Hand drilling in metal

[God mode restorations]

Hi everyone.
Just a post to see what techniques you guys use to drill large holes in thick metal.sometimes we get jobs to do that require the use of a hand drill because we can't get the object the the pillar drill or have limited room.I do a lot of hand drilling in metals of different thickness. I centre punch .and make a pilot hole .then work my way up in 0.5 increasments up to 13mm using cutting fluid. But there are common problems. Like the drill bits snatching and drill chatter as the sizes increase. What's tools and methods do you guys use.finding a drill with hight end torque at low rpm is difficult. What size hole is practical with hand drilling.is there different drill bits to prevent the sudden snatch.

 

[Pete.]

Working your way up in tiny increments is a very common mistake - this is what is causing your snatching. Put in a pilot hole at 1/4 to 1/3 the final size then go in with the 13mm.

 

[God mode restorations]

Working your way up in tiny increments is a very common mistake - this is what is causing your snatching. Put in a pilot hole at 1/4 to 1/3 the final size then go in with the 13mm.

OK. So small increasments is a bad move.

 

[Gareth J]

As above. Lessen the risk of snatching on breaking through by backing right off the pressure at the end and using a high speed on the drill. It must be a nightmare trying to step up in 0.5mm increments, not to mention time consuming.

 

[dan.taylor.1]

I usually go 6mm pilot because I got loads of them cheap, plus they don't snap as easily as smaller ones, then whatever finish size. Or use the mag drill if it's loads of holes or above 12mm.

 

[God mode restorations]

As above. Lessen the risk of snatching on breaking through by backing right off the pressure at the end and using a high speed on the drill. It must be a nightmare trying to step up in 0.5mm increments, not to mention time consuming.

It's time consuming yes.but that's the way I thought it was done. Hence the post.i didn't want to come across as being stupid lol. But if I don't ask if will never know.

 

[God mode restorations]

Thanks for the hints and tips guys. It's very appreciated.

 

[The_Yellow_Ardvark]

As Above, Mag drill for holes over 13mm, or lots of same size.
Dirt cheep to hire or even buy on the Bay Of Fleas.

I start with a small 3mm to break through the surface and locate the pilot. About a 6mm or 5.5mm. As above I have lots.

I was told that once a pilot is drilled, you step up to a size were 1/2 to 1/3 the cutting lands of the drill sits on the edge of the pilot hole.
Then step it up that way.

The only time I step up in small amounts is when drilling out broken fixings, when near the final size.
Or converting a imperial hole to metric, or vice versa.

 

[zx9]

It's time consuming yes.but that's the way I thought it was done. Hence the post.i didn't want to come across as being stupid lol. But if I don't ask if will never know.

No it was not a stupid question, like they say the stupid question is the one that is not asked. The way you were doing it is the most obvious way and I bet many people do it that way in the mistaken belief that they are making it easy for themseves / the twist bits.
Go in with lots of presure on a sharp, decent sized drill and you will see nice little curles of swarf, if you only get swarf from one land you are probably holding the drill at an angle to the work.

 

[8ob]

In the absence of a mag drill I would pilot with a pistol drill and then use a stepped drill in a gut buster.

Bob

 

[God mode restorations]

OK awesome. I will try the methods mentioned latter today. Does the same method apply to drilling with a pillar drill.

 

[Pete.]

Yes, the same applies to most drilling. With a pillar drill you have the advantage of being able to use more weight on the bit. Some materials like cast iron and stainless steel you should drill at slower speeds with more weight to keep the drill cutting and stop it heating the part.

How the drill is sharpened can also help quite a lot. See the attached pdf.

 

[Dieselman 63]

That's interesting, I never knew about magnetic drills but you learn something new every day!

It reminds me of a job I was working on early last year, two greenhouses on a farm were being constructed and required about 250 holes per bay drilling, so 1000 all up. Here's a pic to show the scale.

The gaffer was penny pinching to the extreme, I hated working there. We had one rechargeable 16V B&D chuck-less hand drill which had two 5mm pilot bits and one 10mm HSS bit - the posts were a mix of galv dipped H beam and C beam. The houses were second hand with no instructions so it was a complete mess and none of the holes were aligned properly so it all went crooked but by the end of it all I just thought 'not my problem' - I'd had enough. Look at this lovely days work!

Anyway, the holes needed to be 13mm and the guy would rock the 10mm bit til it reached the size, no goggles no nothing. There were bits and pieces all attached to the house with 10mm tek screws which the guy had for some reason galved over, then tried using a driver bit to remove - the 16V drill spindle cracked and I had to go home because we couldn't work. Still got paid though!

 

[brightspark]

drill the pilot hole the same size as the chisel edge on the end of the larger drill as that only scrapes its way through . as said don't increase in sizes and drill on a slow speed for the large one

 

[God mode restorations]

Yes, the same applies to most drilling. With a pillar drill you have the advantage of being able to use more weight on the bit. Some materials like cast iron and stainless steel you should drill at slower speeds with more weight to keep the drill cutting and stop it heating the part.

View attachment 91703

How the drill is sharpened can also help quite a lot. See the attached pdf.

Thanks for the pdf Pete.

 

[Bill Edwards]

That project sounds well thought out. Must be a relation to my gaffa?

I drill quite a lot of holes up to 13mm with a hand drill with the technique already explained.
If it's a regular thing where access is suitable a mag drill is well worth the investment, each hole takes a fraction of the time and a fraction of the effort. Especially with proper cutters which drill a slug out rather than removing loads of material as a conventional drill does. Cutting oil feed is common too so the bit is always lubricated.

 

[Pete.]

Just a note if you're going to use a mag drill overhead get an old G clamp and a tether and fix it to something, because they don't half make a mess of your foot if the power trips or the magnet lets go

 

[The_Yellow_Ardvark]

@Pete.
There is the voice of experience.

Thanks for the chart, you beat me to putting a similar one up.

 

[dan.taylor.1]

Mag drills usually come with a tether chain.

 

[The_Yellow_Ardvark]

@dan.taylor.1
Very few do now. The old ones normally did, but almost all will have lost them.

I never had a hire one with a safety chain, but we always asked for a clamp or 2.

See this link for new ones, with out chains.
https://www.machinemart.co.uk/p/evolution-evomag50-50mm-magnetic-drill-230v/

Mag rills normally used on a bench or floor.