Thread: How to make a D-type reamer to chamber a barrel

@rupert I'm just about to make a reamer for 32-20 and because its a one off I might do it as a D reamer
I have a long piece of H2 tool steel and was going to make it out of that. Although it needs a very difference hardening and tempering process
So silver steel might be the quick and easy option

Maybe we should get together some time and do some work on this ? I have H2 if its any use to you
Would 32-20 be any use for your project ?
My one is to re chamber a 32 rimfire Stevens 044 1/2 to 32-20 and convert the breech block to center fire

cheers

Thanks for the really good instructions @gundoc and @SixtyTen. I'm going to give this a go for cutting a bullet mould and maybe for a chamber at some stage.

Originally Posted by takbok

Thanks for the really good instructions @gundoc and @SixtyTen. I'm going to give this a go for cutting a bullet mould and maybe for a chamber at some stage.

Just remember to remove as much material from the chamber or bullet mold before trying to use the reamer. For molds, I typically draw up the shape I want in cad and then make a drawing showing the depth to drill for about 5 or 6 different drill bits, so I end up with a stepped hole just a little smaller than the bullet, but more or less the same shape. This reduces the work needing to be done by the reamer to a minimum.
Its not so important if making aluminium bullet molds, but I made some swaging dies from 4140 steel, so the stepped hole was a necessity.

Originally Posted by gundoc

Making a D reamer is a piece of cake. Start with a piece of 10 or 12mm silver steel and a good accurate drawing. Face and centre drill the rod then extend it from the chuck about 75mm to give you working space and support the centered end with a live centre. Turn a pilot about 25mm long that is a neat running fit in the bore then work your way back turning the leed, case and rim to a very high finish about 0.01mm above the desired finish diameter and bring it to size with a fine file and fine grade (400 then 1000 grit) wet & dry paper and oil. Evenly heat the entire length of the turned portion to a good cherry red and vertically quench in oil (SAE 30 is fine, swirling could cause the hardening to be more on one side and cause warping, hence the vertical plunge). With a good bench grinder a pail of cold water, neatly grind the entire length of the leed, case, and rim to exactly half of the diameter, (D shape) quenching frequently to avoid overheating. A light flick across the ground face with a fine slip stone and the reamer is good to go. I recommend boring or drill the chamber to within 0.5mm of the finished size before reaming. I prefer to grind a square on the end of the shaft and use a tap wrench supported by the live centre on the lathe rather than using power as you would with a proper reamer. Use plenty of good cutting oil and withdraw the reamer and clean the reamer and the bore frequently to avoid swarf picking up and grooving the chamber. Go to whoa in less than a hour!

@gundoc

Just wondered is you temper after heat treating ?

I finally had some time and turned up a 32-20 D reamer this afternoon
Heat treated it
Took the magnetic table off my surface grinder and sorted out a V block and hold downs
It should be a nice easy way to grind a perfect D

Will wait until I know about tempering it or not

Cheers

Sitting in the v block on the surface grinder and ready to go

thats a fine looking surface grinder


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Originally Posted by MSL

thats a fine looking surface grinder


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Yes it is @MSL
And look at that nicely dressed stone

Originally Posted by akaroa1

@gundoc

Just wondered is you temper after heat treating ?

I finally had some time and turned up a 32-20 D reamer this afternoon
Heat treated it
Took the magnetic table off my surface grinder and sorted out a V block and hold downs
It should be a nice easy way to grind a perfect D

Will wait until I know about tempering it or not

Cheers

Yes, you must temper after hardening and before grinding. I temper reamers only to light straw colour, still hard enough to cut but some of the brittleness avoided. Care must be taken to avoid heating the steel during grinding (ie; watch carefully and quench often). Tempering after grinding can cause warpage.