I think the choice is between "hand reamers" with a lead-in taper, or "machine reamers" which are entirely parallel. The latter need to be used in a lathe or drilling machine and can ream blind holes as well as through holes.

The choice is yours, but I'd suggest that hand reamers are the most useful in model engineering.

Buy as you need, good reamers are not cheap. They are useful in certain circumstances, producing a closer sized hole with a better finish than drills. Shop-made D-bits can often do as good a job.

I happen to have a range of adjustable reamers, but they are amongst the least used tools in my workshop.

Edited By Clive Brown 1 on 25/01/2021 21:35:30

For a 10V I would call tracy tools and but a set of 1/16" to 1/2" by 64ths drill set. with this and odd metrics you will have all you need. IF you want reamers they also do a good set of imp reamers. No connection but there good boys. Noel.

+1 for machine reamers.

I have both types in most common sizes, but I cannot remember the last time I used a hand reamer in preference to a machine reamer.

As for adjustable reamers, they are for bodging holes IMHO and have no place in my workshop, apart from a couple of genuine David Brown ones that I inherited but have never used.

Phil

Good advice Jon.

Also beware of buying cheap used reamers, they very rarely cut properly and will not give you an accurate hole size.
There is usually a reason they are being sold cheaply. I have drawers full of such reamers purchased when I did not know any better, I only keep them now for regrinding into special odd sizes when needed.

Phil

Apologies if I'm teaching granny to suck eggs, but are you quite clear on what folk are meaning by D-bits? It's not an abbreviation for drill bits which your link and "But you refer to d-bits? Would a decent set like this" seems to indicate. You (may) want these.

Hope this helps.

Rob

Edited By Grindstone Cowboy on 26/01/2021 11:23:03

I needed a 1/4" reamer recently and discovered how much these things can cost when shopping about for one. Instead of buying I just made a D-bit from some silver steel. I turned it to the correct diameter then milled it to half thickness for maybe a 1/4". After hardening and tempering it performed admirably and was a fraction of the cost of buying a reamer as I had the silver steel and all the tools needed to make it.

It's certainly worth having a go at making one and I'll just make more as and when I need them. I've made a 5mm and a 1/4" so far with success. You can just see it in the picture, to the left of the left most arm but it's not a particularly great picture.

It seems adjustable reamers are getting a bit of an unjustified kicking in this thread, so to try and redress the balance, in my experience David Brown adjustable reamers were the reamers of choice at Timson's where I did my time, but as I recall just used in the lathes for reaming holes for ball bearings in gear blanks and the like. We had a tolerance of half a thou. We would drill, then bore, then take out about 10 thou with the adjustable reamer to size. The advantages of the David Brown type included the ability to adjust the reamer when it started to wear a little, and eventually sharpen the reamer blades, and eventually replace them when there was not enough to re-sharpen. I would imagine that solid machine reamers would not last that long machining the EN24 blanks, and replacement expensive while the David Brown reamers would be expensive to buy initially, but over thousands of holes would prove the most economical choice.

This is a different scenario to the modellers workshop I know, so I can understand why they are not used much there, but that does not make them a poor tool. I still use the few I have occasionally, useful for any odd sized hole that needs to be dealt with. If I did not already have them, I probably would not buy them.

Chris Gunn

In My experiece Adjustable reamers were mainly used by the motor trade for sizing various bushes in gear boxes,steering gears, and other parts where new bushes ,nearly all bronze ,were pressed into their housings .Always supposed to be a hand tool,many mechanics have tried them in drilling machines,but with no real success, there is a knack to using them and one chap I knew was really good as he had a job reconditioning lorry steering gears. I have a lot of them but rarely use them. For reaming I prefer machine reamers with spiral flutes ,particularly on small holes,with larger holes I prefer boring holes rather than reaming,I find that a reamer will pick up and damage the finish whereas boring will produce a better finish. Reamer pick up can be a problem with one offs even industrially,a lot depends on the reamer condition,lubrication speeds and feeds,no problem when there are thousands of say bushes to be made,and a couple of scrappers inset dont matter,

If a hole must be reamed to an odd size there is also the homemade toolmaker's reamer, nothing but a piece of drill rod / silver steel the right dia with an angled cutting face between 10 to 15 deg ground on, then the rod is hardened.

https://www.homemadetools.net/homemade-toolmaker-s-reamer

They leave a beautifully finished truly round hole if made well, are dead simple and dirt cheap.

There is lots to think about concerning reamers. Horses for courses.

Sometimes (most often?) a hole is required to a very specific size and tolerance. If position is also important, more than just a drill followed by a reamer may not be be adequate.

Often, if a simply parallel and well finished hole is required, the actual size of the hole may not matter.

The first place I saw adjustable reamers being used was that of fitting a trunnion to a (large) tube. Holes in the tube were likely worn and possibly those in the trunnion, too. For that repair each of about 40-50 holes were reamed to round and match for both elements. Fitted bolts were then made for each and every one of those individual holes. Talking here of hole size in the region of 2-3 inches (50-75mm), but probably at the lower end of that guess.

The item I’m currently making is to be a shrink fit. I will turn the piece such that the end part will be turned to tight fit with the next left oversized. The ‘tight fit’ end will be cut off abd discarded, leaving the next section of slightly over-size to be shrink fitted. The hole is reamed, but clearly does not need to be super accurately sized – only parallel and with a good finish.

Simon,

That looks like a knurling tool you are making.

Would love to have an idea of size since I need to make one sometime soon.