Making bushings for pen kits

[stewart]

Hi all
A happy new year...and then my question! I'm trying to make some bushings for a pen kit. They need a 6.3mm hole (no problem) then a 10mm length with a diameter of 7mm then another 10mm length with a diameter of 9.5mm. I've been trying to make them on my metal lathe (I'm more of a machining novice than I am a woodworker!) but without much success. So as a novice I thought I'd share my approach as it's bound to be wrong and hopefully someone can point me in the right direction.

I'm using a length of round brass stock which is 12mm in diameter. It's being held in a three jaw chuck. I have left about 60mm of the bar protruding from the chuck. I've then used the tailstock with a drill chuck to drill the 6.3mm hole. I've then used a tool in the toolpost to bring the bar to concentricity and reduce it to 9.5mm - except it's 9.5mm at the end nearest the tailstock but 10mm at the headstock end. What am I doing wrong? Or is the lathe not set up correctly??

Any help gratefully received - don't mind waiting until next year... :lol:

 

[stevebuk]

sounds to me like the the rod isn't square in the jaws, or it isn't lining up with the tailstock properly.
What type of bushings are you making stewart? for what pen, and will you use a mandrel with them or not.

 

[stewart]

Hi Steve
They're for a Craft Supplies kit - their Click 1 pen. I'm going to use them on a mandrel. My mandrel came with 4 cones that can be used as 'universal' bushings - i didn't get on very well with them so thought I'd give my metal lathe a go. I didn't have any support at the tailstock end of the metal lathe when making the bushings - perhaps that's part of the problem...

 

[jasonB]

Three things

1. which is the most likely. you have got far too much material sticking out the chuck, if you need 20mm (2x10mm) then have about 25mm sticking out the chuck. with this amount of projection you don't really need tailstock support. Though I would expect the end furthest fron the chuck to be larger

2. Are you using the topslide to turn to diameter, if so make sure this is set to zero degrees eg parallel to the lathe axis. try doing it my moving the carrage as this will eliminate any error on the topslide.

3. Is the tailstock in line with the headstock? many lathes allow you to off set the tailstock for the purpose of turning tapers which is what you are getting. Only applies if turning with tailstock support

4. ensure all gibs are properly adjusted and there is no wear in bed or bearings

Jason

For accuracy the bore should really be reamed (its probably 1/4") failing that drill 6mm then open up with 6.3mm or 1/4" drill as drilling straight in 6.3 will probably come out larger as most drills will tend to cut oversize.

 

[stewart]

Thanks for the tips, Jason - will try them out when I can get back into the workshop.
Happy new year!

 

[CHJ]

Make sure your turning tool is sharp.
Make sure that the cutting tip is EXACTLY on centre.

If you have no other method of checking tool/tailstock centre height then face off the bar, if the tool is on centre there will be no pip in the middle.

If you are intending to use the bushings on a regular basis I would advise making them from mild steel.
Brass will soon wear away whilst sanding unless you are very careful.

If you clamp a STRAIGHT bar about 150mm long in the chuck, does it line up with the bed ways? (rough checking headstock alignment)

 

[stewart]

Thanks, Jason
Not using the top slide seems to cut evenly - I'll have to check the angle setting as it is set on zero. Maybe some grub screw needs tightening...

Chas
I have a load of steel bar which came with the lathe - a gift from my mum's father-in-law - but I think it's all silver steel. I wonder if this too hard to use as my wood chisels might catch the bushings?

 

[CHJ]

Stewart, If your tools are HSS they will not suffer any more than the HSS tools used in your metal lathe to turn them.

Any slight dulling of the edge would be well within the normal edge honing/touchup regime that you should be using to keep a keen edge whilst turning at this diameter and wood wall thickness.

As an aside, Silver Steel suitably hardened and tempered makes good turning tools, even for occasional metal turning use.