Bet you guys thought this subject had gone away for a while?
Well, I've run into a new problem I haven't seen discussed here. I've been using delrin tenons for a while and was completely happy with it. UNTIL, I ran out of the rod I was cutting tenons out of and started using another. After running into problems with loose fit on my last 3 pipes, I did some checking. I thought I might be getting sloppy with my drilling procedure. So today after making my 4th loose mortise/tenon in a row I dug out my digital caliper. Drill bit and drilling procedure is fine, still drilling a mortise at .310 to .311 in diameter. The problem is, my 5/16" delrin rod is also .311! The rods I've measured before usually were around .313 to .315 and I got nice tight fits. But this rod is too small for the mortise I'm drilling.
Anybody else had this problem? Is it a normal occurrance? Or did I get the only delrin rod in existence thats under nominal diameter? (.3125)
bvartist wrote:Bet you guys thought this subject had gone away for a while?
Well, I've run into a new problem I haven't seen discussed here. I've been using delrin tenons for a while and was completely happy with it. UNTIL, I ran out of the rod I was cutting tenons out of and started using another. After running into problems with loose fit on my last 3 pipes, I did some checking. I thought I might be getting sloppy with my drilling procedure. So today after making my 4th loose mortise/tenon in a row I dug out my digital caliper. Drill bit and drilling procedure is fine, still drilling a mortise at .310 to .311 in diameter. The problem is, my 5/16" delrin rod is also .311! The rods I've measured before usually were around .313 to .315 and I got nice tight fits. But this rod is too small for the mortise I'm drilling.
Anybody else had this problem? Is it a normal occurrance? Or did I get the only delrin rod in existence thats under nominal diameter? (.3125)
Thanks
David
Confused by Delrin again!
This wouldn't suprise me very much unless you told me that this is all the same batch of delrin from the same company. Then I'd be worried... :think:
I've had a bittersweet love affair with delrin.. and I have run into the problem you're having. I had to order delrin from a couple of different places before I found a place that fits my needs. I ended up getting it from online metals, and it's perfect every time.
bscofield wrote:
This wouldn't suprise me very much unless you told me that this is all the same batch of delrin from the same company. Then I'd be worried... :think:
Same batch, same company, same order. I don't know if it was all cut from the same stock. But it was all ordered at the same time!
hazmat wrote:I had to order delrin from a couple of different places before I found a place that fits my needs. I ended up getting it from online metals, and it's perfect every time.
Thats where I got this stuff! I'm hoping it isn't a normal thing, just ordered 12 ft more from them before I discovered the problem.
bscofield wrote:
This wouldn't suprise me very much unless you told me that this is all the same batch of delrin from the same company. Then I'd be worried... :think:
Same batch, same company, same order. I don't know if it was all cut from the same stock. But it was all ordered at the same time!
I haven't. Although I use 1/2''. I cut my tenon's for each stem. I also mill small tubes for my bamboo and other extentions, also cut motise liners for bamboo mortises. I know alot hits the floor, but I have all the control !
Dan
Gabrieli Pipes
bvartist wrote:Anybody else had this problem? Is it a normal occurrance? Or did I get the only delrin rod in existence thats under nominal diameter? (.3125)
That's the first time I've ever heard of that. I'd send them an email and ask WTF, and a refund/exchange.
Is there any chance at all that the bit you're drilling your mortise with got jimmied up at all?
And while we're talking about bits.. is there such a thing as a brad-point bit that doesn't leave a lil ridge in the bottom of my mortise around the draft hole???
bluesmk wrote:I haven't. Although I use 1/2''. I cut my tenon's for each stem.
Dan, Doesn't that require a metal lathe? I don't think my turning skills are good enough to accomplish that on a wood lathe. But it would simplify things!
hazmat wrote:Is there any chance at all that the bit you're drilling your mortise with got jimmied up at all?
That was my first thought, but I measured the diameter of the mortises and they were fine. Usually as a bit dulls, it will tend to "wander" a little and drill a hole thats slightly larger. My problem is definitely the delrin.
And while we're talking about bits.. is there such a thing as a brad-point bit that doesn't leave a lil ridge in the bottom of my mortise around the draft hole???
The only bit I know of that won't leave the little ridge is an end mill. Unless you want to use a standard point bit and chamfer the end of the tenon to match.
I'm sorry, I just jumped right in, didn't realize you were working without one. Yes a metal work is required. I do all my stemwork on a 7x12 metal lathe. I use Forstner bits for all my mortises.
Dan
Gabrieli Pipes
bluesmk wrote:I'm sorry, I just jumped right in, didn't realize you were working without one.
Jump in anytime! I hope to have a metal lathe, and a place to use it someday, so little tidbits of wisdom are always welcome!
Some good news! My new order of delrin came today. This time I checked all the lengths I bought and they are all .313 diameter! I think I just happened to get a piece that was missed by QC in the manufacturing process. Good thing it was only a 1 foot piece!!!! I should be set now!(until I run out again!)
Not sure what grade Delrin you are using, but it's probably extruded stock. The tolerance on extruded stock is something like +/- 2% of the stated diameter. It can vary that much from one end to the other. I machine a lot of different plastics at work and have learned not to trust stock to clean up at nominal size. Not the answer you were looking I know, but I believe you're best off to measure each piece and adjust your drill size until you can get a lathe. Just my $.02
JBW wrote: Not the answer you were looking I know, but I believe you're best off to measure each piece and adjust your drill size until you can get a lathe. Just my $.02
8O 8O 8O 8O
Just some rough calculations, for my delrin thats .311 in diameter, I'd need a 159/512 drill bit. Do they make such a thing????
JBW wrote:Not the answer you were looking I know, but I believe you're best off to measure each piece and adjust your drill size
I'm with you JBW. I was supervisor for many years as a tool grinder for plastic mold injection and one thing I can say for sure is nothing is as it seems. On any given job on a mold each and every part of it must be checked even if we did receive stock parts that should theoretically just be inserted and work correctly. I have zero faith in manufacturing. It'll bite you in the ass every time.
I dont think I ever turn off my digital veneer. It's my most used tool.
