Gun drills - how much air pressure?
- Thread starter Ssonerai
- Start date
Don't hold your breath too long. :shakehead:
My crutches are my hands. I try things and if they work, good. If things don't work I try something different. IMO it's a waste of my time and money to send something out that I can do myself much quicker and cheaper and get as good results.....or maybe even better.
Some might call me a redneck for hand holding and grinding my gun drill on a green wheel but if you don't try it how you gonna know.
I've ground buckets full of moulding knives to profile by hand.
Still grind most twist drills that way, up to 1" dia. Can't see the really small ones anymore. Lathe bits as a matter of course, HSS & carbide.
Gun drills are new to me though. If there's a specific grind for wood, i'll try it with fixtures. & diamonds.
I was not careful of dust/fumes/solvents in early years. Taking better care these days and avoiding most. Carbide is pernicious & one that would be nice to avoid but it is too useful. So coolant, & chemical respirator.
Green wheels under the right circumstances can get the job done. I ran a Fitchburg cylindrical with a 20" green wheel in a buddy's shop, nights for a while, spinning port tools in. But the truth of the matter is that green does not really grind the carbide, it erodes the binder around the particles so they fall away. The edge is not as good as when honed with diamonds.
These days new diamond wheels seem about as cheap as any other abrasive substrate at least on ebay..
smt
Still grind most twist drills that way, up to 1" dia. Can't see the really small ones anymore. Lathe bits as a matter of course, HSS & carbide.
Gun drills are new to me though. If there's a specific grind for wood, i'll try it with fixtures. & diamonds.
I was not careful of dust/fumes/solvents in early years. Taking better care these days and avoiding most. Carbide is pernicious & one that would be nice to avoid but it is too useful. So coolant, & chemical respirator.
Green wheels under the right circumstances can get the job done. I ran a Fitchburg cylindrical with a 20" green wheel in a buddy's shop, nights for a while, spinning port tools in. But the truth of the matter is that green does not really grind the carbide, it erodes the binder around the particles so they fall away. The edge is not as good as when honed with diamonds.
These days new diamond wheels seem about as cheap as any other abrasive substrate at least on ebay..
smt
Last edited:
The steel grind on a gun drill still works fine for Maple, just limits the feedrate to about 0.05mm per rev or so. It will overheat if you try to feed it faster. There is plenty of info about the grind detail for gun drills. Basically the point wants to be on centre(for steel) and the outer point position is about 1/2 the area of the drilled diameter. I regrind gund drill on D bit grinder. Just gives more control than by hand, but by hand does work for sure. I mainly resharpen for drilling pre hardened steel and touch up my own ones for home for coring.
Hi,
My shop air pressure is 110 psi. When operating a gun drill it is volume that is more important.
For me, I open the globe valve about 1/3 and my rpm is 400. My feed velocity is about 2 inches per minute.
Everybody has their own bend to the brim. Keeping the heat down is the prime directive IMHO.
Rick
My shop air pressure is 110 psi. When operating a gun drill it is volume that is more important.
For me, I open the globe valve about 1/3 and my rpm is 400. My feed velocity is about 2 inches per minute.
Everybody has their own bend to the brim. Keeping the heat down is the prime directive IMHO.
Rick
I've ground buckets full of moulding knives to profile by hand.
Still grind most twist drills that way, up to 1" dia. Can't see the really small ones anymore. Lathe bits as a matter of course, HSS & carbide.
Gun drills are new to me though. If there's a specific grind for wood, i'll try it with fixtures. & diamonds.
I was not careful of dust/fumes/solvents in early years. Taking better care these days and avoiding most. Carbide is pernicious & one that would be nice to avoid but it is too useful. So coolant, & chemical respirator.
Green wheels under the right circumstances can get the job done. I ran a Fitchburg cylindrical with a 20" green wheel in a buddy's shop, nights for a while, spinning port tools in. But the truth of the matter is that green does not really grind the carbide, it erodes the binder around the particles so they fall away. The edge is not as good as when honed with diamonds.
These days new diamond wheels seem about as cheap as any other abrasive substrate at least on ebay..
smt
I haven't seen this mentioned but you will want to drill/bore about an inch deep in the backside. Otherwise, as the gun drill comes through the other side, it may catch, grab, and can wreak havoc.
Thanks for that.
I'm finishing my 2 man chainsaw restoration/building sprocket and clutch, and also working on a customer furniture piece. So not yet got comfortable starting to set up gun drill on the planer. Almost thinking of drilling from both ends. Have a scrap butt to try it on when time permits.
smt
etiquette question.
Some have asked where i buy gun drills surplus.
Short answer is i went on eBay, researched and bought an order. Next time made a point of searching for vendors that might be close, and found one, turns out i've bought machine tooling from online for at least a 1/2 dozen years, that was close enough to drive to.
Bob's focus as a dealer is machine tools and tooling. But he says he sells a lot of gun drills to cue makers, flute makers, bagpipe, etc. Bob says it's fine with him to post link. He might or might not have sizes or lengths that suit woodworkers at any given time. Points and condition are what they are, though all of mine are sharp/recent regrinds so far.
No connection to those who asked back channel, so would prefer to mention source in the open so it (maybe, possibly) benefits those who have helped me if anyone. It might or might not help anyone let alone Bob, depending on nuisance factor. It's not a big deal.
Should i post business name and town?
smt
Some have asked where i buy gun drills surplus.
Short answer is i went on eBay, researched and bought an order. Next time made a point of searching for vendors that might be close, and found one, turns out i've bought machine tooling from online for at least a 1/2 dozen years, that was close enough to drive to.
Bob's focus as a dealer is machine tools and tooling. But he says he sells a lot of gun drills to cue makers, flute makers, bagpipe, etc. Bob says it's fine with him to post link. He might or might not have sizes or lengths that suit woodworkers at any given time. Points and condition are what they are, though all of mine are sharp/recent regrinds so far.
No connection to those who asked back channel, so would prefer to mention source in the open so it (maybe, possibly) benefits those who have helped me if anyone. It might or might not help anyone let alone Bob, depending on nuisance factor. It's not a big deal.
Should i post business name and town?
smt
You might as well buy some and resell them.
Haha!
I've bought a few surplus on Ebay too, many many years ago.
All of them have rear ports for coolant, not air . Hence , the different thread.
So, I just used them for hole starters.
Lots of them are way too long .
I just ordered a new Sterling .760" by 22". 5/8 shank and side air port .
Like the one on the pic .
That's one is .700.
Attachments
If you'll go back to the title page for this section and look at the topmost subject (it's called a "sticky") you'll see the rules for this forum - the short answer is "No", links to vendors and sources are to be given through PM's and not published.
Being the woodworking forum mod on the largest machinist site on the web, I do tend to read rules and stickies. That sticky is why i asked, it does not seem ironclad/"absolutely "never".
However, having received answer directly and by default - no "ayes" so will not post here. It's certainly not a big deal, anyone can do what i did. If too many ask back channel, I'll post the source on my wood forum and make a note here rather than keep answering individual pms.
Thanks!
smt
I will try not to make this reply too long, but feel compelled to say something since I spent more than 30 years in the deep hole drilling business before I retired. I designed, sold, and serviced gun drilling machines that produced extremely accurate bores in many different types of steel.
The most accurate way of reducing drill drift is to start the drill using a close tolerance drill bushing and rotate both the drill and the work. This is called counter-rotation. Forces tending to make the drill stray (drift) from the center line will counter act each other and, with the right set-up, counter rotating gundrilling machines can produce run-out accuracy of (T.I.R.) of 001" inch per foot.
Counter rotation gundrilling machines use a rotary union attached to the rotating tailstock to induce coolant (or air in the case of drilling wood, graphite, plastics, etc.) to the gundrilling tool.
The total rpm's can be split however you like between the work and the tool. Often 50/50. But, the advantages of counter rotation will still be evident even at a 90/10 ratio.
I would be happy to try to answer any questions you might have, including giving you some names of used machines that can probably be picked up pretty cheap at used machinery dealers. Some manufacturers also sold just the rotating tool tailstocks to those who wanted to make their own machines.
Interesting... thanks for sharing. Never thought about counter rotation (and would have no easy way to do so) but it make perfect sense, especially with rifle barrels.
Speedi -
What a great reply!
You can probably tell that i asked about rotating the drill as well as the work because while i've never run one (or even seen one run) I'm more familiar with gun drills in theory & reading as metal drilling tools.
My planer gets used for nearly everything "large and interesting" as a rigid, convenient set up platform with X/Y/Z capability, and add anything else to the table or railhead. It's got a 92" table with 80" travel. (My lathes are all small 9" & 10" Hardinge 2nd ops, and SB).
Current plan is to make a holder for the tool slide allowing alignment of the drill. Then a Hardinge 2nd op lathe headstock on the table for the cue blanks. Reason being all spindle tooling here fits the H brand taperloc spindles. "At some point" I may contrive a spindle to drive the drill from the rail as well...... Or put the work up there, and the drill in a spindle on the table.... (need a headscratching emoji here)
Still finishing other projects, but will circle back to this one.
Really appreciate your input, thanks for being willing to comment!
smt
What a great reply!
You can probably tell that i asked about rotating the drill as well as the work because while i've never run one (or even seen one run) I'm more familiar with gun drills in theory & reading as metal drilling tools.
My planer gets used for nearly everything "large and interesting" as a rigid, convenient set up platform with X/Y/Z capability, and add anything else to the table or railhead. It's got a 92" table with 80" travel. (My lathes are all small 9" & 10" Hardinge 2nd ops, and SB).
Current plan is to make a holder for the tool slide allowing alignment of the drill. Then a Hardinge 2nd op lathe headstock on the table for the cue blanks. Reason being all spindle tooling here fits the H brand taperloc spindles. "At some point"
I may contrive a spindle to drive the drill from the rail as well...... Or put the work up there, and the drill in a spindle on the table.... (need a headscratching emoji here)Still finishing other projects, but will circle back to this one.
Really appreciate your input, thanks for being willing to comment!
smt