What size drill for a 5/16 reamer?

[ventureoverland]

Guys,
Maybe a simple / stupid question but what size drill should I use to allow a 5/16 reamer to do its job?

Come to think of it, is there a rule of thumb for working this out?


Thx
J


Thx
Jon

[pipeclay]

There probably is some chart with recommendations.

For my own use if its a machine reamer I allow between .010" to .015" for drilled holes over 1/2" diameter.

Around .005" to .010" for smaller drilled holes,and continue to reduce in relation to the size of the reamer.

If its a bored hole I am reaming with a machine reamer I leave between .005" to .010".

If its a hand reamer I tend to try and leave the least as possible around .005" unless you are using adjustable reamers and then you can sneak up on it.

[cba_melbourne]

..........Come to think of it, is there a rule of thumb for working this out?.

The rule of thumb is that the reamer should remove between 0.5% and 1.5% of its diameter.

- The 0.5% is fine for a bored hole (either bored with a single point tool, or drilled and then bored with a borer which is essentially a drill with more than two flutes).

- 1% to 1.5% is appropriate for a hole that has only been made with an ordinary drill bit (better use a fully ground drill bit, not a cheap rolled one, as the former run truer and drill a "rounder" hole)

Remember, never ever rotate a reamer in reverse direction, or its extremely sharp cutting edges will be instantly blunted and may in the extreme even chip. Use lubricant, rpm about 1/4 to 1/10th of the optimal drilling speed, and decisive down-feed in one go.

Remember a reamer may cut slightly over or undersize, depending on workpiece material. For example, in tough Aluminium Bronze the final hole is always smaller than the nominal reamer size.

[Ueee]

Out of interest what do you recommend when removing the reamer? Have it turning or not?

If you reamed holes are ovesize it is often because of bad alignment, a floating chuck helps this for machine reaming.

Ew

[pipeclay]

I would say normal practice would be to keep rotating the reamer in the cutting direction when removing for a hand reamer and maintain rotation of the workpiece with a machine reamer whilst withdrawing the reamer.

[ventureoverland]

Thanks guys, I have a 4 fluted 5/16 machine reamer that I need to put through some bronze to make a bush.

I had planned to drill a hole and then feed the reamer through whilst secured in the Tailstock and chuck turning slowly.

Based on a 1 - 1.5% reduction in drill size, that would then require a 7.8mm drill.

R
J


Thx
Jon

[pipeclay]

Use an N letter drill unless you can find something closer, and easy to obtain.

[ventureoverland]

Use an N letter drill unless you can find something closer, and easy to obtain.

Thanks Pipeclay.

N size = 0.3020" = 7.6mm

I don't have a 7.6 or 7.8, so I'll have to see which is easiest to come by.

In reality / practical terms, does 7.6 or 7.8 really matter? Indeed, could I use a 7.5mm (which I do have), or would this be asking the reamer to remove too much material?

Thx
J

[Michael G]

Depending on your reamer you may be asking it to remove too much material.
Remember too that a normal drill can drill oversize, especially if recharpened (no, let's not start that discussion again), so drilling a trial hole in the same material is a good check to make sure you will not be drilling oversize. As a general rule for that I always factor in that a drilled hole can be 0.1 to 0.2mm over nominal, so you may find that if you drill a hole with a 19/64 " bit, it may be close enough. Try and see I guess.

Michael

[cba_melbourne]

Thanks Pipeclay.

N size = 0.3020" = 7.6mm

I don't have a 7.6 or 7.8, so I'll have to see which is easiest to come by.

In reality / practical terms, does 7.6 or 7.8 really matter? Indeed, could I use a 7.5mm (which I do have), or would this be asking the reamer to remove too much material?

Thx
J

Dependig on several factors, it could mean the difference between seizing up the reamer and thereby damaging both the workpiece and the tool. If you were about to ream hard bearing Alminium Bronze, 7.6 would be very risky. If you were to ream Phosphor Bronze, you could go away with 7.6. If it was just Aluminium, no problem. It also depends what reamer you use. If you are using a fragile expandable reamer, the cylindrical guide at its tip may not even let it enter a 7.6 hole.

You mentioned earlier you intend to do this in the lkathe, with the reamer in the tailstock. If you need an accurate hole that is not a good idea, unless you own a floating reamer chuck. You risk to end up with an oversize hole if the tailstock alignment is slightly off, which it usually is. Is this a very deep hole that you need to ream? Else you could bore it out with a miniature boring bar instead of reaming. Or you could use a hand reaamer with a square on the shaft - put a tap holder on the square, and use a center in the tailstock to engage the center pip at the back of the reamer to guide it.

[ventureoverland]

Wow... What started off as such a simple question has made me realise there is no such thing!!!

I'll try my 7.5mm and see how it "feels", but suspect I will buy a Dormer 7.8mm - they seem fairly available off eBay.

The reamer I have is a 5/16 and is not an expandable type, it does have a square on the end to accommodate a tap wrench.

I don't have a miniature boring bar, just a 12mm one - so that option is out of the window:(

I don't have a floating chuck so I'll put a tap wrench on the end and do it by hand and use the tailstock to hold it on centre. Forgive the next stupid question, but I am guessing that the lathe should be stopped and I turn the reamer by hand and feed into the hole by applying tailstock pressure? Or should the chuck turn slowly under power?

All together I need a bush about 2 inches in length, but I could do 2 x 1" bits and press one in from either end.

Thx
J

[cba_melbourne]

> The reamer I have is a 5/16 and is not an expandable type, it does have a square on the end to accommodate a tap wrench.

then it is a manual reamer

> I don't have a miniature boring bar, just a 12mm one - so that option is out of the window:(

I am just the opposite. 12mm is the largest boring bar I have, but I have about 50 smaller ones.... That is why I always first think of boring....

> I don't have a floating chuck so I'll put a tap wrench on the end and do it by hand and use the tailstock to hold it on centre. Forgive the next stupid question, but I am guessing that the lathe should be stopped and I turn the reamer by hand and feed into the hole by applying tailstock pressure? Or should the chuck turn slowly under power?

I do not have a floating chuck either. Its been on the list to make for 20 years. The way I do it without floating chuck is not to lock down the tailstock. On the small lathe I rest one arm of the tap wrench against the bedway so it can slide freely. On the large lathe I let it rest on the cross slide. Turn on the spindle and push the reamer with the whole tailstock into the workpiece. If it is a through hole, I push the reamer all the way through, then remove workpiece and tap handle and push the reamer through. Otherwise the reamer needs to be pulled back carefully with the entire tailstock and with the spindle still running.

> All together I need a bush about 2 inches in length, but I could do 2 x 1" bits and press one in from either end.

Its better one piece reamed. You can do it in two pieces, but then you still have to bore or ream the 2" long larger hole to press the bushes in, else they wont line up perfectly and bind.

[cba_melbourne]

Here I found a pic I just found on the net to show what I mean:
323743

[Ueee]

I do not have a floating chuck either. Its been on the list to make for 20 years. The way I do it without floating chuck is not to lock down the tailstock.

I have found that is not a guarantee that your bore will be on size. I do this all the time but i use the floating chuck and just push it through. Maybe with a small lathe the weight of the tailstock is low enough that the reamer will dictate its position, but thats not what happens with my lathes.

Interesting that you take the reamer through and out the other side. The reason i asked about removing them is i always get a spiral scratch from the tip of the reamer as i pull it out, even with the floating chuck.

Ew

[cba_melbourne]

I have found that is not a guarantee that your bore will be on size. I do this all the time but i use the floating chuck and just push it through. Maybe with a small lathe the weight of the tailstock is low enough that the reamer will dictate its position, but thats not what happens with my lathes.

Interesting that you take the reamer through and out the other side. The reason i asked about removing them is i always get a spiral scratch from the tip of the reamer as i pull it out, even with the floating chuck.

Ew

Ew,

there are more factors that influence size. If a reamer has stamped on its shaft 10.01mm, it does not mean that it will always produce a 10.01 bore as long as it is fed straight and at the proper rpm and feed rate. It does also matter how much worn the reamer already is. Condition of the cutting edges matters a lot. If the reamer was once, only one, rotated backwards inside a workpiece the cutting edges have had it. A reamer that was previously used in steel may not anymore be sharp enough to ream Bronze to proper size, and it may want to seize up (its like with drills, you should keep a separate set for materials such as brass that you never use for steel). The above 10.01mm reamer may create a slight undersize hole in tough Bronze, maybe 10.00 or 9.99mm, that is enough to completely upset a precise fit. The same reamer in some soft Aluminium alloy may ream oversize, maybe 10.02mm. Together with workpiece material, it also matters what lubricant and how much of it you use.

I own a few "expansion" reamers. I can highly recommend these to slowly approach a dimension in one off workpieces, especially if its a complicated workpiece you do not want to loose. But these are very expensive reamers. Do not confuse these with "adjustable" reamers. Expansion reamers are very sharp precision tools. They can typically only be adjusted over a range of say +/- 0.05mm. Here a picture from the net how an expansion reamer looks like:
323758
These reamers are also quite fragile. No wonder, hollow inside and slitted, and hardened. I can tell you it hurts if one gets broken.... about $120 a good new one.You adjust the diameter with the screw at the tip. But then such an expansion reamer can replace several fixed reamers. For example an 8mm will replace 10 fixed reamers of a 7.95, 7.96.... 8.00....8.05mm. Behind the adjustment screw is a pilot cylinder. On a 10mm reamer, this pilot has a diameter of about 9.82mm, limiting how much a hole to be reamed can be undersize.


Re. The Tailstock method that I described, note I do not always do it that way. It depends how accurate a hole I want. I do know how far off (high) my tailsock alignment is, and I have no hesitatinon to chuck a reamer in the drill chuck I the hole I need just has to be reasonably round and smooth but not deep and dead accurate in dimension. Also, I normally take out the reamer the same side it goes in, smooth movement and lubrication are necessary, and there will be no "spiral marks". With the "sliding the tailstock" method however it is a bit fiddly to retract the reamer straight, and for this reason I sometime prefer the safety of pushing it through. All depends on the task at hand, and the mood of the day I guess.

[ventureoverland]

All this talk of reaming got me thinking about press-fitting the bush into the stainless block I'm machining.

My reamed hole will be 5/6" (approx 8mm).

The outer diameter of my bronze is currently 12.5mm and I had planned to turn this down to a 10.5mm OD (The 10.5mm isn't critical, it could be anywhere between 10.00 and 11.00).

Assuming the bronze bush has an OD of 10.500mm, what size should I aim for on my stainless housing to allow me to press fit it (in the vice)?

Should I heat the stainless a little, or freeze the bronze?


Any thoughts or advice?

Thx
J

[pipeclay]

How are you doing the hole in the stainless ,or is it already an existing hole?

What is the surface finish like in the stainless hole?

Has the stainless hole been drilled,bored or reamed?

Are you going to ream the bush after putting it into the stainless?

If you try for .0005"/.0127mm or less should be sufficient to retain the bush.

You could try either method to install the bush but depending on the overall size of the stainless section you may have to provide to much heat,
I would be more inclined to put the bush in the freezer.

[Ueee]

As a general rule .1% is a nice press fit. So as PC says .01mm or so. If it were me i'd be boring first and then turning the bush to suit as you can use emery to sneak up on the size. I'd be aiming for .01-.015mm. You will also need to run the reamer back through your bush after fitting it.

Ew

[cba_melbourne]

A 2" long Bronze bush with 8mm ID 10.5mm OD has only 1.25mm wall thickness. If your intention was to ream the bush before pressing it in, think again. The press fit may make its ID shrink. Also such a thin walled and long bush will need considerable pressure to fit, if the fit errs only slightly on the tight side - this may inadvertently deform/bulge the bush. Maybe a light interference fit and some Loctite is a better idea.

You could of course make the bush deliberately with an undersize ID, and ream out after pressing it in. If the SS block cannot be clamped onto a drill press for reaming, you may do the reaming by hand. That way you could also use a two part bush. Two part bushes have also the advantage, that the space in between can be useful oil or grease reservoir.

With such a thin walled and small bush you cannot really use heat shrinking. The bush has not enough mass and would take on the temperature of the block before you get it in place. Also, the thermal expansion coefficients of the materials are against you in this case. SS is around 5.5, Copper based alloys are around 10. So if both are heated together, the Broxe expands twice as much as the SS.

Just some ideas...
Chris

[Pete F]

All this talk of reaming got me thinking about press-fitting the bush into the stainless block I'm machining.

My reamed hole will be 5/6" (approx 8mm).

The outer diameter of my bronze is currently 12.5mm and I had planned to turn this down to a 10.5mm OD (The 10.5mm isn't critical, it could be anywhere between 10.00 and 11.00).

Assuming the bronze bush has an OD of 10.500mm, what size should I aim for on my stainless housing to allow me to press fit it (in the vice)?

Should I heat the stainless a little, or freeze the bronze?


Any thoughts or advice?

Thx
J

I'm not sure exactly what you're making here, but in relation to your initial posts of reaming on the lathe, be aware that the reamed hole will close up considerably after a press fit and will need to be reamed after pressing.

[ventureoverland]

Ok, so as the original question has expanded somewhat... The part is for a seized blender.

From this:
http://tapatalk.imageshack.com/v2/14/08/29/9a60817d6d96ab9e2de6ec2404c61de8.jpg

http://tapatalk.imageshack.com/v2/14/08/29/0e53ce5b67cca1bf220402c167bdcd12.jpg

Via this...
http://tapatalk.imageshack.com/v2/14/08/29/4fc3f2d3433d4361a9c6fb1202383520.jpg

I did think about boring the stainless and then creeping up on the outer ID for the bronze, installing it and then drilling & reaming out the bronze.

Sounds like that maybe the way to go as I can easily hold the stainless in the chuck because I purposefully haven't cut the outside away yet.

R
J


Thx
Jon

[Pete F]

A blender! Man I sure hope that thing has sentimental value attached to it! :wink:

[ventureoverland]

No sentiment... Just a good excuse to learn more skills and gain experience and I suppose it avoids having to buy another!


Thx
Jon

[cba_melbourne]

Ok, so as the original question has expanded somewhat... The part is for a seized blender.

From this:
http://tapatalk.imageshack.com/v2/14/08/29/9a60817d6d96ab9e2de6ec2404c61de8.jpg

http://tapatalk.imageshack.com/v2/14/08/29/0e53ce5b67cca1bf220402c167bdcd12.jpg

Via this...
http://tapatalk.imageshack.com/v2/14/08/29/4fc3f2d3433d4361a9c6fb1202383520.jpg

I did think about boring the stainless and then creeping up on the outer ID for the bronze, installing it and then drilling & reaming out the bronze.

Sounds like that maybe the way to go as I can easily hold the stainless in the chuck because I purposefully haven't cut the outside away yet.

R
J
Thx
Jon

Jon, that will work just fine even with some slop or misalignment in the bushing. The design may even need some slop to work. I thought you were making an engine part or similar....

I can very well understand fixing something like a blender. We still use a 35 year old blender in our kitchen. It is swiss made and has been designed for a very long life. I would try to fix it too should it break down, even if the time alone may be more worth than a new one. Same with the espresso machine, 25 years old, also swiss made, needs some attention every odd year but ... still works and works well. It provides great satisfaction beating the landfill mentality of our time and fixing such items.

[pipeclay]

Any reason why you cant fit the unbored bush into your material and then finish the bore.

[ventureoverland]

Any reason why you cant fit the unbored bush into your material and then finish the bore.

Non at all pipeclay.

Indeed, after thinking about it more and feeding off the information provided here I think that is exactly what I will do - Rather than 1 long bush though I think I'll do two smaller ones and press (or lactate) in from both sides and then ream to the finish 5/16 size.

Thx
J

[Steamwhisperer]

Have a look at post #2 in this thread.
http://bbs.homeshopmachinist.net/threads/53123-Tolerances
I have always used the limits fits and tolerances chart and not Loctite :D:D

Phil

[ventureoverland]

Well I got some more time in the garage today... Thought I should post some photos of my new blender base!

The base without blades added:
https://farm4.staticflickr.com/3912/15161544491_2c991cf188_o.jpg (https://flic.kr/p/p6LSXv)2014-09-07 Blender #1 (https://flic.kr/p/p6LSXv)
by Jon_Kelly (https://www.flickr.com/people/100552867@N05/), on Flickr

Underside of Base:
https://farm6.staticflickr.com/5594/14977953998_f8889a97a7_o.jpg (https://flic.kr/p/oPxVUb)2014-09-07 Blender #2 (https://flic.kr/p/oPxVUb)
by Jon_Kelly (https://www.flickr.com/people/100552867@N05/), on Flickr


Base with Blades:
https://farm6.staticflickr.com/5561/14977867830_5b9cd8a5f2_o.jpg (https://flic.kr/p/oPxuhw)2014-09-07 Blender #3 (https://flic.kr/p/oPxuhw)
by Jon_Kelly (https://www.flickr.com/people/100552867@N05/), on Flickr

Its only the second thing Ive ever made on the lathe and Im quite pleased with the results. The finish on the underside isn't brilliant, but it is the right size! I had to Loctite the bottom bush in because I made it a little too small, the top bush however is pressed in (I did that second!)


Thanks for everyones help, really appreciated.
Jon

[Oldneweng]

Very nice job Jon. I hope the motor does not burn out tomorrow:D:D.

Dean

[cba_melbourne]

Well done! But how do you prevent liquid trickling down the shaft? Is there a seal somewhere we cannot see?

[ventureoverland]

Well done! But how do you prevent liquid trickling down the shaft? Is there a seal somewhere we cannot see?

Good question!

Short answer is I don't really know! I simply copied the broken bit!

There is a rubber washer that sits above the bronze bush and below the first blade so that might do the trick.

I've not spun it up yet with food / liquid in it so everything may still be a disaster:) However, the shaft feels a nice fit in the bushes and there is the same vertical end float as the original had so fingers crossed it will OK.




Thx
Jon

[ventureoverland]

It holds water:) At least it did for about 1.5hrs when the jug was full with 1.5L of water. After about 1.5hrs I got about a table spoon of water out of it - plenty long enough to blend / and make a smoothie for brekky!!

Not bad machining tolerences:) I suspect the original plastic and bronze bushing wouldn't have done any better.