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MG Midget and Sprite Technical - Grinders

I am looking for something like a rotary file that can be used in a electric drill or possibly an air fed die grinder tool, for opening up or reshaping small holes (up to about 15mm diameter) in mild steel, stainless steel, weld and CI. I have been disappointed by the small Dremel type stones on a pin that always seem to either wear away very fast or they disintegrate within seconds of use. I have looked at burrs and cutters on a 1/4" shank but the prices vary a lot and it’s impossible to judge which ones are toffee and which might actually do the job.

Any advice or recommendations please? What words in a description do I need to look out for?

GuyW

I picked up an electric die grinder from Lidl's before covid but have not really used it much - not very expensive ISTR.
Its obviously quite a bit bigger and heavier than a Dremmel - think the stones are !/4" or 6mm - will have to check and I got a selection of stones etc at the same time - usual Lidl's longer than most guarantee.

R.
richard b

Thanks Richard. We don't have Lidles up here so I missed that. But I have a die grinder already. It was advice on the grinder bits that I was after. Or, come to that, on normal round or rat tailed files. How does one identify a good one from ones made from a recycled chocolate tea pot?
GuyW

Guy,

Have you looked at the pencil air die grinders, I have one and it's good on small items, I use a set of 1/8" carbide burrs with it and they're very effective and can be used in a Dremel as well. Just be aware they're very good at producing needle like slivers with some materials.
David Billington

Guy

This question for me highlights a similar issue that tools and classic car spares share - how do you know what is good quality and then how can you locate a good supplier.

Depending on your budget I would start looking at places that sell to people who fabricate and repair aircraft (won’t be cheap, but likely to be good quality and fit for purpose as making mistakes costs more) such as LAS Aerospace in the UK: https://www.lasaero.com/parts/?search_part=Burr (or Aircraft Spruce and Speciality elsewhere) and then some of the classic car resto suppliers such as Frosts.

Cheers
Mike
M Wood

Thanks Mike.
My question is really more basic than I think people realise. There are rotary files that have a serrated Criss cross pattern like an ordinary hand file. Then some look the same but are listed as double cut. Then some shaped ones with a sort of fluted pattern. Some say HSS, some diamond and some Carbide (which I thought was some sort of blunderbuss firearm). Then the stones, all different colours, pink, green grey, white. What's that all about?

Then files. I have several large flat files and some spoon shaped bearing scrapers that are around 80 years old (arrowed!) and still cut really well, whilst some plastic handled ones bought a couple of years ago just skate over the surface of mild steel. And they weren't particularly cheap either!
GuyW

Guy
With your stones wearing away quickly, that's usually a sign that they're not spinning quick enough--I've had some really expensive stones wear down super quick in a drill but in my High speed grinder they last forever, my favourite rounded flat stone that is great for cylinder head ports etc. I've had for years---he spins at at 25000 rpm
If you're using a drill, can you get at what you're doing with a stepped drill--you can get them now with long steps for doing up to about 10mm thick material---just depends on what you're up to

willy
William Revit

The specific job is on the front beam axle of a vintage tractor. Not easily removeable to bring into the workshop. There's a hole that a drop link arm from the steering box fits to that has worn oval. I have welded it up and need to run a drill through it but it is off centre so want to use some sort of file to take off one side of the hole. So it needs to cut the new weld metal and the beam axle which loks like some sort of casting but presumably steel rather than cast iron which I suspect would be too brittle for that situation.

But my querey was wider than that - for far too long I have just used whatever cutter or grinder that came to hand without really understanding the whole issue of which tool cuts what material. Unless it's wood, which I understand!
GuyW

Guy

Ah, I see what you mean. My knowledge of engineering practice and tools is lacking - bet this is something that was taught in apprenticeships and technical colleges from the 1930s-1960s; wonder if there are any old basic textbooks that folk on here can ember that could be picked up secondhand?

As for the quality of modern hand tools - I have had the same experience buying files; best ones I have bought have been secondhand from Bills Tools in Glasgow who buy ex-military tools from auctions (what I know as ‘ex-WD’ [‘War Department’, but are mostly a bit later, from 50s/60s/70s but still ex-Ministry of Defence from military use). Got some excellent ex-military sockets/extensions from Bill’s too from manufacturers such as Geodore, Bristol and King Dick.

Have you tried asking vintage tool stockists, such as Pennyfarthing Tools?

Cheers
Mike
M Wood

I have A set of those 1/4" shank steel rotary drill bits with criss cross patterns and in various shapes that I use regularly for awkward to access welds or where you want to clean up, elongate or enlarge a hole, although I think the conical bit is up to about 1/2" max. I thought they'd wear out in 5 minutes but have used them a lot. Bought from ebay quite a while back so I can't now access the item reference.
Bill Bretherton

I use 1/4 burrs at work quite a lot, usually in a pneumatic die grinder. In fact I’ve just bought a nice new one - a Chicago Pneumatic for a bargain £60 on fleabay. I prefer the fluted ones rather than the criss cross ones.

I’ve got some Snap On burrs which are great but I guess you should be ok with any from a reputable supplier. LAS aero have a good selection but I’m shocked at the price. Mine were free so I’ll be looking after them!

I seem to remember Peter Burgess used to sell them so might be worth contacting him. He’ll definitely know the good ones to get anyway.

http://www.lasaero.com/products/category/E02VIKYHT/
John Payne

Guy. You want to check out the industrial supply companies that provide tooling to machinists and machine shops. MSC is the major company here in the US and looking at their website might be of some assistance.

There are two items that might be of use to you: the carbide burrs that have been previously mentioned, and 1/4" carbide endmills which are commonly used in the large milling machines but, in the smaller sizes, be used in a die grinder, Dremel type tool, or the far more rugged Fordam (sp?) hand grinder. Remember that carbide tooling is more fragile than tooling made from high speed tool steel or cobalt, and that the various coatings that some tooling is coated with are of very little value in what you are doing.

Any of these bits and burrs, especially the carbide ones, are rather expensive and I would suggest you only purchase one or two (for testing) before spending money on a larger purchase. And, I would suggest trying both the burrs and the endmill (either a "two flute" or a "four flute" type will work for your purposes) to see which works better and is easier to control. The end mill had the capability of removing more material, significantly faster, than the carbide burr. The end mill is also harder to control with any accuracy. The burr is capable of removing less metal with any single pass, but can be controlled better by had. I use an end mill for rough shaping, followed by a burr, then stones, sanding drums/discs, etc. as needed.

Les
Les Bengtson

I use either of these. Found them in my dads old tool box years ago.

Not sure if anyone sells them. But they’ve last me for years

James Paul

John I have one exactly like that top one. Only it is definitely too worn now to be much good. I have had it for years, probably bought in the early '70s. That is what I was calling a rotary file in my original posting.

Is something labelled HSS better or not as good as something called Carbide?
GuyW

Guy, I have a couple of carbide burrs. Key word carbide. It's hard. I've found it indestructable.

I bought them a number of years ago on ebay; CHEAP, about 6 quid each. UK supplier.

I use them in regular pistol drills, for all kinds of stuff. Opening holes, grinding back weld in difficult to access places, etc.

I'll dig out my purchase history and see who I bought from. But this looks the same-ish.
https://www.ebay.co.uk/itm/194752708206?

And see below.

https://www.eternaltools.com/blog/7-facts-about-tungsten-carbide-burs-and-how-to-use-them

2. Carbide Burrs Commonly Come in Two Cuts; Single Cut and Double Cut (Diamond Cut)
Single cut (one flute) carbide burrs have a right handed (Up cut) spiral flute. These tend to be used with stainless steel, hardened steel, copper, cast iron, and ferrous metals and will remove material quickly. Use for heavy stock removal, milling, deburring and cleaning.

Heavy removal of material
Milling
Deburring
Cleaning
Creates long chips
Double cut carbide burrs tend to be used on ferrous and non ferrous metals, aluminium, soft steel and also for all non-metal materials such as plastics and wood. They have more cutting edges and will remove material faster. These are the most popular cut and will see you through most applications.

Double cut are sometimes referred to as Diamond Cut or Cross Cut (2 flutes cut across each other) . They will leave a smoother finish than single cut due to producing smaller chips as they cut away the material. Use for medium-light stock removal, deburring, finishing and cleaning.

Medium- light removal of material
Deburring
Fine finishing
Cleaning
Smooth finish
Creates small chips
The below image indicates the double cut, single cut and again, the double cut or diamond cut.


anamnesis

I’m no expert Guy but I’ve googled it and carbide is better than HSS.

I’ve been using a cylindrical single cut type carbide burr last week and it cuts great - but that is on T3 aluminium - and it’s 80 year old aluminium! I’ve used them on mild steel and they don’t show any wear from that. Only light use though.

If I were spending my hard earned I’d get carbide and go for 1 cylindrical, 1 pointed and 1 oval. Seem to be the ones I use most. To avoid blunting them I’d say the harder the material then the slower the speed and harder the pressure.

John Payne

I find the opposite John. High speed, on steel, used multiple times, fairly hard pressure, still sharp.
anamnesis

Thanks all, Anam - very comprehensive. I now feel I have information needed to order something to add to me tool chest
GuyW

Used here to open up the hole in my T9 gearbox casing, for long 1st gear conversion. Go easy on cast iron, it attacks it like a knife through butter. Very easy.

Generally, sometimes I start on slow revs, and speed up. It can bounce around if you don't have enough pressure, and if opening up an existing fairly small hole, the burr can 'bounce', rotate, around inside the hole, one side to the other. You just get a knack.

They are great little tools. A die grinder would I'm sure be better than a drill, but I didn't want to buy a cheap one as I read some poor reviews, and an decent one was more than I needed. Hence my use in drills.



anamnesis

I have an air die grinder but my compressor doesn't keep up too well. It works, but only in short spells so gets a bit frustrating when you want to just get on!
GuyW

Guy. Order of hardness is High Speed Steel (HSS and very commonly used), Cobalt, and Carbide. Carbide will hold up the longest when cutting hard steel. Also, the most expensive. I use HSS on aluminum (aluminium) with good service life. HSS was the preferred material, a number of years ago, as it would (with the proper tooling) be resharpened several times, thereby extending the tool's working life. Carbide must be resharpened on a carbide grinding wheel and is much harder to sharpen than the HSS which can be sharpened on the aluminum oxide wheels.

Do you have any form of production company close to you? With the modern CNC machining, carbide has become much more commonly used because it cuts for a longer time and at higher feeds. When a carbide end mill becomes dull (but may still be sharp enough for your purposes), they are replaced rather than have to reset the computer programs for a slightly smaller diameter cutter. If there is a machine shop, engineering shop, etc. near you it might be possible to purchase some used end mills for far less than on the internet. Sometimes, they are willing to give away a couple for free, as I have done with my used end mills when a friend needed one.

End mills cut faster and deeper than a burr as the flutes are deeper. But, that also causes them to be harder to control when doing precision work in a hand held grinder.

Les
Les Bengtson

Thanks Les. I used to think HSS just meant you had to use them at higher speed
GuyW

If you're buying HSS best to buy a reputable brand as some of the cheap stuff from China and elsewhere is junk.
David Billington

How about a simple round file? Far more control, and for the holes you mention it surely will not take that much longer to execute?
Oggers

Oggers, you will have missed my earlier bit where I was also asking about how to identify a decent file from the rubbish ones!
GuyW

Guy,
Hand files - Stubbs English made we’re always the ones to use - no longer in business but sometimes old stock comes up.

Vallorbe available from Axminster tools and Tome Ferreira from Arceurotrade.co.uk (model engineering supplier) are considered good.

For your axle can you get hold of a mag drill (rotabroach) etc and clamp it on - if so a milling type cutter can be used - a 2 or 3 flute slot drill probably best. I think it’s very difficult to file a round hole with high accuracy noting it’s been repaired with weld.
Hope it’s not tapered - if so you may be able to get a suitable cutter to suit or possibly file the bulk and finish with a hand reamer - especially if tapered - depending on what tapered reamer you can get hold of .

R.
richard b

A bit late to this thread Guy, but Thomas Graham's locally sell a selection of 1/4 carbide burs which fit either the air or electric die grinders, expensive, but very good quality. If you need 1/8 size, we last used APT tools for those sizes, again the expensive carbide ones are worth the money. I've used them on Ti and some very hard steels.

Carbide end mills in my experience chip and snap if abused - maybe that's my clumsy milling machine operating though.
Paul MkIMkIV

Thanks Paul. All sorted now but useful to know for another time.
GuyW

This thread was discussed between 22/01/2022 and 16/02/2022

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