How close is close enough?

[Brandon25]

Example: Some people use a J bit for 7mm pens. Others I've heard use a 9/32".
I found 9/32" to be a pretty sloppy fit, personally, so I got the 7mm.

I'm asking specifically because I don't have a 25/64" bit that the Baron calls for, but I do think I have a 10mm, which is only .0031" bigger. Is this good enough?

Also, is there a magic number that's "too big" a difference for penturner's purposes? I guess it matters that I use medium CA to glue my tubes in.

 

[ed4copies]

Brandon,

IF you are making pens from wood that will MOVE a lot, it is better to have the tube "looser".

Drill a hole in scrapwood, see what YOU think.

My holes in Pink Ivory are bigger than I drill in plastics.

YMMV

 

[Brandon25]

Good point. I hadn't considered wood movement. Thanks.

 

[randyrls]

Brandon,

IF you are making pens from wood that will MOVE a lot, it is better to have the tube "looser".

Drill a hole in scrapwood, see what YOU think.

My holes in Pink Ivory are bigger than I drill in plastics.

YMMV

Ed; Yes I have found that too! I want the tube to fit closely in the hole. Wood tends to drill slightly smaller than acrylic. I drill the blank hole slightly smaller than I think is needed, and try the tube. If it fits, good! If it is too small, I step upward until it does fit, then I write the drill size needed on the pen instructions. Usually two sizes, one for wood, one for acrylic.

The bit I use isn't always the one called out on the printed instructions. As always, your mileage may vary

A 115 bit set is a good investment. I would buy better bits in sizes you use commonly or larger than 1/2".

In pens with thin walls, you want the tube to be a snug fit because if it is too loose, you take the chance of breaking thru to the tube.

 

[rherrell]

Example: Some people use a J bit for 7mm pens. Others I've heard use a 9/32".
I found 9/32" to be a pretty sloppy fit, personally, so I got the 7mm.

I'm asking specifically because I don't have a 25/64" bit that the Baron calls for, but I do think I have a 10mm, which is only .0031" bigger. Is this good enough?

Also, is there a magic number that's "too big" a difference for penturner's purposes? I guess it matters that I use medium CA to glue my tubes in.

I also use med. CA and if I have a smaller drill bit than the instructions call for I'll use it. CA doesn't fill gaps like other glues so a tighter fit is OK. If a tube will fit witout forcing it's big enough. On the other hand I don't like to go any more than about .010 over the actual tube size. If you can't get it under .015 then I'd switch to poly or epoxy.
A Baron tube is approx. .383 so a 10mm(.3937) should be fine.

 

[jeffj13]

Remember that .0031 increase in diameter only means an additional .0016 on either side of the tube, so you will probably be ok.

As Ed said, take a piece of scrap and give it a go. In the time it took to make you post, you could have had yoru answer.

jeff

 

[DurocShark]

I use the 9/32 on my 7mm stuff. With epoxy filling any gaps, it's a non issue. I don't use CA anymore for tubes.

 

[Larry Gottlieb]

I use a 9/32 bit and polyurethane glue. This works well.
The 9/32 bit was suggested by Dick Sing in a class.

Larry

 

[avbill]

What's real interesting is on one suppliers web site They recommended buying the "J" drill bit. On their own DVD They use 9/32. Go figure!

"Very Interesting"

 

[Brandon25]

I use a 9/32 bit and polyurethane glue. This works well.
The 9/32 bit was suggested by Dick Sing in a class.

Larry

Don't quote me on this, but IIRC Russ Fairfield also used to use a 9/32" on his 7mm tubes. I suspect with anything thicker than CA this would, in fact, be a non-issue. For me, it is. I've got this handy dandy list in front of me right now that has all the conversions. A 9/32 bit is .0057 bigger than a 7mm, and .0043 bigger than a J bit. That tells me personally I dont want to use anything that's more than .005 bigger than the required bit. Having said this, I could have been experiencing some runout or wobble in my drilling, which changes everything, of course. :befuddled:

Case in point- I dont have a 4-jaw chuck yet, but drill on the lathe. I do this by putting the drill chuck with bit in the headstock, and a live center in the tailstock. I use a punch to put a divot in each end of the blank. I snug up the blank between the points, lock the pin indexer, then rotate the blank by hand, slowly advancing the tailstock, until my hole is GOOD and started, like 3/8" deep. Then I hold he blank with channel lock pliers, remove the index pin, and turn the lathe on. I hold the pliers in my left hand, advance the tailstock wheel with my right. When the squeal starts, I shut off the lathe, retract the headstock, and pull the blank off the bit, clearing the flute and hole. Slide the tailstock back on, starting with the bit already in the hole, and proceed again. Repeat until totally drilled to depth desired.

Last night, I wanted to drill a 1/4" hole to fit my mandrel, for making custom pen mill sleeves for bigger sizes. I drilled a 1/4" hole, and the mandrel was loose in it. I drilled the next size down, and it wouldnt fit. So I drilled that hole again with the 1/4" and it was tight. All this to say that I might be well served to get a drill press and my chuck sooner than later, and in the meantime predrill a smaller hole to start with.

Thoughts? (besides..."dang that guy takes a long time to say what he wants to say") :biggrin:

 

[andyk]

You can get a Delta bench top DP for less than $300.00 Plenty big enough for pens and the like.

 

[ed4copies]

Make sure your drill press has a 3" travel, if you can afford it.

Otherwise, keep a piece of flat 1" or 2" stock nearby. Slide it under the blank, for the last few cm of drilling.

 

[Brandon25]

You can get a Delta bench top DP for less than $300.00 Plenty big enough for pens and the like.

I just had to wheel and deal with a guy to get a scroll saw for $25. Cash is not my strong suit right now.:frown:

 

[randyrls]

To join the thread; For wood 7mm tubes I normally use an "I" (letter I as in India) The 7mm tubes fit just perfect!

 

[ldb2000]

I never follow the kit manufacturers drill size recommendations , the best thing to do is measure each tube with your caliper (if you don't have one , you really should get one) then use the HUT drill size chart that was posted in the library to determine the correct drill size , it only takes a few seconds but it's worth it . I have found that the tube sizes can be different on the same types of kits from the same manufacturers , I guess it depends on who they buy the tubes from on that production run .

 

[thewishman]

Brandon, the picture I got when you described your method made me uncomfortable. Check with your local turning club, they may have a chuck available to borrow. I joined my club, for $25, and got to take home a lathe, stand AND chuck for several months. Used it until I sold enough pens to pay for my own stuff.

 

[Randy_]

For whatever it is worth, I did a comparison of tube sizes and recommended drill bit sizes for about 60 of the most commonly used kits. The greatest majority of the bit size recommendations ranged from about 0.004" to 0.011" over tube size. There were a few bit recommendations that were as much as 0.019" over which is much looser than I am comfortable with.

I think there is quite a bit of personal preference involved in this question. Some folks like to use poly glue and are comfortable with bigger gaps and others are not.

Best recommendation I can give you is to drill some test holes in scrap wood and then make up a few kits to see what you like and what you don't.

 

[rherrell]

Brandon, give this a shot, it can't be any worse than what you're doing now!!
I ASSUME you have a spur center? If so, put your spur in your headstock and your live center is your tailstock. Now turn your blank down to round and put a taper on one end to match the taper in your headstock. Remove the spur center and put the blank in the headstock. Put your drill chuck in the tailstock and go to town. You can tap the blank LIGHTLY to adjust it so it runs true. I'd start with a small bit and work my way up so you're not putting alot of pressure into it. If it want's to spin on you put some DUCT TAPE on that sucker, that's what it's made for!:wink::biggrin:

 

[andyk]

I read some interesting things at the AS website. They say to use 9/32" instead of 7mm and they also recommend not using brad point bits. On some woods I have had problems using 7mm, the hole is such a close fit that using medium CA there is a problem getting the tube in all the way before it sets up. This usually happens with the denser more oily woods.

 

[Daniel]

IN my work trying to figure out pilots for end mills I came to the conclusion that .03 was the point that fit became to sloppy. that was for an end mill pilot that can afford to be even looser than a tube so this would support what Randy said above that 0.02 being to much.

 

[Brandon25]

Thanks, all, for the replies. I've got some good suggestions and ideas here to think about now, and I now know to experiment with my hole size, and not to take what the instructions say as the bible truth. You guys are really helpful to someone getting started as I am.

Brandon

 

[Rmartin]

About this close: holds thumb and finger together real close without touching.