Cutting oil/fluid for diamond bits

Diamond is a poor grinding material for use with steel. It gets funky at high grinding speeds (high enough to see sparks or make noticeable heat, is way too fast), unless kept cool.

Flood with a soluble oil coolant, if machine grinding. Get some proper grinding points, if you are using a Dremel or similar tool. Or, if you are using cheap grinding tips like the Princess Auto ones, accept that their life will be limited, but less so if you keep the rpm down, and the pressure light.

Cheers
Trev
 
What tool? How aggressive? How much do you need to move?

You are going to want different tips (generally called 'mounted points') for different operations, and for use on different sized tools, from a Makita electric Die grinder, on down to a Dental Drill.

Cutting, carving, grinding, polishing, and buffing points are available. generally you get what you pay for, but you can overpay, too, if you don't shop around.

The stones that come with a Dremel tool work pretty well, but use the largest diameter stone you can, and don't expect the material to fly off fast. If you need to move a lot of material, look at carbide burrs. They work best with a fairly light touch, and should be kept cutting rather than allowing them to rub. Having a burr rattling around inside a crevice or hole is death to the cutting edges, and tough on the parts, too.

Then there are the rubber abrasives, aka Cratex tips. $$ but the best thing going for blending radii, and polishing hard materials.

Last time I bought stones for my Dremel was when PA (maybe House of Tools) had a sale on and were selling a plastic box with a bunch of mounted points, and a bunch of cut-off discs, for about $10 per kit, marked down from an unreasonable $35 or so.

Got a Jewler's supply outfit or a rockhound shop around? They usually have a decent selection, if not the best prices. I got a catalog from an outfit called Page and Wilson, (pwltd.com/ ) some years back. They may still be around the wet coast. DAGS for Grobet File Company, and see if you can get hold of a catalog there. Stuff for Jewellers and Watchmakers. Good stuff! It'll give you an idea of what's out there...

Hardened steel grinds just fine with stones, if using a rotary tool like a Dremel or a Die Grinder.


Cheers
Trev
 
Last edited:
Diamonds

For bits like drill or milling cutters I like solid carbide but these are only used in your milling machine and although they're fine dry I would use a soluible oil fluid as above. There's lots of options for that.

Diamond grinding wheels are great for sharpening carbides and carbide insert cutters, by the way.

For metal removal carborundum works best in at least a pedestal or big mounted bench grinder but this is for crude removal type stuff, sharpening axes, etc. if you're talking a surface grinder full flood coolant makes the job so much better and the magnetic table will allow you to adjust your work holding vise any way you need.

More specific recommendations possible if you have more specific questions.

Cheers,

FM
 
Actually i want to grind a weld maybe 4-5mm in diameter. it is actually a weld in a drill and tap screw hole (for mounting a scope), and there is a plug screw in there as well. i want to reverse the process; what i have in mind is to grind the weld and then extract the plug by using a screw extractor. this way i can preserver the thread. i don't really want to drill the weld (with the plug screw in it) and then re-tap the hole...
 
Moisin ex-sniper, by chance?

If so, tough job. If the weld that put the filler screw in is deep, it'll be damn near impossible. If,, on the other hand, the weld is very shallow, it may have a chance of success.
I'd start shopping back-up plans at this point. If you have a good plan to back up the main one, you usually have it thought through well enough to not need it...

In this case, I would be considering the availability of taps and drills to open up the holes to a usable (if somewhat larger than original) diameter, if the plan does not survive first contact.

Access to the back side? Any ability to make up a jig to drill through the center of the filler screw?
If you can drill with a jig, that would be my first choice, rather than grinding. Coming through the screw (what size is it anyway? ) from the back with a drill bit is second.

Can you positively locate the top of the screw?

I'd limit grinding to as much as was required to make a good spot to start a drill bit. Go slow, and carefully drill out the top of the screw/weld, as much undersize as you can, and slowly work up in sizes (got a number size set of drills?) until you start touching thread, or otherwise showin that you are near the parts that you want to 'save'.

Kinda tough to describe it. I do a fair few broken, and/or otherwise munged up very small screws at work, ranging from about #4 on up. Sometimes they can be finessed out, sometimes the only solution is to drill out the hole and install one form of insert or another to bring the thread back to size.

Good luck!

Cheers
Trev
 
Screw plug

Trev pretty much has it nailed. If we follow your description the weld is still proud and not already ground flush with the surrounding surface. That sounds like you might just be able to finesse the most of that away with an air grinder (die-grinder size) with flat disc--if the above scenario is correct. Dremel might be best with the little discs on 1/8 arbors.

Then after adequate clean up you might ask at the tool supply for a left-hand drill bit just about the thread minor diameter. Left-hand drill bits work slick if the plug has been freed from the weld as Trev described. The threaded plug will usually free and back out way better than screw or stud extractors which are a PITA.

Keep us posted it's an interesting dilemma. Why it was ever welded in the first place is puzzling.

FM
 
Yes, it's a mosin ex-sniper! The size of the screws is M6 X 0.75

Yes, i have easy access to the back side:
Izhevsk_1943_xSniper_05.jpg


Thanks guys, i think i will give it a try! but first i will have to shop for grind/drill/tap bits...

i will post my update when i start to work, but it's gonna be a while! :p
 
For access like that, I'd start a hole from both ends of the screw, with say, a 1mm or so drill bit.

If the screw is able to be drilled, it should not be brain surgery to punch the hole through the center. Once the hole is confirmed to be on center, drilling carefully through the weld from the outside, should allow the screw to be removed, without losing too much of the threads.

Alternately, one could drill up the screws until the thread was just a spiral coil, pick that out, then shoot a tap through from the inside, to tap out the weld deposit to match the thread of the rest.

Careful work and some thought, and you should do OK.

Cheers
Trev
 
Drill out.

The way i would do this is to hold the gun in a vise and perferibly in a Milling machine ,locate the centre of the welded hole, you could do this with a finger dial or a pointer Make a small flat on the weld with a slot drill , center drill with a #1 centre drill , then drill out to tap size , then run a tap through . put some anchor lube of similar cutting fluid on the tap . if you don't have acess to a mill or drill press and are doing it free hand , take care and be sure you locate the centre of the welded hole as the other fellows have said.
hope this helps :cool:
 
You must log in or register to reply here.
Back
Top Bottom