Am I ever going to get to use my delrin??

ScoJo · Post by **ScoJo** » Sat Feb 25, 2006 4:09 pm

Okay, here it goes. I bought some delrin to use for tenons since I seem to be incapable of turning a smooth tenon. Bought 5/16" delrin. I used to use a 5/16" brad point bit to drill my mortise, but I got some chatter and the mortise ended up being too big for the delrin. I switched to a small end mill. I am closer now, but the mortise is still too large when I use the end mill.

For those using delrin, do you get the same nominal size as the bit you are using to drill your mortise? How good of a fit do you get? How can I make my mortise the size I intend?

StephenDownie · Post by **StephenDownie** » Sat Feb 25, 2006 4:25 pm

Well I'm not sure if I can help much, but I've never had a problem with my delrin fitting well. I drill my shank mortise 3/8ths and my delrin mortise sleeve 5/16ths to fit a Delrin tenon. I use very sharp and good quality HSS bits, but from the sounds of it if you're using end mills they should have the same accuracy if not better. How are you drilling your mortise? Lathe? Drill Press? If you're using a lathe any chance your chuck is drillong off center? I know I need to adjust my lathe every couple months to keep it accurate.

ScoJo · Post by **ScoJo** » Sat Feb 25, 2006 8:12 pm

I am drilling with a mini-lathe. How do I adjust it or know if it needs adjustment?

Post by **KurtHuhn** » Sat Feb 25, 2006 9:04 pm

I use a 5/16" precision ground Forstner bit to drill my mortis. I drill about 1/12" at a time, and clear the chips/dust after each advancement. I've not had a loose tenon yet.

What speed are you drilling at? Also, it took me a bunch of experimentation to find the right size drill bit for delrin - lots of experimentation with various bits to find the The One True Bit.

ScoJo · Post by **ScoJo** » Sat Feb 25, 2006 9:07 pm

Well, I am drilling at the slowest speed for the Jet (500 rpm?). I have been through a number of bits. Do you use the same size (nominal) bit as your delrin?

JHowell · Post by **JHowell** » Sat Feb 25, 2006 10:09 pm

Kurt speaks the truth. I have a bunch of 5/16" drill bits and one is clearly the best. In addition to making sure your tailstock is accurately centering the bit, you might try slightly dulling the leading edges of the bit. That's an old trick machinists use to drill brass, which otherwise grabs the bit and makes a mess. It used to bother me that my best bit was an old one that has drilled hundreds of holes and by all rights should be worn out, but it may just be that's the reason it works. Or not. All you have to lose is a bit that doesn't work anyway.

Post by **KurtHuhn** » Sat Feb 25, 2006 10:33 pm

Oooh! Jack, thanks for reminding me. The one thing I did to my 5/16" Forstner bit was slightly dull the leading edges with a diamond file. I did this before I used it for the first time, so I don't know what difference it would have made. Mostly I did it because a machinist buddy told me to when I was talking to him about getting a repeatable hole size.

marks · Post by **marks** » Sun Feb 26, 2006 10:11 am

I tried drilling with an end mill, and had the same problem as ScoJo. My neighbor is an engineer, and with his digital calipers (I need to get some of these) discovered that the end mill was ever so slightly larger than the delrin, and so the problem. I sent the end mill back for a refund.

Now I drill the mortise slightly smaller with a drill bit, then follow up with a reamer of the correct diameter. Maybe I got lucky, but the reamer fits the delrin exactly, and I have a perfect mortise and tenon fit everytime. The reamer I bought had a long shank, and I cut about half the length off of it to keep it from wandering.

One thing I did, after drilling too large a hole in briar, was to check my bits and process by drilling several holes into a 2x4 and checking the fit before drilling into expensive briar.

StephenDownie · Post by **StephenDownie** » Sun Feb 26, 2006 3:50 pm

ScoJo wrote:I am drilling with a mini-lathe. How do I adjust it or know if it needs adjustment?

I'm using a Taig for my stem and Delrin work and it has a slide you can adjust the chuck on. If you're using a Taig the bolt is just under the advancing lever. Not sure about other kinds of lathe. Since hearing that end mills may not be that accurate I'd suggest some of the High Speed Steel Twist bits from Lee Valley. http://www.leevalley.com/wood/page.aspx ... ,180,42240 I'm sure there are others that work just as well, but these cut very nicely and are extremely accurate in size.

bscofield · Post by **bscofield** » Sun Feb 26, 2006 9:20 pm

StephenDownie wrote:
ScoJo wrote:I'm sure there are others that work just as well, but these cut very nicely and are extremely accurate in size.

But are delrin sizes accurate? That's the game, right? Finding one to match our size delrin (not necessarily the right size bit). Or do we expect that the molded delrin is SPOT on?

Tano · Post by **Tano** » Sun Feb 26, 2006 11:10 pm

Good day to all,
Can anybody tell me where you buy your delrin rod, and is 5/16" the common size used? Thanks.

StephenDownie · Post by **StephenDownie** » Mon Feb 27, 2006 1:59 am

bscofield wrote:
StephenDownie wrote:
ScoJo wrote:I'm sure there are others that work just as well, but these cut very nicely and are extremely accurate in size.
But are delrin sizes accurate? That's the game, right? Finding one to match our size delrin (not necessarily the right size bit). Or do we expect that the molded delrin is SPOT on?

I get my Delrin in rod form through Tim West and it has always fit perfectly with my drill bit sizes. I get him to chop it up in 6 in lengths so it's cheaper to mail. I've never had any that fit loose that wasn't a fault of my own. I believe the Delrin he's selling is extruded not molded so that might be a factor in diameter accuracy.

ArtGuy · Post by **ArtGuy** » Mon Feb 27, 2006 1:25 pm

Scott, I use a 5/16" Brad point bit from www.leevalley.com and that seems to work fine. You will want to make certain that you are drilling the mortise first before facing off with the forester and then drilling the airway.

ArtGuy · Post by **ArtGuy** » Mon Feb 27, 2006 1:26 pm

Tano wrote:Good day to all,
Can anybody tell me where you buy your delrin rod, and is 5/16" the common size used? Thanks.

I buy mine from mcmaster carr... http://www.mcmaster.com/

bvartist · Post by **bvartist** » Mon Feb 27, 2006 2:27 pm

ArtGuy wrote: You will want to make certain that you are drilling the mortise first before facing off with the forester and then drilling the airway.

Just curious, Is there a benefit to facing off the block after drilling the mortise? I've always faced off the block before any drilling, and was wondering if it is better to face off after drilling.

David

bscofield · Post by **bscofield** » Mon Feb 27, 2006 2:31 pm

bvartist wrote:
Just curious, Is there a benefit to facing off the block after drilling the mortise? I've always faced off the block before any drilling, and was wondering if it is better to face off after drilling.

David

well, facing off afterwards makes certain that your facing is at a 90 degree angle with your drilling. I usually do it twice tho. Once in the beginning to make sure the bit doesn't wander and then again at the end to ensure that it's at a 90 degree angle from the mortise.

ArtGuy · Post by **ArtGuy** » Mon Feb 27, 2006 3:03 pm

bvartist wrote:
ArtGuy wrote: You will want to make certain that you are drilling the mortise first before facing off with the forester and then drilling the airway.
Just curious, Is there a benefit to facing off the block after drilling the mortise? I've always faced off the block before any drilling, and was wondering if it is better to face off after drilling.

David

The reason I suggested drilling the mortise before facing is that I use a brad point bit. With brad points you do not want a pilot hole as that will cause chatter and a misshapen, larger hole. I have found that sometimes if I face before drilling the mortise that the divot left by the point of the forester causes the brad point to wanter a bit and make for a lager opening on the first 4mm or so of the mortise.

I thought that might be some of what is causing Scott's trouble.

StephenDownie · Post by **StephenDownie** » Mon Feb 27, 2006 3:16 pm

ArtGuy wrote:
bvartist wrote:
ArtGuy wrote: You will want to make certain that you are drilling the mortise first before facing off with the forester and then drilling the airway.
Just curious, Is there a benefit to facing off the block after drilling the mortise? I've always faced off the block before any drilling, and was wondering if it is better to face off after drilling.

David
The reason I suggested drilling the mortise before facing is that I use a brad point bit. With brad points you do not want a pilot hole as that will cause chatter and a misshapen, larger hole. I have found that sometimes if I face before drilling the mortise that the divot left by the point of the forester causes the brad point to wanter a bit and make for a lager opening on the first 4mm or so of the mortise.

I thought that might be some of what is causing Scott's trouble.

Good point John, it's second nature to me to face off the Delrin before drilling and I didn't even consider it as a possible problem. Unless the delrin is properly faced the drill bit will not drill true. If you're using a Taig and have the metalworking model you can simply use the cutting bit to face off the delrin as opposed to changing bits. Probably not much faster in the long run, but you don't need to turn off the lathe to do it.

ScoJo · Post by **ScoJo** » Mon Feb 27, 2006 3:40 pm

I used to use a brad point bit like John. I used to face off, then drill the airway, then the mortise. For the reasons John discusses, this ended up very badly. Then I went to facing first and drilling the mortise, then the airway. Not as bad, but still a problem because of the divot from the forstner bit.

Then I switched away from the brad point bit. Although for this last pipe I did the drilling so long ago (last August, I think) that I don't remember what order I did the drilling in - all I know is that the mortise, while closer to the 5/16 I was intending than ever before, was too large to be able to use the delrin.

bvartist · Post by **bvartist** » Mon Feb 27, 2006 4:03 pm

ArtGuy wrote:
The reason I suggested drilling the mortise before facing is that I use a brad point bit. With brad points you do not want a pilot hole as that will cause chatter and a misshapen, larger hole. I have found that sometimes if I face before drilling the mortise that the divot left by the point of the forester causes the brad point to wanter a bit and make for a lager opening on the first 4mm or so of the mortise.

AHHH! I see! Didn't think about that little center point on the forstner. I've been facing my shanks with a skew chisel until I could get a precision forstner bit. I tried my forstners I have for regular woodworking but they were slightly cupped and didn't work. Thanks for the tip.

David