Reamers - what are the basics?

[Beanwood]

I sometimes feel like a complete novice at this engineering lark
I need to create some more punches.
I want to do it better than the last time, so wil be using gauge plate rather than mild steel.
I would like to ream the holes to 4mm rather than rely on my 4mm drills, to get a better 'fit' for the punch.
What are the basics of reaming? (No sniggering at the back!)
Is it as simle as I drill a slightly undersize hole, and run through with a 4mm reamer on my drill press?
What size drill do I need for a 4mm reamer please? Or is there better solution using for example slot drills (Are they more accurate?)

 

[Morrisman]

I’d drill 3.75 and then ream, slow speed with plenty of lube.

 

[ukracer]

I sometimes feel like a complete novice at this engineering lark
I need to create some more punches.
I want to do it better than the last time, so wil be using gauge plate rather than mild steel.
I would like to ream the holes to 4mm rather than rely on my 4mm drills, to get a better 'fit' for the punch.
What are the basics of reaming? (No sniggering at the back!)
Is it as simle as I drill a slightly undersize hole, and run through with a 4mm reamer on my drill press?
What size drill do I need for a 4mm reamer please? Or is there better solution using for example slot drills (Are they more accurate?)

Main thing is never turn them.backwards..

 

[pressbrake1]

For fine finish where possible I ream the pilot using a combination of metric and imperial reamers .
As quoted previously.25mm is nice

 

[Misterg]

“Half the speed and twice the feed” is what I was told.

(i.e. half the RPM that you would drill the hole at, but plunge faster.)

…And plenty of oil.

ETA: I’d probably get closer than 0.25mm under for a 4mm dia hole - maybe .1 to .15 under, but then I’m a chicken.

 

[hotponyshoes]

Adjustable reamers are also available. I've not seen one as small as 4mm but they probably exist. Handy for die making as you can just keep tweaking them until you get the required clearance.

Also, if you look after them, reamers last a lot longer than drill bits so it's sometimes worth pricing up an odd size reamer against odd size drills if the application allows.
Eg, a 4.25mm reamer might be a bit more expensive than a 4.0mm but a pack of common 4.0mm drill bits might be cheaper than a pack of 3.85mm

Might also be worth looking into other types of drill bits & cutters as you might be able to get the necessary finish in one operation although the time saving may not be an advantage if you are only doing small numbers.

 

[Stupoty]

If you use a drill press to ream the holes , use eye protection , the only reamer issues I've ever had is with ones around the 3-5mm range , they kind of just exploded into shards of HSS
first time it happened was a little surprising.

I’d drill 3.75 and then ream, slow speed with plenty of lube.

As he says , very close size, don't even think about a 3.5mm drill slow and lube. Also don't let it dwell in place , either be pushing it in or pulling it out.

Stu

 

[optima21]

and then there are hand and machine reamers, hand reamers have a long taper on the cutting edge and machine reamers have a short on, stick with machine reamers and you'll be fine with a pillar drill

 

[RichardM]

Reamers are made to tolerance specs IE H8, H7 etc so if you want a close tolerance also check the reamer spec to the material you want to go through the hole.

 

[Brad93]

You really need to hold your work rigidly and drill then ream without removing the work or changing position.
To maintain best accuracy.

2-3% smaller is usually the stated size drill hole for a reamer

 

[RWD3M]

Could I add a suggestion? Don't do it twice. The first time through will get you the size you need, if you run the reamer through a second time, you will remove more material.

Don't ask me how I know!

 

[Beanwood]

Reamers are made to tolerance specs IE H8, H7 etc so if you want a close tolerance also check the reamer spec to the material you want to go through the hole.

Thanks yes I started to see those 'strange new' numbers when I was investigating reamers yesterday.

I was also interested to actually read the specifictions for reamers and slot drills (Specs blatantly copied from Zoro).

Slot Drill Diameter: Over 3.00 ~ up to 6.00. Tolerance:+ 0.020 -0.038;
Reamer • Diameter: Over 3.00 ~ up to 6.00. Tolerance: +0.010, -0.005.

I couldn't find ANY tolerance specs for drill bits.

 

[Stupoty]

Thanks yes I started to see those 'strange new' numbers when I was investigating reamers yesterday.

I was also interested to actually read the specifictions for reamers and slot drills (Specs blatantly copied from Zoro).

Slot Drill Diameter: Over 3.00 ~ up to 6.00. Tolerance:+ 0.020 -0.038;
Reamer • Diameter: Over 3.00 ~ up to 6.00. Tolerance: +0.010, -0.005.

I couldn't find ANY tolerance specs for drill bits.

Dormer jobber A002 are listed as hole size tolerance H8.

ISO Tolerances for Holes (ISO 286-2)

ISO Tolerances for Holes (ISO 286-2)

www.tribology-abc.com

Stu

 

[Pete.]

I go for 10 thou smaller than the reamer, or less. Turn it slow and use oil. If youbturnbit fast or leave too much material to ream the hole will come out big.

For your punch die you might be able to put a taper reamer in from the reverse to create a relief for the punch blank to drop through.

 

[Beanwood]

I go for 10 thou smaller than the reamer, or less. Turn it slow and use oil. If youbturnbit fast or leave too much material to ream the hole will come out big.

For your punch die you might be able to put a taper reamer in from the reverse to create a relief for the punch blank to drop through.

Great idea on the taper reamer from the revers thanks @Pete. - I've been making the relief holes by drilling .5mm larger - which looks awful (Even if it's only me that sees it)

I'm trying to get to grips with being more accurate and less 'That will do', but struggling with the 10 thou smaller initial hole - what size drill will get me to a point 10 thou less than a 4mm reamer? If I use a 4mm drill, it's going to be upto 4.018mm (If I've read the table correctly for Dormer drills - (Thanks @Stupoty ) H8 is +18 micrometres) so too large to start with. Next size down in Dormer appears to be 3.7 - so quite a lot more than 10 thou difference?

 

[RichardM]

You could try a 5/32 drill as your finishing size before reaming. Don't drill straight out with it, but go to 3.5 then 5/32 and see what size hole you get.

 

[Stupoty]

Great idea on the taper reamer from the revers thanks @Pete. - I've been making the relief holes by drilling .5mm larger - which looks awful (Even if it's only me that sees it)

I'm trying to get to grips with being more accurate and less 'That will do', but struggling with the 10 thou smaller initial hole - what size drill will get me to a point 10 thou less than a 4mm reamer? If I use a 4mm drill, it's going to be upto 4.018mm (If I've read the table correctly for Dormer drills - (Thanks @Stupoty ) H8 is +18 micrometres) so too large to start with. Next size down in Dormer appears to be 3.7 - so quite a lot more than 10 thou difference?

You should be able to get the dormer drills (and some other brands too) in 0.1mm steps.

RS seem to have the sizes listed , not necessarily the best place to get them but a lot of people probably don't stock all the sizes though.

A0023.8 | Dormer A002 Series HSS-TiN Twist Drill Bit for Steel, 3.8mm Diameter, 75 mm Overall | RS

uk.rs-online.com

Nufield engineering seem to have the full range too and have them listed as each not just pack of 5. I've never used them though.

Dormer A002 HSS Jobber Drill Bits - Nuffield Engineering Supplies

Dormer A002 HSS drill bits features a self-centring split-point for excellent positional accuracy and hole quality, TiN tip coating for extended tool life & in

www.nestools.com

Also orbital fasteners seem to carry the whole range too.

Dormer A002 HSS Drill Bits | Metal Drill Bits - Power Tools

www.orbitalfasteners.co.uk

Stu

 

[Agroshield]

Dormer jobber A002 are listed as hole size tolerance H8.

Please could you provide a link to the document in which you have found that information.

In this one:

https://static-content.cromwell.co.uk/pdfs/s/Medusa_Attachments/Dormer/Data%20Sheets/catalouge-data-sheet-A002.pdf

it states h8 (lowercase h), which is a shaft specification, which would be correct for a shaftularly-shaped object like a drill bit.

In the ISO limits and fits, H8 (uppercase H) is a hole tolerance, for a hole. As far as I am aware, no twist drill will make a hole to that tolerance.

See page 865 here: https://www.guhring.co.uk/downloads/Drilling_tools.pdf

See also here:

https://cdn.mscdirect.com/global/media/pdf/search/dormer/dormer-pramet-drill-tolerances.pdf

where it states H12.

 

[Stupoty]

Please could you provide a link to the document in which you have found that information.

In this one:

https://static-content.cromwell.co.uk/pdfs/s/Medusa_Attachments/Dormer/Data%20Sheets/catalouge-data-sheet-A002.pdf

it states h8 (lowercase h), which is a shaft specification, which would be correct for a shaftularly-shaped object like a drill bit.

In the ISO limits and fits, H8 (uppercase H) is a hole tolerance, for a hole. As far as I am aware, no twist drill will make a hole to that tolerance.

See page 865 here: https://www.guhring.co.uk/downloads/Drilling_tools.pdf

See also here:

https://cdn.mscdirect.com/global/media/pdf/search/dormer/dormer-pramet-drill-tolerances.pdf

where it states H12.

Hello,

I did indeed capitalise the h apologies for any confusion, I got the spec from cromwell tools website , I was having a bit of a time finding it and didn't double check to be honest.

Dormer A002, Jobber Drill, 2.2mm, Normal Helix, High Speed Steel, TiN-Tipped 5967419 | Cromwell Tools

Series A002 HSS Straight Shank Jobber Drills feature a hardy TiN tip coating for increased tool life and performance with 118° self-centering split point for superb hole quality a 5967419 | Cromwell Tools

www.cromwell.co.uk

The chart was a random one as I couldn't remember the tolerance names to numbers off the top of my head.

Stu

edit , yes I see that it's listing the drill bit's diameter accuracy as h8 not the hole size. Thanks for putting me strait.

 

[Beanwood]

See page 865 here: https://www.guhring.co.uk/downloads/Drilling_tools.pdf

OK - I think that says it all. I'm lookig for a drill bit, looking at specs, not finding what I need - and yet there are catalogues out there with over 900 pages on the subject - including which drill angles to use for the initial drill, to allow the second drill (With a different angle) to seat more centrally - all the while bearing in mind the different coatings (Some of which I'm sure they've just made up! and hardness. I'm going for a sit down!