knurling tools

Link

This site has knurling tools and kits that are useful in knurling valve guides.

I used to operate an automotive machine shop in the late '70's and have knurled many, many, many valve guides! There are a lot of DO's and DON'T's to knurling. For me to give a crash course on the subject, may not do justice to you or the job. If you have not knurled a guide before... don't practice on a head that you want to save/keep/use!!!!! !

Problems that you may incur...

*The guide may be so absolutely worn out, that the knurling is a waste of time (not effective) and a waste of money spent by you on the job. {Question; How do YOU determine if the guide is salvagable by knurling it... if you have not had experience in knurling?}

*If the guide is not worn enough and you try to knurle it... you CAN BREAK THE TOOL OFF IN THE GUIDE (at which point you then have a boat anchor)!!!!! You MUST use plenty of lubricant (best lube is one that "is made" for the tool and job) in the knurling process! Not just any lube will work!

*Knurling requires a lot of torque to "FORCE" a tool to displace the metal inside the guide. You may not be able to complete the job (by hand) without the use of a gear-reduction driven drill (with a proper bit attachment). Also a drill style driver keeps the knurling tool moving in the guide.... sometimes, if you stop the forward turning motion of a knurling tool... it seems impossible to start it turning again {at which point, you break it off in the hole... and that is not good! :O }

*Most knurling tools require the use of a "burnishing tool" to resize the guide to the proper valve stem diameter AFTER knurling! A knurling tool WILL NOT SIZE a guide to the proper diameter...!!! It only reduces a worn guide to a "smaller size" ...not THE proper size!

*Guide replacement (as opposed to knurling) is a more permanant repair and will last much longer (knurling is/was a cheap substitute for repairing a worn guide!

*It may be to your benefit to have a qualified automotive machine shop do the job for you! Or better yet... have them replace the guides for you!

*The price of the tools (and fixing your mistakes) may (probably would) outweigh the cost of just having a qualified machine shop do it for you!

(I am very reluctant to recommend anyone doing their own knurling job if they are not an automotive machinist!)

Good luck if you decide to go ahead with this endeavor!!! You will need lots of luck!!!

Chris-se-ILL

No, you don't need to "ream" the guide after knurling... you need to "burnish" the guide! There is a difference!

When a knurling tool goes through the guide it "squeezes" (displaces) the metal along the walls of the guide. When the knurler pushes against the wall it raises "ridges" in a spiral pattern the length of the guide (you may already know the physical mechanics of knurling, but I state it for those that read it and do not fully understand the process). Anyhow, these ridges resemble a pattern as if the guide had been "tapped" (threaded)... but the process has removed no metal. The knurling tool does not regulate the heighth of the ridges and there for the inside diameter of the guide is not of a consistant diameter (I know that you also know this).

Now to bring the inside of the guide to an accurate (parallel the length of the guide) diameter you have to resize the guide. If you "ream" the hole, with a cutting reamer, you will take even more material (than was worn away by the valve stem) from the inside area of the guide wall. When knurling, you want to retain as much original material as possible in the guide. Therefore you need to "burnish" the walls of the guide to the proper diameter! A burnishing tool has smoothed, rounded ridges (as opposed to "cutting edged" ridges) the length of the tool. The tool "pushes" (or rolls) the knurled ridges outward (the knurler pushes the metal inward). The burnishing tool does not take any material off the guide's walls.

Anyway, you should NOT use a reamer on the guide. A reamer is for the purpose of resizing a replacement guide. When a guide is replaced, the "press fit" (interference size) will squeeze a new guide to an undersize diameter. Only then do you remove metal to bring the inside of the guide back to the proper size.

*A reamer is for replacement guides!

*A burnisher is for knurled guides!

(this is all clear as mud, right! :)

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BTW, for best results on cutting valve seats... use a 3 angle cut.

Example; on a 45 degree face, cut the 45 degree angle first (only enough to clean the face of the seat). Then use prussian blue (we used to use a magic marker) to "blue" the 45 degree face. Now cut a 60 degree and a 15 degree angle on the same seat to clean the edges (also makes the seat of uniform width the entire circumference of the seat) of the 45 degree cut. This 3 cut process will narrow the 45 degree face to the proper size. The "rule of thumb" that we used (on the 45 degree face; i.e. middle face) was a .040in. width face for intake valves and .060in. width for the exhaust valves. As you are cutting the seats... "blue" the valve face (after it is properly ground) and check to see that the 45 degree seat face is contacting the valve face (by "popping" the valve against the seat face), in the middle of the valve face.

If you use stones for grinding the seats... reface the stones often (personally, I don't like using stones for facing seats! I like carbide cutters, that cut all three angles at one time).

*After you cut the seats, lap the valves with a fine valve lapping compound... then wipe out ALL lapping compound... put the valve back in the guide and use Marvel Mystery Oil to "oil lap" the valve again (just MMO, no compound). Oil lapping will remove any residual grinding compound from the face of the seat and smooth the seat better than just using compound by itself.

Our shop rate went up by about $10 an hour for "those" projects!

:-)

Chris-se-ILL