Drill bits and tolerances

A set of HF drills bought years ago was Russian cobalt. Have not seen them since. Best cutting I have.
 
You must have lucked out!!!:) How do you know they were Russian cobalt? Was the set labeled? Are the drills correct diameters,sharpened correctly,and straight? If so,you hit the mother lode!!

I buy a few HF products myself. Like acid brushes,twine,and sometimes a $9.00 ceramic kitchen knife. But,first I examine every one in the store. Most are sharp,but about 1 1/2" from the tip,there is a flat spot on the edge,where they were never fully sharpened. The knives can be close to razor sharp farther down. They are useful,cheap knives though,and I can sharpen them with my Sunnen horizontal/vertical diamond disc grinder(200 RPM). Those are ghastly expensive. I lucked out and got a used one for $150.00. At work I spent over $2,000.00 for a bench model of very similar type. The disc can flip up for horizontal,or down for vertical. Great for fine honing HSS at that low an RPM.

Some have reported HF angle grinders and electric drills lasting real well. I think it's a gamble buying such cheap stuff,but sometimes you can get lucky. I'm not buying their drills myself. No real way of knowing if they are even all hardened until you use them.
 
I use the HF cobalt bits that cost $99 for the fractional, number and alphabet I believe its 115 bits in all. I have a 29 bit set that was cobalt and cryogenic treated cost was close to 500 Dollars at the time but got a good deal. They were life time guaranteed but that was 10 yrs ago and can't find them anymore. I have had good luck with the cobalt bits from HF and have looked at several other sets from other companies and swore that they are the same HF ones only $300 range. The HF bits I'm not sure of % cobalt, the other sets at HF don't do the job...good luck
 
mrfeeney said:
So the question -
1. Is this normal? (example the 1/4" bit has a diameter of .2485) or have I managed to get a sub standard USA manufactured set as well?
2. If you really need an accurate hole you ream it, so is a bit within a thou or two common and acceptable?

Thanks
Click to expand...

Sounds about right. If you check you'll find the diameter is larger at the cutting face than near the shank. ASSUMING top quality manufactures, they are giving you a drill designed to cut the size hole you're after. It has to be a tad under to end up with a on size hole.

You can use this fact to drill under size, if needs be.

1 drill hole with next smallest drill.
2. stone outside cutting corner to just slightly round it here. You will get at least a thou under this way. Good quick 'n' dirty way to get a press fit on a roll pin for example.

Karl
 
I am not out to highjack the OP's thread,but this drill bit discussion raised a question for me.Have any of you guys bought a USA made set and found the set to contain more than one name brand?
 
I bought one of those 115 pc TiN-coated sets in a foldable gray plastic case. Most of the drills are so tight in the case it takes pliers to remove them.

I also found many of the number size drills that were the same size. The markings on the shanks were so small, it was hard to tell. I thought of sending them back but I had bought them many months ago and tucked them away in a drawer and didn't realize anything was wrong until the first time I needed a small numbered drill.

You get what you pay for.

PS: I also bought a set of taps, tap drills and dies. Most don't even cut. OK maybe for chasing a bugged or dirty thread but don't even think of tapping or threading from scratch.
 
My cheap set is from HF and they have actually been pretty good but as said earlier the titanium nitride coating is so thin it's see through. But I mainly work with aluminum and that type of plating has a tendency to stick with aluminum but the cheaper plating doesn't seem to cause problems like good heavy plating does.
 
I have to agree with George. Buy good quality USA made drills and they will perform well and last a lifetime, almost. The first shop where I served my apprenticeship gave me a set fractional set of Morse brand drills. That was in 1971 and I am still using the same set for the most part. I've broken a few of the smaller sizes but replaced them with Morse drills.

Have I used Chinese drills? Sure have. Some have worked and others have not. In my mind it's a crap shoot whether the heat treating is correct, the size designation is accurate, or it's sharpened on center. I'm not saying Asian drill bits are useless but don't expect to get USA quality at a third of the price.


Tom S
 
George, I will measure the "Russian" drills and report. I only know the drills came in a nice little metal stand, and , from my amateur experience, they appear cobalt ( the color) and cut better than any other I have. I know we are all open to the possibility that there are some good metallurgists in Russia (ho hum, just landed a probe on a comet :))) and even in China. But most of the stuff from easterrn block I have seen is poor. BTW, I used to belong to the inside track club at HF. Maybe the drills came from that era. I stopped because it turned into a flea market.
 
I bought one of the 29pc HF drill sets and they're pretty crap, but it's what I expected for $10. I've replaced some that have broken and some with drills from another set, the others I regrind and hone whenever I need that size. Bit of a time drag on a project, but I'll get there eventually. I've thought about one of those 115pc sets, but it seems that you need to go to quite a high price ($250+) to be assured of getting a decent USA made set, otherwise you could just end up with another HF set, but at twice the price!
 
You must log in or register to reply here.
Back
Top