Question on drill bits??

[scott_vt]

Mornin Dave,
Lots of good advice from all the guys here. I read through the thread quickly and didnt notice anyone mention pre drilling your 1/2" hole first with something like a 1/8" drill. I usually do this for two reasons. First and most important is that once your intended hole location is prick punched the 1/8" drill wont wander from your layout and second the 1/2" drill will go through the steel plate much easier /forums/images/graemlins/grin.gif I dont do this in the shop on my Bridgeport because I dont need to but its the way to go using a home drill press arrangement.

Any good quality H.S.S. drill set will serve you well. As some others have stated, I sharpen and touch up drills on the grinding wheel. Smaller drills are just replaced because they are inexpensive, drills smaller than 1/8" can be a pain to resharpen manually.

If you do have carbide drills, you would need a diamond wheel to sharpen them, oh and by the way, diamond wheels are quite expensive /forums/images/graemlins/grin.gif Most home shops wouldnt have them /forums/images/graemlins/grin.gif

 

[scott_vt]

Mornin Dave,
Lots of good advice from all the guys here. I read through the thread quickly and didnt notice anyone mention pre drilling your 1/2" hole first with something like a 1/8" drill. I usually do this for two reasons. First and most important is that once your intended hole location is prick punched the 1/8" drill wont wander from your layout and second the 1/2" drill will go through the steel plate much easier /forums/images/graemlins/grin.gif I dont do this in the shop on my Bridgeport because I dont need to but its the way to go using a home drill press arrangement.

Any good quality H.S.S. drill set will serve you well. As some others have stated, I sharpen and touch up drills on the grinding wheel. Smaller drills are just replaced because they are inexpensive, drills smaller than 1/8" can be a pain to resharpen manually.

If you do have carbide drills, you would need a diamond wheel to sharpen them, oh and by the way, diamond wheels are quite expensive /forums/images/graemlins/grin.gif Most home shops wouldnt have them /forums/images/graemlins/grin.gif

 

[Parttimer]

Thanks again. ALL I went to the store on sunday and picked up a hss drill bits, and a package of titanium coated bits. They did not have any of the quality names I have read in this thread. I guess I will be doing a little on-line shopping for these quality bits. For now I have these and I did a practice run with oil at the slowest speed my drill press hass (800 rpm). Wow what a difference. Again Thanks all, it has been an education. PS can't wait to try another project, a little more complicated than just drilling three holes and bolting something together. It was fun though. /forums/images/graemlins/cool.gif

Dave

 

[Parttimer]

Thanks again. ALL I went to the store on sunday and picked up a hss drill bits, and a package of titanium coated bits. They did not have any of the quality names I have read in this thread. I guess I will be doing a little on-line shopping for these quality bits. For now I have these and I did a practice run with oil at the slowest speed my drill press hass (800 rpm). Wow what a difference. Again Thanks all, it has been an education. PS can't wait to try another project, a little more complicated than just drilling three holes and bolting something together. It was fun though. /forums/images/graemlins/cool.gif

Dave

 

[Greenhouseray]

Hi All
The question on what speed to run the drill at was posted earlier.

What speed (RPM)to run a drill at???
This depends on several factors:
What is the drill bit made of?
What grade of steel are you drilling?
What diameter hole are you drilling?
The formula is: When using High Speed Steel drill Bits
4x the cutting speed of the material being drilled divided by the diameter of the drill bit.
Example: drilling a .500" dia hole in common plain carbon hot rolled steel.
the constant is 4
The cutting speed of a HSS drill in HRS is 80 ft. per minute. (this is empirical data compiled from experimentation published in Machinery Handbooks)
Therefore 4x80 divided by .500 (decimal equivelent of 1/2")
gives you the speed to turn the drill bit at 640 RPM.
Use the closest speed setting on your drill press.
Maintain a steady feed rate and cutting fluid does allow higher drill rpm if desired.
Cutting speeds of: When using HSS Drills
Stainless 50 fpm
Soft gray iron 100 fpm
Brass & Copper 200fpm
Aluminum 300 fpm.
This info probably is sufficient for us Farmer Machinists.
For more info get hold of a Machinery's Handbook at the library.
I worked as a Tool & Die Maker early in my career 40 years ago and this subject of cutting speeds was drummed into my head by my apprentice master.
Greenhouseray

 

[patrick_g]

Egon, Greenhouseray and all, neat thread!

I, having no formal training in the manual arts and am an empty sponge ready to soak up info on this stuff. I like the math approach to empirical data that was given and will now be better prepared to drill holes in non trivial pieces of steel. I have twisted and ruined some 1 inch Silver and Deming bits trying to drill a hole in a 3PH implement to mod it using a Milwaukee right angle 1/2 inch drill.

Most recently I had to drill a couple hundred 9/16 holes in 1/4 inch steel flat bar. I was so proud of myself for getting it done with just one bit and no resharpening. I went through a $5 quart bottle of cutting oil and wished I had one of those pumps to circulate cooling/cutting fluid on the workpiece.

I have a 20 year old 16 speed Harbor Freight drill press and for lack of knowlege just went for a really low speed, frequent oiling, and enough pressure to get a continuous curl of removed metal most of the time. I found that pilot drilling a smaller hole, about 1/8 to 3/16 made the larger drill work way better. It was faster drilling two holes than just using the larger bit alone. Of course, if I knew what I was doing maybe that would have made a difference.

I have bits of varying quality including the index boxes from HF with the GOLD toned bits. These cheap Chinese bits are not of consistently bad quality. I have had bits from one index from one source (Cumins traveling tool show) twist off and break one after another and other sets (HF) that actually work pretty well. As I also do a lot of wood, if they prove poor for steel I can demote them to wood working.

Another approach is to buy a nice inclusive set of drills: numbered, lettered, fractional, and then when the reqularly used ones get messed up, replace them with good ones ( and keep spares.) Then you have a breadth of sizes and the ones you use a lot are good ones.

I recently bought a drill Dr. sharpener and just barely started to try to use it. First couple tries proved to me that it isn't fool proof. Drill's cutting edge is sharp but I'm not getting the tips right yet. I'm sure it is me not the tool and with practice I am confident I will get better results. Why not, it works for a lot of other folks.

patrick_g

 

[flusher]

Dave,
There are a lot if different quality bits on the market. I have never tried the titanium coated bits so don't know if they are any good. The are usually sold it sets that are real cheap.
For general use I use drill bits that have the little point on the tip, they are gold colored and I think they are sold by Black and Decker. The little point sets in the center punch mark and holds the drill in line while starting. I do not know how to sharpen the drills with the tip on them, but they work very well for me.
Always use cutting oil, it will increase the life of your drill bits and make drilling much easier.
There may be a possibility that you were trying to drill through metal that had been hardened during the process of being welded. I was a late learner on this, tried to drill a hole in my FEL that was near a weld, my drill bit sat there and did absolutely nothing. Time to drag out the cutting torch or buy a carbide bit the size I needed.
For larger hole sizes in mild steel I use what is called a slug cutter. Mounted in a magnetic drill or drill press I can drill a one inch hole in one inch material in one minute. The hole is very clean.
I am sure that others on TBN have their preferences.
Farwell

"Slug cutter": is this like a Milwaukee bi-metal hole saw? When I got my Markham tooth bar I used one of these to cut the holes in the sides of my FEL for the attach bolts.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=35891

 

[Defective]

"Slug cutter": is this like a Milwaukee bi-metal hole saw? When I got my Markham tooth bar I used one of these to cut the holes in the sides of my FEL for the attach bolts.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=35891

Nope...

try: http://www.wttool.com/p/0126-0800?utm_id=44