Heckler
Well-Known Member
Am impressed!
Stu
Drill bit to cut stainless steel
- Thread starter TiggerToo
- Start date
Stu
skipmac
Well-Known Member
The only thing I have found to cut broken taps (also broken EZ Outs which I will NEVER use again) is a tungsten or diamond bit. I drilled out a broken 3/8" tap with a Dremel in less than 10 minutes with a Dremel brand tungsten bit. Bit was $12-13 at the local hardware store.
Another trick that has worked for me is to use a small drill bit to drill down the sides of the tap to remove some of the jammed metal then use needle nose pliers in that slot to twist out the broken bit. This does leave a bigger hole that you will have to again tap to take a larger screw or use a threaded insert instead.
seaangler23
Well-Known Member
If it's stainless sheet those cheap step drills you get off ebay for a tenner (finest titanium coating) for 3 actually put up with a lot and leave a good finish, I don't use much else for anything up to about 3mm, must be the small increments in size and use plenty lube and watch cause they can snatch. Not saying they are a patch on a decent cobalt bit but I'm bad for loosing/breaking/blunting bits and it always seem to work
KellysEye
Well-Known Member
>Most stainless fabricators that i know use HSS all day.
When I was trying to drill the SS with a HSS drill bit I went to a marine fabricator in Trinidad and said what the problem was and and he said use Cobalt drill bits.
When I was trying to drill the SS with a HSS drill bit I went to a marine fabricator in Trinidad and said what the problem was and and he said use Cobalt drill bits.
sailorman
Well-Known Member
The problem i think as that most folk cant /unable to sharpen hss bits
DanTribe
Well-Known Member
" If you have a broken tap use Alum to disolve it, but only in non-ferrous: http://www.tap-die.com/contents/en-u...nd_Die_Co.html
Read more at http://www.ybw.com/forums/showthrea...cut-stainless-steel/page2#ZfptxUpX46KuxO8x.99 "
I also found the tip about using alum but it's only for non ferrous, not sure it's OK for stainless?
He does say don't use a stainless saucepan.
Read more at http://www.ybw.com/forums/showthrea...cut-stainless-steel/page2#ZfptxUpX46KuxO8x.99 "
I also found the tip about using alum but it's only for non ferrous, not sure it's OK for stainless?
He does say don't use a stainless saucepan.
lw395
Well-Known Member
Plus there's a lot of indifferent quality HSS around these days.
You can buy decent brands of HSS drill, at a premium, instead of a £10 set from Screwfix, but it's not much more to get Cobalt.
I have a few Cobalt drills which I don't use for anything else.
And once the SS is work hardened things just get worse.
The moment you think 'this isn't cutting well' stop and get a better weapon.
John the kiwi
Well-Known Member
Typical hardness of stainless steel = 95 on the Rockwell HRB Scale
Typical hardness of mild steel = 105 on the Rockwell HRB Scale
That's right folks, 316 is softer than ordinary mild steel.
It does have a property that mild steel does not though and that is work hardening under friction.
Cut slowly and with pressure adequate to ensure the tool is cutting and not rubbing and you can cut all day with HSS.
Actually at the right feeds and speeds it is noticeably easier to machine than standard mild steel.
Just let it rub for a few seconds though and its time to learn how to sharpen your bits......
Typical hardness of mild steel = 105 on the Rockwell HRB Scale
That's right folks, 316 is softer than ordinary mild steel.
It does have a property that mild steel does not though and that is work hardening under friction.
Cut slowly and with pressure adequate to ensure the tool is cutting and not rubbing and you can cut all day with HSS.
Actually at the right feeds and speeds it is noticeably easier to machine than standard mild steel.
Just let it rub for a few seconds though and its time to learn how to sharpen your bits......
vyv_cox
Well-Known Member
All metals that I know of work harden. If they did not their stress-strain curves would always be a straight line, which they never are. In fact mild steel shows very marked work(strain) hardening, as shown by its relatively unusual curve.
The yield point of austenitic stainless steel is only 50% of the UTS, which means that it flows rather more easily, and therefore work hardens more readily.
RichardS
N/A
I had to drill out a very long stud during the Summer and needed an 11mm bit to cut through around an inch of steel on an exhaust manifold. I don't know whether hot exhaust gases will harden the steel over 15 years or whether my drilling out with a smaller bit first had work hardened the steel, but the HSS 11mm bit was painfully slow as I had to drill for 10 seconds until the cutting stopped dead, then re-sharpen the bit, then drill for 10 seconds, then resharpen. I was using WD40 as lubricant.
It was painfully slow but after an hour or two, I got through. :ambivalence:
Richard
It was painfully slow but after an hour or two, I got through. :ambivalence:
Richard
vyv_cox
Well-Known Member
Good quality carbon steel studs and bolts might well be made in En 8 (excuse my antiquated terminology) that can have Vickers hardness of 250 or even more, which should not test an HSS drill too much but definitely harder than mild steel. Carbon content is nominally 0.4, so quite strong steel in the hardened and tempered condition.
I worked for a while in a steelworks that specialised in engineering steels. If some of the feed to the arc furnace had a higher than expected carbon content (known colloquially as 'Gippo scrap) it would take a lengthy blow with oxygen to get it down to specification. If the furnaceman was a bit careless the alloy content would be blown down to below specification as well, in which case the jeers of 'En 8!' would be heard all around the steelworks.
KellysEye
Well-Known Member
> HSS 11mm bit was painfully slow as I had to drill for 10 seconds until the cutting stopped dead, then re-sharpen the bit, then drill for 10 seconds, then resharpen. I was using WD40 as lubricant.
You would not have had that problem if you had used a Cobolt drill bit.
You would not have had that problem if you had used a Cobolt drill bit.
pagoda
Well-Known Member
Cobalt drills are the way to go, Steady pressure and proper lubrication- light/med oil not WD40. Its slippy but just burns off. Big holes in SS are not easy. I had a few 10mm holes in 6mm SS to drill last year, making up special brackets. It was not easy. SS also work hardens rather easily, so keep RPM modest. With high RPM all you will make is more work!
KellysEye
Well-Known Member
>Cobalt drills are the way to go, Steady pressure and proper lubrication- light/med oil not WD40. Its slippy but just burns off. Big holes in SS are not easy. I had a few 10mm holes in 6mm SS to drill last year, making up special brackets. It was not easy. SS also work hardens rather easily, so keep RPM modest. With high RPM all you will make is more work!
That's exactly how to do it and I used machine oil.
That's exactly how to do it and I used machine oil.
