8mm drill bit?

[Ryan Mcdermott]

Does anybody have an 8mm drill bit?  Or know where in town to buy something like that after 5:00pm?

Kirk is here trying to drill an 8mm hole in something, and we don't have the bit, and can't find anybody that even sells it :(

(Metric is apparently not something most places stock)

[Larry Campbell]

what is he drilling? does he need precision, often guys use a metric ream on a standard hole.... a 5/16 inch is just a hair under 8mm

5/16 is 3125in or 7.9375mm
8mm is 3150in
....that is .0625mm diff or .0025in diff

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[Aaron Hicks]

Have a micro fly cutter that'll do the job?

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[Will Bradley]

Or the CNC mill?

[Will Bradley]

Wait take that back, what about the rotary table for the manual mill?

[Corey Renner]

I'm assuming (hoping) that you guys are goofing around. In case you're not, know this: drills do not make a precisely sized hole. If you ever need an exact hole, you drill a few thou under and ream to size. 8mm is .815", 5/16 is.8125 close enough. If not, then ream to 8mm after the drilling. Hth c

Sent from my Kindle Fire

---

From: Will Bradley <bradle...@gmail.com>
Sent: Wed Apr 02 20:39:13 MST 2014
To: HeatSync Labs Google Group <heatsy...@googlegroups.com>
Subject: Re: [HSL] 8mm drill bit?

[JR]

Did you try woodcraft or Rockler?  A bunch of the pen turning stuff is metric and so either uses metric drills or letter sized drills. 

[Larry Campbell]

We still do not have the parameters of the project... without knowing the material used or the needed tolerances one cannot determine if the procurement of a ream is needed or justified....

[Corey Renner]

I've found little point in ever buying metric drills in the USA, the reason being that drills aren't very precise anyway, so for a typical hole there is usually an inch hole that is close-enough.  If precision is needed, then you need to ream anyway which is a two step process.

-Step 1: Drill a few thousandths undersize

-Step 2: Ream to size

Step 1 is tolerant of a range of preliminary sizes.  You typically will drill .005 to .010 undersize (for small holes), and the reamer won't care if the initial hole was standard or metric, it cares ONLY that the initial hole was a few thou under.  So, a typical 3-in-1 sae drill index (Numbered, lettered, fractional) will cover all of your needs and you employ metric or inch reamers after drilling only when precision is required.  HTH.

cheers,

c

Blog:

http://coreyrenner.tumblr.com/

 

YouTube Channel:

http://www.youtube.com/user/vandal968

[Ryan Mcdermott]

Hey guys, sorry I didn't respond quicker.

Kirk came back in today with a ream, thanks for the suggestion, Corey.

The material he's using is some form of plastic.  I think it's for bushings for a 3D printer.

[Kirk]

Thanks to everyone for helping me solve this.  I wanted to make six bushings out of a Teflon infused Delrin rod.  The bushings are to be a quieter replacement for the linear ball bearings used in 3D printers (I am making a Rostock printer).  I have learned a lot since yesterday from you guys - the right places to buy tools and about reamers.  I never knew that holes are to be made with reamers.  After spending last night reading, I bought an 8mm reamer at Grainger's today on the way to HeatSync, and spent the afternoon making the bushings with Ryan's help.  I am amazed at the precision - the bushings slide freely on the tool steel rods without any play. The tolerance is so tight that I can feel when the bushings pass over dust on the rods. Again, thanks for the help everybody, and for broadening my knowledge in the mechanical arts.

[Larry Campbell]

We are glad to help pass on knowledge, its one of the many reasons we exist....

(perhaps more of this is what we need mentioned on the iMesa site to help justify our getting a new property) 

On Thursday, April 3, 2014 10:59:20 PM UTC-7, Kirk wrote:

Thanks to everyone for helping me solve this.  I wanted to make six bushings out of a Teflon infused Delrin rod.  The bushings are to be a quieter replacement for the linear ball bearings used in 3D printers (I am making a Rostock printer).  I have learned a lot since yesterday from you guys - the right places to buy tools and about reamers.  I never knew that holes are to be made with reamers.  After spending last night reading, I bought an 8mm reamer at Grainger's today on the way to HeatSync, and spent the afternoon making the bushings with Ryan's help.  I am amazed at the precision - the bushings slide freely on the tool steel rods without any play. The tolerance is so tight that I can feel when the bushings pass over dust on the rods. Again, thanks for the help everybody, and for broadening my knowledge in the mechanical arts.