Hole Drilling Progress and Milling Attachment Update
I took a few hours tonight to practice some of the techniques that you all so graciously shared with me a few weeks ago. If you recall I was having trouble marking centerlines and drilling holes in the right place.
For marking centerlines, I used the technique of setting the machinist square to the middle distance, and running it down both edges of the work with the scribe held against the end. Actually I used the depth gauge on my calipers for this, since the bar was very thin (3/16"). Worked great!
I also used the technique that someone mentioned of adjusting punch marks by making a light punch and then moving it a bit if it isn't dead on.
But I was still having trouble getting holes to drill in the right place. It turned out that there was a big burr on the taper of my drill press. I ran the drill press and held a lathe bit in my hand to scrape it down. Then I used sand paper to smooth out the edges of my gouge.
That worked pretty well, but I still had some runout. I found a neat way to correct that. I rotated the chuck by hand and looked for the point where it was furthest out to one side. Then I gave it a light tap with the hammer to center it.
I also got some screw machine bits in the sizes I need for this project. Those helped quite a bit as well. For starting the hole I had a lot of trouble with the center drill; I switched to a 1/16" bit and things went much more smoothly.
Unfortunately I'm still having a lot of trouble with the countersink bit. I can go from punch mark to 1/16" to #21 to #9 with no trouble, but the countersink bit always wanders off center. It's probably because I'm using a junky countersink bit from Home Depot.
Here's a pic of one of the best series of holes. I highlighted the scribed lines so you can see them. Notice how the holes are well centered right until I get to the countersink.
Also, here's a pic of my progress on the lathe milling attachment. I drilled all of those holes before I worked out the problems with my drill press. The
slats are also not quite parallel, some of them are off by a lot.
I figure it's still usable as long as I can shape up and do better for the next phase of the project. I know it's super ugly but I am trying to avoid the trap of perfectionism. I'm really trying hard to avoid the temptation to throw it out and start over.
So I guess the upshot is, I'm making progress!
Last edited by ldn; 07-20-2010 at 01:52 AM.
It might be the cheap counter sink. Maybe the cutting edges are ground unequal (I'm assuming it is a multi-flute countersink since I've never seen a single flute one at HD). How are you holding the part on the drill press? If the part can float around on the table, then any number of things can pull it off center, including the runout in your spindle. Countersinks also like to be run slow or else they can chatter like crazy, especially the multi-flute ones. I think I see some chatter marks in your picture, so if it is squealing while cutting, then it's also vibrating and could be moving. What's the slowest speed on your drill press?
I have had good success in my metal butchery with a nice single flute countersink. I got a set of nice set from MA Ford. They seem to go on sale and I don't recall them that expensive. Anyway great value.
More chips less frustration.
Keep up the great work and we all like pictures.
Yes, it's a five flute countersink and it was chattering like crazy. It makes an awful noise. The slowest speed on my drill press is 620 RPM. I'm thinking a about hooking up a dimmer to see if I can get it to slow down at all.
I'm holding the part freehand (with a safety clamp nearby to stop rotation). Initially I tried using a fence and the results were terrible. Maybe it would be better now with everything trued up but there is still a lot of play in the quill (not the spindle).
I got a lot of advice earlier where people were telling me to freehand it and let the work move to where the drill bit wants to be. That actually seems to work pretty well, but it requires a little bit of "feel".
I think I'll order one of those MA Ford bits too.
A dimmer will NOT work. Get a 3 phase motor and a VFD. You will never regret it.
too litle feed pressure
You should try a serious hogging feed it will likely give u much better resulting finish. Too light of feed pressure with drills and countersinks is a common mistake that novices make. Imho. Give it a try!
[QUOTE=The Fixer]You should try a serious hogging feed it will likely give u much better resulting finish. Too light of feed pressure with drills and countersinks is a common mistake that novices make. Imho. Give it a try![/QUOTET]
yes , you cant overfeed a countersink, lean on it hard and fast with a shot of oil. Light feed is why it chatters.
If 620 is your lowest speed than I think you've found your prolem. Excessice speed will make a c'sink chatter like sack full of kittens.
While fitting the DP with a 3ph motor + inverter is a great idea, it's also an expensive one. Also consider: jamming in a larger driven pulley someplace, adding a jack shaft with 2 or more reducing ratios, or maybe even looking for a slower motor of the same size - the one in there now is probably 1750 rpm. Look for one that's just 1150 rpm.