1. Reaming question

Hi

I am originally from Europe and am still struggling with the somewhat inconvenient non-metric system.

Let's say I want to over/under ream a 0.125 dowel pin.

The under reamer will be 0.1240

Great.

But what kind of drill do I use to "slightly" "under-drill" the under reamer.

If I use a normal drill bit (1/8) it surely will be way too large.

I am somewhat at a loss - am I supposed to use a #31 (0.12) drill ?
Or rather #30?

Does the same procedure fit for all reamer tasks - just user the next smaller
number drill?

Thanks

2. Sorry, just found an older post.

Drill 1/64th or .3 mm smaller that the reamer diameter.

That will not always fit with the numbered drills, but somehow it must work.
(0.3mm is easier).

3. We've been converting to the metric system since Thomas Jefferson started promoting it in 1790.LOL

Dick Z

4. The reamer for a 1/8 (0.125) dowel pin - tap fit should be .1248.
For drilling find the next drill that is about .012 -.015 smaller. Be it a fractional, number or for larger sizes you may use a letter drill. Great system - isn't it.
So for a 0.1248 reamer you can use a 7/64th or a #35 drill.
The reamer for a 1/4 (0.250) dowel pin - tap fit should be .2498.
Your drill size should be a 15/64th drill or a letter "A" drill.
They are almost the same size - 0.2344 and 0.2340.
For a tighter fit you may reduce the reamer to 0.1245 and 0.2495.
Use the same drills.

• Danke Juergen,

going by your name we probably come from the same neck of the woods.

• Hi, for what it's worth, I "converted" all my drills to Metric sizes simply by measuring them with a micrometer and storing them in a rack made for the job.

All my drill sizes are now Metric, be they number, letter, imperial or without any marking.

I made a wooden holder that had 12 holes across and ten holes down making 120 holes.

The wooden holder is made from hardwood and consists of 10 strips of hardwood all hinged at one end so that you can spread the rack apart and get to the centre easiliy.

The holes across are numbered 1 to 12 and the holes down are numbered 0 .1 .2 .3 etc up to .9......so at the drop of a hat I can locate any drill from 1mm up to 12.9mm.

I measured the drills and stored them in the hole that nearest corresponded to the size measured.....it's so simple....how can you not relate to a drill that measures 5.12mm and use it as if'n it was a 5.1mm size......you can't sharpen the average drill of that size with any degree of accuracy that will cut a hole exact to size anyway, that's why a hole is reamed to size.

I never could relate to 1/64 sizes for drills and having some number and letter sizes also drove me almost to drink....LOL.....but Metric sizes are one system and one system only.

If'n you want to be a real nit picker, when you come to drill a hole to tight limits you'll measure each drill to make sure it is nearer to the size you want than the rack indication.

BTW, you can also hone the point of a drill off centre to make it cut oversize when the next size up is too big, and as the drills I have are in .1mm steps, that gives you a .004" diam difference between drills.
Ian.

• Thanks Handlewanker

I actually have started the same system with my drills.. writing the metric sizes on their storage position.

I have not gone so far to make a 120 hole holder yet.

Thanks

Eriks

• Hi, I know what you mean, making a 120 holer is a task as each hole has to be drilled with the same drill for the hole, but well worth it.

My MK2 version will be made from black nylon strips, 16mm wide X 30mm High, probably also hinged at the back to allow access, but I might make the whole shebang like a cabinet and have the drill holders side by side like a rack to slide in and out.

A firm I worked for in UK used to have a mini filing cabinet (like a CD storage box) with plastic bags, all very neatly numbered with drill sizes....problem was you had to take the bags out to find a drill that got put back in a worn state.....GRRrrRRrrrrr.
Ian.

• Hi Handlewanker

do you have a picture of your holder?
I would probably make the holes with a drill one or two tenths (mm)
larger than the actual drill it will contain -> easier access...???

I was almost driven to drinking, too when I bought my small mill here and the
I am so much happier now.

• Hi, sorry no photo as it's pretty basic...the mk1 model was maded from several lengths of soft Pine wood, rotten stuff, with the appropriate holes drilled etc and held together with metal clips at both ends.....much better when the wood strips are hinged.

The MK2 version will be made from black nylon also hinged at the rear.

One thing I found with the soft wood, especially Pine, and that was to oil the wood after drilling as the moisture in the wood tends to rust the end of the drill shank and they seize solid in the blocks.

I'm going to use the same system with my end mills and slot drills, but as they are in standard shank sizes, about 6 variations from 3mm-1/8" up to 19mm-3/4", the plan will be to have a number of strips with several rows of holes to cater for Imperial and Metric for the ones currently being used, and another set of holes for ball nose and corner radiused ones, and I suppose there will also be a need to seperate any solid carbide ones both in Imperial and Metric, straight and radiused....then remove them when they're blunt and ready for sharpening to another storage block......sharpen all at once.....there's also the aspect that when a cutter is sharpened on the sides it becomes an odd size, so maybe another row of holes for non standard size is needed.....sigh.

Most people would by now have decided to go with the cabinet with plastic draws, but I've not found any cabinet with draws small enough to hold a couple of cutters without taking up a lot of room on the bench.....maybe on the wall...hmmmmmm.

So a bit of planning is in hand to design a holding system for all the cutters I'll use, and at the moment I'm very keen on using, instead of the black nylon originally planned, some hard wood which we have in OZ called Red Gum, which is a very heavy and dense wood, dark red in colour, similar to Mahogany, but much harder, and when it's planed up and finally Poyurethane gloss varnished, looks so good I think I'll go down that path.....it will make a "collecters" item when the polished and laquered brass hinges are added at the rear end of the drill storage version.

Down in OZ the fencing industry uses Red Gum for fencing posts due to it's long life in the weather, and I get my supplies of Red Gum from the off cuts that the fencing people discard when they trim the fence posts to length.....sometimes as much as 600mm long pieces 75mm X 150mm.

BTW, when you drill the holes for the drills or cutters or whatever, (I also use one for my Allen keys, both Imperial and Metric), then it's probably going to be with the size drill you are going to store in that location.....unless you have all the next size .1mm drills in the set, but I just reamed the holes vigourously with the drill, but with a varnishing step it will need rereaming with the drill size to get it to clear.

I would advise varnishing the holes and redrilling when using hardwood as the wood contains some acids etc that need sealing out, or like me youl'll spend an hour or more polishing the rust off of the drill shanks when you can prise them out.....perhaps that's only true for soft pine wood with more water content.
Ian.

• I cheat and use the CNC to make all different size holes with the same size cutter, then only need 3 or 4 size cutters to do a nice range.

Nice helical interpolation.

Sharpening Small Bits

Sharpening drill bits by hand

and the code:
Sharpening Small Bits

• Hmmmmm, CNC, one guy described CNC as moving in ever decreasing circles and dissapearing up your own.......but he was only an operator....LOL.

Using a CNC interpolation method to get a hole diam is pretty nifty.....I think there is a need to be able to do this on a standard drilling machine without having to resort to stepper motor control etc......maybe a chuck that held the drill in a rotating mode and also put it off centre to rotate like a boring bar....I'm working on it.

This would enable you to drill a hole way undersize and just dial in the hole size on the chuck or collet housing same as you would do with a boring head.....the drill would resemble a slot drill rather than a conventional 58 deg pointed drill to enable you to open the hole up by rotating the chuck or collet eccentrically, off centre etc.....one drill does all....almost.

I used to have a boring bar with a fixed tool bit that gave a hole 1" diam + .002" for a special job we had to do.

It was made from an old Herbert reamer shank with a 3 Morse taper and had a tool bit mounted in a hole in the end.

NeilW20, that Wishbone type drill sharpener I made has worked overtime......to be able to put an accurate point on a 2mm drill is kids play, couldn't do without it......I liked the way you brought it "up to date" for your Carbide cutter sharpening.
Ian.

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