Author Topic: Reaming Holes in Fixture Plate - What Type of Reamer  (Read 3554 times)

Online Twizseven

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Reaming Holes in Fixture Plate - What Type of Reamer
« on: October 23, 2020, 08:48:47 PM »
I am currently making a fixture plate for use on my Bridgeport clone milling machine. Plate will be dual purpose as it will be also used to mount a Bison Indexer on the table.

The fixture plate is 7/8" thick cast aluminium tooling plate and is 330mm x410mm in size. It will have rows of holes drilled into it, every alternate row will be drilled and then tapped M10. The alternate rows of holes are intended to take 10mm locating dowels made from 100mm silver steel bar. None of the holes will be through holes. I will be drilling to depth of 20mm and then either tapping or reaming as necessary.

I have a MT1 long M10 reamer which is about 12inches long but I feel this too long.

What type of reamer should I used as these are non through holes. I have seen some advertised which specifically say must only be used for through holes. Am I better with spiral (right or left hand?) blade reamer or straight blade reamer. Would prefer to stay with MT1 but could use chucking if this is all I can get.  The spiral on the reamer I have looks as though it would move the swarf into the hole not out of it, so I guess is meant for a through hole

Colin

Offline derekwarner

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #1 on: October 23, 2020, 09:19:45 PM »
Colin......you say cast aluminium......there are so many varients here.....[not only Grade, but also of Heat]

Is the plate gang milled for flatness?.......if so, it was probably heat treated post casting & before milling

I would be more concerned with a trial drill & ream M10 to see how it responded to the chip/swarf removal..

50 something years ago  :old: as apprentices we were taught to use 100% Kerosene as the cutting fluid........these days, I find Rapid Tap or T-Cut provide a superior finish

Just another thought...have you considered predrilling say 3mm diameter x the full depth of the plate, then set the 9.5?mm diameter drill to say 17mm deep & flat side ream to full available depth [14.5?]....this will allow any 9.5mm diameter drill swarf to be pushed down and also a path for any 10mm diameter reaming swarf as opposed for the possible pickup & galling to be an oversized M10 sloppy hole?

So apart from this, if you did achieve true good fitting M10 diameter fitted dowels, a simple way to remove them....a gentle tap :hammerbash: from underneath

Derek
« Last Edit: October 23, 2020, 09:36:32 PM by derekwarner »
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Offline john mills

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #2 on: October 23, 2020, 09:59:07 PM »
needs to be a machine  or a chucking reamer  the citing is done on the 45 degree chamfer .so will cut closer to the end .the hole should be bored first to get precise position and only leave a minimum amount for the reamer to cut
but clean up the hole .5 would be way to much  the flutes will just fill up .for cutting fluid modern cutting funds work  as apprentices 50 years ago we were shown the hazard of using kerosene machines and factories burnt down factories soluble oil work. WD 40 has to many fumes for me.  try on some scrap first to see how the size comes out   .the long reamer is not a problem if you have the hight.and don't run too fast.


           John

Offline petertha

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #3 on: October 24, 2020, 06:00:54 AM »
I made this fixture plate from 3/8" cast aluminum. It has 8-32 tapped holes every 0.5". The only reamed hole is the center one 0.250". All I have is straight flute style & it was uneventful, but all mine are through holes.

Tapping this stuff is a bit different than regular alloys I found. Rather than a nice spiral swarf (on ejecting style taps kind of suited to aluminum) the cast material kind of like to pack in the flutes a bit more. because I had to do so many mind numbing holes (with a tapping head) I broke up the monotony by trying a row of one cutting fluid then another. Interesting exercise. Tapmatic regular, Tapmatic aluminum, some higher viscosity stuff (didnt like that), some 'natural' cutting oil based... Generally I find WD-40 works as good as any & this was my conclusion again. And seem like the better they work, the more they like to make by face rouge up a bit over time as it heats or vaporizes or whatever. I just happened to have simple N95 mask handy (COVID way of life these days). It made a positive difference so I think I'm going to keep a mask handy.

But what worked noticeably better than any of the liquids was a white creme tapping compound I bought a while back & just haven't used much. You could just feel the tap glide in with less force & the chips had much less propensity to stick. Good luck!.

Offline Jasonb

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #4 on: October 24, 2020, 07:11:22 AM »
Never heard of an M10 reamer, 10mm would be more like it and keep the M10 to describe threads ;)

To reduce risk of drill wandering and any reamer following I'd use a stub length drill of 9.8mm dia and then a plain shank machine reamer held in a collet to finish the hole. Probably H8 reamer as H7 may be a bit loose though a test cut will determine that or if you need to go for an incremental reamer rather than 10mm nominal. Slightly larger chamfer on the dowel than the reamer's end will stop it getting stuck.

As suggested elsewhere you could drill them all and then set the boring head to your desired "fit" on the first hole and then not much longer to move around the plate and finish bore each hole to size

Online Twizseven

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #5 on: October 24, 2020, 10:17:50 AM »
Thanks for all the helpful responses.

Derek,
The plate is made by ALCOA and goes under their trade name of MIC6 Precision Machined Cast Aluminium Plate.

General concensus appears to be to drill through at a small size , e.g. 3mm which will provide somewhere for the drillling and reaming swarf to go and also will stop the dowel from being pushed out of the hole by air pressure.  Will also provide extra way to remove dowels should one get stuck.

Petertha,
I see you used a sacrificial wood substrate whilst drilling.  Was this MDF.  Is MDF considered flat enough, though I guess it will flex slightly when clamped so plate stays flat to the table.  I have put three M14 holes in to hold the Indexer and these cut okay even though the tap was not of the highest quality.  I do have a R8 Tapping Head byt never used as yet and not sure whether it can take a M10 tap.  It would be nice if it did.

John,
I do have the height to use the long reamer (cutting length 254mm), but I think I would prefer to use something a little shorter.

Jason,
I have just ordered a 10mm chucking reamer.  I will try to remember to keep M10 for threads  :D  I have a miniature boring head so will have a play on a piece of scrap.

Colin

Offline derekwarner

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #6 on: October 24, 2020, 10:46:20 AM »
I fully agree that my mention of drilling 9.5 diameter for an M10 H7 straight fluted reamer is expecting that too much for the reamer

Acknowledged, I had no knowledge of the specific ..MIC6 Precision Machined Cast Aluminium Plate.

...http://www.aerodynamicmetals.com/our-products/mic-6-precision-machined-cast-aluminium-plate.html

Which appears to have little equal in technical properties for a cast aluminium [plate] material

However a W Letter drill of 9.8044 unless literally brand new and of reputable quality may actually drill in excess of the diameter stamped on the shank

In Australia, for Metric sizing, we follow both German DIN Standards however as manufactured anywhere in the World.....nomenclature of M10 Reamer to H7 is absolutely common

One could conclude British have a natural dislike to the SI system....probably simply because they did not invent it  :Lol:
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Offline Jasonb

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #7 on: October 24, 2020, 01:12:45 PM »
ha Ha, try clicking the actual link and see how it's listed

https://www.sbsimpson.com/sowa-m10-hss-straight-shank-straight-flute-reamer-143-061-cutting-tools-20-27027

The reason why M$ should not really be use is because that can get confused with hole tolerences such as M6, M7 and M8 and as dowel pins are made to fit M6 tolerence holes it can all get a bit confusing if the Nominal size is not expressed in mm if you have 6mm or 8mm pins/holes

You may find you want an H6 reamer if you want the towels to hold themselves in place if you can find one or a one a few microns under nominal but it will depend on a test fit. You can also get Dowel Pin reamers that have one just under nominal and one just over so the dowel stays in one half of a die and the otherhalf slips on with minimal movement.

« Last Edit: October 24, 2020, 02:30:50 PM by Jasonb »

Offline petertha

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #8 on: October 24, 2020, 05:28:27 PM »
Petertha,
I see you used a sacrificial wood substrate whilst drilling.  Was this MDF.  Is MDF considered flat enough, though I guess it will flex slightly when clamped so plate stays flat to the table.  I have put three M14 holes in to hold the Indexer and these cut okay even though the tap was not of the highest quality.  I do have a R8 Tapping Head byt never used as yet and not sure whether it can take a M10 tap.  It would be nice if it did.

Amazingly these offcuts of MDF are within a couple thou of thickness so I think plenty good for this particular application. My carpentry friend tells me that your dad's MDF may be different (higher) quality than some of the stuff you see on lumber shelves these days, but that might be completely related to your region & brands. My tap for this application was chip ejecting style, meaning coming up out of the hole. They are fluted, intended for softer, gummier materials like aluminum. But the flutes or maybe amount of fluting makes them appear a bit weaker than the conventional taps where chips go outthe bottom. What I didnt consider at the time was just drilling through into the MDF deeper & maybe that would make a sufficient 'well' for chips to go if using a conventional tap? Your material is thicker & bigger threads which means more debris to potentially pile up.

If you have a tapping head you should at least try it on scrap. Reduces workload in this kind of application. I have a Tapmatic RX-30 which goes to M7. I basically rotate the collar to the thread ID & that adjusts the corresponding clutch setting. Now there is no steel vs aluminum setting so on one hand M6 setting for steel should be plenty for aluminum. But if you have a situation where chip packing is the bigger issue (aluminum), then you might find yourself setting it a bit lower because once its packed you are not too far from a broken tap. I am no expert here but treat it as a guideline setting & do some tests beforehand. Tapping heads are so slick. Mine auto reverses out just by pulling up on the quill lever. You can re-enter an existing tapped hole & perfectly pick up the threads with no drama. Feels like cheating. Unfortunately tapping heads are not cheap. There are some clones out there but I have no experience with them.

What I would recommend is use a new, sharp tap if you can. BTW my material was the same MIC-6

This is the tapping creme I found worked well.
https://www.kbctools.ca/itemdetail/1-444-43100

Online Twizseven

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #9 on: October 24, 2020, 10:04:22 PM »
For today just decided to drill and tap holes, whilst I wait for reamer and dowels.  But will test all options suggested.

Picture below shows plate after spot drilling all (well most of) the holes and then drilling a 3mm through hole.  The fixture plate is sat on a 3mm plywood base to prevent damage to the table.  I did not want to raise it any further as the tenons on the bottom of the plate are locating it in the central slot on the table.

I said I had drilled most of the holes.  No matter which way I moved the table in the Y axis and moved the head forward and backwards there was no way I could see to drill the final row of holes. :headscratch:  Rather than disturb the current setup I will complete all the tapped holes and all bar the last row of 8 reamed holes prior to moving the milling head to to an extended position to get to the last row.  Will have to use the edge finder on the outside edge and then move in the required 15mm or possibly it would be more accurate to fit some dowels in the last but one row and take a measurement from there.

All the holes to be tapped have been drilled 8.5mm and have just tapped 18 of them by hand this evening.  (Unfortunately my tapping head can only be used up to M7 taps.)  The next 18 can wait till the morning, need to give my back a rest.

Colin

Offline derekwarner

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #10 on: October 25, 2020, 12:47:33 AM »
Possibly too late, but one alternative concept is the thought Taper Dowels......some may say old fashioned  :LittleDevil: ..

However in score out of 10

10 for repeated installation accuracy of placement
10 for ease in repeated or infrequent removal
10 for absolute minimal galling or damage

With adaquate design, able to hold potentially movable surfaces locked solid.......

Quite a number of British Naval ordinance were built with taper dowels as providing mating component tolerances that were not achievable with any parallel locating element

Mechanical Naval computers were assembled with 100's of taper dowel pins holding all of those disks & rotating wheel elements .......these computers would not have achieved acceptable accuracy with hollow point grub screws, or parallel dowels locking components

The decision to use 1:48 Imperial or 1:50 Metric purely between the costs of taper reamers and  tapered dowels

Derek
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Offline petertha

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #11 on: October 25, 2020, 01:28:56 AM »
Derek, I've heard about tapered pins in jig plates. But I don't quite get the implementation. I assume you mean a tapered reamed hole & matching tapered dowel pin? Because if it was one without the other then you would only have line contact between hole & pin vs. something more like a piston & cylinder with non-tapered surfaces.

But tapered holes brings up interesting questions like how to ensure the reaming depth is the exact. Otherwise if they were not, the tapered pins would stick up at different heights & you could not rely on adjacent pins to provide a common reference plane like cylindrical pins, no?

Offline derekwarner

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #12 on: October 25, 2020, 05:40:42 AM »
In an earlier life, I supervised refit work on missile launchers and gun mounts for our Royal Australian Navy......so earlier Vickers 4.5" Twin Gun Mounts had 100's of Imperial 1:48 taper dowel pins used in the installation of components, many used in jig mountings during alignments

Yes the mating component parallel holes were drilled, then taper reamed, then a taper pin inserted to seating [which was also confirmed by Bluing the hole prior to final 'homing', and the protruding height measured........so then the individual pin was withdrawn and the height machined down so to conform the tolerance height

So yes, whe a taper pin was withdrawn, it was tagged with the location and so was reinstalled in that exact location on reassembly

In these applications, the cronical points on the top of any pins were never used as a referenced dimension

Moreover with the 0000 [Military] size  pins in the mechanical computer wheels [1 x each at 180 degrees to each other at either end of a hub] ensured 100% security in alignment which cannot be necessarily be achieved even with alternate CNC produced components

Derek L Warner - Honorary Secretary [Retired]
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Offline Jasonb

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #13 on: October 25, 2020, 07:07:18 AM »
As peter says in this application a pin tapered it's whole length could cause problems as you are likely to be using the edge of the protruding pin as a location point.

It would work if say half the pin were tapered and the hole tapered to suit but the other half was parallel, that way any slight difference in depth of fit would not affect things. I used to have a mitre cutting jig like this many moons ago, you just move dthe pegs to give one of many common angles.

Offline Doc

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Re: Reaming Holes in Fixture Plate - What Type of Reamer
« Reply #14 on: October 26, 2020, 02:00:31 AM »
  I worked many years with mic6 tooling plate where I worked. The stuff will gaul up easy so you need to keep tools well lubed and only leave about .004 per side for reaming. I would also double drill holes drill with undersized drill leaving about .015 and then with a drill about .008 undersized for holes to be reamed. I use TRIM coolant and it seems to work well. Will not use kerosene or wd40 because of the stink.

 

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