs arent actually driving the gear .... 2 x 8-24 screws are??
Actually, the spindle taper is driving the gear - MOST of it anyway
Any reason you didn't choose to cut a keyway in the gear and drive it with a key? I am worried those small screws are going to shear when a load is put on it.
I don't think they'll shear at all. Most of the turning force comes from the taper. I thought about cutting a keyway, I maybe I will if I experience an issue.
Why do you need a Blind Hole ???? --- Jim
I don't NEED it, I preferred it.
Why not make the drive dogs into keys for the gear?
This is the way I chose to do it. If it becomes an issue, I can always revisit it.