Reamer question

[Shopgeezer]

So what are the opinions on adjustable reamers? I have read bad reviews on cheaper sets saying the blades don’t all adjust to the same height and it is hard to get an accurate setting out of them. Are better quality versions more dependable? They would be handy for sizes between standard instead of a 30 piece fixed set for $900. Or better to put the money into fixed size reamers and build up your set over time?

 

[kuhncw]

My opinion is: Buy fixed reamers as you need them. By buying a set, you may end up with reamers you will never need.

Chuck

 

[Brian Rupnow]

I have a collection of "fixed size" machine reamers, bought "as I needed them". The problem I see with an adjustable reamer (and I could be wrong here) is that you will never know what size you have them adjusted to until it's too late.

 

[XD351]

I hate them , especially the cheap ones . They are really only of use to open up a hole a couple of thousandths and it can be a bit hit and miss . I used to have to use them to ream the piston pin bush on lawn mower engines as they only needed a light scrape to get that nice sliding fit with no play .
Better to save your money and buy what you need as you need it and buy good quality reamers , i have a set of cheap Chinese made straight shank ( machine ) reamers and they are ok , handy to have with a range from 3-13mm and 1/8-1/2 but not as nice as name brand units .
The rest of my reamers all MT up to 40 mm are all NOS bought off ebay over a couple of years just waiting for a 5mm one to come up and my set will be complete !

 

[Charles Lamont]

In my view adjustable reamers are mostly for overhaul jobs.

 

[canadianhorsepower]

I have fix reamer, Chucking, over size, under size.
I also have miniature to 1 inch adjustable reamer
Charles Lamont has the best description, Overhaul job.
if you need to ream a hole to make it round AGAIN cause the bushing failed
that can't be mounted in a lathe or a mill. you would use adjustable one to simply make the hole round.

 

[tornitore45]

It turns out that one rarely need a standard fractional reamer, is always over or under. In most model construction a hole is to run a shaft made of standard size drill rod mostly in 16th or rarely in 32nd. In that case an "over" size is what is needed.
Often one needs a press fit for the same shaft size and a "under" size is the cat's miao saving you a boring job.

I can't think of a case when a "On Size" reamed hole is required.

 

[Shopgeezer]

It turns out that one rarely need a standard fractional reamer, is always over or under. In most model construction a hole is to run a shaft made of standard size drill rod mostly in 16th or rarely in 32nd. In that case an "over" size is what is needed.
Often one needs a press fit for the same shaft size and a "under" size is the cat's miao saving you a boring job.

I can't think of a case when a "On Size" reamed hole is required.

I have seen over/under reamer sets advertised. How much over and under are they? My plans usually say “drill 3/32 ream 1/8”. I am surprised that you say standard fractionals aren’t used. It seems most instructions say to use the reamer to bring the hole up to a standard size from a smaller drill.

 

[tornitore45]

What is the purpose for a reamed 1/8" hole? Not for a #5-40 screw, that will require a clearance hole. Nor for a drill rod dowel to turn in, it will bind badly. Not for a force fit with a drill 1/8" rod, it is not secure enough.
Not for a vent hole or a fluid passage, no need for a reamed hole in that case.

Specifying a reamed hole imply some kind of mild precision fitting. A fitting must hold or allow movement. An on size hole will require either an oversize stud or an undersized shaft.

I have seen the same specs on drawing an regularly ream oversize 0.001" to avoid using my hammer at assembly time.

 

[Cogsy]

I have reamed bores for pistons 'on size' but of course they don't need to be as the pistons are made to suit and being round is really all that's needed. Maybe for an assembly dowel where you don't want a slip fit but don't want to use a press? That's about all I can think of.

 

[Hopper]

I use adjustable reamers quite a bit, mostly older non-Chinese ones. But I usually like to drill the hole to 1/64" undersize then bore it to maybe .005" undersize and finish it with the reamer. Boring ensures the hole is round and straight and concentric with where it was intended to sit. Reaming a drilled hole just follows the wobbly drilled hole all over the place.

But for jobs like drilling and reaming dowel pin holes through two pieces at once, I then drill 1/64" undersize (or less if a metric drill falls in the range etc) and machine ream in position.

I like adjustable reamers for things like motorcycle wrist pin bushings. How do you size them? Measure across the blades at the large end. Trial cut undersize. Adjust in small increments to sneak up on final size.

But for small model engine size stuff, adjustables are too clumsy. Better buying the machine reamers you need as you go. I have found the cheapo fixed machine reamers on Aliexpress are plenty good enough for home use. Surprising at the price but I guess if a million Chinese factories are churning out products using the same tooling it can't be all bad.

 

[Rudy from Norway]

The cheapest ones are crap. Bought another set that looks ok, but I can't get any accurate results with them. They grab, makes poor finish and uneven holes. These are ok for general mechanical work when you need a bigger hole. In fact, I have limited success with fixed reamers too. I like to make things accurate and like to use boring bars instead. With these you can get the accuracy you want regardless of the accuracy of your machines.
Rudy

 

[Shopgeezer]

Boring is the best option for accuracy but hard to do for model sized holes. When drills taps and reamers get small its a whole new ball game. Fumble fingered old geezers like me need lots of support tricks to hold things steady.

I found what appears to be a reasonable set of fixed reamers from 1/16 to 1/4 by 64ths. Might buy that as a starter set and add more as necessary. O/U sets are expensive. Might try just polishing shafts for a slight undersize.

 

[tornitore45]

Reamers make holes that are rounder than a drill bit but not guarantee to be round. They can be lobed. Boring is the thing when one need a hole round onsize and on position.

 

[john_reese]

Adjustable blade reamers really need to be started with a pilot. ID slips onto end of shank. OD is tapered to center in the hole. Chinese and India made reamers are crap. If re-ground they may be OK.

 

[canadianhorsepower]

curious.... how many of you did reply and have adjustable reamer ????????

 

[XD351]

I had some but found throwing them over the back fence more enjoyable than using them !

 

[Charles Lamont]

Well, Luc, I don't own one, but coincidentally I used one, for the first time in many years, last week: to take a tiny shave out of an odd-sized hole so the odd-sized pin would easily go all the way. Even in the busy shop I was working in, it had obviously not been used for ages (which meant that, unusually, it was still sharp) and I had to strip it and clean it before anything would move.

 

[Rudy from Norway]

Shopgeezer, I also started to be curious if someone actually made some use of adjustable reamers. My first sett from India went in the bin, the second set from China is stil in the drawer, but I can't use them the same way as fixed reamers. My fixed reamers does seldom have the dimension I'm aiming for so I figured adjustable reamers would be fine, but not so.. They can be used to force some holes bigger, but not to make accurate holes for shaft and so on. At least mine can't.
So yes, i too wonder if adjustable reamers of good quality can do the same job as fixed.
Rudy

 

[Hopper]

You have to get the right sized fixed reamers too. Some are made to provide a neat sliding fit, such as for reaming a piston pin bushing. Others are made to provide a light press fit, such as reaming a dowel hole. You have to buy the fit or tolerance reamer you want. The cheap ones don't say what they are so I guess you take pot luck and polish your shaft to suit the hole.

I use adjustable reamers a lot for fullsize motorcycle restoration work, not small model stuff. Most of my adjustable reamers are older UK or Australian made ones that still work well. They will ream a hole within a few tenths of a thou, much finer tolerance than boring, and finer finish too.

They work for small-end conrod bronze bushings on Harleys that take a hell of a pounding so can't say they don't work well, if used with care. Those reamed bushings last for many many tens of thousands of miles under adverse conditions in air cooled engines in extreme heat. I do like to bore the bushings out close to finish size before installation and then use reamer for the last few thou only, so they follow the bored hole.