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Reamers question

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AdeV:
Again, apologies for asking this, if it's supposed to be dead obvious...

Currently, I don't have any reamers, just drill bits & end mills/slot drills. I do have a large boring bar, but it won't fit in the mill (it WILL fit in the lathe, however, when I finally get it), and I don't have a boring head for the mill either (that's a future project...)

I'm kind of assuming, therefore, that I need to get some reamers in order to make properly sized holes? But... what to get? I'm guessing chuckable (rather than hand-held - I'd want to use them on the lathe and/or mill)? What's best, straight or spiral flutes? Aren't spiral fluted reamers basically just long thin end mills? Should I get tapered or straight reamers? They look a bit pricey too; where's the best place to get a low-priced starter kit? (I just spent all my spare £££ on the lathe, and other "projects")

So many questions.... I've got lots more stacked up, but it's too late in the evening to ask them now...

Thanks in advance for any replies  :mmr:

sbwhart:
Hi Adev

Your right reamers are costly, I've got a few thats I've got over the years when I was stuck and had no alternative but to buy.

Types of reamers:- hand and machine, and lots a variations in between.

Hand reamers are usually straight fluted and are ground tapered, you need to pass them compleatly through the hole to get size, they have a parallel shank with a square on the end to take a tap wrench.

Machine reamers usually have a spiral flute and are ground parallel, the shank can be parallel or it can be morse tapered.

A reamer is used as the finish cut you have to drill a hole thats slightly below the (0.5mm ish) use a low rpm a slow feed and plenty of coolant, the reamer should give an accurate hole size with a good finish.

Poor mans reamers:- drills

Get yourself some good quality drill sets, metric, imperial, Number and letter sizes.

To get the best out of them:- again as you would a reamer drill the hole slightly under size and then put your drill of the required size through, you should end up with a hole that for most uses perfectly acceptable.

Another poor mans reamer is silver steel (drill rod) you can make D bits or by simple filing a flat at say 15 deg until you got something that looks like a pen nib harden it up and then use as a reamer you can get acceptable results there is a pic of this somewhere on the forum.

Hope this helps

Stew

kvom:
All the machine chucking reamers I have are straight flute and straght shank.

I was taught to ream at about half the speed used for drilling, use cutting oil, and feed in and out smoothly.  The drlled hole is 1/62" smaller if less than 1/4", and 1/32" smaller above that.

In addition to the "standard" hole sizes, a set of over/under reamers (+/- .001") are useful when you want a press or sliding fit.

75Plus:
A cautionary note regarding reamers. NEVER ever turn the reamer backward. Doing so will dull the cutting edges, quickly.

Joe

rleete:
This is probably not the answer you're looking for, but I don't think you need reamers at all.

We're not making anything that needs that perfect diameter.  Well, at least I'm not.  You make the bore, and make it smooth.  If it works out to .250 or .240 or .260 doesn't really matter, because you can make the piston or valve to fit that number.  It's the fit that's important, not the actual size.

So, you drill or mill or bore, and then lap.  Nice shiny, smooth hole.  Take a measurement, and start cutting whatever goes into that hole.  When you get close, you start checking whether that part will fit into your smooth hole. Take a bit off - another cut, a file or even just some emery paper.  Keep checking, more and more, the closer you get.  Using this primitive method, I can get anything from a nice sliding fit to a light press fit.

The only caveat to this is if you are making something like a multi cyclinder engine.  In that case, you can still use the above method, but you'd better be sure to mark the parts in some way to ensure that the parts are a matched set.  I use a tiny carbide scriber to mark the parts in an inconspicuous location.

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