need the exhaust ports opened out on my exhaust a bit, got a die grinder with carbide burrs, but an hour, and i'm not even a quarter of the way on one port yet. the guy who welded the exhaust suggested milling it, but didn't know anyone who has a mill
when i say near me, i'm talking glasgow furthest

try the burrs in an electric drill it a bit quicker and appear to have more torque use a the die grinder for the final smoothing out

ah, interesting, hadn't thought of that. the grinders pretty good, and fast, but will see how that goes tomorrow.
still interested in someone with a mill, but fingers crossed. i'm a bit worried about burning out the burrs too though. i'm using oil on them to keep them cooled, but worried about overheating them and wearing them out too quick. they're tungsten carbide. should i be worried about that? they're pretty hard aren't they?

use the slowest speed on the drill and oil to cool

Theres no need to use any coolant , carbide is still just as hard at red heat.I use them for steel with no coolant with no problems, part of the problem may be the oil is clogging them and preventing them from cutting.
Paul

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Originally posted by blakep82
ah, interesting, hadn't thought of that. the grinders pretty good, and fast, but will see how that goes tomorrow.
still interested in someone with a mill, but fingers crossed. i'm a bit worried about burning out the burrs too though. i'm using oil on them to keep them cooled, but worried about overheating them and wearing them out too quick. they're tungsten carbide. should i be worried about that? they're pretty hard aren't they?

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I thought tungsten burrs were for speeds in excess of 10,000 rpm, up to about 20,000+ rpm. An electric drill is only good for about 3,000 rpm when not under load. Surely a die grinder is the tool designed for the job.

air powered die grinders slow down easily when pressure is placed on them or so I found, my trusty old B&D drill with 2 speeds was grest for this I then used the die grinder to grind the ports smooth then finished off with a piece of 10mm dowel with a slit in it where i placed emery cloth put it in the drill added oil and polished the chambers.

An industrial die grinder will not slow down as long as its got a good air supply, but I agree for home use a drill is quite capable of doing the job of removing the bulk and then use a die grinder for polishing.
Paul

Or a B&D Powerfile get belts from Screwfix - cheaply.

ATB

Simon

[Edited on 30/11/10 by Simon]

I would recommend using WD40 as a coolant/ lubricant.

Tungsten carbide cutter on a die grinder should cut through mild or cast steel like butter. Is it sharp if not you could go to Bills tool store in the barrows and buy a good quality one.

Are you cutting the valve seat cos that's a different kettle of fish - stones work best here (cutters dull quicker) but still slow.

Nearest petrolhead machinist I know is Raymond over Edinburgh direction he can machine anything to incredibly tight tolerances and does not rip us petrolheads off.

Cheers

David

Ive just got a small mill but it's up in oban and Im not sure how you would do about clamping it.

My die grinder is pretty quick in steel, Im using garryson (sp) cutters I got off ebay in a lidl die grinder, so nothing amazing. A good air supply is a must though! Dont use a drill, youll kill the bearings in no time.

thanks everyone i should have said though, its a clarke die grinder, using a 3hp, 14cfm compressor with 150 litre tank. should be well up to the job, but i'm grinding a 10mm thick stainless (not sure which grade) flange. so not mild steel.
so, paul, you say don't use any oil or coolant? thought that would wear the burrs down quicker, but i'll give it a shot, i've got a few spare i think. will need to look wor them. the burrs are from machine mart too, so make what you will on the quality

Ah! Stainless!

This stuff work hardens so if you try and take a fine cut all it does is to make it more difficult. The trick is to do a few very heavy cuts. You really need a kick ass die grinder. Make hose as short as poss and even couple up compressors.

Could Andy waterjet cut it?

nope he cut the plates for me, i made a few mistakes with them, as the holes on the original plate were ground out. the pipes don't actually line up with the ports on the head. they never did. to save another plate being cut with holes in the wrong place i asked the holes were made smaller all round and i'd grind them out. didn't think it would take so long. so now the exhaust is all welded up, and the holes need opening up.

It does sound like you've made life difficult for yourself! How much do you need to remove? Is it enough so that you could drill out some of the metal?

nope, beleive me, its the best way it could be done, i've not made things difficult, sure i could have kept getting more plates done making small changes til i get on perfect, but that would cost me a fortune in stainless steel and postage, so how could i have done it better?

Would have been better to have made a cardboard template or even a thin piece of sheet steel to match the ports before transfering it to the final article.My Xflow inlet is 12mm ally plate , I was lucky I could use a gasket for the shape and size, just had a little fettling before welding. A Clarke die grinder isn't up to any heavy usage, as said already a decent die grinder will do the job

You might find it a lot easier to grind it out rather than trying to use a burr. Trying to hold a burr steady enough to cut the stainless is going to be very difficult indeed!Each cut you make (as has been mentioned) is only going to make it harder as the surface work hardens. this will also happen with a milling cutter. Hand cutting alloy is one thing but stainless is a lot different!

Not to mention that the burr is gonna take a pounding from the constant chatter and they cost far more than a fistfull of stones!

Unless there is a specific reason that I could not use a grind stone, then that is how I would do it

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Originally posted by blakep82
nope, beleive me, its the best way it could be done, i've not made things difficult, sure i could have kept getting more plates done making small changes til i get on perfect, but that would cost me a fortune in stainless steel and postage, so how could i have done it better?

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