A question about the pen turning mandrel.

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Earl_J13

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I'm pretty new to wood turning. I've been making pens using the Slimline and Summit kits which both use 7mm tubes. My mandrel is a 7mm. How do I use the mandrel on kits that are 10mm or other sizes? Do I need different mandrels or is it the bushing sets that fill the void between 7mm and the other sizes?

Thanks in advanced.
 
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wfsteadman

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Each kits requires a set of bushings that will work with the 7mm mandrel. So your assumption is correct.
 

eharri446

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The bushing inner diameter is not exactly 7mm. According to what i found it it 6.3 mm. That is not an issue unless you plan to create your own bushing then it can be a problem.
 

farmer

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Mandrels

The sanding mandrel I buy are carbide and last forever .......
Rockler has and makes them .

I only use my mandrels for the finish, I don't cut wood next to my mandrels .

I own and use digital calipers and own a outside micro meter set .
 

eharri446

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Curly, I measure the diameter of the mandrel rod itself using my digital calipers.

Also, if you check some of the vendors, they will give you the dimension of the mandrel rod of .248 inches.

Berea Hardwoods says that their "A" type mandrel is .247 inch in diameter which is a little smaller than 7mm which is .275 inches.

The slimline tube outer dimension is 7mm however the inner dimension is between .247 and .248 inches.
 

Mr Vic

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Never measured my "A" mandrel shaft or the replacement but a 1/4 drill worked perfect for making plastic finishing bushings and barrel trimer sleeves. The basic barrel trimmer shaft is the same diameter as the mandrel. Don't think I ever turned any pen that called for the "B" mandrel
 

Curly

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Curly, I measure the diameter of the mandrel rod itself using my digital calipers. Also, if you check some of the vendors, they will give you the dimension of the mandrel rod of .248 inches. Berea Hardwoods says that their "A" type mandrel is .247 inch in diameter which is a little smaller than 7mm which is .275 inches. The slimline tube outer dimension is 7mm however the inner dimension is between .247 and .248 inches.

Sorry about the question. I use as a rough conversion of 0.040" per millimeter and 0.004" per 0.1 millimeter. So when you were saying you had 6.3 as a measurement and not 7.0 the first thought that came to mind was that your caliper had bent points or wasn't zeroed correctly because things didn't add up. Too many years as a quality inspector I guess. ;) Now I realize the 7.0 millimeters is the outside diameter of the brass tube that slides over the mandrel which is smaller by the thickness of the brass and a bit for clearance. The bushing inside diameter is nominally 0.250".
 

ed4copies

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Actually, 7mm is the size of the HOLE you drill for your tube.

This is one of the "accepted notations" in penmaking that is misleading and, actually dead wrong. NONE of the tubes are 7 mm or they would not fit in the hole.

This is also true of "3/8", 10mm, 10.5mm, 12.5mm, etc. All are drill bit sizes, NOT tube sizes.
 

eharri446

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I found that out a couple of weeks ago when I put my caliper onto a tube for a pen with a 27/64 drill bit and came up with 15/32. I was confused for a bit, then I realized that some space had to be left for glue between the tube and the inside of the blank.

That seems to be why there are voids between the blank and the tubes from time to time.
 
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