Being a clueless newby I am not clear on what tooling works with which mills.
Am I correct that what varies is the COLLET taper but that the tools themselves are interchangeable provided you have a collet with the proper nominal diameter to hold the tool?
I ask this question because I'm hoping to find deals on tooling at estate sales. Sometimes the seller, being an heir, doesn't have a clue. And of course, neither do I.
In my case our machine is an old Bridgeport with R8 taper. We have neither collets nor any tooling for it. Therefore, I'm hoping to find useful tooling at a price I can afford.
A moment ago, I watched this auction roll by. I was tempted to bid but did not because I'm clueless as to whether: a) I need most of this stuff; and/or b) It is suitable for a Bridgeport with R8 collets; and, c) There are some basic things I need to do before I start buying tooling (such as get the machine installed).
Now that the temptation is gone I will appreciate hearing your collective views on this particular lot.
Now that the temptation is gone I will appreciate hearing your collective views on this particular lot.
Thanks, Vernon
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You didn't miss out on a deal, IMHO. I didn't see any R8 stuff there. Search for R8. Also keep in mind that there are sources for new useable imported R8 tooling at affordable prices.
Just a suggestion based on hard experience... avoid R8 collets, especially used ones.
Purchase some endmill holders that fix the cutter into position with a set screw. 1/4", 3/8", 1/2", and 3/4" dia, capacity will suffice. Maybe a face mill arbor and a fly cutter. Add a boring head later.
To hold the cutter in its holder back-out the set screw until the end mill slips in, visually align the flat on the end mill with the set screw; for the first few times it may be worthwhile to take out the set screw so that you can see the flat in location. Replace screw and snug it up, make sure the screw bears on the flat! Now loosen the screw very slightly and pull the end mill out until it stops. Now re- tighten the set screw firmly, and you are good to go.
The reason for this song-and-dance is that end mills tent to pull out of the holder in use, having it tight against the screw stops this.
If you must use R8 collets get new ones... they are pretty cheap. With larger shank cutters, say 1/2" and up in diameter the draw bar requires very hard tightening to prevent the end mill from walking out of the collet during use.
Used collets are probably bell-mouthed which aggravates this condition.
Wolfgang. I'm sorry but I don't understand. I thought you had to use whatever taper the mill was manufactured with. In this case it's a Bridgeport 2J series 1, 2 hp mill with R8 collets. Are you talking about some kind of adapter?
An end mill holder can be though of as a specialized collet. They look and act similarly. The difference lies in the fact that the end mill holder does not contract radially as does the collet. Instead, the holder has a setscrew that is used to clamp the end mill in place.
They are more secure than collets for holding end mills, particularly in the larger diameters.
The longer the end mill sticks out the worse it gets... Then the next thing you see is some poor fellow stripping the drawbar threads???
When I am using collets I put the flute just short of the collet (even the super TG types) and just tighten moderately. Cleanliness is vital (I'm ANAL about clenliness).
If can't get a close grip then "plan B" is an end mill holder or collet extension for odd sizes.
R8 tooling is easy to recognize, I am not sure what is the problem.
To test whether a garage or estate seller knows what he is selling, there is a simple trick. Take what you are interested in, make a stupid face, and ask the seller "this looks neat, do you know what it is" and then await the response.
R8 describes the internal configuration of your spindle nose, ie. that hole that accepts the tooling/adapter. I believe that the R8 spindle nose is exclusive to Bridgeport.
Other standard spindle noses are Morse tapers, which vary from #0 (smallest) to #5 (largest I think). These are mostly found in lathes, larger drill presses, and small imported milling machines.
On larger milling machines you would find a standard milling machine taper, from #30 (smallest) to #60 (largest I have seen on a 100 HP spindle).
Then there are 8mm collet for watch maker's lathes, followed by all the other "standards" of which there are dozens.
The ones I listed are STANDARD, made to accurate tolerances so that any tooling made to the same standard and tolerances will always fit, regardless of who made it.
Now then a collet, more complete name would be "split collet", holds the tool when it is drawn into a tapered bore thus closing the collet bore onto the tool shank.
An endmill holder is not split, but has a bore that accepts the endmill shank with very little clearance. The endmill is held by tightening a setscew in the holder, as described earlier.
Except for drill presses where the tool loading is always axial thus pressing the tool/holder into the spindle nose, all collets, holders, adapters, etc. need to be held in position in the spindle nose because side loading forces from milling will cause the adapter to "walk-out" from the spindle bore.
This holding is most often accomplished by a draw bar that extends axially through the length of the entire spindle, and is usually tightened by hand. This is the case in your Bridgeport mill. These draw bars occasionally break... they are highly stressed items and replacements are available. Large machines have motorized draw bars...
Trust this helps... The advice given above is excellent, especially cleanliness.
Any and all tooling/adapters that fit your Bridgeport spindle must have the EXTERNAL R8 configuration. It is easy to recognize once you are familiar with it. If commercially made R8 is R8 and ought to always fit.
You've mentioned the setscrew holders which are available in the UK, but also commonly available in the UK is the Clarkson Autolock holder and copies which use cutters with a threaded end and I understand are more accurate and better for smaller cutters. Are the Clarkson style not readily available in the US?.
Wolfgang and Winston. It finally sank in. God, it's tough being spatially challenged! As soon as we get the machine wired in I'll go on a tooling shopping spree.
Winston and Wolfgang (or anybody else!) I do have another question about "R8" cutting tool holders and the tools they hold. Would the tools that sold on the ebay auction link I included at the beginning of this thread have worked? I noticed that those tools had flats on 'em. It seemed like a lot of tools for less than $200. Thanks! Vernon
I must be getting blinder because I didn't see any R8 - specific items in that collection. I saw drills, cutters and reamers that would work in an R8 collet, but no collets, endmill holders or boring heads.
I'm glad you spotted the flats on the milling cutters. That is the surface the setscrew bears upon to secure it in the endmill holder.
As others have said, collets are best bought new. They aren't all that expensive even for decent quality tools.
R8 endmill holders and split collets, as described earlier, are only suitable to hold tool shanks of a specific diameter, such as 1/4",
3/8", 1/2", 5/8", & 3/4", or hard millimeter equivalent. It is VITALLY important that the tool shank be within +/- .001" or so of the collet size and burr-free!... much greater variation in diameter may deform the collet or hold the tool less securely. For the endmill holder with set screw the shank obviously has to fit into the hole, but you don't want too much clearance here either. If the shank is too small the cutter will orbit or run eccentrically in the holder, this can be detected by the shiny wear marks left on the tool shank. Note that the shank of QUALITY endmills is usually ground to the nominal dia. +.0000" -.0005".
On small dia. endmills any eccentricity will lead quickly to dulling the cutter or breaking it because one cutting edge may do all the cutting:
Suppose a 1/4" dia, endmill is turning with a run-out of .005" total indicator reading (TIR),which means its axis has an eccentricity of .
0025" from the machine spindle. The chip-per-tooth load is about .
002" CPI. With automatic feed set to a speed of: {(rpm spindle) x (# of teeth on cutter) x (CPI) =3D (feed in inches/minute)} one tooth would cut at .004" per rev. This overloads one tooth and would probably break the cutter.
Hence my admonition: Large cutters with shank dia. of say 1/2" and up are better held in endmill holders (more secure) while small cutters are better off in collets (better concentricity). Really small cutters should be checked with a test indicator to verify acceptable run-out. Where run-out is unavoidable reduce the feed to an acceptable chip load per tooth.
In-between shank sizes are usually held in drill chucks; typically drills and reamers fall into this category. Note that drill chucks should not be used for milling because the side forces will walk the chuck off its taper shank.
On occasion it may be necessary to hold a drill in a collet because of space restrictions, especially in a small milling machine. If the drill is 1/64" or 1/32" smaller that the standard-sized collet the difference in dia. may be made up with a sleeve bent from shim stock .
From reading some of the responses it looks to me as though most folks are getting hung up on the R8 bit of your query. There doesn't appear to be any R8 *specific* tooling in that ebay auction, but there is plenty that would be useful (1) with a machine with an R8 spindle. In other words, none of it has a built-in R8 shank, but lots could be held in R8 collets or toolholders. The flats you see on the milling cutters are for the set screw in a toolholder -- this is sometimes referred to as a Weldon shank.
A minimal set of R8 collets should include 3/16, 3/8, 1/2, 5/8 and
3/4. That'll cover the vast majority of high speed steel endmills you're likely to encounter. Add 1/8, 1/4, and 5/16 if you want to run small carbide endmills.
(1) Useful if the tools are sharp, and remain sharp after being tossed in a box and making a cross-country UPS trip. That's a very big "if." I'd avoid auctions like that unless you can inspect the stuff in person, and have the experience to tell the difference between sharp, marginally useful, and uselessly dull cutters.
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