Deep hole drilling

I have only a standard home shop manual lathe and want to do a projectthat will require drilling a strait hole in a round piece of stainless about 13in long.

Now from what I know I would not expect to be able to drill a hole that deep and expect it to be strait. I know there are way to do it and was wondering if I could be done on a standard home rig or do I need something more to get it to work.

Thanks

Feed needs to be as uniform as possible.
using a toolpost-drill holder and your cariage feed will help.

also the drill tip configuration ....the included angle being flatter rather than Teepy shaped helps.

And as infrequent of pecking as possible.

Can the hole be made first, then use it for the center reference for the remainder of the work ?

having the hole wander is a big deal

center drill
stub drill
jobber drill
taper drill
then whatever else you have

all new bits or freshley ground on a proper drill sharpening rig

tattooed_machinist said:

having the hole wander is a big deal

center drill
stub drill
jobber drill
taper drill
then whatever else you have

all new bits or freshley ground on a proper drill sharpening rig

Click to expand...

This can be done on a home lathe but a lot of care is required.

Believe it, the hole WILL wander.
To try and eliminate ANY wandering, use NEW DRILLS, that's stub, jobber and then an Extension Drill of the appropriate size. These can be bought as an over the counter item as there are a lot of standard and non-standard sizes available.
You need NEW drills to start the hole to try and eliminate any chance of starting the hole off centre or wandering, remember that a hand held home sharpened drill will create/cause this wandering, I don't care how well you think you can sharpen them by hand, it's not good enough for this application.
If you want it to be smack on centre at the 13" deep end, then you are going to have to go about it with a bit of boring involved.
If there is a length of DRILL ROD available over the counter, that is the exact finished size to the hole you want to drill, then use the drill rod to make a simple gun drill out of it. Start the hole with the smaller sized drills and then sneak up to about 1/32nd" under the finished size and then use the gun drill you have just made as a boring bar/ reamer.
This will work like a single point cutter and bore the hole true. There has been quite a lot posted about making gun drills and hardening the cutting end, so no need to go there.

Stainless steel eh, have you been warned about this stuff work hardening, you get the working point very, very hot or red, games over, you just made that bit of stainless go rock hard up at that point, chuck it and start again, got to keep liquid on it , easy speed and slow cutting feed is the way to go.

Have fun and hope you get the job done.

regards greenie.

If at all possible I'd have oversize material and turn the OD after the fact to bring the hole back on center via a 4 jaw chuck and the tailstock center.

Do they make this stuff in hollow bar?

I've drilled plenty of holes that deep in stainless steel, and all of the suggestions made here will get you the best results you're ever going to get. The hole will wander. That is a fact. The object is to try and minimize the wandering as much as possible by centering, stubbing, using shorter drills and then gradually going to longer ones. All of the drills need to be new or machine sharpened. If the project needs a dead straight hole with no wander, you need to look at some other way of getting the hole in there. Possibly EDM or laser ???

The deeper you go the more the drill will lead off line. To minimize the amount of lead off I drill fron each end of the shaft if possible.

When I was having a lot of stuff gundrilled, the driller could keep about 90% of the parts within .001in/inch of length for runout. Do not confuse this with straightness, they are not the same. On long parts, I have seen a perfectly straight hole come out the side.

For a manually drilled part, figure out what you will do if your hole runs out .003 per inch of length on the back side. That would be .039. If you can't make this work, you are better off to start with an oversized od, and then finish the od off the through hole.

What size hole are you drilling?

What's the OD of the piece?

What's the tolerances?

Will the hole be reamed or bored for a better finish than drilled?

What is the diameter of the hole you want to have in the 13" long piece? All the above suggestions are more or less worthless if the hole is 0.1" in diameter for example. If the diameter of the hole is large, meaning the wall thickness is small, you are looking at finding a piece of heavy wall tubing as a starting place. Gun drilling is they way long holes are made in most cases. EDM processes can also make holes where the length of the hole is much larger than the diameter. If you know how to weld you can start with a hand full of square rods of stainless steel, clamp together a bundle of them with shims on the rod in the center, weld the outside rods together and fill the gaps to make a complete solid. Use a press to push the center rod out that you shimmed and then turn the OD to get it round and to size. You have a square hole down the center which you can round out with a drill. The easiest way is to find the sellers of heavy wall tubing and get some you can open up to the size you need. If you just want to abuse yourself you can do as suggested earlier but drill from both ends with under size drills until the two wandering holes intersect near the middle. After that is done you use a larger diameter long drill to go the full length opening up the hole. This will get you a hole that comes out in the center of both ends of the piece although it may not be perfectly straight. What is the OD of the piece?

I disagree. The size of the hole definitely makes a difference, but doesn't make it impossible. I have personally drilled .093 holes 14" deep in 440C and 17-4 Stainless Steel. We used to have a part that I drilled a .06 hole at least 10" deep, and I'm sure I could have drilled deeper. The deepest hole I ever drilled was around 3/16" and was drilled in 4150 about 28" deep. The suggestions above will work with small drilled holes. Above all, you have to be able to FEEL the drill cut and clear it CONSTANTLY to keep it from crowding and moving over. It is a slow and careful process.

I'm with rockfish on this.

We still need the info I listed above to give valid recomendations. All prior offerings are general at best.

I agree with FranH...
If the material is oversized on the OD, I would drill the hole, then ream if possible to get a fairly straight hole.
Then I'd turn the OD between centers, (instead of using the 4-Jaw).

Thanks for the help guys.

I'm drilling a .280 hole in stainless that is 1.5in O.D.

I would like to keep it to with in say .020 straitness and I can turn it down afteward but if I drop a straitness gauge down it I'd like to go through.

What do shops charge to do gun drilling like this on say 6 pieces??

I'm not looking to get my eyes poked out.

Thanks
Da Grinch

Gundrilling was not expensive as I recall, but it depends on whether the driller has the drill bit to start with. If you are looking for concentricity, make sure you get a driller that spins the part, not the drill.

grinch said:

I'm drilling a .280 hole in stainless that is 1.5in O.D.

Click to expand...

You mean .2812 (9/32)?

You won't find the drills you need in .280.

I drilled a hole through a 18" long piece of propeller shafting (the really tough naval brass) and had it come out only .002" at the far end. I made an old fashioned "D" bit out of drill rod. They drill very true if used well. To make a "D" bit,mill down about 1/2" of your .280" dia drill rod. Mill it down to .001" above the center line of the rod. That is,leave the rod you do not mill away 1/2 dia. + .001". I recommend you buy a piece of .280 drill rod,or make the D bit about 3" long and silver solder it to a .250" drill rod. I'd drill the one rod,and make a tennon on the other that fits well. The two need to be in alignment with each other. Harden only the tip of the D bit so it won't warp. Grind a 10* relief angle and a 5* sideways angle on the tip,so that the OUTER EDGE of the D bit,where it starts to cut,touches the hole being bored first. Drill a hole abt 1/2" deep in the end of your stainless rod,and single point bore it to exactly the diameter of the D bit,or .280" The accuracy of the whole job depends upon getting this right. Clear the bit often- don't let the small flat area on the D bit to get packed tight. Go slow- you are boring with carbon steel. This is a very old way to do it,but it works. They used it on a larger scale to bore out solid cast cannon at Woolwich arsenal in the 18th.C.. Works for me. I'll probably catch flak for my old fashioned ways,but when i was young,and had little equipment for metal working,I had to resort to old stuff to get by,and sometimes still do if it isn't production and doesn't warrant buying an expensive tool.

Can you buy a gun barrel blank in stainless steel? Do you have any special requirements for stainless alloy? Barrel blanks are relitively cheap for the type of hole length form factors. They are also very staight in comparison to average gundrilling work.

One of the gunsmith guys on the site should be able to provide a link to a manufacturer. Or maybe somebody with a shot out .280 Remington barrel lives on the group.

Good luck.

Tom Lipton

I don't know what his "Standard Home Shop Lathe" is but he is going have to have about 30" between centers for this job.

His best bet is to 4 jaw it, dial it in end to end, center drill it, stub drill it to .280?, then drill as deep as he can with the longest drill he can get to just past half the length. Flip it over go through the above setup and drill to break through. If he is careful and lucky the holes will match up.

If the ends have to be faced he will have to use a steady rest.

We used to do that all the time and most the time the hole was straight. It requires a correctly sharpened drill.

A word of caution---even a brand new drill may not have a correctly ground point. You would be smart to check it with a gauge and resharpen if needed.