Internal Grooving

Terry Vanpool said:
Yes this is a pellet gun. The barrel is made from (LW19, a chrome-molybdenum type steel). I am not sure what LW19 is exactly but it is a fairly soft steel. The "O" ring is 1.5mmx4.5mm so the groove will need to be about .060 wide and .050" deep.
Click to expand...
 
You are going to be dragging this grove . .050 deep doesn't leave much for the bar diameter in a .177 bore. You most likely do not have the rpms to effectively use carbide and thus it would snap . If you have the means to grind a scrap HSS end mill and make yourself a groove tool , I would approach this option and save your $$ .
 
We used hss for internal grooves, you want to keep the length of the necked down as short as possible to keep the cutter rigid and chatter to a minimum. Something like a grinding wheel used on a 4 1/2" grinder and take your time so you don't burn the cutter
 
Mini-grove.JPG Thanks for all the suggestions. I made up a test piece from 4140 and ground a tool from 1/4" HSS. I was real proud of myself the tool fit the bore just fine , the profile looked good but I overheated it during the grinding and it dulled before I completed the groove. Oh well.
Thinbit makes tool that will be perfect if I can find someplace to get it.
 
Last edited by a moderator:
Have you thought about boring the major dia of oring from the end of bore and then press fitting a bushing in from the end?
jimsehr
 
I did think of a solution similar to what you suggest. I thought about turning the barrel to the major dia. and pressing a cap over it but the end is unsupported and is subjected to burst of pressure exceeding 1000 psi and I was afraid to would not stay together. I made another stab at grinding a tool like the one above being careful not to overheat it and was able to cut a groove in a test piece but it still needs some tweaking. Getting some chatter probably from being to much above center but if I take any more off the bottom of the tool there won't be much left.
 
Would the center height be any different if you turned the toolbit upside down and ran the lathe in reverse? If it's low on center you could shim it up.
 
+1 on the bushing, some people make a threaded bushing, turn down and thread OD of the barrel, and locate transfer port in barrel, space/gap for o-ring goes between where the bushing meets the barrel. That way you can bore pretty easily and don't have to fool with more difficult grooving operation. I think that's how it's done,but of course you have to be able to fit that all together.

If you do the grooving thing, work something in there to take any burrs out. Keep us posted.
 
congrats for giving it a shot Terry, you should be proud of yourself. Looking at the cutter above, I'd suggest creating some clearance on both sides of the cutting edge, not just on the front side or it will rub. Also, make the cutting edge narrower and do more than one plunge cut to get the groove width you want. think of this as an internal parting tool - too wide and it'll chatter.

For the getting it on center problem, you can either make the grooving part shorter, if it's much longer than the depth you need. Or grind a similar tool from an old endmill or piece of round HSS and rotate the cutter, so that it's more of a negative rake.

I'm guessing that you have the work as far into the chuck as you can or supported by a steady?
 
Thanks Matt, I do have generous side clearance ground on both sides but so far I have been trying to go full width (.060"). I like the idea of reducing that to .030" or .040" and I will try that next. I only had square 1/4" HSS but I have ordered some 1/4" round so I can control the height problem. Thanks all for the help.
Terry
 
You must log in or register to reply here.
Back
Top