Making accurate bushings

[Tiger]

There are plenty of posts on these forums about the lack of concentricity on bought bushings. I have a metal lathe and would like to make an accurate set of bushings for pens. I would have turned to outside diameter and then drilled a tight fitting hole to run on the mandrel, I gather from some posts that that may not result in the most accurate bushing so would it be better to drill the hole first, chuck some sort of mandrel and then turn to the required outside diameter. What is the recommended method for ensuring accurate bushings?

 

[plantman]

Tiger; Start out with a longer than needed piece of stock, chuck it in your drive, center drill your stock first, without removing your stock from the headlstock, turn down the stock to the size and length bushing you are looking for, or better yet, turn a tapered bushing so it will fit all size tubes. If you don't have a tapering unit on your lathe, use a metal file to taper your bushings. You only need a pressure fit, not a slip fit for a tapered bushing. One tapered bushing for each end, and one double tapered bushing for the center when you have 2 barrels. You can make these bushing out of metal, corian, or any nonstick material. The taper will also make removing the bushings easier after apply a CA finish. Also, never trust the bushing for final measurements to match your fittings!! Always use a digital calapers for that purpose and measure both fittings and bushings. Different kit makers may vary in their sizing of fittings. Jim S

 

[Rockytime]

There are plenty of posts on these forums about the lack of concentricity on bought bushings. I have a metal lathe and would like to make an accurate set of bushings for pens. I would have turned to outside diameter and then drilled a tight fitting hole to run on the mandrel, I gather from some posts that that may not result in the most accurate bushing so would it be better to drill the hole first, chuck some sort of mandrel and then turn to the required outside diameter. What is the recommended method for ensuring accurate bushings?

Hi Tiger,
It is all but impossible to make an accurate hole by drilling. Drilling at best is a roughing operation. First chuck up your material. Turn the OD to your desired size. Then without removing the material from the chuck drill the hole a bit undersized. Don't forget to start with a spotting drill. Then bore the hole to near size, about .003 under. with a boring bar and finishing with a 7mm reamer. Buying tools is even more fun than making things.
Les

 

[Tiger]

Thanks Jim and Les for the quick responses. I've pretty much converted to TBC and attempted to make some eliminator bushings ie the type that are stepped so that part of them fit inside the barrel. I have found that if the tube inside the pen blank has a spot of glue or I've been too aggressive with the pen mill that the fit is not perfect and I get Out of Round barrels. Les I have a set of boring bars but nothing small enough to do a 7mm hole, that is one tiny bar, good point about the reamer, think I have to add that to the list.

 

[Marker]

First of all, I would take whatever type of material you wish to use, and cut off a piece .75"-1" long.

Next I would face that piece on both sides.

Then I would drill my hole through it. it is impossible to dill a perfectly concentric hole in anything....so the first step would be to drill the hole, and then to turn it around this hole, so that it will find center.

Then I would turn it between centers.

Turning between centers is the most accurate way to get something concentric.

I would even consider making a set of BTC bushings to make your mandrel bushings. Make them sort of like a set of Slimline BTC bushings....only shorter.

I myself no longer use the mandrel bushing....I only use Between center bushings....I used to buy them from Johnycnc....but now I make all of my BTC bushing myself on my metal lathes.....I have made lots of them....