[Rodrigo]

Dear Sirs

I have spent many hours searching the internet for information on rifling single point hook cutters or broaches, but besides some articles on barrel making and rifling, I found nothing about the cutters or broaches geometries for rifling a .22 LR barrel.

Can any one post here photographs or drawings of a single point hook cutter or broach ?

Even a hand made drawing ( preferably with some dimensions ) will be very useful !

If you know about sites that have information about this subject please share the links with me.

I found information about ram mounted cutter boxes for single point hook cutters, but they are to be used for larger bore barrels, I think that for a .22 LR barrel with such a narrow bore the machining procedure is different.

Thank You Very Much for Your Help.

[MrWild]

Saw a movie about Kentucky long rifle production the old way. The machine was two and a half times longer than the barrel. The barrel broach is keyed to a screw shaped cam longer than the length of the barrel. Only one rifling is done at a time. The broach itself is just as long stiff rod that has a groove at the tip for a HSS cutter. The cutter was reset for cut depth after every pull through. After each rifling is cut, the broach is twisted a bit and remounted for the next groove. Slow and tedious, that's the way it was done.

[jerryjoeed]

Get a copy of "Modern Gunsmith" by James Howe. It has excellent descriptions of how to machine and fit a rifling head as well as dimensioned drawings for .22 and .30 cal. heads. The book is from the '40s so, for example, the information about reaming and burnishing is out of date. But, there is so much good information that the book is a must read. You just have to understand that manufacturing and firearms technology have changed much since the book was produced.

[Rodrigo]

Dear MrWild

Thank you for replying.

During the search for rifling cutters I have found a lot information about rifling machines ( old and modern ).

At the web we can find designs of rifling machines to build at home, unfortunately there is scarce information about the rifling cutters / broaches.

If you came across something like that please let me know.

Best regards.

[Rodrigo]

Dear Mr JerryJoeed

Thank you for replying.

Very nice direction you pointed me to !

I have heard before about rifling heads for hook rifling cutters but I thought they were used only to put rifling in the large bores of larger caliber rifles / handguns.

I followed your suggestion and had a look at Mr. James Howe book.

Now... to make such a tool for a .22 LR barrel... It's not easy task !

For a " not much " experienced machinist like me, it almost looks like watchmaker precision machining !

I didn't understood very well the drawing and dimensioning of the described .22 LR " hook " cutter, the scanned page of the book is too blurred.

I am attaching a drawing in JPEG format with this post, can you tell me if it is correct ?

Do you know the correct dimensions / geometry of the hook cutter ?

[centrefire]

Dear Sirs

I have spent many hours searching the internet for information on rifling single point hook cutters or broaches, but besides some articles on barrel making and rifling, I found nothing about the cutters or broaches geometries for rifling a .22 LR barrel.

Can any one post here photographs or drawings of a single point hook cutter or broach ?

Even a hand made drawing ( preferably with some dimensions ) will be very useful !

If you know about sites that have information about this subject please share the links with me.

I found information about ram mounted cutter boxes for single point hook cutters, but they are to be used for larger bore barrels, I think that for a .22 LR barrel with such a narrow bore the machining procedure is different.

Thank You Very Much for Your Help.

To drill a concentric tube to hold the cutter using a work held in a lathe, you drill either with one of the following: 1) a deep hole drill, difficult because you need a forced lubrication system, A standard jobber drill from both ends, difficult to meet exactly in the centre. Drills go off course. 3) Extra long twist drills, starting with small one and increasing to a larger finishing one.

The tube should be 4 , 5 or 6 inches long, depending of your capabilities.

The material should be a bit better than mild steel and should be soft to start with. EN8 is ideal. Tube outside diameter should be half inch. When the hole through the axial centre is finished to your satisfaction, turn the outside diameter to fit the inside of the bore .22 . With .22, the inside hole will be small, about .12 inch. Tread one end to a dept of 3 quarter inch with fine tread for adjuster. The other end is fixed to the pull rod with a small bar straight across and clinched. (or solder in place) Countersink the area where clinched to avoid snagging. You have to mill the opening for the cutter, to the width of the groove of the rifling.

There are different designs of cutter. I made a few just to see would they work and for cutting internal slots in long inside holes for key ways etc.

The design in Howes book is puzzling, more later

[centrefire]

To cut the slot for the cutter, mount a piece of mild steel or brass in the tool holder of the lather and drill to a tight fit for the head body. This hole will be perfectly central with the
the chuck. turn 90 degrees until its facing the chuck. Mount a milling cutter in the chuck and cut the slot to one and 3 eight inches long. Any bevel in the slot ends can be cut at this stage.
The problem with Howes design is that as you adjust the cutter upward to take more material from the barrel groove, the cutter moves a little forward and this changes the position of the cutter slightly. I prefer to mount the cutter with a pin through the body on which it can swivel. The disadvantage with this is you cannot let it down when passing back through the bore and that requires more frequent sharpening. I designed one so that when you pushed the rod back through the bore, the cutter moves down away from the cut and out of harms way.

[centrefire]

Previous post of mine contained misspelling, miss-laid my glasses, sorry.

This will not allow copy and paste, See Howes book on line.

The scrape type cutter in Howe’s book and in Vicory’s also should work fine. The problem with these books is 1) its very hard to explain mechanical procedures and 2) sometimes the writer may not have actually tried out the design he shows. The scrape cutter shown in many books could tend to pull out of the box with the pressure of the cut and I propose 2 retaining screws to hold it down. When adjusting the cutter, the screws need to be loosened first, then turn the adjusting screw a little and re-tighten the screws again. This way the scraper is rock solid. You might get away with no screws, but its better with them. I have used this design to cut straight splines and grooves in the inside of small shafts for models etc. The finish is more a burnish and can be excellent. It is important that there is no backlash in the guide rod or machine because it cuts in both directions. You may be able to stop backlash by a strong rubber tie to stop backlash. The scrape type is slow to do and slow to adjust after completing the cycle, but it is a labour of love. It can be made out of tool steel hardened and tempered after shaping. Better use cobalt high speed steel flat stock. This must be ground to shape with a small angle grinder and finished with a Dremil tool.. Wear eye protection and keep the work cool. If pumped lubrication can be used, great, if not a good cutting paste or what I find best is goose grease (same), available from supermarket shelves. Goose grease is about the best cutting fluid. The bore should be swiped with a rag on a dowel regularly to remove scrapings which grate between the head casing and the bore. If pumped lubrication is used there must be a filter to remove chips. While I have not tried it, this design could also be used to scrape the lands as well as the grooves. The box would have to be supported by lead in the grooves. The advantage of this is that the surface of both the lands and grooves would be finished in the direction of the missile, whereas with a reamer it’s at 90 degrees to it. Such a barrel should be better than any other type produced. A real purist might finish the last ten fine scrapes in one direction (from breach to muzzle) . to do this the head must be removable and this is time consuming. This results in the microscopic direction of the bore being grained in the missile’s direction. All books advise a hardened box, but a soft one will be OK as the lands will imprint their impression on the side of the box opposite the cutter. This means that more adjustment is needed on the cutter to compensate, a soft box must only be used for the exact same twist and groove each subsequent job. See page 136 of Howe’s second volume. The biggest problem is sharpening the scraper. Get a ¾ inch length of steel tube finished to the bore plus the depth of one groove. You can hold it to the light and stone the edge so that there is no light visible between the edge and the tube wall. The edge should not be sharpened for the last 20 cuts as it will burnish the finished surface. Very fine abrasive paste mixed with the lubricating paste for the last 50 strokes will lap as you cut. But for high class work it might be better do this separately. Usually 150 passes per groove (900 for a 6 groove) will be good for .006" depth, the more and the finer the adjustment the better the finish. For other engineering jobs much more passes is needed. Clean the cutter well regularly. This design avoids all the pitfalls of a hook type cutter.

[centrefire]

Howe book is available on line, copywrite must be expired. Page 136 of the 2nd volume. See the hook single point cutter. You can see Pratt and Whitney or a Diamond rifling machine on You tube. On that clip, the chips from the cutter are not removed and they appear to be left inside the barrel. However it is possible that the pumped lube system does this in some way. See the design of the basic hook type cutter. As the cutter is adjusted up it moves slightly towards the pull rod. This is very small but not for the purist, if the cutter can move to the front, then it would technically cut a wider groove than itself due to the spiral path.

One thing I cannot understand is that the Diamond machine appears to be able to push the cutter down on the return stroke. It is not a good idea to have the cutting edge rubbing the groove on the return stroke. It appears that some one has found a way to lower the hook on the return stroke. For antique restoration, the old hook type would be best for wide deep grooves. The cutter should not be a hook, but have an included angle of approach. ( the cutting edge should not be like a hacksaw blade or at 90 degrees to the work, but angled slightly backwards. Aggressive cutting could produce a chiselled finish. Best finish would be slightly scraped. I am scratching my head to figure how the cutter is lowered, the wedge prevents it being pushed back, so how is it done. ?