Tapping phenolic

Dave38

Dave38

theemperorhasnoclotheson
Silver Member
I'm attempting my first phenolic insert and am looking for any tips on tapping it. It is canvas based, as this is all I have. My main question is how large of a dia. hole will do the best for deep threads, etc.? I'm using a 3/8 x 10 tap, non-piloted. Thanks,
Dave
 
.312" i what i would use and tap it with the largest tap you have several times.we have 3-4 3/8-10 taps and really only use 2 of them.one has a major which is .003" bigger than the other.
 
> According to the tap drill chart,a letter Q drill (.332) is the right one for 3/8-24 threads,a 5/16 for 16 TPI,but none exist for 3/8-10,but the 5/16 is closest,so I'd use that. It SHOULD fit nice and snug that way.

The standard tap drill chart bases the drill recommendation for approx. 75% of the depth of a full thread,with variations on drill size for diff materials/thread percentage. These variations are usually for tapping tough materials like stainless or tool steel,or when tapping a hole in a part that is to be heat-treated/hardened,to allow for shrinkage.

This won't apply to your canvas phenolic however. Unless someone with more knowledge shows up to correct me,the 5/16 is the right one to use here,although you might get away with drilling a .250 hole and using a very small boring bar to bring it out to .305-.310.

You might want to wear a simple paper air mask when drilling phenolic,no coolant is needed other than air,but even with phenolic,make sure you break the chips up,and back it out if you have to so you get the crap out of the hole. Tommy D.
 
the .312 will make it very tight as Tommy sadi,but if you tap it 5-6 times it will loosen up enough to screw on the butt.
 
Dave38 said:
I'm attempting my first phenolic insert and am looking for any tips on tapping it. It is canvas based, as this is all I have. My main question is how large of a dia. hole will do the best for deep threads, etc.? I'm using a 3/8 x 10 tap, non-piloted. Thanks,
Dave
Click to expand...
The standard formula for a tap drill is nominal size minus 1/pitch. For a 3/8-10 that would be .375 - .100 = .275 diameter. Cuemakers cheat and use a larger hole in wood because the threads tear when tapped. Live tooling solves that problem.

With phenolic, I'd try a 9/32 drill to get closer to a full thread. It shouldn't be any tighter than if you used a 5/16 drill (the tightness is caused by a "dirty" thread form caused by canvas fibers torn rather than cut - not by the minor diameter size) but you will have a stronger thread by virtue of its size. If it is tight, you can run the tap thru a few times (as others have suggested) or try using beeswax to lubricate the tap before running it in the first time.
 
dzcues said:
The standard formula for a tap drill is nominal size minus 1/pitch. For a 3/8-10 that would be .375 - .100 = .275 diameter. Cuemakers cheat and use a larger hole in wood because the threads tear when tapped. Live tooling solves that problem.

With phenolic, I'd try a 9/32 drill to get closer to a full thread. It shouldn't be any tighter than if you used a 5/16 drill (the tightness is caused by a "dirty" thread form caused by canvas fibers torn rather than cut - not by the minor diameter size) but you will have a stronger thread by virtue of its size. If it is tight, you can run the tap thru a few times (as others have suggested) or try using beeswax to lubricate the tap before running it in the first time.
Click to expand...

or try using beeswax to lubricate the tap before running it in the first time.
ivory bar soap works well also
i've also chucked up a 3/8x10 pin in tailstock and lubricate that with bar soap, especially into phenolic
run in & out a few times , loosens up nicely
 
Dave38 said:
I'm attempting my first phenolic insert and am looking for any tips on tapping it. It is canvas based, as this is all I have. My main question is how large of a dia. hole will do the best for deep threads, etc.? I'm using a 3/8 x 10 tap, non-piloted. Thanks,
Dave
Click to expand...

Dave I suspect you are putting the insert into a shaft. I core a hole 1 1/4 inch deep into the shaft that is 7 /16 diameter. Normally I use Canvas Phenolic Rod stock the same type I use for Jump Break Ferrules which is .500 OD. Next, I turn down the rod to .423 od and I normally thread the insert and screw it it into the shaft. However, you do not have to do so, if the insert fits snug. I use West System epoxy with 206 hardener and let if cure for 24 hour's before boring the Phenolic. I normally bore a 5/16 hole into the Phenolic and tap it with no wax, or anything else for a lubricant. Sometime s you must run the tap in and out more than once. This will give you a snug fit, I have also bored the hole at 19/64th for a real tight fit. Either way it will work the same, the reason you do not need to the thread the insert into the shaft, is because when you tap your hole in the Phenolic, it will grip the wood where the Phenolic and wood meet.

I have been doing this for more than two years, I have never had one fail, and I suspect I have done around 100 or more. I have done this using 3/8-10, 5/16-14, 5/16-18 it is all I use when making new shafts.

Hope this helps.
 
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Thanks guys, I have been using a 9/32 hole with pretty good luck, but thats in wood. I figured the canvas fibers may play into the equation.
The reason I'm using this method is I drilled a lam. shaft blank, to .300, then tapped it, and most of the threads were torn out, It would screw on to a butt, but you could tell it would strip out if tightened the proper way. Therefore I bored the threads out, 1.5" deep by .500 dia. then made the phenolic plug to fit, complete with grooves every 1/8" then epoxied it in.
I'll do the drilling and tapping on tuesday nite after work and post my success, or failure.
Have a good one.
Dave
 
It's pretty easy to do IMO. Just do a couple of tests to find the fit you like. Personally, I drill, ream, then follow up with a tiny boring bar to get My final diameter, of which size depends on the pin. I bought a batch of 3/8 pins, and found out that they all weren't to the same specs, this discovery came after I had used some of them in cues, so I had to learn to compensate for that to match the shafts snug. I don't have any problems with tearing the threads, and can still get a snug fit from the taps I use, but I'm certainly aware of that issue, and It is easier to tap with a larger Inside bore.

I just recently cored a purpleheart break shaft for 3/8-10 with a canvas phenolic insert a few weeks back. A good glue seems to be enough. That stuff really takes glue well, especially if You leave the OD of the insert kind of raw, with the pores open, as to soak the glue up.

As far as tapping, It's not bad, but not as easy as maple, and even with lubrication, in order to get the fit snug, You'll probably have to work the tap back and forth, cleaning and blowing chips out in between, otherwise You'll probably jam It up, and get It stuck. A bigger diameter ID, and something to lubricate the tap, may make It easier to tap in one or 2 shots though.

Greg
 
Just my 0.02$ You gotta spin the shaft fast when tapping. You won't get as much tear out on the threads. Go in bout 4 to 5 threads and back out to clean out then go again.
 
grind your threads or use and undersized tap if you have one, it makes it easier without forcing it.
 
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