The lathe is running and I started on the list. I got halfway through the first drill hole pulverized the drill bit. All I know it was supposed to be titanium coated.
Thanks,
Bill
The lathe is running and I started on the list. I got halfway through the first drill hole pulverized the drill bit. All I know it was supposed to be titanium coated.
Thanks,
Bill
What material, hole diameter, and spindle speed? Was it a new sharp bit? Did you use a center drill to start the hole?
Im going bet the drill bit was Chinese....
..............Not enough info. A Titanium coating isn't magic, and depending upon what you're doing probably isn't really necessary. Remember too, the first time you sharpen it the coating is gone on the business end.
Personally for most of my drilling in the lathe or milling machine I really like parabolic flute type bits. And yes this one is TiN coated but I don't specifically buy them so. Their benefit is primarily chip clearance/flow. Don't know what you mean by 'Pulverize' either. There are quite a number of possible reasons. Everything from poor quality bits, simple lack of coolant/lube, to chip packing, or a material issue.
..................Buckshot
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Usually you have to run small drill bits pretty fast, clearing chips often and use a good lube. I have found, generally speaking cheaper drills are usually pretty dull and ground improperly right out of the package. All Chinese drills need sharpened before using and then their kinda "ok" for not too demanding tasks. It is dang near impossible to sharpen real small bits in the home shop environment so I have an assortment of higher quality drill bits and center drills that are used frequently and save the marginal/Chinese for projects that require me to enlarge existing holes.
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Titanium coatings mostly just reduce wear on a drill which is working properly in a suitable material. So they benefit factory production more than the amateur with one job to do in less than ideal circumstances.
Deep-hole drills are about the most effective of all, and they have a point off-centre, so that the bottom of the hole is slightly W-shaped. A good drill sharpening jig is valuable, but an incorrectly sharpened drill can work quite well, if you already have a hole and a drill chuck or collet which are precisely located on the axis of rotation. A really good stub or centre drill to start the hole, followed by a cheap long drill, can do a good job.
Speed? Material? Drill size? Coolant? Cutting oil? Power feed or manual?
Lots of factors here.
Holy cow:
Grade 5 bolt
1/4"
600RPM +/-
Center drill used
New or close to new
Though parabolic were for aluminum
Chinese ?
Manual feed
Drilled as far as the quill would allow, kept oiled, cleaned the chips regularly. It broke half way through the second pass. First time I broke anything over 1/8".
Was a little apprehensive about Harbor Freight.
Thanks,
Bill
Last edited by just bill; 01-27-2017 at 08:23 AM. Reason: Computer word generators, spelling and added info.
Usually what I run into drilling a deep pocket on the lathe is chip packing. The deeper you go the more frequently the chips need cleared which can be tedious if you have to unbolt the tailstock each time as you're past the travel of the quill. Lots of cutting fluid and a sharp bit will help keep the bit temp down will help it from heating up to the point where the OD of the bit expands and wants to lock up in the bore. Chinese bits are all over the board on quality. Some soft, some brittle. I've even received a set as a gift a few years back where they weren't sharpened. Almost like the sharpening jig was 90 degrees off and the cutting edges were ground off.
Even the best of bits will dull if you let them rub. The cutting action depends on curling away material, if the bit is touching the material and not cutting it is rubbing.
6000 rpm is pretty fast for a .250 bit.
I have feeds and speed program, I punched in steel, medium carbon alloy (1045)
.250 highspeed steel bit
1.5 " hole depth
it returned
722 rpm 1.45 inch per minute feed, with a peck depth of .250
My program is limited to 1 1/2 horsepower machine.
At 2'' depth of cut I was warned to use a parabolic bit.
A parabolic bit refers to the shape of the flute, they are more expensive to manufacture. But give greater volume to hold and flow chips with good bit strength.
Last edited by clodhopper; 01-27-2017 at 11:30 AM.
To lazy to chase arrows.
Clodhopper
I think I've narrowed it it speed and chip removal. I'm trying again later with a new drill.
Bill
Cobalt drill bits work good. I have a set and really like them. They don't give them away that's for sure. Center drilling I have found is a must.
Dont pee down my back and tell me its raining.
HS-Cobalt drills, 135 degree split point.
TiN or TiAlN coatings, usually a little pricey for the home shop machinist are helpful in resisting abrasion, heat buildup and chip welding.
If your going to be doing more than occasional deep hole drilling you might want to consider getting an air compressor and a coolant mister. Not as good as a coolant-thru drill, but will reduce greatly the peck-drilling.
I avoid VA, Hanson, Greenfield and all China made cutters. Greenfield used to be real good, but back in the 1990s they started buying off-shore HS and HS-Cobalt and just doing the grinding here. They don't hold an edge for karp.
For drills I stick with Union, Chicago Latrobe, Cleveland, Precision Twist Drill (PTD), Guhring and one or two others.
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I bought the Harbor Freight 105 piece cobalt set on sale for 79 bucks or something. Most of the bits were pretty good, One so far was not sharp from the factory.
I set it up in a cnc mill with proper speed, feed and lube, it immediately started screeching and smoking. Rechecked the feed, and speed, no go
You get what you pay for, with the harbor freight set I got a nice index for storing bits, number bits from 1-60, letter bits A-Z, and 1/64-1/2 by 64ths. Of the 20 or so bits I have used in the set so far only one was bad, it was so bad that it showed up first try. The set was all I had at first, now it is a back up.
Since then I have been building a stock of screw machine length bits.
The shorter lengths bits suffer less from deflection. Mostly buying the sizes useful for an immediate project.
I am fortunate to have supplier very close to home, I can take a mile detour from dog walking, go in the store, and buy at reasonable prices endmills, bits, coolant, carbide inserts and more.
To lazy to chase arrows.
Clodhopper
A little tip to help out, Make sure all the old drill bit is out of the hole before trying again or come in from the other end. Center drill and drill with a good black sulfar oil clearing chips every .050 or so and making sure oil is getting up to the point. On small holes deep holes this can be tricky. Deep hole drills are hollow and oil is pump thru the drill under high pressures to the cutting edges this keeps things cool and clears chips much better. We would set the machines up to "peck" drill .050 or so ( depending on drill dia.) and clear break the chips. On manual machines about a 1/4 -1/2 turn on the tailstock for 1 revolution then clear chips works.
Speeds and feeds, speeds and feeds. And sharpness, and oil, and material. All a learning process. Whatcha makin' wit de bolt? A die?
The most important thing I learned about the chinese lathes is to make sure everything is solidly locked down. Any loose parts in the chuck, tailstock, drill chuck, or feeds and you will break bits.
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |