Pin vices and valve lapping

[Brian Rupnow]

Many of you folks will know about pin vices, (also called finger chucks) but some are not aware they exist. This set of four cost me $30 including tax. They will hold round diameters from 3/64" (0.047") up to and including 3/16" (0.1875"). They are the perfect thing for lapping small valves into seats on model engines. As you can see, the part which you hold between your thumb and finger are knurled, and are small (-1/4") The chuck end on them is also relatively small, which means that you can grip the stem of an intake valve to lap it without having to remove the exhaust valve to get room to do it. (or vice-versa). When I make valves I turn them from cold rolled steel with a 92 degree included angle, and make the valve seats from brass with a 90 degree included angle. Then I insert the valve into it's guide and using first #300 grit and then 600 grit lapping paste I grip the stem of the valve in the appropriate pin vice, and while applying mild pressure of valve into seat I spin the pin vice back and forth between my thumb and finger. I generally put some #300 compound on the face of the valve, then spin it back and forth ten times, lift it up and turn it 90 degrees, and repeat another set of ten, until I reach a total count of 100. Then wipe off all of the compound and repeat with #600 grit compound. This will not give a wide contact area on the valve face where it fits against the seat, but it will give a very good air tight seal, which is all you need.-Be sure not to get any compound on the stem of the valve because you don't want the valve to be sloppy in it's guide.--And---never ever try and lap valves with a power tool. This must be done manually, with finger power only.

 

[XD351]

Thanks Brian !
I now know what i am going to use to lap in the valves on my hit and miss engine .

 

[Technical Ted]

Where did you get them? I did a search and couldn't find them for $30.

Thanks,
Ted

 

[Brian Rupnow]

I bought mine from a local tool shop, but they come in from USA, or China. Do a search for Groz dealers in your area.

 

[Gordon]

Where did you get them? I did a search and couldn't find them for $30.

Thanks,
Ted

https://smile.amazon.com/SE-Pin-Vis...ords=pin+vise&qid=1552073386&s=gateway&sr=8-8

 

[Wizard69]

Thanks for the little write up on pin vises and valve seating. One question though, why no power tools for valve seating?


To add to this, pin vises can be supllemented with short sections of hex or round stock that one might have left over from a project. This is a usage I’m transferring from work but I believe it is 100% transferable to engine building. I take two approaches here.

The first approach is to drill a hole slightly over 1/8” (couple of thousands) in the end of your stock. I’d aim for 3/4” deep. Then Loctite a burr in place. If you use reasonably thin stock you can then spin that burr between you fingers. Great for deburring, reaming and even filling. Just choose a burr that fits the need.

I have a need to use very small drill bits to clean out ports and passages so my second approach is slightly different. Often the same sized drillbit gets used a often. So the obvious thing to do here is to make up a small holder. In this case a copy of a pin vise but with a set screw clamp and a bore for a single drill bit size. That saves tieing up a pin vise for a commonly used drill size. The set screw because it is very easy to damage or break the drill bits. A collet design might make more sense here but at the time I was in a hurry.

Pin vises have other uses too. Just think anything small in diameter needing grabbing. For example pins for pin and socket connectors can be gripped in a pin vise of the right size. The pin vise can then be put in a vise of a larger sort to hold the pin for soldering. There are many other uses for this little tool.

 

[Wizard69]

Where did you get them? I did a search and couldn't find them for $30.

Thanks,
Ted

http://www.starrett.com/metrology/m...isplayMode=grid&itemsPerPage=24&sortBy=wp/asc

Above should be the Starrett link. These are probably the ultimate In pin vises. I ordered a cheap set from one of the big catalog companies years ago and frankly wasn’t too impressed with the quality. So you kinda get what you pay for. Deal with a supplier you trust or buy the Starrett.

As it is the whole idea behind pin vises is to be able to grab and manipulate small stuff like drill bits. It is pretty easy to DIY a solution on your own.

 

[Bob44]

I usually do my final lap on the valves with toothpaste, I think it gives a nice finish and seal on the valves and seats.

 

[Technical Ted]

[QUOTE="Wizard69, post: 321324, member: 14419"As it is the whole idea behind pin vises is to be able to grab and manipulate small stuff like drill bits. It is pretty easy to DIY a solution on your own.[/QUOTE]

I've been using my smallest Albrecht chuck up to this point, which is probably the smallest one they make. I would like a set of actual pin vises though... I'll keep my eye open for a good name brand set on eBay.

Ted

 

[Brian Rupnow]

Generally, when I make valves, I don't part them off from the "parent" stock. I leave about 3" of the parent stock attached to the head of the valve and use that as a "handle" when lapping the valve into the seat, then cut the "handle" part off, leaving just the valve. However, on the most recent engine I built I had to be able to grip the stem of the valve to lap the valve, couldn't do it with the "handle" still attached. I have known about pin vices for years, in fact I have a set of really poor Chinese ones that I never used because they had way too much runout. I just recently bought the ones in the picture, and thought it would be worthy of doing a post about them because many people aren't even aware that there are such things.---Brian

 

[Lloyd-ss]

I don't have any pin vises but they look like the type of thing that after you get them, you wished you had bought them 10 years ago, LOL. I will have to add them to my "next tool order" list.
I too am curious about why the "no power tools" aspect of lapping. Lack of control and feel; slinging the compound, I guess? Other negatives?
I am new to this engine building (and eager to learn!) but have built high powered air rifles for years. Their valves are similar to an engine valve except the valve head is Delrin or PEEK and the seat is usually aluminum or 303 stainless. The tricky part is that they need to hold 3,000 psi air for months without leaking when held shut with only a light valve spring and the air pressure itself. For lapping those I'd use automotive rubbing compound, and if necessary, would follow it up with automotive polishing compound. I bet I've had those 2 containers of compound for 30 years and still have plenty left.

Thank you for being so free with the information. It is soooo helpful.
Lloyd

 

[Gordon]

I am somewhat confused about the need for precision for the pin vise. For what I use them precision is not necessary. I frequently use them as a tap wrench for small taps or small drills for hand feed and also for holding a valve stem as shown in the original post. For those uses precision is not important. My cheap set which I have had for years has worked just fine. I guess that if you use them for a sub chuck in a drill press then precision would be important but I have a drill chuck for that.

 

[popnrattle]

I use these components to check my valve seat seal until almost no hissing is heard at 140 psi. BTW, I leave the valve seats sharp on the head and let the pounding of combustion create the seat to the valve.

 

[bobden72]

I use these components to check my valve seat seal until almost no hissing is heard at 140 psi. BTW, I leave the valve seats sharp on the head and let the pounding of combustion create the seat to the valve.
View attachment 108060
View attachment 108061

Nice simple and easy set up for testing, Think I will modify mine which has four bolts and fiddle to assemble each time.

 

[popnrattle]

Nice simple and easy set up for testing, Think I will modify mine which has four bolts and fiddle to assemble each time.

Thanks...just felt that using compressed air on an engine assembly might stress parts too much depending on psi.

 

[editor123]

Compressed air is OK, you cannot get the pressure above the combustion chamber pressure with most air compressors. Put the test rig in water to really check for bubbles without having to worry about hearing acuity. Any bubbles mean the lapping is not good enough.

 

[canadianhorsepower]

the easiest way, take a pencil, mark your valve face and your valve seat
spin it around a couple of time. If you have a nice small line all around in the middle of your
valve face and seat you are in business .

 

[Longboy]

Brian, have you chucked up these pin vices in a three jaw on mill or lath to see if small number drills would run true? Using #50's drills for carburetor jets for the needles and half inch chucks just don't hold the smaller sizes.

 

[Brian Rupnow]

No, I haven't done that. I have a couple of smaller three jaw chucks with shafts that I have salvaged from old power hand drills, and I lock them up in my normal lathe three jaw chuck for very small drills like 0.040" and 0.050". The smaller chucks close up completely and will hold drills that small. The smallest drill my lathe chuck will hold securely is .125".---Brian

 

[Vietti]

Late to the party but I've had good luck just slipping a short piece of fuel hose over the end of the valve and spinning with my fingers or the drill press while pulling back slightly. Also does away with alignment problems.