Drilling question - burns

[Aggrajag]

This is going to make me sound like an silly person, but if I don't ask then I'll never learn...

How do you drill without leaving burn marks?

I've done a couple of patterns recently (I'm a scroll sawer, or at least I try to be) and I needed lots of holes in 3/4" pine (I think it's pine, it's a soft light wood) and no matter what speed I drilled at, each hole had burns at the back. (Edit to clarify - these aren't just entry holes I'm drilling, these are part of the final pattern.)

I'm using a Dremel 3000 on a Dremel Workstation as a drill press, a 2mm drillbit made for wood and a backing piece of wood to help with (rather unsuccessfully I thought) breakouts.

All I can think is a) I've no idea what I'm doing or b) it's a cheap drill bit.

Thanks in advance.

 

[DaveyP]

Many factors come into play.. but burn is caused by heat in both wood or metal

1. heat is caused by friction, so reduce speed and pressure
2. drill tip angle can be a factor
3, drill flutes should / must clear the swarf away from the cutting edge

Slow down, and don't try to push the bit through the wood in one go, lol

Edit: your drill has a min speed of 10,000 rpm.. which is very fast, you will get away with it on thin pieces but not '3/4" pine' of unknown quality.

Are you really sure you want to use that thickness...

 

[Racers]

Sounds like the chips aren't being cleared and building up in the flutes causing friction and burning.
Withdraw the drill several times to clear the swarf.

Pete

 

[oakmitre]

As mentioned above you have wood waste in a hole moving fast - like rubbing two sticks together to make fire.

The small drill bits have very little metal mass to absorb the heat and heat up very quickly.

I have a dremel, the bits I have are only fluted for the first 1/3 of the drill bit, similar to a stub drill.So if you are drilling deeper beyond the flutes, there is no escape for swarf or heat.

Try operating the drill stand plunger handle with a lighter grip - if you start to feel an increase in resistance then back off and clear.

If it is not going to affect the finishing process (which it probably will), swiping the bit lightly on a bar of soap may help.

 

[Aggrajag]

Thank you guys, some good advice there and I realise my mistakes - I confess I'm pushing through in one go, whether quickly or slowly, because I'm fearful of making a mess of the entry hole by moving the wood between attempts - I never thought about the waste not being able to get out of the way. See I was right, I *AM* an silly person!

Worried about the speed of the Dremel I've looked at their spec sheet online and it says minimum is 5000rpm, is that slow enough? (hmmm just found conflicting info, plus mine doesn't have 10 steps as most seem to, only 5.)

Makes me wonder about using it as a router, is that bad?

 

[Aggrajag]

I think the 5,000 rpm is the US version, you are very probably correct Davey with it being 10,000 rpm.

 

[oakmitre]

If this a flat piece of wood that you are drilling.

Can you put the backer board onto a non slip mat ?

As long as the mat is thin and flat (doesn't bulge) it will keep the wood still and enable you to dip in and out with out making a mess.

 

[Aggrajag]

That's a good idea Oakmitre, obvious when you think about it, thanks.

 

[DaveyP]

See I was right, I *AM* an silly person!

No... your not, no one was born with skills (apart from suckling, lol)

All other skills come from study / watching or most importantly, asking questions.

Anyway ..recommended drill speed would would be in the 3000 rpm area

 

[Aggrajag]

Cheers Davey.

That's a mite annoying; I bought the Dremel Workstation pretty much to guarantee vertical holes for drilling stacks when I'm cutting two or more patterns at once. I hadn't considered the Dremel would be too fast. I guess I'll see how it goes doing the holes in stages and if necessary reconsider my setup.

 

[DaveyP]

I guess I'll see how it goes doing the holes in stages

That alone will solve the problem... or you could of course throw money at it and get a decent drill press (which then comes with different issues)

 

[ED65]

or b) it's a cheap drill bit.

It's not the bit I'm sure. As your Dremel appears to have a minimum speed of 10k as the expression goes, there's your problem right there. From using this type of drill for years the speeds mini drills run at are great for abrading jobs, less good for drilling jobs.

Even if your Dremel did have a minimum of 5k that's still faster than would be preferable, a good speed for this might be under 1,000 RPM.

You can do a few things to help, number one of which is what was already suggested which is to drill a bit, back out, drill some more etc. Having to do this every time gets tedious in no time at all (ask me how I know!) but it can't be helped.

and a backing piece of wood to help with (rather unsuccessfully I thought) breakouts.

Is the backing sheet clamped to the workpiece? The backing must press firmly against the back of the piece being drilled to work as intended, I think particularly when drilling thinner wood.

 

[Aggrajag]

Thanks ED, I didn't know the wood had to be clamped and I was just pressing down.

I tried the "in and out" method last night (!) and successfully drilled a hole without scorching. I love this forum, you're all so helpful.

On another unrelated note of idiocy, I cut a 43mm hole last night in a new piece, to fit a clock I'd bought. I knew it was 43mm, I've used one before but doofus here forgot that was the exterior size so now I've got a hole that fits a clock perfectly, inside! :/ Been back online and bought a 46mm clock. Anyway I'm pleased with the piece and hopefully my Dad will be too once it's varnished.

 

[AES]

Hullo Aggragig,

I echo the sentiments already expressed, you're NOT an silly person (my wife always says no one fell down to earth knowing how to do things, they had to learn someway or other).

And at least you had the sense to ask! (Don't ask me who posted on here a while back about really burning ply - LOTS & lots of smoke - and was very gently and politely told that I'd got the blade on facing backwards - now that really WAS idiocy)!

About your Dremel, at 10 K rpm it is too fast for drilling into thick wood - slower (MUCH slower) would be much better. Have you got another drill that will handle 2mm drills (ideally brad point drills - available down to 2mm dia from Dieter Schmidt in Germany BTW, usual disclaimers)?

Ideally use a pillar drill, but if not, how about a normal electric (pistol-type) drill, battery or electric?

I know you're using the Dremel plus stand to make sure your holes are vertical, but if you have no pillar drill then you can either make a L-shaped block of wood to make a vertical guide to use when drilling with the pistol drill, or even better, you can use a few blocks of Lego to quickly make a dead accurate vertical guide.

That last idea is not my own, I found it somewhere on the net I think, but I've tried it for small stuff myself and it works very well indeed. So if you send me a PM I'll send you a "plan" detailing exactly how to make it, using which Lego blocks. (I'd post that here but have it only in .pdf format which doesn't post here).

In the meantime as others have said, keep the drill rpm as low as possible, and keep clearing the swarf from the flutes regularly, especially on small dia drills.

(BTW, my Dremel, an old mains model, does go down to 5K rpm, but IMHO, even that is a bit fast for small holes in thick stock. And I'm not sure how slowly the modern ones go down to).

HTH

AES

 

[Aggrajag]

Thanks for that AES, I confess I laughed at the real way to burn Ply

I do have a pistol drill, a rather fabulous Makita that I covet, but as you note the Dremel jig was to get straight cuts. I'll keep the Dremel cleared of debris in future, which helps of course, but I'll certainly bear your angled-wood design in mind for the next time I have a lot to drill and it's still getting too hot or is too slow going.

 

[AES]

Glad to have given you a laugh Aggragig!

To SLIGHTLY defend myself, the subject SCMS (a real cheapo) is the ONLY tool with a rotating blade that I've ever owned which does not have a big arrow on it showing the direction of rotation. But you're right, I should have engaged brain first, and worse, I didn't even notice much at all (I was sawing outside) until the dust bag started to smoulder!!!! Beat that for "maximum dunder-headed-ness".

About the Lego vertical drill guide, no probs mate, shout any time if you need it.

AES

 

[ED65]

On another unrelated note of idiocy, I cut a 43mm hole last night in a new piece, to fit a clock I'd bought. I knew it was 43mm, I've used one before but doofus here forgot that was the exterior size so now I've got a hole that fits a clock perfectly, inside! :/

I bet most here have made at least one mistake that, in retrospect, seemed impossibly dumb. Not much different to cutting a mitre on the wrong side of the stock so you end up with /_/ not /_\. Not that I've done anything like that personally you understand #-o

 

[DTR]

Not much different to cutting a mitre on the wrong side of the stock so you end up with /_/ not /_\. Not that I've done anything like that personally you understand #-o

Of course not, me neither :-"

 

[DaveyP]

I bet most here have made at least one mistake that, in retrospect, seemed impossibly dumb. Not much different to cutting a mitre on the wrong side of the stock so you end up with /_/ not /_\. Not that I've done anything like that personally you understand

Errrrrr.... nor me :roll: sometimes I feel like --> (homer)

 

[mind_the_goat]

Not much different to cutting a mitre on the wrong side of the stock so you end up with /_/ not /_\. Not that I've done anything like that personally you understand #-o

Some people have even done that twice in a row.