Jump to content


Boring out brass tubing

  • Please log in to reply
7 replies to this topic

#1 Fred_J


    Mid-Pack Racer

  • Full Member
  • PipPipPip
  • 135 posts
  • Joined: 15-August 06
  • Gender:Male
  • Location:Nutley, NJ

Posted 21 May 2020 - 02:13 PM

If I wanted to overbore a front axle tube on a slot car, how would I go about it? Would I use, a drill bit or a reamer, or something else?
  • airhead likes this
Fred Jespersen

#2 Dave Crevie

Dave Crevie

    Posting Leader

  • Full Member
  • PipPipPipPipPipPipPip
  • 2,183 posts
  • Joined: 16-February 09

Posted 21 May 2020 - 02:24 PM

Depends on how much bigger you need to go. Generally a reamer would be the choice since it will follow the bore and not walk off center like a

drill bit could. But don't try to take more than 1/64th at a time. I.E., if you are going from 3/32nds to 1/8th, use a 7/64ths ( .109 ) dia, reamer first,

then follow up with the 1/8th reamer. And use Marvel Mystery Oil to lube the reamer during the reaming operation if the tube is brass. Don't use

a hand drill to drive the reamers. Do it by hand if you have a large pin vice, or loose drill chuck.   

#3 MarkH


    Race Leader

  • Subscriber
  • PipPipPipPipPip
  • 500 posts
  • Joined: 26-November 12
  • Gender:Male
  • Location:St. Louis

Posted 21 May 2020 - 04:05 PM

If you use a drill bit, dull the cutting edge about .003 to .006". It then become more of a scraper eliminating the chatter and self screwing into the tube.

A small fine stone and a couple passes over the cutting will get you there.

Mark Horne

SERG - www.slotcarenduro.club
"Racing is life... everything else is just waiting." Steve McQueen - LeMans
There are only two things in life that make me feel alive. Racing is one of them.

#4 Matt Sheldon

Matt Sheldon

    Duffy's HMI Executive

  • Full Member
  • PipPipPipPipPipPipPip
  • 2,018 posts
  • Joined: 19-January 10
  • Gender:Male
  • Location:Platteville, CO

Posted 21 May 2020 - 04:59 PM

Reamer if you have the proper sizes to progress from. Mark's advice on using a dull bit is great! When I have to open up motor brackets regardless if for an axle tube or pinion clearance, I chuck the bit up and then just turn by hand.

Matt Sheldon

#5 airhead


    Race Leader

  • Subscriber
  • PipPipPipPipPip
  • 720 posts
  • Joined: 13-January 09
  • Gender:Male
  • Location:Prattville, AL

Posted 22 May 2020 - 06:31 AM

McMaster - Carr  has any size reamer you would need.

Billy Watson

#6 Dave Crevie

Dave Crevie

    Posting Leader

  • Full Member
  • PipPipPipPipPipPipPip
  • 2,183 posts
  • Joined: 16-February 09

Posted 22 May 2020 - 08:54 AM

A drill bit, being two flute, will not cut a truely round hole, even with the rake broken to eliminate the cutting angle. A reamer is always the best choice.

You may be able to borrow what you need from another racer or a local machine shop. You are not the first to run into this problem. It goes way back

to when slot racing began.

#7 Eddie Fleming

Eddie Fleming

    Checkered Flag in Hand

  • Subscriber
  • PipPipPipPipPipPip
  • 1,571 posts
  • Joined: 27-April 14
  • Gender:Male
  • Location:Fayetteville, GA

Posted 22 May 2020 - 09:52 AM

Why are you wanting to bore it out in the first place?


Just curious as to what problem you are trying to solve.

Eddie Fleming

#8 MSwiss


    Grand Champion Poster

  • Advertiser
  • PipPipPipPipPipPipPipPip
  • 22,819 posts
  • Joined: 16-April 06
  • Gender:Male

Posted 22 May 2020 - 10:06 AM

I asked him the same question in the other thread by the same name.


As my post also alludes to, Fred isn't real anxious to answer follow up questions, related to his original question.

Mike Swiss
Inventor of the Low CG guide flag 4/20/18
IRRA® Components Committee Chairman
Five-time USRA National Champion (two G7, one G27, two G7 Senior)
Two-time G7 World Champion (1988, 1990), eight G7 main appearances
Eight-time G7 King track single lap world record holder

17B West Ogden Ave., Westmont, IL 60559, (708) 203-8003, mikeswiss86@hotmail.com (also my PayPal address)

Note: Send all USPS packages and mail to: 5858 Chase Ave., Downers Grove, IL 60516

Electric Dreams Online Shop