• Thanks for visiting The Penturners Forum today.

    There are many features and resources that currently you are unable to see or access, either because you're not yet registered, or if you're already registered, because you're not logged in.

    To gain full access to the forum, please log in or register now. Registration is completely free, it only takes a few seconds, and you can join our well established community of like-minded pen makers.

I have a question …..

P

PeterB

Apprentice Member
Joined
Jan 13, 2024
Posts
4
Location
Warrington
First Name
Peter
Why are the drill holes in my blanks wider the start of drilling the blank? I am drilling holes in the blank on the lathe, but the drill wanders away from the centre for a millimetre or so leaving the hole with a gap between tube and blank.
I am trying to up load a photo but can’t for some reason.
Any advice welcome.
 
pittswood

pittswood

Fellow
Joined
Mar 14, 2016
Posts
1,346
Location
Rhigos, South Wales
First Name
Kelvin
Only two reasons holes can wander, (1), the sides of the drills cutting edges are not the same length, all drills should be 118° point and you need to start with a centre drill before drill your tube diameter.
(2), Ensure you are not cutting at a negative point.
Even new drills need to be "touched" up before using.
Drill at a slow speed without screaming and don't push the drill in to fast.
Also, I find holding the tailstock quill when drilling helps against any chatter or digging in one side only to start.
Hope this helps.
Kelvin
 
C

Curly

Graduate Member
Joined
Nov 3, 2019
Posts
473
Location
RM of Aberdeen, Saskatchewan, Canada
First Name
Peter
On cheaper lathes the tailstock may not be aligned to the axis of the headstock. Your bit will touch off centre making the hole bigger before straightening some where it exits. Most of the time it can be minimized by holding the tailstock to one side or the other of the lathe bed when you tighten the locking handle. Quick way to check is to put the tips of good centres, one in the headstock taper and the other in the tailstock to see if the points touch.

Pete
 
Chriscb

Chriscb

Full Member
Joined
Feb 23, 2014
Posts
208
Location
Sutton Coldfield
First Name
Chris
What Kelvin said, with emphasis on the centre drill - ALWAYS use a centre drill. Slow and steady is the game, especially in acrylics. I tend to use DeWalt bullet drills when making kit pens.

Do let use know what you've found/how you get on.

Chriscb
 
flexi

flexi

Executive Member
Joined
Sep 12, 2014
Posts
6,526
Location
Maidstone
First Name
mark
It can also be heat build up on acrylic, if the swarfs not clearing it makes the bit a little bigger and friction will do the rest as it tries to exit the blank:duh:
 
21William

21William

Fellow
Joined
Jan 21, 2016
Posts
1,647
Location
Dorset
First Name
William
Centre Drills are ok for starting holes but their true purpose is to produce a recess for a Centre - hence the name.
The best bit for accurately starting a hole is a Spotting drill. They come in a couple of different angles, 90 and 120 and are far more robust than Centre Drills. I like the 90 but many say you should use a 120 for starting most holes.

IMG_3256.jpeg


They come in HSS or Carbide. There should be plenty on eBay, you don’t need to pay a lot. I generally have 5, 6 and 8mm to hand.
 
pittswood

pittswood

Fellow
Joined
Mar 14, 2016
Posts
1,346
Location
Rhigos, South Wales
First Name
Kelvin
Spotting drills are used in CNC and milling applications, not general used for normal drilling apps. They should also be ground at 118°.
Kelvin
 
ValleyBoy

ValleyBoy

Graduate Member
Joined
Jul 9, 2019
Posts
774
Location
Cardiff
First Name
Ash
I use my largest Centre Drill, but just use the very tip of it. It is 118 degrees and does the job really well.

Cheers
Ash
 
21William

21William

Fellow
Joined
Jan 21, 2016
Posts
1,647
Location
Dorset
First Name
William
pittswood said:
Spotting drills are used in CNC and milling applications, not general used for normal drilling apps. They should also be ground at 118°.
Kelvin
Click to expand...
120° Spotting drills will accommodate a standard 118° twist drill. Spotting drills pre-date CNC machines by at least several decades according to machinists I’ve worked with. Given the modest cost it’s daft not to get one or two.

Centre drills have very fragile tips in the smaller sizes so I’ve generally stopped using them for metal work. In fact I only use them for creating centres now.
 
C

Curly

Graduate Member
Joined
Nov 3, 2019
Posts
473
Location
RM of Aberdeen, Saskatchewan, Canada
First Name
Peter
I'm in favour of a spot drill over a centre drill but another option is a stub drill. Like a jobber drill bit )regular length), just shorter. Being shorter it is still stiff and not as easily deflected. The spot drill is still best. An example below.

Dormer A022 TiN-Tip Coated HSS Stub Drills - Arc Euro Trade

Dormer A022 stub drills ≥ ø2mm have 118° split point geometry which helps to self-centre the drill resulting in more accurately sized holes.
www.arceurotrade.co.uk www.arceurotrade.co.uk

Pete
 
P

PeterB

Apprentice Member
Joined
Jan 13, 2024
Posts
4
Location
Warrington
First Name
Peter
Thank you all for the tips, advice and helpful suggestions. My first time on this site seeking help and it exceeded expectations.
I made a pen today using the advice given and I now know a lot more than a week ago.
Thank you all so much.
 
21William

21William

Fellow
Joined
Jan 21, 2016
Posts
1,647
Location
Dorset
First Name
William
Due to any slight errors in tailstock alignment I’d be inclined to drill blanks with a drill press. Some don’t have them though so if a lathe is all you have I would, after spotting, use a slightly smaller bit first before using the finished size. You stand more chance of getting an accurate sized hole this way.
 
P

PeterB

Apprentice Member
Joined
Jan 13, 2024
Posts
4
Location
Warrington
First Name
Peter
I do have a cheap drill press but it only has a 60mm drop and I am thinking a larger drill press might be better, and I see the advantage of a small pilot hole for the initial drilling.
 
Chriscb

Chriscb

Full Member
Joined
Feb 23, 2014
Posts
208
Location
Sutton Coldfield
First Name
Chris
Afternoon,
Purely based on my own experience, as a non-engineer, I would suggest that drilling on the lathe is going to be more accurate than using a drill press. You've already pointed out the 60mm drop being problematic, which doesn't exist when using lathe. Also you're more likely to have an accurate and heavy wood chuck to hold the wood when compared to the free standing chucks used for presses.
But in saying all this, which ever works for you is the way to go.

Chriscb
 
21William

21William

Fellow
Joined
Jan 21, 2016
Posts
1,647
Location
Dorset
First Name
William
Chriscb said:
Afternoon,
Purely based on my own experience, as a non-engineer, I would suggest that drilling on the lathe is going to be more accurate than using a drill press. You've already pointed out the 60mm drop being problematic, which doesn't exist when using lathe. Also you're more likely to have an accurate and heavy wood chuck to hold the wood when compared to the free standing chucks used for presses.
But in saying all this, which ever works for you is the way to go.

Chriscb
Click to expand...

I’m not a machinist but I know that drilling on my milling machine ( basically a big drill ) produces holes to size better than using my lathe.
I’ve not checked the travel on my tail stocks but I’m not sure either is much over 60mm if at all.
 
B

Brian

Full Member
Joined
Mar 23, 2023
Posts
15
Location
Leics
First Name
Brian
Could you possibly try drilling with a 1mm smaller drill than your finished size? That’s what we used to do for reaming holes to a specific size, that way you are using your size drill as a reamer.
 
Top