quick question

Rule of thumb for HSS on mild steel is 70 feet/minute.Sounds like a countersink you have so could drop to lower speed,try 50 FPM.Main thing is to cut rather than rub and chatter.Always start slow and work up so you don`t burn the tool out.

I sometimes do hole chamfers for flush rivetting with a 3-flute countersink in a mini mag drill, which runs at 450 rpm. If everything isn't 'just so' it will tend to chatter, I should think a hand-held drill would be worse. Holes are usually around 5/8" dia.
Tim

"Austin Shackles" wrote in message news: snipped-for-privacy@4ax.com... A good rule of thumb, and easy to remember, is 100mm dia -> 100 RPM Then 50mm dia -> 200 RPM etc Likewise, double the RPM for brass, halve for exotics ...
Well, i'd use a chamfering tool, which is just a triangular-shaped normal lathe tool (triangle looking down from the top) with a flat top. Speed say about a third 'normal', just a bit faster than parting.
If you use the 6-flute cutter, i'd think it would need to be VERY slow,
Hope that helps, Peter

On or around Wed, 30 Apr 2008 20:42:58 +0100, Tim Leech enlightened us thusly:
this is going to be done in the new toy, which is the floor-mounted version of this:
cheap but not too badly made. The 6-flute 'sink is supposed not to chatter so much...
hmmm.
say 1" dia, that's about 3" circumference or abotu a quarter of a foot, and 450 rpm... 112.5 FPM. bit fast, then, I really want about a couple of hundred rpm. arse, that means bringing the wheels here from the tyre place, working on them and taking them back to have tyres fitted. The big machine that goes slowly doesn't have enough overhang.
That or modify the drill, of course - I had been thinking about an idler pulley set and 2 belts to get more speeds, and I've got a spare pulley block somewhere...
However, Ideally I want it done tomorrow, provided the wheels are to hand.

Good countersink bits are expensive to buy
and wont last long, if turned at 450 rpm ....
Turn them at below 100 rpm, with rtd fluid to lube .and they will last a long time .
all the best..markj

YEAH right ....."TOY"
and to blinking fast .
have a look at this beauty
all the best.markj

On or around Wed, 30 Apr 2008 14:11:53 -0700 (PDT), mark enlightened us thusly:
too fast for this job, but handy for drilling small stuff, which is mainly what it's for, and it was cheap.
I can address "too fast" as well, given time - I looked at it and there's scope to make an idler pulley mount in the middle of the belt case, there are even mounting holes for it. But not today. I'll look into that when I have time and put a double belt on.

On or around Wed, 30 Apr 2008 13:59:54 -0700 (PDT), mark enlightened us thusly:
yeah, it was a bit. aye, I'll have to do the job in 2 stages. I was hoping to avoid that, but nemmind. The bigger drilling machine will go down to sub-100 speeds, but the wheels won't fit under it with tyres on, as it's not got enough throat depth.

Can you tie a strap around the tyre and pull it towards the rim to clear the drill pillar? Ratchet tie down straps work well for this sort of thing.
John

On or around Thu, 1 May 2008 08:11:15 -0700 (PDT), John enlightened us thusly:
did it in 2 stages, got the rims, machined 'em, which went very nicely at 90 rpm, didn't even run warm without coolant, then took 'em back to get tyres on 'em.
The ratchet strap idea wouldn't have worked - there was only about an inch or two of clearance from the rim to the pillar.